Unit #3: Biology Course Notes and Study Notes 7.1 Homeostasis and Control systems (pg334): · Human body likes to function at 37 degrees Celsius, 0.1% blood sugar level and a blood pH of 7.35. · Rarely does your environment provide for these perfect conditions. The weather outside, the food you eat, the exercise you do all takes into account. Homeostasis: · The body’s attempt to adjust to a fluctuating external environment. A constant internal environment is maintained despite changes in external environment. · The body maintains a constant balance (steady state) through a series or monitored adjustments. Requires constant monitoring and feedback. · Ex of adjustments made by regulators: · release of glucose from the liver to restore blood sugar levels during exercise. · Evaporation of water helps regulate body temp · Hypothalamus regulates temp and changes is osmotic pressure · Kidneys maintain water balance · Blood distributes heat throughout the body · Skeletal muscles contract and release heat · Pancreas regulates blood sugar All homeostatic control systems have three functional components 1. A monitor (located in the organ of the body signal) 2. A coordinating centres (relays the info to the appropriate regulator, restores normal balance) 3. A regulator Dynamic equilibrium:(pg 335 for diagram) · Condition that remains normal within fluctuating limits. · Blood glucose, blood pressure, temp and blood pH vary · Homeostatic control ensures that this is within range to sustain life. Homeostasis and Feedback · Adjustments that are used to bring the body back to acceptable range are negative feedback. · Ex: a thermostat is turned on when the temp drops to 20 degrees but once it reaches 24 degrees the furnace will shut off. (Negative Feedback) Negative Feedback Systems: · Process by which a mechanism is activated to restore to their original state. · Prevent small changed from becoming too large. Resist change. · Most common systems Positive Feedback Systems: · Less common within our body · Reinforce change. · Allows a discrete physiological event to be accomplished rapidly and return to normal. · Process by which a small effect is amplified. · Ex: Childbirth process. A decrease in progesterone (hormone) will initiate small contractions in the womb. The contractions release oxytocin (hormone) which cause stronger contractions or the uterus. The baby will move closer to the opening of the uterus and cervix with these contractions. Which builds the release of oxytocin and contractions until the baby is released. Once the baby is born the release of hormones and of contractions stops. 7.2 Thermoregulation · Each animal has an optimum temp range. Thermoregulation: · Maintenance of body temp within a range that enables cells to function efficiently. · Invertebrates + fish, amphibians and reptiles are known as ectotherms. They depend on air temp to regulate metabolic rates, partially regulated by environment. They have created adjustments such as sunning themselves on rocks or seeking shade. · Mammals (humans) + birds are known as endotherms. They can maintain their body temp regardless of their environment. Decrease in external temp means that the mammals will increase their rate of cellular respiration to produce heat. Hypothalamus: · Region of the vertebrate’s brain responsible for coordinating many nerve and hormone functions. Some humans have body temp higher than others. Body temp even varies from day and night (lower at night). · Core temps are found in the abdominal cavity, chest cavity and the central nervous system. Temp is higher or at 37 degrees. · The peripheral temps can be 4 degrees lower on very cold days. Response to Heat Stress: - When sensors in the brain detect a high rise in body temp, a nerve message is coordinated within the hypothalamus and a signal is sent to sweat glands to start sweating. - The evaporation from sweat causes cooling on the skin. There is also a message sent to the blood vessels to cause them to dilate, allows for more blood flow to the skin. Water and salts are carried to the skin’s surface as it is losing water. Response to Cold Stress: - It mirrors the heat stress. - When external temp drops, thermoreceptors in the skin send a message to the hypothalamus (aka: coordinating centre). It will send messages to the organs and tissues to increase body temp. The smooth muscles will contract and the arterioles will constrict in the skin which decreases blood flow. Retains heat in the core of the body. - Smooth muscles that surround the hair follicles in your skin will cause the hair to “stand on end”. These small numbs are referred to as goosebumps. The erect hairs trap warm air to heat the skin. - Hypothalamus sends messages that initiate shivering (Rythmetic contraction of skeletal muscle). Increases metabolism which increases heat. Contractions between 10-20 per min. - There can be hormonal responses that will elevate metabolism, adipose tissue called brown fat. Converts chemical energy into heat. Very important in newborns, can’t shiver. Have them in their necks, armpits and near kidneys. Hypothermia: - Body core temp falls below the normal range. Could leave to coma or death. Survive thanks to diving reflex, submerged into cold water, heart rate slows down and blood is diverted to the brain and other vital organs. Research in Canada: Freezing Cells: · Anthropologists huddled around a primitive person frozen in ice. As the ice began to melt, we could tell that the human looked the same as it did 3000 years ago. And the ARM moves!! · This is a myth no human has ever survived after being frozen in ice but this process does indeed occur with frogs in the winter/spring time. · The ice pieces get lodged in your cell membranes. Many nutrients and organelles leak through the injured cell membrane which causes the cell to die. The affects to organs are much more severe as nerves are crushed, and blood vessels rupture. Thawing may be way more dangerous as the cells may melt together and be formed of water and will push against each other. · There is a protein in fish that prevent ice crystals from forming therefore avoiding damage to the cell. · In frogs, high levels of glucose can also act as an antifreeze in the blood. Wood frogs may lose up to 60% of its cell water during freezing reducing the dangers proposed by ice. 7.3 The Importance of Excreting Wastes (pg342): - To maintain life processes, the body must eliminate waste products. - Lungs eliminate CO2, Large intestines eliminates toxic wastes, liver transforms ingested toxins into soluble compounds that can be eliminated by the kidneys. - Kidneys: they play a role in removing waste, balancing blood pH and maintaining water balance. - Proteins contain nitrogen and two hydrogen molecules which must be discarded. - Deamination: removal of an amino group from an organic compound. Occurs in liver. - The by-product is of deamination is ammonia a water-soluble gas. This is very toxic and could kill humans. - Fish avoid it but always releasing it through their gills. - Land animals must store these wastes. - The liver is responsible for this. The liver forms urea. - Urea: nitrogen waste formed from two molecules of ammonia and one molecule of carbon dioxide. - Urea is way less toxic than ammonia. - Uric acid: waste product formed from the breakdown of the nucleic acids. - Kidneys help maintain water balance. Water is lost throughout the day and more during exercise. Humans must always consume water to replace the loss of water. - A drop of 1% of water will cause thirst and 5% will cause extreme pain and 10% will be fatal. Excretion: From Simple to more Complex Animals: - For unicellular organisms, getting waste out is equally important to bringing in nutrients. - Without getting rid of toxins, the cell would die. - In unicellular organism like a sponge where every cell is in contact with its external environment, wastes are released directly from the cell. Water currents carry the wastes away. - A big challenge is fluid regulation. - Unicellular organisms are hypertonic to their freshwater environment. Without fluid regulation, the cells would draw in water by osmosis, expand and eventually burst. - Contractile vacuole: a structure in unicellular organisms that maintains osmotic equilibrium by pumping fluid out from the cell. - Complex multicellular organisms have same issues. Not all cells are in contact with the external environment therefore trash must be stored. Not every cell is designed to remove waste. Waste must then be transported to the cells that are capable. These cells work together to remove wastes from the body or store the wastes until signalled to remove them. The execratory system helps regulate water. 7.4 The Urinary System (pg346): - Renal arteries branch off from the aorta to carry blood to the kidneys. Kidneys can hold up to 25% of body’s blood. - Wastes are filtered from the blood by the kidneys and conducted to the urinary bladder by ureters. - Ureters: tubes that conduct urine from the kidneys to the bladder. - A urinary sphincter muscle located at the base of the bladder acts as a valve, allowing the storage of urine. - When 200mL of urine has been collected, the bladder stretches slightly, nerves send signals to the brain. When more water, more stretches and message more urgent. - When 600mL of urine is contained, voluntary control is lost, the sphincter relaxes, urine enters the urethra and it is voided. - Urethra: tube that carries urine from the bladder to the exterior of the body. - The cross section of the kidney has three sections. The cortex, the medulla and the renal pelvis. - Cortex: outer layer of the kidney. - Medulla: Area inside of the cortex. - Renal pelvis:area where the kidney joins the ureter. Nephrons: - Nephrons: functional units of the kidneys, slender tubules. - Afferent arterioles: small branches that carry blood to the glomerulus. Supply nephrons with blood. - Glomerulus: high-pressure capillary bed that is the site of filtration. - Unlike other capillaries, this one does not transfer blood to a venule. - Blood leaves the glomerulus by way of other arterioles, the efferent arterioles. - Efferent arterioles: small branches that carry blood away from the glomerulus to a capillary net. - Blood is carried from the efferent arterioles of a net of capillaries called… - Peritubular capillaries: network of small blood vessels that surround the nephron. - The glomerulus is surrounded by the bowman’s capsule. - Bowman’s capsule: cuplike structure that surrounds the glomerulus. - Bowman’s capsule, the afferent arteriole and the efferent arteriole are located at the cortex of the kidney. - Fluids to be turned into urine enter the Bowman’s capsule from the blood. The capsule tappers to a thin tubule… called - Proximal Tubule: section of the nephron joining the Bowman’s capsule with the loop of Henle. - Urine is carried from proximal tubule to loop of Henle which descends to the medulla of the kidney. - Loop of Henle: carries filtrate from the proximal tubule to the distal tubule. - Distal tubule: conducts urine from the loop of Henle to the collecting duct. - Urine moves through distal tubule to the last segment of the nephron into the collecting ducts. - Collecting ducts: tube that carries urine from nephrons to the pelvis of a kidney. 7.5 Formation of Urine (pg349): - Urine formation depends on flirtation, reabsorption and secretion. - Filtration: process by which blood or body fluids pass through a selectively permeable membrane. - Reabsorption:transfer of glomerular filtrate from the nephron back into the capillaries. - Secretion: movement of materials such as ammonia and some drugs, from the blood back into the distal tubule. Filtration: - Each nephron has an independent blood supply. - Blood moves through the afferent arteriole into the glomerulus, a high-pressure filter. - Pressure in glomerulus is 65mm Hg and usually in a capillary bed its 25mm Hg. - Dissolved solutes pass through the walls of the glomerulus into the Bowman’s capsule. - Materials move from areas of high to low pressure. So not all materials enter the capsule. - Plasma, protein, blood cells and platelets are too large to move through the wall of the glomerulus. Reabsorption: - Examines the concentrations of fluids as they move through the kidneys. - About 600mL of fluid flows through kidneys every minute. - About 120mL of it, is filtered by the nephrons. - If this did not occur you would need to drink 1L of water every ten minutes. - Only 1mL of urine is formed for every 120mL of fluid into the nephrons. The remaining 119mL are reabsorbed. - Selective reabsorption occurs by passive and active transport. - Carrier molecules move Na+ ions across the cell membrane of the cells that line the nephron. - Negative ions like Cl- and HCO3- follow the positive Na + ions by charge attraction. - Mitochondria’s supply the energy for active transport. But the energy supply is limited. - Reabsorption occurs until the threshold level is reached. - Threshold level: maximum amount of material that can be moved across the nephron. - Excess NaCl stays in nephron and is excreted with urine. - Other molecules are actively transported from the proximal tubule. - Glucose and amino acids are attached to carrier molecules going out of the nephron. - Substances to be reabsorbed is limited. Excess glucose won’t be removed from nephrons. Therefore, people with high blood glucose will excrete glucose. - Solutes actively transported out of the nephron create an osmotic gradient that draws water from the nephron which helps reabsorption. - Proteins remain in bloodstream and draw water from interstitial fluid into the blood. - Interstitial fluid: fluid that surrounds the body cells. - as water is reabsorbed from nephron, the remaining solutes become more concentrated. - Urea and uric acid will diffuse from the nephron back into the blood, less is reabsorbed than originally filtered. Secretion: - Movement of waste from blood into the nephron. - nitrogen waste, excess H+ and minerals like K+ ions, penincilin, are examples of substances secreted. - cells loaded with the mitochondria line the distal tubule. - Like reabsorption, tubular secretion occurs by active transport but unlike reabsorption molecules are shuttled from blood into nephron. 7.6 Water Balance (pg353): - Body adjusts for increased water intake by increasing urine output. It also adjusts for increased exercise or decreased water intake by reducing urine output. This involves the nervous and endocrine system. Regulating ADH: - Antidiuretic hormone (ADH): causes the kidneys to increase water reabsorption. - When ADH is released, a more concentrated urine is produced, conserving body water. - ADH produced by specialized nerve cells in the hypothalamus move along specialized fibres from the hypothalamus to the pituitary gland, which stores and releases ADH in blood. - Osmoreceptors: specialized nerve cells in the hypothalamus that detect changes in the osmotic pressure of the blood and surrounding extracellular fluids (ECF). - When you lose water, blood solutes become more concentrated. Increases blood’s osmotic pressure. - Water moves in bloodstream causing the cells of the hypothalamus to shrink. A nerve message is sent to the pituitary signalling the release of ADH to be carried in bloodstream to the kidneys. - By reabsorbing more water, the kidneys produce a more concentrated urine, preventing osmotic pressure to increase. - Shrinking cells of hypothalamus causes the sensation of thirst. - More water, absorbed by blood and the concentration of solutes in the blood decreases. - Blood is more dilute, fluids move from blood into hypothalamus. - Cells of hypothalamus swell and nerve messages pituitary to stop. - Less ADH is released and less water is reabsorbed from the nephrons. ADH and the Nephron: - About 85% of the water filtered into the nephron is reabsorbed into the proximal tubule. - Proximal tubule is permeable to water and the descending loop of Henle is permeable ONLY permeable to NaCl. - Without ADH, the rest of the tubule remains impermeable to water but will actively transport Na+ ions from the tubules. The last 15% of water filtered into the nephron will be lost if no ADH is present. - ADH makes upper part of distal tubule and collecting ducts permeable. - As water passes, from the nephron to the intercellular spaces and the blood, the urine remaining in the nephron becomes more concentrated. - Kidneys control the last 15% of the water found in the nephron. Kidneys regulate the osmotic concentrations of body fluids. Kidneys and Blood Pressure: - kidneys play a role in blood pressure regulation by adjusting blood volumes. - Aldosterone: hormone that increases Na+ reabsorption from the distal tubule and collecting duct. Produced in cortex of the adrenal glands which lies above the kidneys. - NaCl reabsorption increases, the osmotic gradient increases and more water moves out of the nephron by osmosis. - Increased blood fluid can decrease blood pressure, reducing oxygen and nutrients to tissues. - Blood pressure receptors in the juxtaglomerular apparatus detect low blood pressure. Specialized cells release renin, an enzyme that converts angiotensinogen a plasma protein produced by liver into angiotensin. - Angiotensin has two roles. - 1. Activated enzymes causes constriction of blood vessels. Blood pressure increases when the diameter of blood vessels is reduced. - 2. It stimulates the release of aldosterone from the adrenal gland. Aldosterone is then carried in the blood to the kidneys where it acts on the cells of the distal tubule and collecting duct to increase Na+ transport. Increase fluid levels. pH Balance: - Kidneys maintain pH balance. - pH is between 7.3-7.5 - Cellular respiration produces carbon dioxide which forms carbonic acid. Carbonic acid and other excess acids ionize to produce H+ ions. The buildup of H+ ions lowers the pH. - Acid-base balance is maintained by buffer systems that absorb excess H+ ions or ions that act as base. - Excess H+ from metabolic processes are buffered by bicarbonate ions in blood. Carbonic acid is produced. - CO2 is transported to lungs to be exhaled. - It is called the bicarbonate-carbon dioxide buffer system. - Buffer system of blood removes excess H+ ions but the buffer has to be restored if the body is to be protected. - Kidneys restore buffer by reversing the reaction. - The bicarbonate ions diffuse back into the blood restoring the buffer. - The H+ ions recombine with either phosphate or ammonia and are excreted with the filtrate from the nephron. 7.7 Kidney Disease (pg357): Diabetes Mellitus: - Caused by inadequate insulin from islet cells in the pancreas. Blood sugar levels rise. The excess sugar remains in the nephron. The excess sugar provides an osmotic pressure that opposes the osmotic pressure created by other solutes that have been actively transported out of the nephron. - Large volumes of urine, thirsty. Diabetes Insipidus: - Destruction of ADH-prodcuing cells or the destruction of the nerve tracts leading to the hypothalamus to the pituitary gland. - Urine output increases, need to drink A LOT. Bright’s disease: - Inflammation of the nephrons. Affects the tiny blood vessel of the glomerulus. Proteins remain in the nephron and create an osmotic pressure that draws water into the nephron. This increase the output of the urine. Kidney Stones: - Caused by precipitation of mineral solutes from the blood. Two types: alkaline and acid stones. They can lodge in the renal pelvis and move to the narrow ureter. It can find itself in the urethra and be painful when it passes. Dialysis technology: - Dialysis machine can restore proper solute balance. - Hemodialysis: machine connected to patient’s circulatory system by a vein. Blood is pumped through series of dialysis tubes. Urea is released during this treatment. - Peritoneal dialysis: 2L of dialysis fluid is pumped into the abdominal cavity. Kidney Transplants: - Places a new kidney and ureter in the lower abdomen near the groin, where they are surgically attached to the blood vessels and bladder. 8.1 Importance of the Endocrine System: · All cells interact with one another. · Hormones are classified according to their activation site. Hormones: - Chemical regulators released by cells that affect cells in other parts of the body. Only a small amount of hormone is required to alter cell metabolism. Endocrine Hormones: - Chemicals which are produced in the glands and secreted directly into the blood. The circulatory system carries these hormones to the various organs of the body. Nontarget Hormones: Growth Hormones (GH): - Produced by the pituitary gland, that stimulates growth of the body. It is also known as somatotropin (STH). Insulin: - Hormone produced by islets of Langerhans in the pancreas; Insulin is secreted when blood sugar levels are high. Epinephrine (adrenaline): - Produced in adrenal medulla, it accelerates heart rate and body reactions during a crisis (fight or flight response): known as adrenaline. Other Hormones: Parathyroid Hormone: - Regulates calcium levels in the body. Gastrin: - Stimulates cells of the stomach to produce digestive enzymes. Chemical Control Systems: - Both the nervous and endocrine system provide integration and control of the organs and tissues. - Malfunctions of one organ can affect other organs but the animal will stay alive thanks to these systems. - The nervous system:allows the body to adjust quickly to changes in the environment. - The endocrine system: maintains control over a longer duration. Some hormones will regulate and sustain the development for many years (aka: sex/growth hormones). - The division of these two systems is found in the hypothalamus. - The hypothalamus regulates the pituitary gland through nerve stimulation. This gland secretes chemicals that affect the nerve activity of the hypothalamus. - Hormones are regulators which either speed up or slow down bodily processes. Joseph Von Mering and Oscar Minkowski (1889) - Discovered the relationship between chemical messengers and the activity of organ systems within the body. - Chemical messenger in pancreas is responsible for the regulation of blood sugar. - They removed the pancreas from dogs and noticed that they lost weight, were tired and displayed some symptoms of diabetes. Ants also started surrounding themselves around the sick dogs but not around the healthy dogs. - Ants were attracted to the sick dogs as there was glucose in their urine. They discovered that insulin is the chemical messenger responsible for the regulation of blood sugar. - Most hormones are found in very limited amounts and the concentration of it varies throughout the day. Technology: - Radioactive tracers allow scientist to follow how the chemical messenger is broken down into other compounds and remove as waste. They can measure the amounts of hormone which respond to internal and external changes in environment. - High-power microscopes allow for the same results. Chemical Signals: Steroid and Protein Hormones: - Hormones DON’T affect all cells, may have receptors for one hormone but not the other - Cells have a different quantity of receptors in them as well. - TWO hormones which differ chemical structure and action. - Steroid Hormones:made from cholesterol (lipid), contains male and female sex hormones and cortisol. Made of complex carbon rings.Not soluble in water but soluble in fat. - Cortisol:hormone that stimulates the conversion of amino acids to glucose by the liver. - Protein Hormones: Includes insulin and growth hormones. Contain chains of amino acids and are soluble in water. They diffuse from the capillaries into the interstitial fluid and then into the target cells, where they combine with receptor molecules located in the cytoplasm. The hormone-receptor complex moves into the nucleus and attaches to a complementary shaped chromatin. The hormone activates a gene that sends a message to the ribosome in the cytoplasm to start making the protein. - Steroid hormones diffuse into the cell. - Protein hormones combine with receptors on the cell membrane. Some of the protein hormones form a hormone receptor complex that activates the production of an enzyme called adenylyl cyclase. This causes the cell to convert adenosine triphosphate (ATP) (primary source of cell energy) into cyclic-adenosine monophosphate (cyclic AMP). This functions as a messenger which activates enzymes in the cytoplasm to carry out their normal functions. Cyclic Adenosine Monophosphate (cyclic AMP): Secondary chemical messenger that directs the synthesis of protein by ribosomes. Thyroxine: - Iodine-containing hormone, produced by the thyroid gland, that increases the rate of body metabolism and regulates growth. The pituitary gland: the master gland: - The pituitary gland: gland at the base of the brain that, with the hypothalamus, functions as a control centre, coordinating the endocrine and nervous system. It is a sac like structure. Has control over all other endocrine glands. - The interaction between the nervous and endocrine system is made apparent through this pituitary hypothalamus complex. - The pituitary gland produces and stores hormones. - The hypothalamus stimulates the release of hormones by the pituitary gland by way of nerves. - The pituitary gland has two lobes: the posterior lobe and the anterior lobe. - The posterior lobe: stores and releases hormones such as antidiuretic hormone (ADH) (acts on the kidneys and helps regulate body water) and oxytocin (helps initiate strong uterine contractions during labour), which have been produced by the hypothalamus. - The hormones travel by way of specialized nerve cells from the hypothalamus to the pituitary. - The pituitary will store the hormones and release them into the blood when necessary. - The anterior lobe: It produces its own hormones. Supplied with nerves from the hypothalamus (regulates the release of hormones from the anterior pituitary) as well. - Hormones are secreted form the nerve ends of the cells of the hypothalamus and they are transported in the blood to the pituitary gland. - They activate specific cells in the pituitary, causing the release of pituitary hormones, which are carried by blood to target tissues. - There are two hypothalamus-releasing factors which inhibit the secretion of hormones from the anterior lobe. - 1. The releasing factor: dopamine, inhibits the secretion of prolactin (PRL), a pituitary hormone that stimulates milk production in women. - 2. The hormone somatostatin inhibits the secretion of somatotropin the pituitary hormone associated with growth of the long bones. - Regulator hormones stored in anterior lobe: Thyroid-stimulating (TSH) stimulates thyroid gland to produce its hormone, thyroxine. Releases reproductive, growth- stimulating hormones, prolactin and adrenocorticotropic hormone (ACTH), the hormone that stimulates the adrenal cortex. 8.2 Hormones That Affect Blood Sugar (pg378): PANCREAS: - Contains two types of cells, produces digestive enzymes and produces hormones. - Hormone producing cells are located in structures called the islets of Langerhans. - Multiple islets with thousands of cells each are scattered throughout the pancreas. - Islet contain alpha and beta cells that are responsible for the production of two hormones: insulin and glucagon. GLUCAGON: - Hormone produced by the pancreas; when blood sugar levels are low, glucagon promotes conversion of glycogen to glucose. - Increase in blood sugar level. - Produced in the alpha cells of islets of Langerhans. - Ex: used when long periods of fasting. - When converted to glucose in liver, blood sugar level returns to normal. INSULIN: - Produced in beta cells of islets of Langerhans when blood sugar levels increase. Like after a meal. - Causes cells of muscles, liver and other organs to become permeable to glucose. - Allows blood sugar levels to return to normal. - Insulin helps maintain homeostasis. - Causes a decrease in blood sugar level. DIABETES: - Chronic disease that occurs when the body cannot produce any insulin or enough insulin, or is unable to use properly the insulin it does make. - Can cause death, blindness, kidney failure, nerve damage, nontraumatic limb amputation if not treated. - Hyperglycemia: High blood pressure. When there aren’t enough levels of insulin, blood sugar levels will rise. - Symptoms for all Diabetes: kidneys cannot reabsorb all the blood glucose that is filtered through them, so it appears in urine. They will urinate a lot and are very thirsty. Low levels of energy. Breath smells like acetone in severe cases. - In general: cells of people with diabetes soon become starved for glucose and must turn to their sources of energy that are not as easily accessible as carbohydrates such as lipids and proteins. - Three types of diabetes - Type 1 (juvenile-onset diabetes): pancreas can’t produce insulin because of early degeneration of the beta cells in the islets of Langerhans. Must take insulin to live. Usually found young. - Type 2 (adult-onset diabetes): decreased insulin production or ineffective use. Diagnosed in adult hood. Controlled by diet, exercise or drugs: sulfonamides. - Type 3 (Gestational Diabetes): temporary condition in pregnancies. Increases diabetes in mom and child. Research in Canada: Banting and Best: - Frederick Banting in 1921 and Charles Best (graduate student) - Asked Professor MacLeod for lab use - Wanted to isolate a hormone - They tied the pancreatic duct of dogs and waited seven weeks for the pancreas to shrivel. Cells producing digestive enzymes deteriorated. Cells from the islet of Langerhans stayed. - When they inserted the hormone extracted from the pancreas into the dogs without a pancreas, the dog’s symptoms of diabetes disappeared. Frontiers of Technology: Islet Cell Transplants: - Insulin therapy monitors blood sugar levels and balances injections of insulin with carbohydrate intake and exercise. - Transplanted islet cells could replace the body’s natural mechanism for monitoring and producing insulin. It could reverse the effects of diabetes. - Worried about immune rejection. - Dr. James Shapiro discovered a treatment which uses a steroid-free combo of 3 drugs to prevent rejection of these cells. - Transplant of islet cells is non-invasive with less risks. They are extracted from the pancreas of a donor and infused into the patient’s liver by way of a large vein. Ultrasound to check that the vein is frozen and a syringe to properly put the cells. Liver used as it can usually build new blood vessels and cells when damaged. - It will produce enough insulin to control blood sugar. In TYPE 2. Adrenal Glands: - Located above each kidney. - Made up of two glands encased in one shell. - Adrenal Medulla: inner gland, surrounded by the adrenal cortex. Regulated bu the nervous system, hormones regulate the adrenal cortex. Produces epinephrine (adrenaline) and norepinephrine. - Norepinephrine (noradrenaline): initiates the fight/flight response by increasing heart rate and blood sugar. - Hormone producing cells in the adrenal medulla are stimulated by sympathetic nerves when stressed. - When stressed, epinephrine and norepinephrine are released into blood. Blood sugar rises. Glycogen (carbohydrate storage in liver and muscles) is converted to glucose and available to use for energy. - Increased blood sugar level ensures that a greater energy reserve will be available for the tissues of the body. - Hormones increase heart, breathing rate and cell metabolism. Blood vessels dialate so more oxygen + nutrients can reach tissues. Iris in eye dilates to allow more light to reach retina. - Adrenal Cortex: Outer region of the adrenal gland that produces glucocorticoids and mineralocorticoids and some sex hormones. - Glucocorticoids:associated with blood glucose levels. Most important: cortisol which increases level of amino acids in the blood to help body recover from stress. Amino acids converted into glucose by liver, increasing the level of blood sugar. Provides greater energy source to help cell recovery. Any amino acids not converted are used from protein synthesis. Proteins used to repair damaged cells. - Fats in adipose tissues are broken down into fatty acids, creating a second source of energy used during fasting times. - Influence of cortisol= blood glucose uptake in many tissues, muscles **. - BRAIN is not included as it would lead to convulsions. Process of stressful Reponses: - Brain identifies them - Hypothalamus sends releasing hormone to anterior lobe of the pituitary so it can secrete corticotrophin (ACTH). - Blood carries ACTH to target cells in adrenal cortex. - These cells secrete mineralocorticoids and glucocorticoids. Then carried to cells in liver and muscles. - Cortisol levels rise, cells in hypothalamus and pituitary decrease production of regulatory hormones and soon level of cortisol will decrease. - Process is called long term stress response. - Short term response is regulated by adrenal medulla. - Mineralocorticoids: aldosterone is the most important. Second major group produced by adrenal cortex. Secretion of aldosterone increases sodium retention and water reabsorption by the kidneys which helps maintain body fluid levels. 8.3 Hormones That Affect Metabolism (pg384) - Three different glands that affect metabolism 1. Thyroid Gland: a two-lobed gland at the base of the neck that regulates metabolic processes. Produces triiodothyronine, thyroxine and calcitonin. Regulates body metabolism or the rate at which glucose is oxidized. 2. Parathyroid Glands: Four pea-sized glands in the thyroid gland that produces parathyroid hormone to regulate blood calcium and phosphate levels. Regulates Calcium levels in the blood and lower phosphate levels. 3. The anterior pituitary gland: produces growth hormones and other regulator hormones. Influences the growth of long bones and accelerates protein synthesis. Thyroid Gland: - Located in the base of the neck, immediately in front of the trachea/windpipe. - Important thyroid hormones that regulate body metabolism and the growth and differentiation of tissues are thyroxine (T4) and iodothyronine (T3). - Thyroxine is produced a little bit more. - People who secrete higher levels of thyroxine oxidize sugars and other nutrients at faster rates. - Glucose is usually oxidized by heat (60%), explain why these people are warm. - The other 40% is transferred to ATP, the storage form for cell energy. This is usually consumed during exercise. Therefore, they won’t gain weight! - People with lower levels of thyroxine don’t oxidize nutrients as quickly hence gaining weight. - Excess blood sugar is converted into liver and muscle glycogen. When glycogen stores are filled, excess sugar is converted to fat. The slower blood sugar is used, he faster the fat stores are built up. - People with hypothyroidism (low thyroid secretions) experience muscle weakness, cold intolerance, and dry skin and hair. - Control of thyroid hormones is done by negative feedback. - If metabolic rate decreases, receptors in hypothalamus are activated. Nerve cells secrete thyroid releasing hormone (TRH), stimulates pituitary to release thyroid-stimulating hormone (TSH). This hormone is carried by blood to the thyroid gland which releases thyroxine. Thyroxine raises metabolism rate. Higher levels of thyroxine will turn off a pathway. Thyroxine inhibits the release of TRH from the hypothalamus and turns off the production of TSH from the pituitary. - Thyroid gland contains Calcitonin. - Calcitonin: hormone produced by the thyroid gland that lowers calcium levels in the blood. Acts on bone cells. Thyroid Disorders: - Iodine is important, usually found in diet. It is transported from blood into the follicle cells of the thyroid. - Concentration of iodine in cells may be 25% more than in the blood. - When iodine levels begin to fall, the thyroid enlarges and produces a goiter. - Goiter: disorder that causes an enlargement of the thyroid gland. Emphasizes the presence of a negative feedback control system. - Production and secretion of thyroxine will drop. More TSH will be produced and the thyroid is stimulated more and more. - Due to increased TSH, the cells of thyroid continue to develop and the thyroid enlarges. Parathyroid Glands: - four parathyroid glands are contained in one thyroid gland. - Usually nerves or other hormones regulate the endocrine glands. Parathyroid glands are the exceptions. - These glands maintain homeostasis by responding directly to chemical changes in immediate surroundings. - Low calcium levels in the blood stimulate the release of parathyroid hormone (PTH). - Parathyroid hormone (PTH):Hormone produced by the parathyroid glands, which will increase calcium levels in the blood and lower levels of phosphates. - Rise in PTH causes calcium levels in blood to rise and phosphate levels to decrease. - Hormone does this by acting on the kidneys, the intestines and the bones. - Calcium will be mostly stored in bones but some in kidneys + gut. - Bone cells break down and calcium is separated from phosphate ions. - Calcium is returned to blood but phosphate is peed out. - As PTH levels increase, the absorption of calcium ions will also increase. - Once PTH levels have elevated calcium levels, the release of PTH is inhibited. Calcium won’t increase beyond demand. - Really high levels of PTH will cause problems. - High levels of calcium could collect in blood vessels or form stone like structures in kidneys. - Calcium levels signal the release and inhibition of PTH. - PTH activates vitamin D. - Low levels of vitamin D can cause rickets, too little calcium and phosphorus is absorbed from food so bones are deformed. Growth Hormone (Somatotropin): - Low secretions of growth hormone in childhood, will result in dwarfism. - High secretion of growth hormone will result in gigantism. - Most effects of hormone of cartilage and bone cells. - If production of growth hormones continues after the cartilaginous growth plates have been fused, other bones respond. - One they have been fused, bones can no longer increase in length but bones in jaw, forehead, fingers… will increase in width. - Acromegaly causes a broadening of the facial features. - Cells of soft tissues and bone begin to grow by increasing the number of cells (hyperplasia) and increasing the size of cells (hypertrophy). - They promote protein synthesis while inhibiting protein degradation breakdown to grow cells. - Amino acids are increased. - Growth hormones stimulate ribosomes to follow the genetic instructions for protein synthesis. - As a person age’s, growth hormone production decreases and cellular repair and protein replacement is compromised. Protein is replaced by fat. - Growth hormones stimulate the production of insulin-like growth factors which are produced by liver. These are secreted in the blood where they stimulate cell division in the growth plates causing elongation of skeleton. - Growth hormones promote elongation of long bones, increase fatty acids levels in blood. - Muscles use fatty acids instead of glucose as a source of metabolic fuel. - By switching fuel sources, growth hormone causes an increase in blood glucose levels. Important for the brain which depends on glucose. - Brain cannot use fat as an energy source. - Growth hormones increase the utilization of fat stores and promotes protein synthesis, changing body form away from adipose tissue toward an increase in protein and muscle. 8.4 Adjustments to Stress (388): - Dr. Hans Selye identified human response to long-term stress from a noxious stimulus. - when an initiator of stress is identified, the endocrine and nervous system make adjustments so the body can cope with the stress. - Nervous system will increase heart rate and divert blood to muscles. - A slower response from the endocrine system: provide a response for the stimulus. Hormonal Changes in Response to Stress: 1. Epinephrine will increase. Mobilizes carbohydrates and fat energy stores. Increases blood glucose and fatty acids. Accelerates heart rate and the activity of the respiratory system. 2. Cortisol will increase. Mobilizes energy stores by converting proteins to glucose. Elevates blood amino acids, blood glucose, and blood fatty acids. 3. Glucagon will increase. Converts glycogen to glucose. 4. Insulin will decrease. Decreases the breakdown of glycogen in the liver. - Stress hormones provide more blood glucose - Primary stimulus for insulin secretion is a rise in blood glucose. - If insulin release were not inhibited, hypoglycemia caused by stress would lead to an increase in secretion of insulin and lower blood glucose. Would not be able to elevate blood glucose to deal with stress. - There are other hormones which regulate blood pressure and blood volume during stress. - Nervous system will activate angiotensin-aldosterone pathway in response to reduce blood flow to the kidneys. - Increasing Na+ reabsorption will help the kidneys maintain increased fluid volume. Sustains blood pressure. - The hypothalamus will be activated which will cause an increase release of antidiuretic hormone (ADH). - ADH will help water reabsorption from the nephron to maintain body fluids. - During activity, the cardiovascular activity will provide oxygen delivery to the tissues for cellular respiration. - Increase blood sugar and fatty acids = more fuel for metabolic processes. - More difficult to adjust emotional or psychological stress since increased energy supply is not always used. - Increased nerve activity means more energy but ATP will usually outstrip this demand. New Operating Limit Problem Created Higher blood sugar - - Osmotic balance between blood and extracellular fluids varies. Leads to increase fluid uptake by blood and increased blood pressure Increased water loss from nephron Increased blood pressure - Rupture of blood vessels. Increases blood clotting. Increased heart rate - Leads to higher blood pressure Destruction of heart muscle. - Prostaglandins: - Mediator cells will detect changes in environment. They produce prostaglandins. - Prostaglandins: Hormones that have a pronounced effect in a small localized area. (More than 16 diff types). - Generally, not highly secreted unless a change is taking place. - These cells are absorbed rapidly by tissues when released. Not many are absorbed by capillaries or carried in blood. - Two diff prostaglandins for stress adjusting blood flow. - Stimulated by release of epinephrine, increases blood flow to local tissues. - Others will trigger the relaxation of smooth muscle in the passages leading to the lung. - They are released during allergic reactions. Chemically Enhanced Sport Performance: - Caffeine has same effects as epinephrine: increases heart rate and pressure. - Weight lifters injected themselves with anabolic steroids. - Anabolic Steroids: Substances designed to mimic many of the muscle-building traits of the sex hormone testosterone. - Enhances strength but not agility or skill level or ability of cardiovascular system to deliver oxygen. - Detrimental for marathoners - Banned from Olympics!!! - Health risks are elevated with this drug. EX) teens may be reduced height wise. Mood swings, feelings of rage. - Sharpshooters and archers use beta blockers to slow heart beat which helps steady their aim. - Endurance athletes use erythropoietin (EPO) which will decrease fat mass and promote protein synthesis for muscle development, increases strength = more training. - These are hard to detect compared to the natural body produced ones. - Esters of testosterone= muscle-building drug difficult to detect. Slow down metabolism of testosterone, keeping it in longer (usually metabolized in few hours). - LIST OF SYMPTOMS WITH DRUGS PG391 8.5 Reproductive Hormones (pg393) - Male gonads, the testes produce male sex cells = sperm - Female goßnads, the ovaries produce eggs - Fertilization is when an egg and a sperm meet to form a zygote. It divides itself to form an embryo and eventually a fetus. The Male Reproductive System:(include diagrams) - The male sex hormones are andosterone and testosterone. - Testosterone: male sex hormones produced by the interstitial cells of the testes. - Interstitial cells are found between the seminiferous cells. - Testosterone is more potent and stimulates spermatogenesis. - Spermatogenesis: process by which spermatogonia divide and differentiate into mature sperm cells. - Testosterone also develops puberty such as maturation of testes and penis. They are also associated with their sex drive. - Causes the growth of hair, development of larynx (deeper voice) and strengthening of muscles. Acne also increases and body odor. When testosterone levels increase these leaves. - Hypothalamus and pituitary gland control the amount of sperm and male sex hormones in testes. - Negative feedback is used to ensure that testosterone levels are constant and that there are enough sperm cells. - Pituitary gland produces gonadotropic hormones - Gonadotropic hormones: hormones produced by the pituitary gland that regulate the functions of the testes in males and the ovaries in females. - Follicle-stimulating hormone (FSH): in males, hormone that increases sperm production. - Luteinizing hormone (LH): in males, hormone that regulates the production of testosterone. - Gonadotropin-releasing hormone (GnRH): chemical messenger from the hypothalamus that stimulates secretions of FSH and LH from the pituitary. - FSH acts directly on sperm producing cells of the seminiferous tubules. - LH stimulates the interstitial cells to produce testosterone. - Once high levels of testosterone are detected, negative feedback system is activated. - Testosterone inhibits LH production by the pituitary gland by deactivating the hypothalamus. Hypothalamus releases less GnRH which leads to decreased production of LH. - Decreased GnRH slows the production and release of LH = less testosterone. The Female Reproductive System: (include Diagrams) Oogenesis and Ovulation: - Follicles: structures in the ovaries that contain the egg and secret estrogen. - Follicles contain: primary oocyte and granulosa cells. - Primary oocyte has 46 chromosomes and goes through meiosis to be transformed into a mature oocyte or ovum. - Granulosa provides nutrients for oocyte. - Ovaries undergo decline after puberty begins. - Usually a signal follicle becomes dominant and reaches maturity. The others deteoriate. - When menopause is reached (50 years old) few follicles remain. - Menopause marks the end of a female’s reproductive life. - When primary oocyte begins to divide majority of cytoplasm nutrients move to one pole to form a secondary oocyte (23 chromosomes). The other cell dies. - Eventually the dominant follicle will push outwards, ballooning the outer wall of the ovary. - Blood vessels around the ovary collapse and the wall weakens. - Outer surface of the ovary wall bursts and the secondary oocyte is released. - This is known as ovulation!! - Ovulation: release of the egg from the follicle held within the ovary. - Surrounding follicle cells remain within the ovary and are turned into the corpus luteum. - Corpus luteum: a mass of follicle cells that forms within the ovary after ovulation; secretes estrogen and progesterone. - If pregnancy does not occur, the corpus luteum degenerates after 10 days. The secondary oocyte enters the oviduct and begins meiosis II which is completed after fertilization. The division is again not even so the side with the most cytoplasm and nutrients is known as the mature oocyte or the ovum. The other body deteoriate just like meiosis I. Menstrual Cycle: - Takes an average of 28 days - Four phases: flow phase, follicular phase, ovulatory phase and luteal phase. - Flow phase: the phase of the menstrual cycle marked by the shedding of the endometrium. Only phase to be determined externally. Used to mark the beginning of a menstrual cycle. Five days for the uterus to shed the endometrium - Follicular phase: phase marked by the development of ovarian follicles before ovulation. As the follicle cells develop, estrogen is secreted. Estrogen concentration in the blood will increase. Takes place during day 6-13. - Estrogen: female sex hormone that activates the development of female secondary sex characteristics including development of the breast and body hair, and increased thickening of the endometrium. - Ovulation: Third phase. The egg bursts from the ovary and follicular cells differentiate into the corpus luteum. The development of the corpus luteum marks the beginning of the luteal phase. - Luteal phase: Phase of the menstrual cycle characterized by the formation of the corpus luteum following ovulation. - The corpus luteum secretes both estrogen and progesterone. - Progesterone: female sex hormone produced by the ovaries that maintains uterine lining during pregnancy. - Progesterone continues to stimulate the endometrium and prepares the uterus for an embryo. It inhibits further ovulation and prevents uterine contractions. - If progesterone levels fell, uterine contractions would begin. - Luteal phase: day 15-28 prepares the uterus to receive a fertilized egg. - If the fertilization of the ovum does not happen, the concentrations of estrogen and progesterone decrease which cause weak uterine contractions. - The weak contractions cause the endometrium to pull away from the uterine wall. The shedding of the endometrium marks the beginning of the next flow phase. Summary of Female reproductive system: 1. Flow phase = menstruation during day 1-5 2. Follicular phase = follicles develop in ovaries and endometrium is restored. Estrogen is produced by follicle cells. Days 6-13 3. Ovulation phase = oocyte bursts from ovary. Day 14. 4. Luteal phase = corpus luteum forms and endometrium thickens. Estrogen and progesterone is produced. Days 15-28. Hormonal Control and Female Reproductive System: - The hypothalamus- pituitary complex regulates the production of estrogen and progesterone (hormones of the ovary). - Follicle-stimulating hormone (FSH): a gonadotropin that promotes the development of the follicles in the ovary. - Luteinizing hormone (LH): a gonadotropin that promotes ovulation and the formation of the corpus luteum. - Ovarian hormones are part of a negative feedback system which regulate the gonadotropins. - Puberty is signaled by the release of GnRH from the hypothalamus. - GnRH activates the pituitary gland which is the storage site of FSH and LH. - In follicular stage, the blood carries PSH secretions to the ovary where follicle development is stimulated. The follicles secrete estrogen which begins the development of endometrium. - When estrogen rises, negative feedback system sent to pituitary gland to turn off secretions of FSH. The follicular stage has ended. - The rise of estrogen exerts a positive message on the LH-producing cells of the pituitary gland. LH secretions rise and ovulation occurs. - After ovulation, the remaining follicular cells, are transformed into functioning corpus luteum thanks to LH. - Luteal phase has then begun. - Cells of the corpus luteum secrete both estrogen and progesterone. The buildup of these will further increase the development of the endometrium. - As progesterone and estrogen build up within the body, a second negative feedback system is activated. They work together to inhibit the release of FSH and LH. - Without gonadotropic hormones, the corpus luteum begins to deteriorate which slows estrogen and progesterone productions. Drop in ovarian hormones = menstruation. - Androgens and estrogen can be produced by either gender. - Males: androgen levels are higher than estrogen and females vice-versa - Males excrete these hormones at an accelerated rate. - Secretions of androgens will stimulate the development of male’s prostate gland but injections of estrogen will slow the process. Cancerous tumors can be slowed down by injections of estrogen. 9.1 The Importance of the Nervous System (pg412): · Nervous system and endocrine system control actions of the body. · The chemical messengers are usually carried by blood and they are known as hormones. They are produced by glands and require more time response than a nerve. Vertebrate Nervous System: - Two parts: central nervous system (CNS) and peripheral nervous system (PNS). - Central Nervous System: the body’s coordinating centre for mechanical and chemical actions; made up of the brain and spinal cord. - Peripheral Nervous System (PNS): all parts of the nervous system, excluding brain and spinal cord, that rely information between the central nervous system and other parts of the body. - Peripheral nervous system is divided into somatic and autonomic nerves. - Somatic nervous system controls the skeletal muscle, bones, and skin. Sensory somatic nerves will rely info about the environment to the central nervous system. Motor somatic nerves initiate an appropriate response. - Autonomic nervous system contains special motor nerves that control the internal organs. - The two divisions of autonomic are sympathetic and parasympathetic. Anatomy of a Nerve Cell - Two types of cells found in nervous system: Neurons and Glial cells. - Glial Cells: nonconducting cells important for structural support and metabolism of the nerve cells. - Neurons: nerve cells that conduct nerve impulses. - Three types of neurons: sensory neurons, interneurons and motor neurons. - Sensory neurons: neurons that carry impulses from sensory receptors to the central nervous system; also known as afferent neurons. Ex:photoreceptors in the eyes respond to light, chemoreceptors in nose are sensitive to chemicals… - Ganglia: collections of nerve cell bodies located outside of the central nervous system. - Interneurons will link neurons within the body. Found in the brain and spinal cord mostly. They integrate and interpret the sensory information and connect neurons to outgoing motor neurons. - Motor neurons: neurons that carry impulses from the central nervous system to effectors; also known as efferent neurons. Effectors: muscles, organs, glands because they produce responses. - Neurons contain: dendrites, cell bodies and axons. - Dendrites: projections of cytoplasm that carry impulses toward the cell body. Receive info from sensory receptors or other cells. - Axon: extension of the cytoplasm that carries nerve impulses away from the cell body. Carries the nerve impulse towards other neurons or to effectors. - Myelin sheath: insulated covering over the axon of a nerve cell. A white coat of fatty protein. - Schwann cells: special type of glial cell that produces the myelin sheath. - Nodes of Ranvier: regularly occurring gaps between sections of myelin sheath along the axon. - Nerve impulses jump from one node to another, speeding the movement of nerve impulses. Nerve impulses move faster along myelinated nerve fibers than ones that aren’t covered. Speed is affected by diameter of the axon. Smaller = faster. - Neurilemma: delicate membrane that surrounds that axon of some nerve cells. It promotes the regeneration of damaged axons. - Not all nerves contain a neurilemma and a myelin sheath. - Nerves in the brain that contain myelinated fibers and a neurilemmal are called white matter because they appear white. - Spinal cord nerves are grey as the lack a myelin sheath and a neurilemmal and don’t regenerate after injury. Damage is usually permanent. Neural Circuits: - The sensation of heat is detected by specialized temperature receptors in your skin and a nerve impulse is carried to the spinal cord. - The sensory neuron passes an impulse onto an interneuron which relays the impulse to a motor neuron. - Motor neuron causes the muscles in the hand to contract and pull the hand away. Happens before info even travels to the brain. Afterwards it becomes noticeable and you may scream. - Reflexes are involuntary. - Reflex arc: neural circuit through the spinal cord that provides a framework for a reflex action. The simplest nerve pathway. Most reflexes occur without brain coordination. - Reflex arcs contain: the receptor, the sensory neuron, the interneuron in the spinal cord, the motor neuron and the effector. 9.2 Electrochemical impulses: - Nerve impulses are electrochemical messages created by the movement of ions through the nerve cell membrane. - Action potential: the voltage difference across a nerve cell membrane when the nerve is excited. (+40mV) - Resting potential: voltage difference across a nerve cell membrane during the resting stage (usually negative) (-70mV). - Neurons, unlike cells, have positive and negative ions both outside and inside the cell. - Negative ions do little to create a charged membrane. They are usually large ions that cannot cross the membrane and stay in the cell. - The electrochemical event is caused by an unequal concentration of positive ions across the nerve cell membrane. - The highly concentrated potassium ions inside the nerve cells have a tendency to diffuse outside the nerve cells. - The highly concentrated sodium ions outside the nerve cell have the tendency to diffuse into the nerve cell. - Potassium diffuse out and sodium diffuse into the neuron. - Positive ions move in and out of the cell. - The resting membrane is way more permeable to potassium than it is to sodium. So, more potassium ions diffuse out of the nerve cell. - The rapid diffusion of potassium ions out of the nerve membrane means that the nerve cell loses a greater number of positive ions than it gains, the exterior is positive compared to the interior. - Ion gates control the movement of ions across the cell membrane. - Excess positive ions along the outside of the nerve membrane and excess negative ions along the inside of the nerve membrane. - Polarized membrane: (resting) membrane charged by unequal distribution of positively charged ions inside and outside of the nerve cell. - The separation by the membrane has the potential to do work. - A charge of -70mV means the difference between the number of positive charges found on the inside of the nerve membrane relative to the outside. -90mV on inside of nerve membrane would mean fewer positive ions inside the membrane relative to the outside. - When excited the nerve cell membrane becomes more permeable to sodium than potassium. - Sodium gates open and potassium gates close. - Sodium ions go into the cell by diffusion and charge attraction. - Depolarization: diffusion of sodium ions into the nerve cell resulting in a charge reversal. - Once volateg inside nerve cell is positive, sodium gates close and sodium intake is slowed down. - Sodium-potassium pump: an active transport mechanism that moves sodium ions out of and potassium ions into a cell against their concentration gradients. Ratio of 3 Na+ ions out to two K+ ions in. The energy supply from adenosine triphosphate (ATP) fuels the pump to keep polarization of the membrane. - Repolarization: process of restoring the original polarity of the nerve membrane. - Nerves conducting an impulse cannot be activated until the condition of the resting membrane is restored. - Period of depolarization has to be completed and the nerve must repolarize before the next action potential can be conducted. - Refractory period: recovery time required before a neuron can produce another action potential. Lasts 1-10ms. Movement of the Action Potential: - Movement of sodium ions into the nerve causes depolarization of the membrane and signals an action potential in that area. - For impulse to be conducted along axon, impulse must move from the zone of depolarization to adjacent regions. - Action potential is characterized by the opening of the sodium channels in the nerve membrane. Sodium ions rush into the cytoplasm of nerve cells, diffusing from area of high concentration (outside of nerve cell) to area of lower (inside of nerve cell). - Influx of positively charged sodium ions causes a charge reversal (depolarization) in that area. - Positive ions rushing in cell are attracted to negative ions which are aligned on the inside of the nerve membrane. - Outside of nerve membrane, the positive charged sodium ions of the resting membrane are attracted to the negative charge that has accumulated along the outside of the membrane in the area of the action potential. - Flow of positive ions from the area of the action potential toward the adjacent regions of the resting membrane causes a depolarization in the adjoining area. - Electrical disturbances cause sodium channels to open in the adjoining area of the nerve cell membrane and result in the movement of the action potential. - A wave of depolarization moves along the nerve membrane and then the initiation point of the action potential enters a refractory period as the membrane once again becomes more permeable to potassium ions. - Depolarization of membrane causes the sodium channels to close and potassium channels to reopen. Following is a wave of repolarization. Threshold Levels and the All-Or-None Response: - Nerve cells respond to changes in pH, changes in pressure and to specific chemicals. - Threshold level: minimum level of a stimulus to produce a response. - Increasing the intensity of the stimuli above the critical threshold value will not produce an increased response-intensity of nerve impulses and speed of transmission will stay the same. - All-or none response: a nerve or muscle fibre responds completely or not at all to a stimulus. - Each neuron has its own threshold level. Synaptic Transmission: - Synapses: regions between neurons or between neurons and effectors. - A single neuron may branch many times at its end plate and join with other neurons. - Synapses rarely involve only two neurons. - Neurotransmitters: chemicals released from vesicles into synapses. Located in the end plate of axons. - Impulse moves along the axon and releases neurotransmitters from the end of the plate. - Neurotransmitters are released from Presynaptic neuron: neuron that carries impulses to the synapse. - Create a depolarization of dendrites of the postsynaptic neuron: neuron that carries impulses away from the synapse. - Space between neuron very small will cause the nerve transmission to slow across the synapse. Diffusion is slow. - Greater the synapses, slower the speed of transmission over a specified distance. - Stimulus in a reflex arc has few synapses. - Acetylcholine: neurotransmitter released from vesicles in the end plates of neurons, which makes the postsynaptic membranes more permeable to Na+ ions. It can open sodium ion channels. Once open, sodium ions rush into the postsynaptic neuron causing depolarization. Reversal of charge causes the action potential. - Problem: with sodium channels open, the postsynaptic neuron would remain in a constant state of depolarization. - Cholinesterase: enzyme which breaks down acetylcholine that is released from postsynaptic membranes in the end plates of neurons shortly after acetylcholine. - Only acetylcholine is destroyed, the sodium channels are closed, and neuron begins recovery phase. - Acetylcholine may act as an excitory neurotransmitter on one postsynaptic membrane, it could act as an inhibitory neurotransmitter on another. Many inhibitory neurotransmitters make the postsynaptic membrane more permeable to potassium. - Opens more potassium gates, potassium ions on the inside of the neuron follow the concentration gradient and diffuse out of the neuron. - The rush of potassium ions out of the cell increases the number of positive ions outside of the cell relative to the number found inside the cell. - Hyperpolarized: condition in which the inside of the nerve cell membrane becomes more negative than the resting potential. - More sodium channels must be open to achieve depolarization and an action potential. - Summation: effect produced by the accumulation of neurotransmitters from two or more neurons. - The interaction between the excitatory and inhibitory neurotransmitters is what allows you to throw a ball. Upper arm receives, excitatory impulses contract the muscles. Inside of arm relaxes thanks to inhibitory impulses. - Inhibitory impulses help you prioritize information. Found in central nervous system. - Disorders associated with neurotransmitters: Parkinson’s and Alzheimer’s. 9.3 The Central Nervous System (pg427): - Central nervous system consists of brain and spinal cord. - Meninges: protective membranes that surrounds the brain and spinal cord. The three membranes form the blood-brain barrier which determines which chemicals will reach the brain. - Cerebrospinal fluid: cushioning fluid that circulates between the innermost and middle membranes of the brain and spinal cord; it provides a connection between neural and endocrine systems. The Spinal Cord: - It carries sensory nerve messages from receptors to the brain and relays motor nerve messages from the brain to muscles, organs and glands. - Spinal cord emerges from the skull through an opening called foramen magnum downward through a canal within the backbone. - A cross section in the cord reveals two different tissues: white matter and grey matter. - White matter is composed of myelinated nerve fibres from sensory and motor neurons. - Grey matter is not composed of myelinated nerve fibres. - Interneurons are organized into nerve tracts that connect spinal cord to brain. - A dorsal nerve tract brings sensory info into the spinal cord - Ventral nerve tract carries motor info from the spinal cord to the peripheral muscles, organs and glands. The Brain: - The human brain comprises three distinct regions: the forebrain, the midbrain, and the hindbrain. - The forebrain has paired olfactory lobes and the cerebrum. - Olfactory: areas of the brain that process information about smell. - Cerebrum: largest and most highly developed part of the human brain, which stores sensory information and initiates voluntary motor activities. - Cerebral cortex: outer lining of the cerebral hemispheres. - The cortex is composed of grey matter it has many folds that increase surface area. The deep folds are known as fissures. - The right side of the brain is associated with visual patterns or spatial awareness. - The left side of the brain is linked to verbal skills. - Corpus callosum: nerve tract that joins the two cerebral hemispheres. - Each hemisphere has four lobes: the frontal lobe, the temporal lobe, the occipital lobe and the parietal lobe. - Human speech depends on subtle changes in the position of the tongue and mouth. - Thalamus: Below the cerebrum. Area of the brain that coordinates and interprets sensory information and directs it to the cerebrum. - Below the thalamus is the hypothalamus. - Connection of hypothalamus and pituitary gland connects the nervous system with the endocrine system. - Midbrain is less developed than the forebrain. Contains four spheres of grey matter. It acts as a relay center for some eye and ear reflexes. - The hindbrain is found posterior to the midbrain and joins with the spinal cord. - The cerebellum, pons and medulla oblongata are the major parts of the hindbrain. - Cerebellum: part of the hindbrain that controls limb movements, balance and muscle tone. Largest part of the hindbrain. - Pons: the region of the brain that acts as a relay station by sending nerve messages between the cerebellum and the medulla. - Medulla oblongata: region of the hindbrain that joins the spinal cord to the cerebellum; one of the most important sites of autonomic nerve control. Controls involuntary muscle action like breathing, diameter of blood vessels… 9.4 Homeostasis and the Autonomic Nervous System (pg435): - The autonomic nervous system is part of the peripheral nervous system. - All autonomic nerves are motor nerves that regulate the organs of the body without conscious control. - Blood carbon dioxide and oxygen levels are monitored throughout the body. Once carbon dioxide levels exceed or drop below normal range, autonomic nerves act to restore homeostasis. - The autonomic nervous system maintains the internal environment of the body by adapting to the changes and demands of an external environment. - Made up of sympathetic and parasympathetic nervous system. - Sympathetic nervous system: nerve cells of the autonomic nervous system that prepares the body for stress. Nerves have a short preganglionic nerve and a shorter postganglionic nerve. - Parasympathetic nervous system:nerve cells of the autonomic nervous system that return the body to normal levels after adjustments to stress. - The preganglionic nerve from both systems releases acetylcholine and the postganglionic nerve from the sympathetic nervous system releases norepinephrine. - Nerves that exit directly from the brain are referred to as cranial nerves. - Vagus nerve: major cranial nerve that is part of the parasympathetic nervous system. Natural and Artificial Painkillers: - Endorphins: natural painkillers belonging to a group of chemicals called neuropeptides; contains between 16-31 amino acids. - Enkephalins: natural painkillers belonging to a group of chemicals called neuropeptides; contain 5 amino acids and are produced by the splitting of larger endorphin chains. - Pain is interpreted by the substantia gelatinosa (SG) cells. When they are stimulated, they produce a neurotransmitter that informs the injured organ or tissue of damage. If endorphins or Enkephalins connect to the SG cells, the pain is reduced and the pain transmitter is not released. - Opiates such as codeine and morphine work just like endorphins. - Opiates will attach to the SG neurons in the central nervous system preventing the production of pain transmitters. The intake of opiates causes the production of the body’s natural painkillers to decrease. - Drugs that act as depressants like Valium or Librium enhance the action of inhibitory synapses. - Alcohol does not act directly on synapses. Alcohol acts directly on the plasma membrane to increase threshold levels which is why it is a depressant. - https://www.menstrupedia.com/articles/physiology/cycle-phases Leptin - produced by fat storage cells. Target appetite control in the brain. - Leptin treatment for obesity in 1949: obesity gene in obese mice found. Mice do not produce leptin and when treated with leptin mice lost weight but this did not work on humans. There was no weight loss observed but some side effects like skin irritation. Most people have high leptin. Melatonin: - produced by the pineal gland at night and synchronizes circadian rhythms and regulating BP. - Dopamine inhibits the receptors in the pineal gland. - Jet lag: circadian rhythm set by point of origin rather than current time zone. Taking melatonin close to sleep of destination can reduce symptoms. Countercurrent multiplier: - Kidneys have a mechanism for reabsorbing water from the tubular fluid. - It is the process of using energy to generate osmotic gradient that enables you to reabsorb water from the tubular fluid to produce concentrated urine. This mechanism prevents you from producing litres and litres of dilute urine every day, and is the reason why you don’t need to be continually drinking in order to stay hydrated. - https://www.khanacademy.org/test-prep/mcat/organ-systems/the-renal-system/a/renalphysiology-counter-current-multiplication - cOsmoregulation: - Process of maintaining salt and water balance across membranes within the body. - Fluid inside cells are composed of water, electrolytes and nonelectrolytes. - Electrolytes dissociate into ions when dissolved in water and nonelectrolytes do not. - Membranes of the body are semipermeable. - There is a constant input of water and electrolytes into the system. Excess water or electrolytes and waste are transported to the kidneys to be excreted to help maintain osmotic balance. - Logical systems constantly interact and exchange water and nutrients with the environment by consumption of food and water through sweat, urine or feces. - Without a mechanism to regulate osmotic pressure, disease may happen or there would be an accumulation of toxic wastes and water. - Osmotic pressure is regulated by the movement of water across membranes, the volume of the fluid compartments can also change temporarily. - Since blood plasma is one of the fluid components, osmotic pressure has a direct bearing on blood pressure. - Some fluid components are blood plasma, interstitial fluid and intracellular fluid. Excretion: Removal of metabolic waste products from the body.
