Homeostasis & Excretion Draw & Research Task Draw and label the section of a human skin which includes the following terms: Epidermis Dermis Fat tissue Sweat gland Sweat duct Hair erector muscle Skin capillary Arteriole supplying blood to the skin Venule collecting blood If we are too hot – we want to lose heat: 1.Vasodilation – hypothalamus sends nerve impulses via parasympathetic nervous system to blood vessels near skin. Smooth muscle in vessel walls relaxes, but ‘shunt vessel’ constricts so more blood goes to the surface. Increase sweat rate – more sweat secreted onto skin surface. As the water evaporates, it removes the heat from the body and so cools the skin. Pilorelaxation – little effect, parasympathetic nerve impulse to the muscles at base of hair cause them to relax, so hairs lie flat. Less air is trapped next to the skin so less insulating effect. Behavioural response – controlled by cerebral cortex – become more inactive (less respiration, so less heat), open windows etc Hormone – less thyroxine is produced and so metabolic If we are too cold – we want to gain/conserve heat ● ● ● ● ● ● Vasoconstriction – sympathetic nerve impulses to blood vessels near skin. Smooth muscle in vessel wall contracts so less blood flow, shunt vessel relaxes so less blood flows to the surface capillaries. Less heat lost by radiation. Lower sweat rate – less sweat secreted onto skin, so less heat is used to evaporate water. Piloerection – muscles at bottom of hairs contract, causing hairs to stand on end and traps an insulating layer of air, reducing heat loss. Behavioural response – (cerebral cortex) – putting on a jumper Shivering – involuntary response where skeletal muscles contract and relax quickly. Increases respiration rate, so more heat generated. Hormone – adrenaline is released which increases metabolic rate. If very cold, more thyroxine produced, increasing metabolic rate. Pancreas LOCATION: The pancreas is located deep in the abdomen. Part of the pancreas is sandwiched between the stomach and the spine. The other part is nestled in the curve of the duodenum (first part of the small intestine). Pancreas Exocrine ● secretes enzymes to break down the Endocrine ● secretes the hormones insulin and proteins, lipids, carbohydrates, and glucagon to control blood sugar levels nucleic acids in food. throughout the day. Insulin Basics: How Insulin Helps Control Blood Glucose Levels The endocrine portion of the pancreas controls the homeostasis of glucose in the bloodstream. Blood glucose levels must be maintained within certain limits so that there is a constant supply of glucose to feed the cells of the body but not so much that glucose can damage the kidneys and other organs. Functioning: The pancreas produces 2 antagonistic hormones to control blood sugar: glucagon and insulin. ● The alpha cells of the pancreas produce glucagon. Glucagon raises blood glucose levels by stimulating the liver to metabolize glycogen into glucose molecules and to release glucose into the blood. Glucagon also stimulates adipose tissue to metabolize triglycerides into glucose and to release glucose into the blood. ● Insulin is produced by the beta cells of the pancreas. This hormone lowers blood glucose levels after a meal by stimulating the absorption of glucose by liver, muscle, and adipose tissues. Insulin triggers the formation of glycogen in the muscles and liver and triglycerides in adipose to store the absorbed glucose. What is Excretion? •Excretion is the removal of toxic materials, the waste products of metabolism and excess materials. •Metabolism means the chemical processes going on in the body. •One type of waste that is not excreted by the body faeces! •It is egested (the removal of undigested food) Our focus : Kidneys. Where are our kidneys? What is urine? Anatomy of the Kidneys Anatomy of the Kidneys Kidneys The NEPHRON is the basic structural unit of the kidney.Each kidney normally contains between 800,000 and 1.5 million nephrons The nephrons are often referred to as the kidney tubules. Kidneys In the nephron nearly everything is squeezed out of the blood. The substances we need to keep are reabsorbed back into the blood. Unwanted substances are released as urine. KIDNEYS KIDNEYS KIDNEYS Dialysis Kidney disease sufferers have most likely heard about dialysis. It is used to provide people an artificial replacement for lost kidney function. Currently, there are two techniques used for dialysis. Peritoneal Dialysis Hemodialysis Transplant
