Homeostasis
Done by: Olicia-ann Sylvester
• With the aid of a diagram, name the endocrine glands in the
body and briefly outline the hormones they secrete and
their function.
• With the aid of diagrams show the internal structure of the
pancreas, showing the A (alpha) cells, B (beta) cells, Islets
of Langerhans and acinar cells.
• Give careful treatment to the pancreas and how its
hormones (glucagon and insulin) control blood glucose
levels.
• State the set point or normal levels of glucose in the human
blood, and use the terms Hypoglycemia and Hyperglycemia
in explaining how the glucose levels are controlled.
Objective
• Homeostasis generally refers to stability, balance or
equilibrium. It is the body's attempt in maintaining a
constant internal environment.
• Maintaining a stable internal environment requires
constant monitoring and adjustments as conditions
change. This adjusting of physiological systems within
the body is called homeostatic regulation.
Definition
• The endocrine system is a system of glands, each of which
secretes a type of hormone directly into the bloodstream to
regulate the body.
• The endocrine system is in contrast to the exocrine system, which
secretes its chemicals using ducts.
• It derives from the Greek words "endo" meaning inside, within,
and "crinis" for secrete.
• The endocrine system is an information signal system with
effects that are slow to initiate, and prolonged in their response,
lasting for hours to weeks.
• The endocrine system is made of a series of glands that produce
chemicals called hormones.
Endocrine System
• Glands are small but powerful organs that are located throughout the
body. They control very important body functions by releasing
hormones.
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The following list of glands make up the endocrine system:
Pituitary Gland
Hypothalmus
Thymus
Pineal Gland
Testes
Ovaries
Thyroid
Adrenal Glands
Parathyroid
Pancreas
Organs and Glands of the
Endocrine System
Diagram Of The Endocrine
System
Name them:
Diagram of organs involve in
the endocrine system
• Hormones are substances (chemical mediators)
released from endocrine tissue into the bloodstream
where they travel to target tissue and generate a
response.
Endocrine System cont’d
• The pituitary gland is sometimes called the "master gland" because of its
great influence on the other body organs. It consist of an anterior and
posterior section.
• The anterior pituitary produces several types of hormones:
• Prolactin or PRL - PRL stimulates milk production from a woman's
breasts after childbirth and can affect sex hormone levels from the
ovaries in women and the testes in men.
• Growth hormone or GH - GH stimulates growth in childhood and is
important for maintaining a healthy body composition.
Pituitary Gland
• Adrenocorticotropin or ACTH - ACTH stimulates production of cortisol
by the adrenal glands. Cortisol, a so-called "stress hormone," is vital to
survival. It helps maintain blood pressure and blood glucose levels.
• Thyroid-stimulating hormone or TSH - TSH stimulates the thyroid
gland to make thyroid hormones, which, in turn, control (regulate) the
body's metabolism, energy, growth and development, and nervous
system activity.
• Luteinizing hormone or LH - LH regulates testosterone in men and
estrogen in women.
• Follicle-stimulating hormone or FSH - FSH promotes sperm
production in men and stimulates the ovaries to release eggs (ovulate) in
women. LH and FSH work together to allow normal function of the
ovaries or testes.
Pituitary Gland
• The posterior pituitary produces two hormones:
• Oxytocin - Oxytocin causes milk letdown in nursing
mothers and contractions during childbirth.
• Antidiuretic hormone or ADH - ADH, also called
vasopressin, is stored in the back part of the pituitary
gland and regulates water balance. If this hormone is
not secreted properly, this can lead to problems of
sodium (salt) and water balance, and could also affect
the kidneys so that they do not work as well.
Pituitary Gland cont’d
• Diagram of pituitary
Pituitary Gland
• The hypothalamus is part of the brain that lies just above the pituitary gland.
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It releases hormones that start and stop the release of pituitary hormones.
• The hypothalamus controls hormone production in the pituitary gland
through several "releasing" hormones.
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Some of these are:
Growth -releasing hormone, or (controls GH release)
Thyrotropin-releasing hormone, or TRH (controls TSH release).
Corticoptropin-releasing hormone, or CRH (controls ACTH release).
Gonadotropin-releasing hormone (GnRH) tells the pituitary gland to make
luteinizing hormone (LH) and follicle-stimulating hormone (FSH), which are
important for normal puberty.
Hypothalamus
• Located at the front of brain
Diagram of the Hypothalamus
• The thymus is a gland needed early in life for normal
immune function.
• It is very large just after a child is born and weighs its
greatest when a child reaches puberty. Then its tissue
is replaced by fat.
• The thymus gland secretes hormones called humoral
factors.
• These hormones help to develop the lymphoid system,
which is a system throughout the body that help it to
reach a mature immune response in cells to protect
them from invading bodies, like bacteria.
Thymus
The Thymus
Diagram of Thymus
• Scientists are still learning how the pineal gland
works.
• They have found one hormone so far that is produced
by this gland: melatonin.
• Melatonin may stop the action of (inhibit) the
hormones that produce gonadotropin, which causes
the ovaries and testes to develop and function.
• It may also help to control sleep patterns.
Pineal Gland
• Pineal Gland
Diagram of Pineal Gland
• Males have twin reproductive glands, called testes, that
produce the hormone testosterone.
• Testosterone helps a boy develop and then maintain his
sexual traits.
• During puberty, testosterone helps to bring about the
physical changes that turn a boy into an adult male, such as
growth of the penis and testes, growth of facial and pubic
hair, deepening of the voice, increase in muscle mass and
strength, and increase in height.
• Throughout adult life, testosterone helps maintain sex
drive, sperm production, male hair patterns, muscle mass,
and bone mass.
Testes
• Scrotum
Diagram of Testes
• The two most important hormones of a woman's twin
reproductive glands, the ovaries, are estrogen and
progesterone.
• These hormones are responsible for developing and
maintaining female sexual traits, as well as maintaining a
pregnancy.
• Along with the pituitary gonadotropins (luteinizing
hormone or LH and follicle-stimulating hormone or FSH),
they also control the menstrual cycle.
• The ovaries also produce inhibin, a protein that curbs
(inhibits) the release of follicle-stimulating hormone from
the anterior pituitary and helps control egg development
Ovaries
• Ovum
Diagram of the Ovaries
• The thyroid is a small gland inside the neck, located in front
of your breathing airway (trachea) and below your Adam's
apple.
• The thyroid hormones control your metabolism, which is
the body's ability to break down food and store it as energy
and the ability to break down food into waste products
with a release of energy in the process.
• The thyroid produces two hormones, T3 (called triiodothyronine) and T4 (called thyroxine).
Thyroid
• The Thyroid Gland
Diagram of the Thyroid
• Each adrenal gland is actually two endocrine organs. The outer
portion is called the adrenal cortex. The inner portion is called the
adrenal medulla.
• The hormones of the adrenal cortex are essential for life. The types
of hormones secreted by the adrenal medulla are not.
• The adrenal cortex produces glucocorticoids (such as cortisol) that
help the body control blood sugar, increase the burning of protein
and fat, and respond to stressors like fever, major illness, and injury.
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The mineralcorticoids (such as aldosterone) control blood volume
and help to regulate blood pressure by acting on the kidneys to help
them hold onto enough sodium and water.
• The adrenal cortex also produces some sex hormones, which are
important for some secondary sex characteristics in both men and
women.
Adrenal Glands
• The adrenal medulla produces epinephrine
(adrenaline), which is secreted by nerve endings and
increases the heart rate, opens airways to improve
oxygen intake, and increases blood flow to muscles,
usually when a person is scared, excited, or under
stress.
Adrenal Glands cont’d
• Adrenal Gland
Diagram of the Adrenal
Glands
• Located behind the thyroid gland are four tiny parathyroid glands. These
make hormones that help control calcium and phosphorous levels in the
body.
• The parathyroid glands are necessary for proper bone development.
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In response to too little calcium in the diet, the parathyroid glands make
parathyroid hormone, or PTH, that takes calcium from bones so that it will be
available in the blood for nerve conduction and muscle contraction.
• If the parathyroids are removed during a thyroid operation, low blood
calcium will result in symptoms such as irregular heartbeat, muscle spasms,
tingling in the hands and feet, and possibly difficulty breathing.
• A tumor or chronic illness can cause too much secretion of PTH and lead to
bone pain, kidney stones, increased urination, muscle weakness, and fatigue.
Parathyroid Gland
• Parathyroid
Diagram of the Parathyroid
Gland
• The pancreas is a large gland behind your stomach that helps the
body to maintain healthy blood sugar (glucose) levels.
• The pancreas secretes insulin, a hormone that helps glucose
move from the blood into the cells where it is used for energy.
• The pancreas also secretes glucagon when the blood sugar is low.
Glucagon tells the liver to release glucose, stored in the liver as
glycogen, into the bloodstream.
• Diabetes, an imbalance of blood sugar levels, is the major
disorder of the pancreas.
• There are two types of diabetes. Type I, and Type II diabetes.
Pancreas
• Type I diabetes occurs when the pancreas does not produce
enough insulin.
• Type II diabetes occurs when the body is resistant to the insulin
in the blood).
• Without enough insulin to keep glucose moving through the
metabolic process, the blood glucose level rises too high.
• In Type I diabetes, a patient must take insulin shots. In Type II
diabetes, a patient may not necessarily need insulin and can
sometimes control blood sugar levels with exercise, diet and
other medications.
• A condition called hyperinsulinism (HI) is caused by too much
insulin and leads to hypoglycemia (low blood sugar).
Pancreas cont’d
• Pancreas
Diagram of the Pancreas
• Pancreatic endocrine tissue consists of cell clusters known
as islets of Langerhans.
• These cells produce and secrete hormones into the
bloodstream.
• Two of the main pancreatic hormones are insulin and
glucagon.
• These hormones work together to maintain the proper
level of sugar in the blood.
• Insulin works to lower blood sugar and glucagon works to
increase blood sugar.
• When the insulin-secreting cells fail to function properly
diabetes occurs
Pancreas Cont’d
• The endocrine tissue of the pancreas includes the islets of
Langerhans. This area is responsible for the production and
release of certain hormones into the
bloodstream. The main three types of cells that produce
hormones in the islets of Langerhans are:
• Alpha cells - release the hormone glucagon, which triggers the
release of glycogen form liver stores and helps to raise the level of
glucose (sugar) in the bloodstream
• Beta cells - release the hormone insulin, which help regulate
carbohydrate metabolism into the bloodstream, and
• Delta cells - release the hormone somatostatin into the
bloodstream that acts as an inhibitor to the pituitary hormone
called somatotropin and helps tell the body when to make other
hormones like insulin, glucagon, gastrin, renin, and secretin
Islets of Langerhans
• Internal View
Islets of Langerhans
• Cross section
Pancreas
• Showing the different sections through the pancreas
Diagram of Pancreas
• Pancreatic acinar cells are functional units of the
exocrine pancreas.
• They synthesize, store, and secrete inactive proforms
of digestive enzymes into the lumen of the acinus.
• Pancreatic alpha-amylase breaks down starch to
dextrins.
Pancreas cont’d
• Hperglycemia refers to chronically high blood glucose levels.
Persistent hyperglycemia can cause a wide range of chronic
complications that affect almost every system in your body. When
large blood vessels are affected, it can lead to:
• Stroke (cerebral vascular disease)
• Heart attack or Congestive Heart Failure (coronary heart disease)
• Circulation disorders and possible amputation (peripheral
vascular disease)
• When smaller blood veshsels are affected, it can lead to:
• Kidney disease (nephropathy)
• Nerve damage (neuropathy)
• Eye disease (retinopathy)
Hyperglycemia
• Hypoglycemia refers to dangerously low blood glucose levels that
drop below 70 mg/dL ( this is the set point or normal levels of
glucose in the human blood).
• It is an acute complication of diabetes and occurs in individuals who
use insulin or specific kinds of oral diabetes medication. Symptoms
of hypoglycemia include the following:
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Sweating
Rapid pulse
Shakiness, dizziness, weakness
Decreased coordination
Difficulty concentrating
Blurred vision
Headache
Trouble performing routine tasks
Hypoglycemia
• Blood sugar levels are regulated by negative feedback in order to
keep the body in homeostasis.
• The levels of glucose in the blood are monitored by the cells in
the pancreas's Islets of Langerhans.
• If the blood glucose level falls to dangerous levels the Alpha
cells of the pancreas release glucagon, a hormone whose effects
on liver cells act to increase blood glucose levels.
• They convert glycogen into glucose (this process is called
glycogenolysis).
• The glucose is released into the bloodstream, increasing blood
sugar levels.
Regulation of Blood
Glucose
Negative Feedback
• When levels of blood sugar rise, whether as a result of glycogen conversion,
or from digestion of a meal, a different hormone is released from beta
cells found in the Islets of Langerhans in the pancreas.
• This hormone, insulin, causes the liver to convert more glucose into glycogen
(this process is called glycogenesis), and to force about 2/3 of body cells to
take up glucose from the blood through the GLUT4 transporter, thus
decreasing blood sugar.
• When insulin binds to the receptors on the cell surface, vesicles containing
the GLUT4 transporters come to the plasma membrane and fuse together by
the process of exocytosis and thus enabling a facilitated diffusion of glucose
into the cell.
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As soon as the glucose enters the cell, it is phosphorylated into Glucose-6Phosphate in order to preserve the concentration gradient so glucose will
continue to enter the cell.
Regulation of Blood
Glucose cont’d
Regulation of Blood
Glucose
• Action of hormones and cells
Diagram showing how blood
glucose is maintained
Blood Glucose control
Blood Glucose control
Videos of Blood Glucose
Regulation
Videos of Blood Glucose
Regulation
Videos of Blood Glucose
Regulation
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