Biology 30
Unit A – Endocrine System Notes
General Outcome 2
Students will explain how the endocrine system contributes to homeostasis.
A. Endocrine System
• helps control body responses
• generally slower acting than the nervous system (except adrenaline)
• glands are scattered throughout the body - connected by the bloodstream
• chemical messengers are called hormones
• endocrine glands secrete hormones directly into the bloodstream - the go
throughout the entire body to target cells that respond to the hormone.
• exocrine glands secrete into ducts which go directly to where they are needed
• tear, sweat glands, salivary glands, mammary glands, pancreatic fluid
• Secretory vesicles in the cells of the endocrine gland release hormone molecules
directly into the blood system
• Neurosecretory cells are a second type of hormone-secreting cells that not only
conduct nerve signals but also make and secrete hormones.
B. Chemical Signals
• Two Types
1) Steroid Hormones – male and female sex
hormones
– are lipids made from cholesterol
– non-polar, they are able to pass through the phospho-lipid membrane of a cell and enter the
cytoplasm.
– bind to a receptor protein in the cytoplasm which carries out the transduction
– becomes a gene activator which attaches to a site on the cell’s DNA in the nucleus.
– stimulates the transcription of DNA into messenger RNA
– is than translated into a new protein or enzyme in the endoplasmic reticulum of the cell.
2) Protein or protein related hormones –
insulin, growth hormone, and epinephrine
− Unable to diffuse through the phospholipid
bilayer
− Must combine with a specific receptor on
the cell membrane
− The hormone receptor complex promotes
the formation of cyclic AMP (adenosine
monophosphate)
− Cyclic AMP acts as a messenger
activating enzymes in the cytoplasm to
produce/carry out specific function
(hormone production, glucose
production)
C. Hormones
protein molecules manufactured by our bodies
come into contact with many cells but only affect certain target cells
target cells can detect the hormone and respond
produced in minute amounts
released in response to signals from nervous
system, other glands, or presence of some
substance in the blood
all work in negative feedback loops
the presence of a given hormone in the blood
stream inhibits its own release.
hormone levels are always changing (dynamic,
not static)
Endocrine System
the major glands are
Pituitary Gland
Thyroid Gland
Parathyroid Gland
Pancreas
Adrenal Gland
Gonads
Provide labels for the following diagram.
1. / 6.2. / 7.
3. / 8.
4. / 9.
5. / 10.
D. Pituitary Gland
found at the base of the brain
about the size of a pea
called the ‘master gland’ because its secretions activate other glands
2 parts; - posterior pituitary
-Anterior pituitary
-Posterior Pituitary
stores ADH - raises blood water levels
tells nephron to become more permeable to water
stores oxytocin - causes uterus contractions during birth
causes secretion of milk from mammary glands after childbirth
ADH – Antidiuretic hormone
· Stimulates reabsorption of water by the kidneys.
Oxytocin –
· Causes uterine contractions during birth and secretion of milk from the mammary glands after birth.
A negative feedback mechanism controls the secretion of ADH from the hypothalamus.
Anterior Pituitary
produces many hormones
1. HGH – Human Growth Hormone
target organ is the liver
it promotes bone and muscle growth
insufficient production at birth causes dwarfism
high production at birth causes giantism
high production in adults causes
acromegaly- coarse features etc
2. FSH – Follicle Stimulating Hormone
target organs are the testes or the ovaries
stimulates development of follicle (egg) in females and sperm in males
3. TSH – Thyroid Stimulating Hormone
target organ is the thyroid gland
causes it to release thyroxin (increases cell metabolism)
4. LH – Luteinizing Hormone
target organs are the testes or the ovaries
causes ovulation in females and testosterone production in males
5. ACTH – Adrenocorticotropic Hormone
target organ is the adrenal cortex
signals it to release its hormones (Cortisol and Aldosterone)
6. Prolactin
target organ is the mammary glands
stimulates milk production
Provide labels for the following diagram.
1. / 7. / 13.2. / 8. / 14.
3. / 9. / 15.
4. / 10. / 16.
5. / 11. / 17.
6. / 12. / 18.
Evaluating Potential Uses for Human Growth Hormone (hGH)
Issue 1Until recently, the use of synthetic hGH was approved only for those children who had malfunctioning pituitary glands and could not produce adequate amounts of the hormone themselves. Recently, the use of synthetic hGH has been approved for children who are genetically of short stature. Should people have the option to take synthetic hGH just to increase their genetically predetermined height?
Issue 2
In adults, the production of natural hGH declines with age. This makes it increasingly difficult to reduce one’s body fat as one ages. Given that obesity has reached epidemic levels in the North American population, and one of the functions of hGH in the body is to reduce cellular fat, should synthetic hGH be approved as a diet treatment for obesity?
Issue 3
Because one of the functions of hGH in the body is to build lean muscle mass, its use has become widespread among various athletes. In fact, many athletes at the 1996 summer Olympic games in Atlanta, Georgia, referred to the event as the “hGH Games.” Despite its expense, many athletes, from baseball players to weightlifters, are acquiring synthetic hGH because it is difficult for drug testers to detect. Should competitive athletes be allowed legal access to synthetic hGH?
Gathering Data and Information
1. Suppose Health Canada is re-evaluating its regulations for the use of synthetic hGH and is asking for input on the matter. Your group will address one of the issues described in the table above. Read the description of the issue. You may wish to research it further using library or Internet resources. As a group, you will write a list of questions that you think should be addressed before Health Canada takes action on this issue. Your questions should address ethical and safety concerns, and possibly specific guidelines for any new regulations.
Organizing Findings
2. Suppose you are attending a forum on hGH use held by Health Canada. Your group has 5 min to present your list of questions to the delegates (your class). You may use visual aids such as computer generated slides, overheads, or a poster. You will have another 5 min to respond to questions from the audience.
Opinions and Recommendations
3. Listen to the other presentations, and then answer the following questions:
a) What are the main questions that Health Canada should investigate before changing its regulations on the use of synthetic hGH?
b) Why might parents want synthetic hGH for their children? What should parents be aware of before deciding to obtain hGH for their children?
c) Should athletes be allowed to use synthetic hGH? Why or why not?
d) Should health insurance cover the use of synthetic hGH, and if so, in which circumstances?
4. Create a table to record the major societal risks and benefits of approving the use of synthetic hGH in the three situations discussed in the forum. As a class, discuss the arguments for both sides of the issues.
E. Thyroid Gland
found at the base of the neck
produces 2 hormones
1. thyroxine
target organ is most body cells
thyroxine gives a general increase in the metabolic rate of the body
essential to proper development
TSH from the pituitary tells the thyroid when to release thyroxine
feedback loop
Disorders:
Goiter - caused by a lack of iodine in the diet
iodine is needed to make thyroxine
increased TSH makes the thyroid work harder but to no avail
thyroid starts to swell and causes a large lump on the neck
cured by addition of iodine to diet(iodized salt)
hypothyroidism - not enough thyroxine being produced
in adults it causes puffiness, weight gain, slower mental & physical reactions
it may be reversed with thyroxine injections
in infants it causes cretinism - severe mental & physical handicap
hyperthyroidism - too much thyroxine produced (aka Graves’disease)
causes increased blood pressure, nervousness, irritability, perspiration, release of heat
may be cured by the removal of part of the gland
2. Calcitonin - produced by the thyroid
lowers blood calcium levels
target organ is the bones
causes Ca+ to be stored in the bones
too little means a weaker bone structure
F. Parathyroid Glands
4 glands found on the surface of the thyroid
releases PTH - parathyroid hormone
increases blood calcium levels
3 target organs
− tells the bones to release Ca2+
− tells the intestines to absorb Ca2+
− tells the kidneys to reabsorb Ca2+
insufficient production causes continuous muscle contraction - Tetany
release is controlled by the blood Ca2+ levels
Calcitonium lowers the calcium level in the blood, whereas PTH (parathyroid hormone) raises it.
said to be antagonistic because they have opposite effects.
G. Pancreas
1. Insulin - lowers blood sugar
· works in two different ways
− causes the liver & muscles to convert glucose to glycogen and store it
− causes the body cells to absorb more sugar in order to metabolize it
· Produced by the alpha cells in the islets of Langerhans.
· Release of insulin by the pancreas increases the permeability of muscle cells to glucose – lowers blood sugar levels.
· Banting and Best
2. Glucagon - causes the liver to convert glycogen to glucose
· results in increased blood sugar
· Produced by the beta cells in the islets of Langerhans.
· Release of glucagon by the pancreas stimulates the conversion of glycogen (stored form of glucose) to glucose – increases blood sugar levels.
H. Diabetes Mellitus - (sugar diabetes)
not enough insulin is produced
mild diabetes may be controlled with diet
severe diabetes is controlled with insulin injections
symptoms
− sugar in urine
• -heavy urination
• -weight loss
• -fatigue
• -infections on the skin
blood sugar is extremely high, but cells cannot use it without insulin
the body cells are starving
the body starts to convert stored fat and protein into sugar
the kidneys excrete the sugar and water follows along by osmosis
A diabetic is in a constant state of flux between hyperglycemia and hypoglycemia. They need to try to stabilize their sugar levels as much as possible or serious complications may arise.
Gestational Diabetes – sometimes during pregnancy a woman can develop diabetes. Usually it goes away once the baby is born, but the baby and mom have to learn to stabilize (regulate) their blood sugar levels. This is dangerous as it often leads to very large babies being developed in a high sugar environment.
Islet Cell Transplants -
Blood Glucose Regulation and Homeostasis
Case Study
Procedure
Compare the following blood glucose concentration data provided for Maria and Tamika. One of these young women has diabetes. Blood glucose concentrations were monitored over 15 h for both. Both women ate identical meals at the same times, and got equal amounts of exercise at the same times. Neither is presently taking insulin.
Maria’s and Tamika’s Blood Glucose Levels over 15 h
Event/Time / Blood Glucose Concentration (mmol/L)Maria / Tamika
Wake up: 8:00 A.M. / 4.0 / 10.0
1 h after breakfast: 9:00 A.M. / 7.0 / 14.0
Pre-lunch: 12:00 noon / 4.5 / 10.0
2 h after lunch: 2:00 P.M. / 6.0 / 15.0
Mid-afternoon: 3:00 P.M. / 4.5 / 10.0
1 hr after vigorous exercise: 4:00 P.M. / 4.0 / 4.0
Pre-supper: 6:00 P.M. / 4.5 / 9.0
1 h after supper: 7:00 P.M. / 6.5 / 18.0
Bedtime: 11:00 P.M. / 4.5 / 12.0
Source: Data provided by Dr. Edmund A. Ryan, Professor of Medicine, University of Alberta,
Medical Director of the Clinical Islet Cell Transplant Program.
Analysis
1. Plot both sets of data on the same graph and draw a line of best fit for each. Label your graph appropriately.
2. A healthy range for blood glucose is between 4.5–5.0 mmol/L. In general, a person with moderate diabetes would take an insulin shot if the blood glucose level went above 13–15 mmol/L. On your graph, indicate which woman is diabetic and which is not. Write a paragraph to explain your answer.
3. Indicate the times and activities during which the pancreas of the healthy person would release insulin. How did insulin affect her body at these times?
4. Indicate the times and activities during which the pancreas of the healthy person would release glucagon. How did glucagon affect her body at these times?
5. Suggest a medication that the woman with diabetes could take to help her blood glucose levels return to healthy levels after a meal. Explain how this treatment would work.
6. During exercise, Tamika’s blood glucose drops dramatically. What could she do to help raise her blood glucose to a healthy range?
Identification of Hyperglycemia – Lab (Page 498-499)
I. Adrenal Glands
found on top of the kidneys
two parts: cortex and medulla
1) Medulla (adrenal medulla)
produces adrenaline(epinephrine) and noradrenaline(norepinephrine)
linked to the hypothalamus and the sympathetic nervous system
excitement or stress causes the release of adrenaline
it prepares the body to meet some emergency
effects: increases heart rate, relaxes bronchi, dilates pupils, dilates blood vessels,
contracts skin muscles, converts glycogen to glucose, contracts sphincter muscles
Adrenaline is secreted in response to low blood levels of glucose as well as exercise
and stress;
− it causes the breakdown of the storage product glycogen to the sugar glucose in
the liver,
− facilitates the release of fatty acids from adipose (fat) tissue,
− causes dilation (widening) of the small arteries within muscle
− increases the output of the heart.
Noradrenaline is a neurohormone, a neurotransmitter, for of most of the so-called
sympathetic nervous system.
2) Cortex (adrenal cortex)
produces cortisol - causes liver to convert amino acids to glucose