Endocrine System Review

1. Distinguish between endocrine glands and exocrine glands.Exocrine glands have ducts that they secrete their products out of and those secretions are used locally (very close to where they are produced). Endocrine glands do not have duct. They secrete their products into the blood stream. Therefore, their secretions can be taken all over the body and used far away from where they are produced.

2. Describe positive and negative feedback mechanisms in the endocrine system. Which is responsible for maintaining homeostasis?Positive feedback is used to amplify a signal, kind of like a snowball effect. An example of positive feedback is during childbirth. The pressure of the baby’s head on uterine wall stimulates the production of oxytocin from the pituitary gland. Oxytocin causes the uterus to contract, making the baby’s head push on it more, making the pituitary release more oxytocin and so on.

Negative feedback is responsible for maintaining homeostasis. It keeps things within a comfortable range. If something gets too high, there is a response to lower it. If something gets too low, there is a response to raise it. For instance temperature regulation. If you get too hot, you start sweating. It you get too cold, you start shivering to produce heat.

3. Know where the following hormones are produced, what their target cells are, what their effect is, and what can result from hypo and hypersecretion:

HGH, ADH, Parathormone (PTH), insulin, oxytocin, glucogon, TSH, FSH, LH, epinephrine, corticoids, androgens, estrogen, testosterone, thymosins, thyroxin, calcitonin

Produced Target cells

Effect Hypo Hyper

HGH (Human Growth Hormone)

Pituitary Bones and muscles

Growth Dwarfism If starts in childhood-Gigantism, If starts in adulthood - Acromegaly

ADH (Antidiuretic Hormone)

Pituitary Collecting ducts of the kidneys

Regulates water balance

Large amounts of dilute urine

Thick, dark urine

PTH (Parathormone)

Parathyroids

Bones Causes bones to release calcium into the blood (regulates blood calcium levels)

Low blood calcium

Osteoporosis

Insulin Beta cells of the pancreas

Body cells and liver

Allows glucose to move from the blood into the cells, signals liver to use glucose molecules to build glycogen, lowers blood sugar

High blood sugar, diabetes

Hypoglycemia (low blood sugar)

Oxytocin Pituitary Uterus, mammary glands

Stimulates labor and milk production

Glucagon Alpha cells of the pancreas

Liver Signals liver to break glycogen down into glucose

TSH (Thyroid Stimulating Hormone)

Pituitary Thyroid Signals thyroid to produce thyroxin

FSH (Follicle Stimulating Hormone)

Pituitary Gonads Stimulates production of eggs and sperm

LH (Leutinizing Hormone)

Pituitary Gonads Stimulates ovulation and maturation of sperm

Epinephrine Adrenal glands

Heart and other muscles

Speeds up heart rate and ATP production to respond to emergency

Corticoids Adrenal glands

Wide range

Regulate long-term stress

Addison’s Disease

Cushing’s Syndrome

Androgens Adrenal glands

Wide range

Secondary male sex characteristics

Estrogens Ovaries Wide range, uterus

Regulate menstrual cycle, secondary female sex characteristics

Testosterone Testes Wide range

Regulate sperm production, secondary male sex characteristic

sThymosins Thymus White

blood cells

Cause maturation of T cells for the immune system

Thyroxin Thyroid Wide range

Increases metabolism

Hypothyroidism – gain weight, fatigue, weakness

Hyperthroidism – weight loss, hyperactivity, bulging eyes

Calcitonin Thyroid Bones Increases uptake of calcium into bones

Osteoporosis Low blood calcium

4. Why is the pituitary gland called the “master gland”? What are tropic hormones?It releases many tropic hormones – hormones whose target cells are other endocrine glands, so it controls the function of other endocrine glands.

5. How does the pancreas work as both an endocrine and an exocrine gland?In the digestive system, the pancreas is an exocrine gland, secreting digestive enzymes such as amylase, lipase, and trypsin as well as sodium bicarbonate through a duct into the small intestine. In the endocrine system, the alpha cells of the pancreas produce glucagon and the beta cells produce insulin which they release into the blood to regulate blood sugar.

6. Why is it important to have enough iodine in your diet?Iodine is an essential component of thyroxin. If you cannot produce thyroxin, you cannot regulate your metabolism. Your thyroid tries to compensate for this by growing larger, creating a goiter (a large lump on your neck).

7. Know where the following glands can be found in the body and be able to label them on a diagram:

Pituitary, adrenal glands, thyroid, thymus, pancreas, testes, ovaries, placenta, parathyroids

8. What is a goiter and how is it caused?A large growth of your thyroid gland, usually resulting from a lack of iodine in the diet.

9. Describe the control of blood calcium levels by PTH and calcitonin.

10. Describe the control of blood sugar by insulin and glucagon.

11. Distinguish between type I and type II diabetes – what is it? what are the causes? What symptoms are associated? What are treatments? At what age are they most commonly diagnosed? What is insulin-resistance?Type I diabetes is an autoimmune disease in which the immune system attacks and kills the beta cells of the pancreas, making the patient unable to produce insulin and therefore making blood glucose levels high. It is more often diagnosed during childhood and must be treated using insulin injections or a pump. It usually comes about quickly and causes excessive weight loss in the patient.

Type II diabetes is associated with insulin resistance. The patient can still produce insulin, but his cells do not recognize it and it can no longer open glucose channels on the cells to allow glucose to move from the blood into the cells. It also make blood glucose levels high. It is more often diagnosed in adulthood and develops slowly. Patients are usually overweight. It is treated with diet, exercise, and a plethora of other medicines that can help regulate blood sugar in various ways.