16. The Endocrine System

For a nerve impulse to travel from one neuron to another, the signal must be transmitted across a synapse. At the synapse, the axon releases a neurotransmitter that then diffuses across the synapse and activates receptors on the subsequent dendrite. While this is an example of a nervous signal using a neurotransmitter, the action of neurotransmitter at a synapse is also sometimes considered an example of what other type of signaling?

Epinephrine (also known as adrenaline) is produced by your adrenal cortex during stressful situations. The adrenal cortex is part of the adrenal gland, located just superior to the kidneys. One of the targets for adrenaline is the heart, where it increases the heart rate. Based on this description, what type of signaling molecule is adrenaline?

Between the statements below, which one correctly describes a significant difference between how the endocrine and nervous systems function?

True or False: if false, choose the answer that best corrects the statement.

Target cells can be defined as cells that possess a receptor that binds a particular hormone.

Ghrelin is a hormone produced in the stomach with target cells in the anterior pituitary. Its release is associated with feelings of hunger, and its release is lowest immediately after eating. Considering this, why do you think the stomach is not usually considered as an organ of the endocrine system?

Which statement below correctly identifies the difference between the endocrine system and other body systems?

Insulin operates by activating a receptor on the outside of the target cell. Based on your knowledge of hormone types, do you expect insulin to be an amino acid-based hormone or a steroid hormone, and why?

Why do steroid hormones use a transport protein?

Which of the following correctly describes the functions of the endocrine system?

a. Transport of blood through the body and through the lungs

b. Regulation of body functions through hormone secretion

c. Regulation of body functions through nerve impulses

d. Immunity and returning extra tissue fluid to the blood vessels

Mark the following statements as true or false. If a statement is false, correct it to make a true statement.

b. Autocrine signals affect the same cells that secrete them.

Mark the following statements as true or false. If a statement is false, correct it to make a true statement.

e. Excess secretion of thyroid hormones produces weight gain, cold intolerance, and slow heart rate.

Mark the following statements as true or false. If a statement is false, correct it to make a true statement.

a. The cells of the nervous system communicate via action potentials, whereas the cells of the endocrine system communicate via hormones.

Mark the following statements as true or false. If a statement is false, correct it to make a true statement.

d. Steroid hormones are hydrophilic molecules that bind to plasma membrane proteins as part of a second-messenger system.

Mark the following statements as true or false. If a statement is false, correct it to make a true statement.

e. The secretion of most hormones is regulated by a negative feedback system.

Which of the following is not a potential effect that a hormone could have on its target cell?

a. Activating genes in the DNA

b. Stimulating cellular division

c. Altering the permeability of the plasma membrane

d. All of the above are potential effects of a hormone on its target cell.

How does ADH affect the amount of water in the body, and how does it accomplish this? How does this affect the osmolarity of the blood?

List the target tissues and effects of the following anterior pituitary gland hormones.

a. Thyroid-stimulating hormone

b. Adrenocorticotropic hormone

c. Prolactin

d. Gonadotropins

e. Growth hormone

Mark the following statements as true or false. If a statement is false, correct it to make a true statement.

a. About 90% of the thyroid hormone produced is triiodothyronine (T3).

Mark the following statements as true or false. If a statement is false, correct it to make a true statement.

b. Thyroxine (T4) is the more active of the two thyroid hormone

Mark the following statements as true or false. If a statement is false, correct it to make a true statement.

d. Iodine atoms are a key component of parathyroid hormone.

Fill in the blanks: A rise in free T3 and T4 would be expected to produce a(n)______ in TRH and TSH secretion. A decrease in free T3 and T4 would be expected to produce a(n)_____in TRH and TSH secretion.

Which of the following statements correctly describes the role of parathyroid hormone?

a. Parathyroid hormone regulates the metabolic rate.

b. Parathyroid hormone increases the blood calcium ion concentration.

c. Parathyroid hormone decreases the blood sodium ion concentration.

d. Parathyroid hormone causes water retention by the kidneys.

Which of the following is not an effect of aldosterone?

a. Increased excretion of hydrogen ions from the fluid in the kidneys

b. Increased retention of sodium ions from the fluid in the kidneys

c. Increased retention of potassium ions from the fluid in the kidneys

d. Increased retention of water from the fluid in the kidneys

Cortisol is:

a. a potent inhibitor of the inflammatory response.

b. an important part of the stress response.

c. Both a and b are correct.

d. Neither a nor b is correct.

Which of the following hormones is not an integral part of the stress response?

a. Epinephrine

b. Cortisol

c. Insulin

d. Glucagon

Explain how insulin and glucagon are antagonists.

Type 1 diabetes mellitus is characterized by______ , and type 2 diabetes mellitus is characterized by_____.

a. hypoglycemia; destruction of the pancreatic β cells

b. destruction of the pancreatic β cells; destruction of the pancreatic α cells

c. insulin resistance; destruction of the pancreatic β cells

d. destruction of the pancreatic β cells; insulin resistance

Match the following hormones with their correct descriptions.      

_____Leptin      

_____Atrial natriuretic peptide      

_____Melatonin      

_____Estrogens      

_____Erythropoietin      

_____Testosterone

a. Produced by the pineal gland; regulates the sleep/wake cycle

b. Produced by the kidneys; regulates red blood cell production

c. Produced by the heart; promotes sodium ion loss in the kidneys and vasodilation

d. Produced by the testes; promotes androgenic and anabolic actions

e. Produced by adipose tissue; promotes satiety

f. Produced by the ovaries; regulate the menstrual cycle and the development of secondary sex characteristics

Mark the following statements as true or false. If a statement is false, correct it to make a true statement.

a. Both ADH and aldosterone increase the amount of water in the body and decrease the solute concentration of the blood.

Mark the following statements as true or false. If a statement is false, correct it to make a true statement.

b. Thyroid hormones and insulin maintain blood glucose concentration during fasting.

Mark the following statements as true or false. If a statement is false, correct it to make a true statement.

d. Insulin secretion rises during feeding; growth hormone and glucagon are secreted during feeding if protein is present in the meal.

Predict the effects of a pancreatic tumor that secretes insulin. How would the effects change if the tumor secreted glucagon instead?

Females with hormone-secreting tumors of the adrenal cortex occasionally develop male secondary sex characteristics. Explain why this may happen.

A new diet guru claims hypersecretion of cortisol is the reason why so many people are obese. He is marketing a dietary supplement that is supposedly able to block cortisol secretion and lead to weight loss. How would cortisol hypersecretion cause weight gain? Would blocking normal cortisol secretion lead to weight loss? Why or why not?

Let's say that the dietary supplement in question 2 actually works and successfully blocks cortisol secretion. Could this drug potentially be harmful? Predict its effects on overall homeostasis.

Mr. Montez is a patient with type I diabetes mellitus. He presents with dizziness, rapid breathing, confusion, and weakness. You find out that he forgot to inject his normal dose of insulin this morning. Will his blood glucose concentration be normal? Explain. Your colleague suggests that Mr. Montez needs to ingest some sugar. Is this going to help him? Why or why not? 

What has likely happened to the pH of Mr. Montez's blood? What does this mean about the hydrogen ion concentration in his blood? How will his buffer systems respond to this change in pH?

You have read that aldosterone causes sodium ion retention from the kidneys. How would blocking aldosterone secretion decrease the amount of water retained from the fluid in the kidneys?