Hormones

Question 1

Steroid vs. Nonsteroid hormones

Answer 1

Steroid hormones:

• Derived from cholesterol
• Lipid soluble; diffuse through membranes
• Secreted by adrenal cortex, ovaries, testes and placenta

Non steroid hormones:

• Not lipid soluble; cannot cross membranes; bind to receptors on the cell membrane instead
• Divided into protein/peptide hormones and amino acid-derived hormones
• Most are protein-peptide secreted by the pancreas, hypothalamus and pituitary gland

Question 2

How do hormones function as a whole?

Answer 2

• Hormones affect all aspects of human function
• Used by endocrine system to maintain homeostasis
• They are chemicals that control and regulate cell and organ activity and act on target cells
• Classified by their source, receptor type or chemical structure

Question 3

Hormones effects on enzymes

Answer 3

1. Stimulate enzyme synthesis
2. Combines with the enzyme to change its shape, which increases or decreases the enzymes ability to interact with a substrate
3. Activate many inactive enzyme forms to increase total enzyme activity

Question 4

How are glands stimulated?

Answer 4

1. Hormonal stimulation:
   - Caused by another hormone (a tropic hormone).
   ex. Hormones from hypothalamus stimulate the anterior pituitary gland to secrete hormones that stimulate other endocrine glands to secrete hormones
2. Humoral stimulation:
   - Caused by altered levels of certain critical ions or nutrients
   ex. Low concentration of calcium in capillary blood stimulates Parathyroid glands to secrete PTH to increase blood calcium
3. Neural stimulation:
   - Caused by neural input
   ex. Action potentials in preganglionic sympathetic fibers to adrenal medulla stimulate adrenal medulla cells to secrete epinephrine and norepinephrine

Question 5

Hormone-hormone interactions

Answer 5

1. Synergism
   - Different hormones act together to augment the effect on specific tissues
   ex. Pancreas secretes glucagon, with cortisol and epinephrine causing glucose levels to increase
2. Permissivenes
   - One hormone cannot exert its full effect without the presence of a second hormone, or a greater quantity of the first hormone
   ex. Thyroid hormone increases number of receptors available for epinephrine at its target
3. Antagonism
   - Some hormones oppose the action of another hormone to diminish the first hormone’s effectiveness
   ex. Glucagon and GH counteract insulin response

Question 6

Circadian rhythm

Answer 6

Most hormones respond to peripheral stimuli on an as-needed basis, while others release at regular intervals during a 24-hour cycle

Question 7

Which hormones increase and maintain blood glucose concentrations? (specifics about each)

Answer 7

Glucagon:

• Stimulates liver gycogenolysis and gluconeogenesis and lipid catabolism
• Regulated by blood glucose level
• Contributes to blood glucose regulation during endurance exercise and starvation
• Secreted by alpha cells from islets of langerhans in pancreas

Epinephrine and Norepinephrine:
- Amino avid-derived hormones secreted from Adrenal medulla

Cortisol

• Promotes protein and fat catabolism, raises blood glucose levels, adapts the body to stress
• Secreted by Adrenal cortex

Question 8

Hormones released by the pancreas (specifics about each)

Answer 8

Insulin and amylin from Beta cells

• Insulin regulates glucose metabolism by facilitating cellular glucose uptake in all tissues except the brain
• Amylin is released with insulin to help satiety, decrease plasma glucose levels and decrease gastric emptying

Glucagon from Alpha cells

• Stimulates liver gycogenolysis and gluconeogenesis and lipid catabolism
• Regulated by blood glucose level
• Contributes to blood glucose regulation during endurance exercise and starvation
• Secreted by alpha cells from islets of langerhans in pancreas

Somatostatin from D cells
- Governor for insulin and glucagon

Pancreatic polypeptide from PP cells

Question 9

What regulates fat metabolism during exercise?

Answer 9

• FFA mobilization

- Lipolysis stimulated by epi, norepi, cortisol and GH

Question 10

Which hormones help with the regulation of fluid and electrolytes?

Answer 10

• Antidiuretic hormone (ADH) from posterior pituitary increases water reabsorption at kidneys
• Adrenal cortex secretes the mineralocorticoid, aldosterone, to increase sodium retention by kidneys, increase water retention via osmosis and increase potassium excretion