Endocrine Physiology

Question 1

What is the difference between a tropic hormone & a non-tropic hormone?

Answer 1

-Tropic hormones regulate the production and secretion of another hormone
-Non-tropic hormone exerts its effects on non-endocrine target tissues

Question 2

What are the general principles of endocrinology?

Answer 2

-Endocrine system relies on duration not speed
-Tropic hormone
-Non-tropic hormone
-Single endocrine gland may produce multiple hormones
-Single hormone may be secreted by more than one endocrine gland
-Single hormone may have more than one type of target cell and thus induce more than one type of effect
-Single target cell may be influenced by more than one hormone
-The same chemical messenger may be either a hormone or a neurotransmitter
-Some organs are exclusively endocrine in function, while other organs of the endocrine system perform non-endocrine functions in addition to secreting hormones
-Endocrine system provide a temporal coordination of function

Question 3

How are peptide hormones transported?

Answer 3

-Transported dissolved in the plasma

Question 4

How are peptide hormones stored?

Answer 4

-Stored in secretory vessels

Question 5

How are peptide hormones released?

Answer 5

-Released through exocytosis into bloodstream mediated by specific stimuli

Question 6

What is a pro-hormone?

Question 7

Amine hormones are derived from what amino acid?

Answer 7

-Tyrosine

Question 8

How are thyroid hormones transported?

Answer 8

-Transported bound to plasma proteins

Question 9

How are catecholamines transported?

Answer 9

-Transported dissolved in the plasma

Question 10

How are steroid hormones transported?

Answer 10

-Transported bound to plasma proteins

Question 11

Are steroid hormones stored?

Answer 11

-Steroid hormones are not stored after their formation
-Only the cholesterol is stored

Question 12

How is the rate of secretion of steroid hormones controlled?

Answer 12

-Rate of secretion is controlled entirely by rate of hormone synthesis

Question 13

What is the difference in the targets for hydrophilic hormones vs lipophilic hormones?

Answer 13

-Hydrophilic hormones bind to specific receptors of the cell membrane
-Lipophilic hormones are able to cross the membrane and mind to receptors located within the cell membrane -

Question 14

What are the 3 mechanisms by which hormones elicit their effects in their target cells?

Answer 14

-Hydrophilic hormones alter cells permeability by the conformational change of channel proteins
-Hydrophilic hormones activate second messenger systems within the target cell which alter intracellular proteins produce desired effect
-Lipophilic hormones function by activating specific genes in the target cell; induce the formation of new intracellular proteins

Question 15

What are the 3 common actions of hormones?

Answer 15

-The actions of hormones are greatly amplified at the target cell
-Hormones regulate the rates of existing reactions instead of initiating new reactions
-Hormone action is relatively slow

Question 16

What hormone is secreted by the pineal gland? What are the functions of this hormone?

Answer 16

-Secretes melatonin (hormone of darkness)
-Functions: regulates biological clock, induces natural sleep, inhibits reproductive activity, shuts down ovulation, slow aging via the removal of free radicals, enhance immunity

Question 17

What hormones are secreted by the anterior pituitary gland? What are their functions?

Answer 17

-Growth hormone: regulating overall body growth
-Thyroid stimulating hormone (TSH): Stimulates thyroid hormone secretion; growth of thyroid gland
-Adrenocorticotropic hormone (ACTH): Stimulates cortisol secretion by adrenal cortes; growth of adrenal cortex
-Follicle stimulating hormone (FSH): Stimulates gamete production
-Luteinizing hormone (LH): Stimulate ovulation; secretion of estrogen and progesterone in females; testosterone in males;
-Prolactin: Enhances breast development and milk production

Question 18

What hormones are secreted by the hypothalamus? What are their functions?

Answer 18

-Thyrotropin releasing hormone: TSH and prolactin
-Corticotropin releasing hormone: ATCH
-Gonadotropin releasing hormone: FSH and LH
-Growth hormone releasing hormone: GH
-Prolactin releasing factor: Prolactin
-Prolactin inhibiting hormone: Prolactin

Question 19

What hormones are secreted by the posterior pituitary? Where were these hormones produced (be specific)?

Answer 19

-Oxytocin: Increases uterine contractility; stimulates milk ejection
-Vasopressin: Increases H2) permeability in kidneys collecting tubules; induces arteriolar vasoconstriction

Question 20

What are the functions of the thyroid gland?

Answer 20

-Increases basal metabolic rate
-Calorigenic (heat) effect
-Promote synthesis and degradation of carbohydrates, proteins, and fat
-Sympathomimetic effect by increasing cell responsiveness to catecholamines via increasing receptor density
-Facilitates cardiovascular output
-Facilitates the effects of growth hormone
-Necessary for proper growth and functioning of the nervous system

Question 21

What is calcitonin & what cells secrete it?

Answer 21

-C cells are located between follicles and secrete calcitonin for proper calcium metabolism

Question 22

What are T3 & T4?

Answer 22

-Regulate own release at the level of the anterior pituitary (inhibit TSH release)

Question 23

What are the 3 layers of the adrenal glands cortex? What hormones are produced by them?

Answer 23

-Zona glomerulosa: aldosterone production
-Zona fasciculata: cortisol production, sex hormone production
-Zona reticularis: cortisol production, sex hormone production

Question 24

What hormone classes are secreted by the adrenal glands?

Answer 24

-Mineralocorticoids: mineral balance
-Glucocorticoids: energy metabolism
-Sex hormones

Question 25

What are the functions of aldosterone? How is its release stimulated?

Answer 25

-Na+ retention in distal and collecting tubules
-Enhances K+ secretion
-Activated by renin-angiotensin system due to blood pressuredrop/Na+ decrease
-Direct stimulation of adrenal cortex by elevated K+
-Angiotensin stimulates growth of the zona glomerulosa
-ATCH regulation is weak

Question 26

What molecule stimulates the growth of the zona glomerulosa?

Answer 26

-Angiotensin stimulates the growth of the zona glomerulosa

Question 27

What globulin transports cortisol?

Answer 27

-Corticosteroid-binding globulin (transcortin)

Question 28

What is the function of cortisol?

Answer 28

-Cortisol negatively feedbacks onto both hypothalamus and anterior pituitary gland
-Stimulates hepatic glucogenesis=conversion of non-carbohydrate sources into carbohydrates
-Inhibits glucose uptake by tissues, except the brain
-Stimulates protein degradation
-Facilitates lipolysis=lipid breakdown

Question 29

Cortisol is regulated by what hormone?

Answer 29

-Adrenocorticotropic hormone

Question 30

What is the function of DHEA? What hormone regulates it?

Answer 30

-DHEA: Only adrenal hormone of significance, overpowered by male testosterone, significant in females to induce public and axillary hair; enhance pubertal growth spurt; development and maintenance of female sex drive, inhibits gonadotropin-releasing hormone (GRH)
-Adrenocorticotrophin (ACTH)

Question 31

Where in the adrenal glands is epinephrine & norepinepinephrine released from?

Answer 31

-Catecholamine Secreting Inner Medulla of the adrenal gland
-Epinephrine (primary secretion = 80%)
-Norepinephrine (20%)

Question 32

What are the metabolic effects of epinephrine?

Answer 32

-Stimulates hepatic gluconeogenesis and glycogenolysis
-Increases overall metabolic rate

Question 33

What cells secrete insulin? What is its function?

Answer 33

Secreted by B cells and used to decrease glucose levels/blood sugar

Question 34

What is the difference between glycogenesis, glycogenolysis, gluconeogenesis?

Answer 34

-Glycogenesis: glucose to glycogen
-Glycogenolysis: glycogen to glucose
-Gluconeogenesis: amino acids to glucose

Question 35

What effects does insulin have on lipid metabolism?

Answer 35

-Increase transport of glucose into adipose tissue, which is converted to fatty acids and glycerol for triglyceride synthesis
-Activates enzymes for fatty acid production from glucose
-Promotes fatty acid entry into adipose tissue cells
-Inhibits lipolysis (fat break down)

Question 36

What effects does insulin have on protein metabolism?

Answer 36

-Increase transport of amino acids into muscle and other tissues
-Increase protein synthesis
-Inhibits protein degradation

Question 37

What causes insulin to be released?

Answer 37

-Increase in blood glucose: primary stimulus
-Increase in blood amino acid levels
-GIP (gastric inhibitory peptide) is released in response to food
Parasympathetic stimulation

Question 38

What is the difference between type I and type II diabetes?

Answer 38

-Type I diabetes: lack of insulin secretion
-Type II diabetes: reduced sensitivity of insulin target cells

Question 39

What cells secrete glucagon? What is its function?

Answer 39

-Pancreatic islet A (alpha) cells secretes glucagon
-Opposite action to insulin
-Carbohydrate metabolism

Question 39

42. What effects does glucagon have on carbohydrate, lipid, & protein metabolism?

Answer 39

-Carbohydrate metabolism: Increase blood glucose-decreases glycogen synthesis (glycogenesis), stimulates glycogenolysis, stimulates gluconeogenesis
-Lipid metabolism: Promote fat breakdown and inhibiting triglyceride synthesis, increases blood fatty acids
-Protein metabolism: inhibits hepatic protein synthesis, promotes degradation of hepatic protein synthesis which does not affect blood amino acid levels since it is not the major protein storage

Question 40

What do the levels of blood glucose, blood fatty acids, & blood amino acids do to glucagon secretion?

Answer 40

-Blood glucose (depressed) stimulates glucagon release
-Blood fatty acid (depressed) stimulates glucagon release
-Blood amino acid (elevated) stimulates both glucagon and insulin release (critical during high protein meal)