Peripheral Endocrine Glands Flashcards
What are the major peripheral endocrine glands?
1.) thyroid gland
2.) adrenal glands
3.) endocrine pancreas
4.) parathyroid glands
What types of cells make up the thyroid gland?
follicular cells (arranged into spherical layers forming a follicle)
What is a follicle in the thyroid gland?
spheres of follicular cells that are filled with colloid (substance containing thyroid hormone) seperate from ECF
What are the two molecules that are referred to as thyroid hormone?
1.) tetraiodothyronine (T4)
2.) triiodothyronine (T3)
Where is the receptor for thyroid hormone? What does its activation do?
thyroid-response element:
causes transcription and synthesis of new proteins that bring about hormone’s effect
What thyroid hormone is more prevalent in the body?
While T4 is 90% of the hormone secreted, T3 is 10 times more potent, and most of T4 is converted to T3, making T3 the most abundant
Could you identify the physiological effects of thyroid hormone from a list?
1.) increases cellular respiration, which increases basal metabolic rate, which increases body heat
2.) increases number of NE and E receptors on target cells of sns, increasing effects of sympathetic nervous system stimulation (sympathomimetic effect)
3.) increases heart rate and force of contraction
4.) promotes secretion of growth hormone and production of IGF-1 by liver, necessary for proper growth
How is thyroid secretion regulated?
controlled by a 3-hormone chain starting at the hypothalamus, constant secretion of thyroid hormone— negative feedback prevents runaway secretion
What is hypothyroidism? Why would too much thyroid-stimulating hormone lead to a
goiter?
hypothyroidism: due to failure of thyroid gland, lack of TSH production or lack of dietary iodine
Why would too much thyroid-stimulating hormone lead to a
goiter?
TSH is a tropic hormone with trophic properties, stimulates maintenance of target gland
excessive TSH levels –> leads to hypertrophy and hyperplasia of follicular cells (in thyroid gland)
Do the adrenal cortex and medulla secrete the same hormones?
no, they secrete different hormones
adrenocortical: aldosterone, cortisol, DHEA
medulla: epinephrine, norepinephrine
what are the 3 layers of the adrenal cortex?
1.) zona glomerulosa
2.) zona fasciculata
3.) zona reticularis
Is hormone stimulation the same in the adrenal cortex and medulla?
adrenal cortex: stimulated by hormones from the pituitary gland (ACTH)… except aldosterone secretion primarily regulated by RAAS and K levels in blood (not by ACTH)
medulla: stimulated directly by the sympathetic NS
What are the three categories of adrenocortical hormones?
1.) mineralocorticoid
2.) glucocorticoids
3.) sex hormones
What is the main mineralocorticoid produced by the adrenal cortex?
aldosterone (influence balance of Na+ and K+)
produced in zona glomerulosa
What is the main glucocorticoid produced by the adrenal cortex?
cortisol (plays role in glucose metabolism, also lipid and protein, and stress response)
produced in zona fasciculata (also zona reticularis)
What is the main sex hormone produced by the adrenal cortex?
DHEA
produced in zona fasciculata and reticularis
How do lipophilic hormones move through the blood? How about hydrophilic hormones?
lipophilic: (steroid and thyroid hormones)… bind to transport proteins in blood (longer half-life)
hydrophilic: (peptide hormones (insulin, glucagon), epinephrine and norepinephrine)… soluble in blood plasma and circulate freely in blood stream and interact with cell-surface receptors on target cells
Are adrenocortical hormones lipophilic or hydrophilic?
lipophilic
Where are the target cell receptors located for lipophilic hormones?
lipophilic target cell receptors located in the cytoplasm
What is the main function of aldosterone? What organ does it mainly act on?
acts to increase sodium reabsorption in distal and collecting tubules of the kidneys (increases ECF volume)
What directly controls aldosterone secretion?
Direct detection of increased plasma K+
How is cortisol regulated?
3-hormone chain command starting at hypothalamus, cortisol acts as a negative feedback signal
What are the effects of cortisol? Why is this important?
1.) stimulate gluconeogenesis (conversion of amino acids into glucose)
2.) stimulate protein degradation, especially in muscle (making amino acids available for gluconeogenesis and repair of damaged tissues)
3.) facilitates lipolysis (breakdown of fat stores in adipose tissue into free fatty acids in the blood)
help ensure brain has adequate glucose supply in between meals and during fasting
Could you identify the physiological effects of cortisol from a list?
1.) increased blood glucose (by stimulating gluconeogenesis and inhibiting glucose uptake)
2.) increase blood amino acids (by stimulating protein degradation)
3.) increase blood fatty acids (by stimulating lipolysis)
Could you identify the physiological effects of DHEA on females from a list?
1.) governs growth of axillary and pubic hair
2.) enhancement of pubertal growth spurt
3.) sex drive
what controls the secretions of DHEA?
controlled by ACTH from pituitary gland (not gonadotropins)
Why is the adrenal production of DHEA not as relevant for males as it is for females?
because the production of testosterone in males make DHEA insignificant
What type of cells make up the adrenal medulla?
chromaffin cells: modified postganglionic sympathetic neurons that comprise the adrenal medulla
What does the adrenal medulla release in response to sympathetic nerve activity?
release epinephrine and a little norepinephrine into capillaries (E and NE act as hormones in this case)
Does epinephrine activate the same receptors as norepinephrine? How about vice
versa: does norepinephrine activate the same receptors as epinephrine?
Epinephrine can activate the same receptors as NE, as well as activate additional receptors that NE cannot.
E can both minic NE action and produce individual, unique effects
What effect does epinephrine have on the arterioles of skeletal muscles?
on arterioles:
- NE and E cause vasoconstriction of arterioles, increasing blood pressure
- BUT… E additionally activates receptors that vasodilate arterioles in cardiac and skeletal muscles (diverts b. flow to these tissues)
What effect does epinephrine have on the bronchioles?
bronchodilates bronchioles in the lungs, decreases airflow resistance in lungs
Would cold exposure cause general adaptation syndrome? How about physical pain?
How about psychosocial stress?
all of these would trigger general adaptation syndrome (set of common responses evoked by all stressors)
Could you identify mechanisms of the general adaptation syndrome from a list?
What is anabolism and catabolism?
anabolism: synthesis of larger molecules
- materials needed by cell (structural proteins, secretory products)
-storage molecules for excess nutrients not immediately needed for energy production or material needs
catabolism: breakdown of larger molecules
-cellular respiration (glucose or fatty acids -> ATP)
-hydrolysis of storage or structural macromolecules (either used in the same body cell or released into blood to be used elsewhere)
What is the difference between metabolism and fuel metabolism?
metabolism: general term for all chem reactions within body cells
fuel metabolism: reactions involving the degradation, synthesis, or transformation of carbs, fats, and proteins (fuel)
Can amino acids be transformed into glucose? How about glucose to fatty acids?
amino acid -> glucose
= gluconeogenesis (increase blood glucose)
glucose -> fatty acids
= lipogenesis
Can all nutrients be created from other organic molecules in the body?
essential nutrients cannot be formed in body from other organic molecules, must be ingested
Can glucose, amino acids, and fatty acids all be used as sources of energy? Can they all directly enter into cellular respiration?
all can be used as energy sources, but only glucose can directly enter cellular respiration
How is the balance between anabolism and catabolism shifted during growth?
during growth the balance shifts toward anabolism, with a focus on building tissues and storing energy reserves
Where do nutrients come from in-between meals?
from stored forms of energy built up from nutrient excess during meal absorption
What do body cells do during the absorptive state? How about during the
postabsorptive state?
absorptive state: state while absorbing nutrients from a meal – - - - most cells preferentially use glucose, excess nutrients stored (anabolism)
post-absorptive state: state in-between meals or sleeping when not absorbing
- energy stores used. synthesis pf protein curtailed (catabolism)
- cells that can burn fatty acids switch to that, reserving glucose for brain
- amino acids converted to glucose for brain (gluconeogenesis)
What are the storage forms of carbohydrates, proteins and fats in the body? Where are
the main storage sites for each of these? Which contains the most stored energy?
carbs: glycogen, liver/muscle
proteins: body proteins, muscle
fats: triglycerides, adipose tissue
What is the nutrient that the brain relies on? Does it store this nutrient?
brain is dependent on a constant source of glucose, but the brain does not store glucose
What signals the body to switch from the postabsorptive to absorptive state?
mostly via effects of the pancreatic hormones insulin and glucagon
What are the structures in the pancreas that secrete hormones?
beta cells (insulin and some amylin)
alpha cells (glucagon)
delta cells (somatostatin)
gamma cells (pancreatic polypeptide)
epsilon cells (ghrelin)
Which pancreatic cell secretes insulin and which secretes glucagon?
beta cells secrete insulin
alpha cells secrete glucagon
What is the effect of insulin on blood levels of glucose, amino acids, and fatty acids?
glucose: lower blood glucose and promote carbohydrate storage
amino acids: lower blood amino acid levels and promote protein synthesis
fatty acids: lower blood fatty acid levels and promote triglyceride storage
What is the effect of glucagon on blood levels of glucose, amino acids, and fatty acids?
glucose: increase blood glucose levels
amino acids: since these don’t affect muscle (main protein storage) NO effect on blood amino acid level
fatty acids: increase blood fatty acid levels
Does insulin increase or decrease carbohydrate storage? How about protein synthesis?
How about fat storage?
insulin promotes carbohydrate storage, protein synthesis and fat storage
Does increased insulin lead to increased or decreased permeability of cells to glucose?
How does this change in permeability occur?
increased insulin increases glucose permeability (transporter recruitment)
increased insulin -> exocytosis of vesicles lined with GLUT-4 -> increased glucose permeability
If given a list of possible events, could you correctly list the process by which beta cells
secrete insulin in response to a change in insulin level? What is this process called?
The excitation-secretion coupling process of β cells:
1) Glucose enters β cell via GLUT
2,3) Glucose used during cellular respiration to create ATP -> more intracellular glucose, more ATP
4) Increased ATP closes ATP-sensitive K+ channel
5) Decreased K+ outflow -> cell depolarizes
6,7) Depolarization crosses threshold of voltage-gated Ca2+ channels -> Ca2+ floods in
8,9) Increased [Ca2+] causes insulin-containing vesicles to undergo exocytosis (secretion)
Could you explain how insulin and glucagon act as a negative feedback system for
blood glucose?
Insulin is the main regulator in both absorptive and postabsorptive states -> operates as a negative feedback for blood glucose
-Increased blood glucose -> increased insulin -> actions that remove glucose from blood
-Decreased blood glucose -> decreased insulin -> actions that allow blood glucose to stop decreasing
Glucagon acts during the postabsorptive state to additionally increase blood glucose, mainly by acting on the liver
What organ does glucagon mainly act on?
the liver
What is the difference between Type 1 and Type 2 diabetes mellitus?
T1: lack of insulin secretion
T2: loss of insulin sensitivity of target cells
