Chapter 21: Endocrine system function Flashcards
5 functions of endocrine system
- differentiation of reproductive and CNS system in fetus
- stimulation of sequential growth and development
- coordination of male and female reproductive systems
- maintenance of optimal internal environment
- initiation of corrective and adaptive responses
3 basic secretion patterns
- circadian or diurnal pattern
- pulsatile and cyclic
- patterns that depend on levels of circulating substrates
Most common mechanism for regulation of hormone release
negative feedback
Transport of protein hormones
Water soluble
Circulate in unbound forms
Short half life
Can not cross membranes–require a receptor to bind
Transport of lipid hormones
Transported via carrier protein
Can cross membranes
Target cell response depends on
Blood levels of hormone, concentration of receptors, affinity of receptor for hormone
Upregulation
Low concentration of hormone increase the number of receptors per cell
Downregulation
High concentration of hormone decrease the number of receptors per cell
HPA
Contains hypothalamus, anterior pituitary and posterior pituitary
What is synthesized by hypothalamus
ADH + oxytocin
Releasing and inhibiting hormones: PIH, PRH, TRH, GnRH, somatostatin, GHRH, CRH, Substance P
How do ADH and oxytocin travel to posterior pituitary
via hypothalamohypophysial nerve tract
2 cell types in anterior pituitary
Chromophobes: nonsecretory
Chromophils: secretory
Tropic hormones
Affect physiologic function of specific target hormones
Hormones produced and secreted by anterior pituitary
ACTH, melanocyte stimulating hormone, LH, FSH, TSH, GH, Prolactin
GH is controlled by what hypothalamic hormones
GHRH: Increases GH secretion
Somatostatin: decreases GH secretion
What increases synthesis and release of prolactin
Stimulation of nipples and mammary gland during nursing
Serotonin + GF also stimulate
What inhibits prolactin
Dopamine
What does posterior pituitary secrete
ADH and oxytocin
Major stimulus for release of ADH and oxytocin
Glutamate
Major inhibitor for release of ADH and oxytocin
GABA
ADH also called
Arginine vasopressin
ADH action
acts on vasopressin receptors of kidney to increase permeability to increase water reabsorption into blood
What inhibits ADH
Increased Ca, prostaglandin E, hypokalemia
What regulates secretion of ADH
Osmoreceptors of hypothalamus and baroreceptors in left atrium
What causes ADH secretion to decrease
high blood volume, hypertension, estrogen, progesterone, angiotensin II, alcohol
Pineal gland
Releases melatonin in response to dark
Tryptophan–>serotonin–>melatonin
What directly affects secretion of thyroid hormones
Ach and catecholamines
C cells in thyroid secrete
Calcitonin
Causes decrease in serum Ca by inhibiting osteoclast activity
What causes increase in TRH
Exposure to cold or stress
TSH is synthesized and stored in
Anterior pituitary
Thyroid hormone affects
Metabolic, neurologic, CV, respiratory, cell metabolism, heat production, O2 consumption
Increase in TH will cause
Increase in contractile proteins, increase in RR, increase in bone resorption, increased heat production
Parathyroid hormone
Regulates serum calcium concentration
Released in acute hypocalcemia–stimulates osteoclasts
PTH acts on kidneys
To increase Ca reabsorption and decrease phosphate reabsorption
Alpha cells
Secrete glucagon
Glucagon
Antagonist to insulin
Increase blood glucose during fasting, exercise, hypoglycemia
Acts on liver to increase blood glucose by stimulating glycogenolysis
Glucagon stimulated by
Low blood glucose and SNS
Beta cells secrete
Insulin and amylin
C peptide
Can be measured in the blood as an indirect measure of serum insulin synthesis
Factors increasing insulin secretion
Increased blood glucose, GI hormones, amino acids
Factors decreasing insulin secretion
Decreased blood glucose, increased insulin, SNS, prostaglandins
Net effect of insulin
Stimulate protein and fat synthesis and decrease blood glucose
What organs do not require insulin for glucose uptake
Brain, RBC, kidneys, lens of eye
Insulin and K+
Facilitates K+ entry into cell
Amylin
Co-secreted with insulin
Regulates blood glucose by delaying gastric emptying and suppressing glucagon secretion after meals
Has an anti hyperglycemic effect
Delta cells secrete
Gastin and samatostatin
Samatostatin
Essential for carb, protein, fat metabolism
Inhibits insulin, glucagon, pancreatic polypeptide
F cells secrete
pancreatic polypeptide
Pancreatic polypeptide
Released in response to hypoglycemia and protein rich meals
Promotes gastric secretion
Adrenal cortex is stimulated by
ACTH
What hormones does adrenal cortex secrete
Glucocorticoids and aldosterone and adrenal estrogen/androgens
Fx of glucocorticoids
Anti-inflammatory, immunosuppressive, growth suppressing
Glucocorticoids are released under what conditions
Stress
What do glucocorticoids do
Increase blood glucose by promoting gluconeogenesis in liver and antagonizing insulin to deliver more glucose to the brain
Causes protein catabolism and muscle wasting
Suppresses innate and adaptive immunity
Inhibits bone formation and ADH
Stimulates gastric acid secretion
Pathologically high levels of glucocorticoids causes
Increase in RBCs, increased appetite, fat deposition promotion, increased uric acid excretion, decreased serum Ca, decreased ACTH, decreased somatic growth
Aldosterone
Causes sodium retention and K+/H+ loss by increasing Na pump of epithelial cells in kidney
Synthesis/secretion of aldosterone regulated by
RAAS
activated by Na/H2O depletion, increased K+ and decreased blood volume
Primary stimulant of aldosterone
Angiotensin II
Degradation and excretion of aldosterone
Degraded in liver, excreted by kidneys
What does adrenal medulla secrete
Epinephrine and norepinephrine
What triggers release of catecholamines
Physiologic stress through Ach
Aging and thyroid gland
Atrophy and fibrosis, TSH increases slightly, peripheral metabolism of TH decreased
Aging and pancreas
Impaired glucose tolerance or diabetes common, increased distribution of fat tissue
Aging and GH
Decreased
Decrease in muscle size and function
Decrease in fat and bone mass
Aging and adrenal cortex
Atrophy
More fibrous tissue
Metabolic clearance of cortisol is decreased
Somatopause
Decrease in growth hormone and insulin like growth factor that occurs with aging
Permissive effect
Hormone induced changes that facilitate the maximal response or functioning of a cell
Incretins
Released by GI tract and act to decrease postprandial blood glucose concentration
Storage of thyroid hormones
Thyroid gland can store about 2 months worth of thyroid hormone at a time
