Fundamentals of endocrine physiology Flashcards
Describe synaptic extracellular signaling (message transmission, local or general, and specificity depends on ____)
Across synaptic cleft, local, anatomic location and receptor
Describe paracrine and autocrine extracellular signaling. (message transmission, local or general, and specificity depends on ____)
by diffusion in interstitial fluid, locally diffuse, receptors
Describe endocrine extracellular signaling (message transmission, local or general, and specificity depends on ____)
by circulation body fluids, general, receptors
Describe neuro-endocrine extracellular signaling (message transmission, local or general, and specificity depends on ____)
by circulating body fluids, general, receptors
Hormones released by hypothalamus
Releasing hormones: TRH, GnRH, CRH, GHRH, DA (PIH), somatostatin (SS;SRIF),
Oxytocin +vasopressin
Define hormone. What is included and what is not included?
a chemical substance released in small quantities from certain glands (the endocrine glands) that travels through the circulatory system to elicit a typical physiological response in other cells and tissues, called target cells and target tissues. Including neurohormones. Not including CO2 or intracellular messengers like cyclic AMP.
Hormones released by anterior pituitary
Growth hormones (somatotropin, GH, STH)
Thyroid stimulating hormone (TSH, thyrotropin)
Adrenocorticotropic hormone (ACTH, corticotropin)
Prolactin (PRL)
Gonadotropic hormones: Follicle stimulating hormone (FSH), luteinizing hormone (LH)
Major function of hypothalamus is control of:
secretion by the anterior pituitary (up or down)
Major function of anterior pituitary is control of:
Growth; organic metabolism; secretion of somatomedin by liver + cartilage
Thyroid gland (increase size, activity, secretion)
Adrenal cortex (mainly increase of cortisol)
Breasts (increase milk secretion)
Gonads (gamete production + sex hormone secretion)
Increase adrenal androgen secretion
Hormones released by posterior pituitary
oxytocin, vasopressin (ADH)
Major function of posterior pituitary is control of:
Milk “let-down”; uterine motility
Water excretion by kidneys, body water
Major function of adrenal cortex is control of
organic metabolism; responsive to stress; permissive
Growth: men and women; sex drive
increase sodium and decrease potassium excretionby kidneys; thus body Na + K +fluid volume
Hormones released by adrenal cortex
cortisol, adrenal androgens (androstenedione + DHEA)
Aldosterone
Hormones released by adrenal medulla
epinephrine, NE
major function of adrenal medulla is control of
organic metabolism; CV function; response to stress
Hormones released by thyroid
Thyroid hormone: mainly thyroxine T4, triiodothyronine T3, calcitonin CT
Major function of thyroid is control of
energy metabolism; growth Plasma calcium (lower Pca); weak in adults
Hormones released by parathyroids
PTH
Major function of parathyroids is control of
Plasma Ca and Phosphate (increase Ca and decrease po4)
3 general categories of hormones
steroids and steroid-like hormones, amino acid derivatives (catecholamines and thyroid hormones), peptides and proteins
Major stimuli that cause increase/decrease secretion of aldosterone
BP, plasma vol, renin, A-2
Steroids that are androgens
Testosterone, dihyrotestosterone (DHT), and weaker androgens from adrenal like andosternedione, DHEA; DHEA-S
Steroids that are progestagens
progesterone
Steroids that are estrogens
estradiol-17b, weaker estrogens (estrone, estriol)
Steroids that are mineralcorticoids
aldosterone, deoxycorticosterone (DOC)
What vitamin is steroid-like?
Vitamin D- cholecalciferol
Steroids that are GCs
cortisol, corticosterone
Steroid hormones are derived from _____
Cholesterol
What are the amino acid derivatives
catecholamines, thyroid hormones, melatonin
What hormones are peptides?
insulin. PTH, OT, ACTH, relaxin, A-II, thymosins, glucagon, CT, VP, MSH, inhibin, ANPs, GI tract hormones, releasing hormones except dopamin (CRH, TRH, GnRH, GHRH, SS)
What hormones are proteins?
GH, PRL, FSH, LH, FSH, LH, TSH, hCG, hPL, EPO, renin, leptin, resistin, FGF23
Effects of direct hormone action
fast or slow in onset, end quick or linger
Effects of indirect hormone action
Not readily observed
T or F whether it is going to be acting directly/indirectly, the hormone must have receptors.
T
Describe how permissiveness affects fatty acid release from adipose tissue.
TH alone–> no fatty acids released
Epi alone–> small amount of FA released
Epi+TH–> large amount of FA released
What is the effect of increasin the number of receptors on response to a hormone?
Decreased the percent change in hormone concentration required for 50% max response
Second messengers ____ the signal from hormone.
Amplify and disperse to many places in the cell
Describe the significance of free and bound Thyroxine
99.6% is bound. Free T4 can play a role in negative feedback, tissue action, hormone metabolism, and fecal excretion
What acute and compensatory effects occur after increasing the amount of binding protein in plasma?
Acute: decrease amount of free hormone
New steady state: amount of free hormone back to normal
Describe the distribution of steroids in the blood.
Can be free or bound to SHGB,CBG, albumin
How are hormones measured?
competitive binding assay
What are the different types of episodic secretion of hormones?
Circadian: cortisol
Ultradian (multiple times a day), pulsatile
Stimulus-induced
Rhythms with longer time intervals
What are the three ways that blood levels of a hormone can be altered?
change in secretion rate, change in binding protein, change in clearance
What are some general causes of endocrine diseases?
over/under production, alterations in receptors, post-receptor events in target cells, altered metabolism
____ is the endocrine system’s response to stimulus reinforces that stimulus, such as labor.
Positive feedback
_____ is the endocrine system’s response to a stimulus is to reduce that stimulus.
negative feedback
What is the major difference between the endocrine and nervous system?
The endocrine system has an intervening blood vessel
What are 3 examples of glands that are controlled directly by the nervous system?
posterior pituitary, adrenal medulla, hypothalamic RH
What are 2 examples of nervous system activity that are affected by hormones?
mating behavior, epi–> anxiety, fear
Amino acid derivatives are derived from ____.
tyrosine
How must peptide hormones be admitted?
Not orally!!
Chemical nature of posterior pituitary hormones
peptide
Major stimuli that increases secretion of ADH from posterior pituitary
increase osmolarity, decrease plasma volume
Chemical nature of aldosterone from adrenal cortex
steroid
Major stimuli that increase secretion of aldosterone from adrenal cortex
decrease BP, decrease volume, increase renin, increase AII
Major stimuli that decrease secretion of aldosterone from adrenal cortex
increase BP, increase volume, decrease renin, decrease AII
Describe the chemical nature of RH secreted by hypothalamus.
All are peptides except dopamine–> amino acid derivative
6 classes of steroid hormones
androgens, estrogens, progestagens, mineralcorticoids, glucocorticoids, steroid-like
3 classes of amino acid derivatives
catecholamines, thyroid hormones, melatonin
What PROTEIN hormones are secreted by the Ant. Pit.
GH, PRL, FSH, LH, TSH
What protein hormones are secreted by the placenta?
hCG, hPL
What protein hormones are secreted by the kidney?
EPO, renin
What protein hormones are secreted by the fat?
leptin
What protein hormones are secreted by the bone?
FGF23
What does 5a reductase do?
Testosterone–> dihydrotestosterone
What does aromatase do?
testosterone–> estradiol; androstenedione–>estrogen
What does 11-B hydroxylase do?
deoxycorticosterone–> corticosterone; 11-deoxycorisol–> cortisol
The major circulating form of thyroid hormone is _____.
T4
The major active form of thyroid hormone is _____.
T3
Is there a greater percent change in hormone concentration needed for 50% max action when the number of receptors is increased or decreased and why?
Decreased. There are spare receptors
What hormones use intracellular receptors?
steroid and TH
Cortisol usually begins an hour before waking up. What are 2 exceptions?
jet lag and shift workers
Synthesis of peptides, proteins, catecholamines
nearly continuous; mild regulation
Storage of peptides, proteins, catecholamines
granules
Secretion of peptides, proteins, catecholamines
regulated and taken from stores
Transport of peptides, proteins, catecholamines
mostly free
Half life of peptides, proteins, catecholamines
pep: few min; proteins: minutes; catecholamine-few minutes
are peptides, proteins, catecholamines activated?
no (except renin–> peptide)
receptor binding of peptides, proteins, catecholamines
P/P: surface on plasma membrane
C: surface a/b
Mechanism of peptides, proteins, catecholamines
second messengers
Rapidity of peptides, proteins, catecholamines
Fast
Duration of peptides, proteins, catecholamines
Brief
Degradation of peptides, proteins, catecholamines
much
Excretion of peptides, proteins, catecholamines
p/p: little
c: VMA, metanephrine, nor-metanephrine
Synthesis of steroids and thyroid hormones
S: little until stimulated–> regulated!
T: partially–> precursors
Storage of steroids and thyroid hormones
S: little
T: in precursor from (thyroglobulin)
Secretion of steroids and thyroid hormones
S: as synthesized
T: slow, continuous
Transport of steroids and thyroid hormones
mostly bound
Half lives of steroids and thyroid hormones
S: hours-days
T: 3: 1 day/ 4: 6 days
are steroids and thyroid hormones activated?
S: Yes- Testosterone–> DHT; Vitamin D–> 1,25 (OH)2-vit D
T: Yes- (T4)–>(T3)
Binding to receptors for steroids and thyroid hormones
nuclear
Mechanism of steroids and thyroid hormones
gene activation
Rapidity of steroids and thyroid hormones
slow
Duration of steroids and thyroid hormones
long
degradation of steroids and thyroid hormones
liver
excretion of steroids and thyroid hormones
S: urine
T: very little
