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32 Cards in this Set
- Front
- Back
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How do freshwater fish get enough salt?
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-no drinking
-active pumping of salt into the body -loss of salt through diffusion/urine |
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How do saltwater fish get water
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-drink constantly
-actively pump salt out of body -some minerals excreted in urine |
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Osmoregulatory strategies in fish
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saltwater: below external osmolarity
freshwater: above external osmolarity some fish (chondricthyes, agnatha) maintain at or above external osmolarity |
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Types of salt adaptability
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stenohaline- restricted to a narrow salinity range
-euyrhaline- wide range of salinities |
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organs responsible for maintaining osmolarity in fish
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gills (chloride cells)
intestine kidneys |
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gills make use of which system to control chloride
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countercurrent multiplier system
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blood flow to gills is controlled by
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arginine vasotocin- decreases flow (also other nonapeptides)
epinephrine increases blood flow to gills |
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actions by hormones on chloride cells
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GH/IGF-I- saltwater adapting
PRL- freshwater adapting Cortisol- stimulates the effects of both aforementioned hormones |
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Osmoregulatory strategies in tetrapods
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-impermeable integument (mammals, reptiles, birds)
-permeable integument (amphibians) -kidneys (only mammals can produce a concentrated urine) -birds have nasal excretory salt glands |
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antidiuretic hormones in tetrapods
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ADH (vasopressin)
Corticosteroids/ Aldosterone: mammals, nonmammals also use corticosterone Angiotensin II |
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Atrial natriuretic factor
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induces salt excretion, produced by heart
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regions of the adrenal gland
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glomerulosa: aldosterone
fasiculata: cortisol reticularis: cortisol, DHEA medula: epinephrine and norepinephrine |
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effects and binding of cortisol/corticosterone
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increase plasma glucose
CBG binds corticosteroids- t1/2 for glucocorticoids is 1-2 hours |
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adrenal androgens
hypersecretion of adrenal androgens |
DHEA, DHEA-sulfate, androstenedione
-Hirsutism- appearence of masculine features in women -Virilism- extreme masculinization |
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enzymes present in different regions of the adrenal gland
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18 hydroxylase is present in the zona glomerulosa
17a hydroxylase is present in the zona reticularis |
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receptors present in different regions of the adrenal gland
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zona fasiculata- ACTH receptor
zonqa glomerulosa- angiotensin II receptor |
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Type I corticosteroid receptors
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mineralcorticoid receptors (high affinity for cortisol and aldosterone)
expressed in kidneys, GI tract, salivary glands, heart, brain MR is an important mediator for aldosterone actions |
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Type II corticosteroid receptors
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high affinity for cortisol, low affinity for aldo
expressed in most tissues important mediator of stress response |
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Isoforms of the MR/GR receptors
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MR receptor has 1 isoform
GR has 2- alpha is for biological responses beta is a dominant negative inhibitor of alpha |
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Ancestral corticosteroid receptor
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AncCR- high affinitty for ALDO, but ALDO had not yet been evolved
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Why does cortisol not affect MR receptor activities
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11B hydroxysteroid dehydrogenase (makes cortisone from cortisol)
licorice inhibits this and can lead to hypertension |
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Where do mineralcorticoids affect stuff
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areas of high Na/K pump activity
-control blood volume and ionic homeostasis promary goal is to regulate plasma Na |
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Parts of the Kidney that absorb Na
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Proximal/Distal tubule-> active transport of sodium out
Descending loop of henle: passive transport |
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aldo effects on distal tubule
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increases NA+ reabsorbtion in distal tubule, increaseed extracellular Na increases water reabsorbtion
-increased apical surface Na channels -increased basolateral Na/K pump activity |
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result of aldosterone effect on kidney
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serum Na increases
(peritubular capillaries return the extracellular fluid to the general circulation) |
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aldosterone secretion is stimulated by
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high K/Na ratio
presence of angiotensin II |
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roles of specific kidney cells in renin release
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JG cells- release renin, baroreception'
Macula Densa Cells- sense changes in Na, send signal to JG cells Sympathetic cells- innervate JG cells |
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other methods of ALDO secretion regulation
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1) ACTH, but only in extremely high amounts
2) catecholamines stimulate ALDO secretion |
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how is the renin-angiotensin system controlled
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by a drop in blood pressure--- angiotensin II will vasoconstrict, act on hypothalmus
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ADH- where is it released and how is its release regulated?
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-released by posterior pituitary
-stretch receptors in posterior pituitary negatively control it |
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What does ADH do?
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increases reabsorbtion of H20 through collecting ducts
pressor activity- decreased blood flow to kidney |
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Atrial Natriuretic Factor (ANF)
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potent vasodilator- BP down
degreases NA reabsorbtion ingibit renin sectretion |
