osmoregulation 5

Question 1

angiotensin 2

Answer 1

vasoconstrictor, decreases GFR

Question 2

prostoglandins

Answer 2

vasodilator, increases GFR

-paracrine hormone produced throughout blood vessels, and released locally when bp decreases

Question 3

extrincsic regulators of GFR

Answer 3

• occur when nervous or endocrine system detects changes and sends a signal or releases a chemical to facilitate change in another system
• nervous system response: myogenic and tuuloglomerular feedback
• endocrine response: vasopressin/adh, renin-angiotensin-aldosterone pathway, and atrial natriuretic peptide

Question 4

vasopressin

Answer 4

• aka adh
• peptide hormone produced in hypothalamus and released by post pit gland
• increases the permeability of collecting ducts
• increases water reabsorption from collecting duct by increasing number of aquaporins
• urine concentration depends on adh secretion/water reabsorption
• impermeable collecting duct=less water reabs., and more dilute urine; permeable c. duct=more water reabsorbed and more conc urine
• release is stim’d by increased plasma osmolarity, inhibited by increased BP detected by stretch receptors in atria

Question 5

vasopressin regulation pathway

Answer 5

high plasma osmolarity=need to dilute plasma=more adh=inc water reabs
high bp=need decrease blood volume=less vasopressin=dec. water reabs.

Question 6

aldosterone

Answer 6

controls ion excretion, functions similarily to cortisol in fish

• produced in adrenal cortex
• targets distal tubule and collecting duct, stims Na+ reabs, along w/ secondary water reabs. from urine
• also enhances K+ excretion
• stimulated by increases in K+ levels
• stimulates transcription of ion transporter genes, so it is much slower than vasopressin
• also regulated by angiotensin

Question 7

renin-angiotensin-aldosterone pathway

Answer 7

-hormone system regulating blood pressure and water balance

Question 8

renin

Answer 8

-secreted when decreasing bp and GFR
-juxtaglomerular cells secrete renin
controlled 3 ways:
1. baroreceptors in juxtaglomerular cells release renin when bp is low
2. macula densa cells in distal tubule respond to decreases in flow via signal to juxtaglomerular cells to release renin
3. symp. neurons in medulla oblongata trigger renin secretion in response to low BP

Question 9

angiotensin 2 production

Answer 9

angiotensinogen produced in the liver

• renin converts angiotensinogen into angiotensin 1, and angiotensin converting enzyme (ACE) on epithelia of vessels converts it into angiotensin 2
• acts on kidney, brain, heart, adrenal cortex, and blood vessels

Question 10

angiotensin 2 function

Answer 10

• synth and release of aldosterone from adrenal cortex
• synth and release of vasopressin/adh from pituitary gland
• reabsorption of Na and water (in conjunction w/ aldosterone)
• vasoconstriction of postglomerular vessels

Question 11

RAA pathway and regulation of blood pressure

Answer 11

• angiotensin 2=vasoconstrictor, raising bp by increasing resistance
• aldosterone increase Na+(and water) retetion, increasing bp by increasing blood volume
• vasopressin increases water reabsorption and peripheral resistance, increasing bp by increases volume and resistance

Question 12

atrial natriuretic peptide

Answer 12

produced in atria

• secreted in response to stretch associated with increase in blood volume
• ANP increases urine output and therefore lower blood volume and pressure
• acts as an antagonist with RAA pathway:increasing excretion of Na+ in urine
• increases GFR by relaxing contractile cells controlling size of filtration slits of glomerulus
• inhibits secretion of vasopressin

Question 13

thirst

Answer 13

detected and controlled by hypothalamus

• osmoreceptors monitor levels of body fluids
• receptors monitor levels of angiotensin 2 active in water reabs
• increased osmolarity and decreased fluid levels stims thirst centers

Question 14

control during dehydration

Answer 14

-decrease water intake=dec plasma vol=dec bp=> fluid shift from interstitial to blood, causing increased plasma volume, along with decreased GFR (and therefore dec urine production) from vasoconstriction, and increased h2o reabs from high plasma osmolarity

Question 15

mean arteria pressure=

Answer 15

cardiac output * total peripheral resistance

Question 16

GFR control during dehydration

Answer 16

• increase water reabs
• increase water intake
• decrease sodium reabs

Question 17

why does alcohol make you urinate

Answer 17

-is a diuretic, interferes with post pit, inhibiting vasopressin/adh, so water is not reabs

Question 18

why does scuba cause urination

Answer 18

• blood shunted to core in response to cold
• increases MAP
• increased cardiac flow triggers baroreceptors in atria to produce ANF
• ANF inhibits renin secretion ( thus production of angiotensin and adh)
• stims aldosterone release
• leads to increase excretion of water and sodium, and lowers blood pressure, reducing workload of heart

Question 19

vascular response to dehydration

Answer 19

1. fluid shitft mechanism moves water from interstitial to blood
2. increased h2O recovery from medulla
3. increased cardiac output, increasing stroke volume and rate
4. increased total peripheral resistance by inducing vasoconstriction on arerioles
5. decreased GFR: not due directly to dec BP, but vasoconstriction

Question 20

hormonal response to dehydration

Answer 20

1. increased angiotensin 2: dec flow at distal tubule sensed by macula densa cells, signal to juxtaglomerular cells to increase renin production
2. inc Na+ and H2O reabs due to high osmolarity
3. increased vasopressin due to atrial,carotid, aortic baroreceptors
4. signal to increase thirst at hypothalamus, results in increase water reabs and intake

Question 21

vascular vs renal response to dehydration

Answer 21

• cardiovasular responses aim to restore bp in short term
• excretory system aims to restore osmotic balance in short term and bp in the long term
• systems closely linked, can result in linked disease

Question 22

hormone response to decrease osmolarity during dehydration

Answer 22

1. increase vasopressin due to osmoreceptors in hypothalamus
2. increased thirst due to osmoreceptors
3. decreased aldosterone, dec Na reabs at distal tubule, and decrease in water reabs

Question 23

wonders of urea

Answer 23

1. converts ammonia to less hazardous substance for excretion
2. allows lower NaCl load while still be largely osmoconformer
3. allows adaptation to lower osmotic environments without altering salt balance
4. helps maintain osmotic gradient within kidneys

Question 24

fish kidneys freshwater vs seawater

Answer 24

fresh: larlger glomerulus, ion reabs from primary urine, excretion larger volume of very dilute/hypoosmotic urine
seawater: smaller role in ion/water balance, produce small amounts of isosmotic urine, most excretion done at gills, less complex glomerulus
- some marine fish lack glomerulus, but all fish nephrons LACK loop of henle

Question 25

amphibian kidney

Answer 25

most contend with demands of freshwater and terrestrial life

• water loss controlled by reg of GFR, H2O recovery in bladder
• structure and function changes durign metamorphosis: pronephron in larval, and more mammal-like nephron as adult

Question 26

terrestrial animals

Answer 26

• have kidneys that help with water conservation
• major innovation is LOOP OF HENLE, allowing productinog of concentrated, hyperosmotic urine in birds and mammals
• birds and reptile without loop of henle conserve water by excreting URIC ACID, which is non-soluble
• some reptiles have reduced or lack glomerulus

Question 27

mammals producing more concentrated urine have…

Answer 27

longer loop of henle and thicker medulla