module 12 regulation

Question 1

concentration gradient in loop of henle

Answer 1

longer loop -> inc. concentration of filtrate

Question 2

steps of concentration gradient

Answer 2

1. solutes leave ascending loop -> interstitium
   - > inc. concentration gradient in interstitium, inc. osmolality
2. water leaves descending loop -> interstitium
   - > inc. solute concentration in descending loop, dec. osmolality in interstitium
3. H2O not permeable in ascending loop, lose solutes -> dec. concentration in ascending loop.

Question 3

countercurrent multiplier

Answer 3

blood of capillaries is running opposite of nephron

continuous cycle of ascending removing solutes and descending release H2O to try and equalize

Question 4

ADH

Answer 4

ADH released in response to high blood osmolality and by low blood volume
-> dec. blood flow to renal medulla -> minimizing depletion of solutes in blood stream
ADH causes walls of collecting ducts to become more permeable to water -> absorption of water into interstitium -> vasa recta

Question 5

dilution of urine

Answer 5

excess extracellular fluid dec. ADH secretion

-> reduce water channels in the collecting ducts

Question 6

GFR determined by

Answer 6

filtration pressure in glomeruli and by permeable surface of glomerular membrane

• affected by hydrostatic/oncotic pressure on either side of membrane
• • main driving force is hydrostatic pressure in capillaries
• • oncotic pressure d/t proteins in blood opposes filtration

Question 7

factors affecting filtration pressure

Answer 7

blood volume
autoregulation 
altering pressure in bowmans capsule
low plasma proteins 
mesangial cells in glomerulus

Question 8

Blood volume and filtration pressure

Answer 8

• inc. blood volume -> inc. BP -> inc. glomerular hydrostatic pressure -> inc. GFR and inc. filtrate
• dec blood volume -> dec. BP -> dec. glomerular hydrostatic pressure -> dec. GFR and dec. filtrate

Question 9

auto-regulation and filtration pressure

Answer 9

adjusts arterial resistance to maintain relatively steady state of blood flow despite perfusion pressure

• stretch response of afferent arterioles
• inc. BP -> vascular smooth muscle constriction to keep blood flow at same rate.
• • myogenic autoregulation

Question 10

altering pressure in bowmans capsule and filtration pressure

Answer 10

obstructin in tubules or collecting ducts -> inc. pressure in bowmans capsule -> dec. GFR r/t inc. hydrostatic pressure in bowmans.

Question 11

low plasma proteins and filtration pressure

Answer 11

dec. albumin -> inc. GFR r/t dec. oncotic pressure

Question 12

mesangial cells in glomerulus and filtration pressure

Answer 12

alter surface area for filtration

• contraction -> squeezing capillary cells together -> dec. GFR
• relaxation -> inc. premeable surface area -> inc. GFR

Question 13

RAAS

Answer 13

renin acts upon liver -> angiotensinogen -> inc. angiotensin I -(ACE)-> Angiogensin II -> adrenal cortex -> inc. aldosterone -> distal nephron -> reabsorption of Na and H2O

Question 14

juxtaglomerulo apparatus

Answer 14

regulatory structure, composed of

• glomerulus
• macula densa cells
• juxtaglomerular cells

Question 15

macula dense cells

Answer 15

near end of ascending loop of Henle, which is in contact with glomerulus and JG cells

• sense change in NaCl concentration:
  inc. GFR -> inc. NaCl delivered to distal tubule -> inc. Na-K pump activity -> adenosine and ATP production
• Adenosine: contraction of afferent arterioles and relaxation of efferent arterioles -> dec. GFR
• Helps distribute GFR evenly among nephrons

Question 16

Justaglomerular cells

Answer 16

around glomerular arterioles, release renin
Baroreceptor mechanism:
- inc. blood pressure in afferent arteriole -> inhibition of renin release
- dec. blood pressure -> renin release
SNS mechanism:
- B1-adrenergic nerves stimulate renin release

Question 17

ADH (vasopressin)

Answer 17

secreted from post pituitary in response to inc. osmolality

• > principal cells in collecting tubules translocate aquaporins to apical membrane
• > H2O reabsorption in vasa recta

Question 18

insufficient ADH

Answer 18

DI
nephrogenic DI (collecting tubules unresponsive to ADH)

Question 19

aldosterone and AII

Answer 19

produced when JG cells release renin in r/t
- dec. blood flow to kidney
- dec. Na levels
- activation of SNS
restore blood volume and pressure to nml
reabsorption of Na and H2O

Question 20

ANP

Answer 20

released from atrial cells in response to inc. blood volume -> inc. stretch

• inhibits actions of AII
• > Na and H2O excretion
• > dec. blood volume, osmolality unchanged

Question 21

urodilatin

Answer 21

peptide secreted by distal and collecting tubules in response to inc blood volume
- inhibits Na and H2O reabsorption

Question 22

uroguanylin and guanylin

Answer 22

peptide hormones produced by neuroendocrine cells in intestine in response to NaCl ingestion

• receptors on proximal tubule and collecting ducts
• inhibit NaCl and H2O reabsorption