Structure and function of the kidney III

Question 1

What can you say about homeostatic regulation of BP and blood volume

Answer 1

integrated

Question 2

response to low blood volume and low BP

Answer 2

volume receptors in atria and cartoid and aortic baroreceptors trigger homeostatic reflexes
CV: incr cardiac output
Behaviour: thirst causes incr water intake, incr ECF and ICF volume
Kidneys: conserve H2O to minimise further volume loss

Overall incr blood pressure

Question 3

Response to high blood volume and BP

Answer 3

Volume receptors in atria, endocrine cells in atria and cartoid and aortic baroreceptors trigger homeostatic reflexes
CV: decr cardiac ouput, vasodilation
Kidneys: excrete salts and h2o in urine, decr in ECF and ICF volume

Overall decr BP

Question 4

renin-angiotensin-aldosterone system

Answer 4

controls responses of the CV and renal systems to decreases in BP/volume

Question 5

How does the renin-angiotensin aldosteone system work

Answer 5

1. Increased blood K+ or decr Na+ cause adrenal cortex to incr secretion of aldosterone into circulation
2. Kidneys detect decr BP and so incr secretion of renin into circulation- renin converts angiotensinogen (from teh liver) into angiotensin I. A converting enzyme converts angiotensin I to angiotensin II, causing contraction of blood vessels and incr BP
3. Angiotensin II causes incr secretion of aldosterone, which affects the kidneys
4. Aldosterone stimulation of kidneys causes Na+ retention,, K+ secretion and decr water loss

Question 6

Angiotensin II

Answer 6

stimulus: low blood volume or pressure stimulates renin-induced production
at PCT
Effects: incr Na+, Cl- and water reabsorption–> incr BV

Question 7

Angiotensin II

Answer 7

stimulus: low blood volume or pressure stimulates renin-induced production
Site: at PCT
Effects: incr Na+, Cl- and water reabsorption, which incr blood volume

Question 8

Aldosterone

Answer 8

Stimulus: incr angiotensin II levels promotes release from adrenal cortex
Site: at collecting duct
Effects: incr K+ secretion and Na+, Cl- and water reabsorption, which incr blood volume

Question 9

ADH

Answer 9

regulates reabsorption of water in the collecting duct

vasopressin

Question 10

What happens with high plasma osmorality (incr Na+ intake or dehydration)

Answer 10

sensed by hypothalmic osmoreceptors, leading stimulation of thirst and release of ADH from the posterior pituitary.
Leads to increased water reabsorption by distal nephron

Question 11

Feedback for low BP/

Answer 11

Hypothalamic nerve cells detect incr osmotic pressure
Baroreceptors detect decr BP.
ADH secreted whih leads to vasoconstriction of blood vessels and incr reabsorption in the kidney, less urine.
Leads to incr blood volume and pressure

Question 12

How does ADH work

Answer 12

regulates reversible insertion of water pores in the apical membrane of cells in the collecting duct

1. Vasopressin binds to membrane receptor on basolateral membrane of collecting duct epithelial cell
2. Receptor activates cAMP second messenger system
3. Cell inserts AQP2 water pores into apical membrane via vesicles carrying Aquaporin -2 water pores
4. Water moves by osmosis into the blood

Question 13

Atrial Natriuretic Peptide - main action

Answer 13

Decreases reabsorption of Na+ and water in the DCT an CCD (cortical collecting duct)

Heart full of fluid due to incr in blood volume, incr BP in right atrium, ANP secretion, leading to more Na+ secretion and more water loss. More urine so decr BP.

Question 14

ANP-other actions

Answer 14

decr aldosterone secretion

decr ADH secretion

Question 15

clearance of a solute

Answer 15

rate a which a solute disappears from the body by excretion/metabolism

Question 16

Inulin

Answer 16

Freely filtered through the glomerelus, but is neither reabsorbed nor secreted.
Filtration and excretion are the same.
All inulin filtered in kidney is recovered in the urine and the following can be stated:
GFR= inulin clearance
100mL plasma cleared/min
(where GFR = 100)

Question 17

Glucose clearance

Answer 17

All glucose that filters is reabsorbed

0 mL plasma cleared/min

Question 18

Urea clearance

Answer 18

net reabsorption
If filtration is greater than excretion, there is net reabsorption.
If clearance is less than GFR, there is net reabsorption.
50mL plasma cleared/min

Question 19

Penicillin clearance

Answer 19

net secretion
If excretion is greater than filtration, there is net secretion.
If clearance is greater than GFR, there is net secretion.
150mL plasma clearance/min

Question 20

If clearance of a solute is zero

Answer 20

can conclude it’s been reabsorbed

Question 21

If clearance less than GFR

Answer 21

can conclude net reabsorption

Question 22

if clearance more than GFR

Answer 22

can conclude net secretion

Question 23

H+ input

Answer 23

fatty acids and AAs in diet

CO2 and lactic acid from metabolism

Question 24

Buffers

Answer 24

HCO3- in ECF
Proteins, haemoglobin, phosphates in cells
Phosphates, ammonia in urine

Question 25

H+ output

Answer 25

Renal: H+, delayed response, long term
ventilation: CO2, rapid response, short term

Question 26

What does acid base balance depend on

Answer 26

respiratory and renal systems

Question 27

acidosis

Answer 27

pH too low

Kidney secretes H+ and reabsorbs HCO3- and K+

Question 28

Alkalosis

Answer 28

pH too high

Kidney excretes K+ and HCO3- reabsorbs H+