regulation of homeostasis by the kidney

Question 1

Body pH

Answer 1

Between 7.35 and 7.45

Death occurs at <6.8 or >8.0

Question 2

Types of buffer systems

Answer 2

Carbonic acid/bicarbonate
Protein
Phosphate
HCO3- (must be reabsorbed by kidneys)

Question 3

Relationship between pH and plasma CO2

Answer 3

Inverse relationship

Question 4

Changes in pH detected by

Answer 4

Peripheral chemoreceptors

These act on respiration centres in the brain to adjust respiration rates

Question 5

Regulation of acid base balance

Answer 5

HCO3- in filtrate is reabsorbed, and H+ is secreted or Renal Tubular Acidosis occurs
& vice versa
Intercalated cells help H+ secretion and HCO3- reabsorption

Question 6

Preventing acidosis

Answer 6

Excretion of CO2 from lungs

Secretion of H+ from kidneys

Question 7

Acidosis

Answer 7

Inadequate ventilation

Loss of HCO3- in diarrhoea and urine

Question 8

Treatment of metabolic acidosis

Answer 8

IV isotonic HCO3-

IV lactate solution

Question 9

Treatment of respiratory acidosis

Answer 9

Restore ventilation
Treat underlying dysfunction
Give IV lactate solution

Question 10

Alkalosis

Answer 10

Hyperventilation
Use of H+ in metabolism
Loss of H+ in vomit/urine

Question 11

Treatment of metabolic alkalosis

Answer 11

Electrolytes
IV Cl- solution
Treat underlying disorder

Question 12

Treatment of respiratory alkalosis

Answer 12

Treat underlying disorder
Breathe into a paper bag
IV Cl-solution

Question 13

Osmoreceptors and baroreceptors

Answer 13

Increased plasma osmolality stimulates osmoreceptors = ADH release = increased ECV
Increased plasma osmolality also triggers different osmoreceptors which trigger thirst

Question 14

Low pressure blood volume receptors - v important

Answer 14

Large systemic veins
Cardiac atria
Pulmonary vasculature

Question 15

High pressure arterial stretch receptors - less important

Answer 15

Carotid sinus
Aortic arch
Renal afferent arteriole

Question 16

Baroreceptors

Answer 16

Detect changes in ECV
Central vascular sensors
Sensors in CNS and liver

Question 17

Parallel effector pathways which act on kidney

Answer 17

RAAS
Sympathetic NS
ADH release
ANP release
These change renal haemodynamics and Na+ transport by renal tubule cells

Question 18

What stimulates renin release from JGA cells

Answer 18

Decreased renal perfusion pressure detected in afferent arteriole
Decreased Na+ in distal tubule - macula densa - the renal Na+ sensor
Decreased systemic BP -> symptoms NS supplying JGA

Question 19

Actions of Ang II

Answer 19

Enhances tubular Na+ transport in kidney
Stimulation of aldosterone release from adrenal cortex
Acts on hypothalamus to stimulate thirst and ADH release
Vasoconstriction of renal/systemic vessels so BP increases
Renal cell hypertrophy so more protein synthesis of Na+ transporters and channels

Question 20

Actions of Aldosterone

Answer 20

Stimulates Na+ reabsorption in DT and CD
Increases ECV and lowers plasma K+
Conserves Na+ and water - but variation in plasma K+ levels

Question 21

ANP

Answer 21

Lowers ECV
Increased ECV causes stretch -> ANP release, promoting natriuresis and renal vasodilation (again more Na+ excreted)
More Na+ reaches macula dense -> reduces effects of Ang II

Question 22

What synthesises and stores ANP

Answer 22

Atrial myocytes