L26: Glomerulus and Filtration pt. 2

what stimulates activation of the RAAS system?

1. hypotension

2. hypovolemia

3. increased beta-sympathetic

what inhibits activation of the RAAS system?

1. hypertension

2. hypervolemia

3. decreased beta-sympathetic

what cells are responsible for producing renin?

juxtaglomerular cells

what is different about the baroreceptor mechanism in the kidneys compared to the heart?

• not a reflex since no integrating center

• local = only works on afferent arterioles

what drug inhibits ACE?

enalapril

how does enalapril affect preload?

decreases because it reduces blood volume and venous return

how does enalapril affect afterload?

decreases by reducing vascular resistance

what is the short-term affect of the RAAS?

increases blood pressure

what is the long-term affect of RAAS?

aldosterone increases blood volume

why is renal vascular resistance maintained?

from endothelial vasodilatory function

why does systemic blood pressure increase from RAAS?

increase in total periphery vascular resistance and blood volume

what are the affects of angiotenin-2?

1. promotes vasoconstriction of efferent arterioles

2. promotes vasoconstriction of systemic blood vessels

3. promotes aldosterone release to increase sodium and water reabsorption

4. stimulates release of ADH to increase fluid intake

what stimuli directly stimulate the secretion of renin by stimulating aldosterone?

1. hyponatremia

2. hyperkalemia

what stimulates afferent arteriole vasodilation?

decreased GFR leads to release of nitric oxide

what stimulates efferent arteriole vasoconstriction?

decreased GFR leads to release of Angiotensin 2

what stimulates afferent arteriole vasoconstriction?

high GFR leads to release of adenosine

what stimulates efferent arteriole vasodilation?

GFR high leading to decreased release of renin

MCQ: what happens to renin release when the tubular flow speed decreases?

renin release increases

what do the afferent arteriole vasoconstriction and efferent arteriole vasodilation feedback mechanisms work on?

juxtaglomerular complex

what happens when GFR is too high (EFFERENT ARTERIOLES)?

1. increased filtrate volume = increased flow speed

2. increased flow speed = increased sodium and chloride to macula densa cells

3. increased absorption of ions in distal tubule= release of adenosiene from macula densa

4. release of adenosine = vasoconstriction

5. macula densa signal to reduce release of renin

6. reduced renin = vasodilation of efferent arteriole

7. vasodilation of efferent arteriole = normal GFR

what activates the efferent arteriolar vasoconstrictor feedback mechanism?

by decreasing the concentration of sodium and chloride ions in the macula densa

what happens when GFR is too low (EFFERENT ARTERIOLES)?

1. decreased tubular flow speed = decreased sodium and chloride ions

2. decreased ions = increased release of renin

3. renin forms angiontensin 2

4. vasoconstriction of efferent arterioles

5. increase in GFR

MCQ: what is the primary response of the afferent arteriole during the myogenic reflex when arterial pressure increases?

vasoconstriction to normalize blood flow

what happens when GFR is too low (AFFERENT ARTERIOLES)?

1. tubular flow increases = increased reabsorption of sodium and chloride

2. increased reabsorption of sodium and chloride = less ions at macula densa

3. macula densa dilates the afferent arteriole via nitric oxide

4. increase GFR

what two autoregulatory systems control the glomerular perfusion and the GFR?

1. myogenic reflex

2. tubuloglomerular feedback

myogenic reflex

is a mechanism that helps maintain constant blood flow to the kidneys through vasoconstriction and vasodilation of arterioles

what happens when there is an increase in arterial blood pressure?

wall of arteriole is stretched and blood vessel will respond with vasoconstriction to return blood pressure back to normal

what happens when there is a decrease in arterial blood pressure?

afferent arteiole is less stretched decreasing the GFR and relaxing smooth muscle

what range is the myogenic reflex efficient over?

blood pressure range of 80-189 mmHg

what happens when GFR is too low?

increased retention of waste products

what happens when GFR is too high?

excess excretion of valuable solutes and water

pressure diuresis

an increase in blood pressure is accompanied by a slight increase in GFR to increase urinary output

autoregulation

intrinsic mechanisms to maintain teh GFR at almost constant

MCQ: how does the tubuloglomerular feedback contribute to the autoregulation of the GFR?

by detecting sodium concentration at the macula densa and signaling afferent arteriole changes

MCQ: what is the main purpose of autoregulation in renal blood flow?

maintain constant GFR despite blood pressure changes