Test 2 General Questions Flashcards
JG Cells release renin in response to…?
- Decreased BP in AA (JG acts like a baroreceptor)
- A paracrine secretion by the Macula Densa
- Catecholamines
What does the Macula Densa measure?
-“flowmeter” measures electrolyte delivery
What is Renin?
-An enzyme with angiotensinogen (plasma protein made by the liver) as its substrate.
What does Renin do?
Cleaves angiotensinogen into Angiotensin 1.
What is Angiotensin 1?
A substrate for ACE (angiotensin converting enzyme).
What does ACE (angiotensin converting enzyme) do?
Converts angiotensin 1 into angiotensin 2.
What does angiotensin 2 do?
- potent systemic vasoconstriction
- potent vasoconstriction at AA and EA (more so at EA)
- Increases activity of Na+K+ATPase at proximal tubule
- Promotes ADH secretion
- Promotes Aldosterone secretion
- Inhibits renin release by JG cells
- Stimulates thirst center in brain
What is the effect of increased activity of Na+K+ATPase at the proximal tubule?
Increased (higher than 67%) reabsorption
What does Aldosterone do?
- Increases activity of Na+K+ATPase in aLOH
- Increases # of luminal ports in DCT, MCD, and CCD
- Overall, increases reabsorption of water
What happens when Aldosterone increases the activity of Na+K+ATPase in aLOH?
Increase reabsorption of water
What happens when Aldosterone increases the # of luminal ports in the DCT, MCD, and CCD?
Increase reabsorption of water
What does ADH do?
- potent systemic vasoconstrictor
- promotes contraction of mesangial cells
- Increases activity of Na+K+ATPase in aLOH
- Increases AQUAPORINS in the luminal membrane which increases H20 permeability of entire CD
- Increases UREA TRANSPORTERS in the luminal membrane which increases urea permeability of inner medullary portion of CD
What happens when ADH ncreases the number of aquaporins in the luminal membrane?
Increases water permeability of entire CD
What happens ADH increases urea transporters in the luminal membrane?
Increases urea permeability of inner medullary part of the CD
What is ANP?
Atrial Natriuretic Peptide
- released by atrial myocytes in response to stretch
- the atrial myocytes act as baroreceptors
What does ANP do?
- potent systemic vasoDILATOR
- promotes relaxation of mesangial cells
- Opposes aldosterone by decreasing reabsorption of Na+ in the MCD
- Acts to decreases secretion of ADH, Aldosterone, and Renin
- Decreases sensitivity of macula densa
What happens when ANP decreases sensitivity of the macula densa?
As ANP levels increase, the macula densa secretes less paracrine vasoconstrictor than it would in response to electrolyte delivery
What is Norepinephrine and Epinephrine?
Catecholamines
What does NE/E (catecholamines) do?
-Stimulates JG cells which have B1 receptors that secrete renin
-Stimulates AA and EA that have a1 adrenergic receptors that results in vasoconstriction, decreased GFR, and increased filtration fraction
-increase reabsorption in proximal tubule (adds to angiotensin 2 effect)
increase solute reabsorption at aLOH (adds to ADH and aldosterone effect)
What does prostaglandins and NO do?
- Vasodilatory
- combats constrictive effects of angiotensin 2 at AA and EA
What is the most common hydration state?
Hypertonic dehydration
What happens when BP decreases?
- Decreased stretch and thus firing of baroreceptors
- Decreased PNS
- Increased SNS
What are the direct effects of increased SNS due to a blood pressure decrease?
- decreased venous capacitance
- vasoconstriction
- increased contractility
- increased heart rate
When SNS increases, venous capacitance decreases. What does this cause?
-increased venous return–>increased preload–>increased stroke volume–>increased CO–>increased BP
What is a direct effect of vasoconstriction due to SNS increase? What does this cause?
Capillary fluid shift and increased TPR–>increased BP
