Renal Circulation and Autoregulation

Question 1

The renal artery bifurcates into smaller blood vessels in what order?

Answer 1

Renal artery > Segmental artery > Interlobar artery > Arcuate artery > Interlobular artery > Afferent arteriole

Question 2

Blood leaving the Glomerulus travels into a venule.

True/ False

Answer 2

False

Blood leaving the Glomerulus travels into an Efferent arteriole

Question 3

What is Glomerular filtration rate (GFR)?

Answer 3

This is the volume of blood filtered through the Glomerulus of both kidneys each minute

Question 4

The Glomerulus allows the passage of plasma, proteins, red blood cells and solutes.

True/ False

Answer 4

False

The Glomerulus does not permit the passage of proteins and red blood cells. Plasma and solutes however, are permitted through

Question 5

Renal blood flow is inversely proportional to __________

Answer 5

Arteriole resistance

Question 6

Renal blood flow is directly proportional to __________

Answer 6

Blood pressure i.e. difference in pressures between renal artery and vein

Question 7

__________ and __________ hormones act to increase arteriolar resistance

Answer 7

Adrenaline (Epinephrine)
Angiotensin II

Question 8

Adrenaline is secreted in response to __________

Answer 8

Sympathetic stimulation

Question 9

How does adrenaline affect arteriolar resistance?

Answer 9

Binding to alpha-1 adrenergic receptors on afferent and efferent arterioles.
Causing smooth muscles to contract and arterioles to constrict.
Arteriolar resistance increases

Question 10

Angiotensin II is synthesized in response to __________

Answer 10

Low blood pressure

Question 11

How is Angiotensin II produced from its precursor Angiotensinogen?

Answer 11

JG cells of kidney afferent arterioles produce renin
Renin cleaves Angiotensin I from Angiotensinogen (produced in Liver)
ACE converts Angiotensin I to Angiotensin II

Question 12

Prostaglandin E2 and I2 are secreted during sympathetic stimulation for what purpose?

Answer 12

To dilate the afferent and efferent arterioles to ensure renal blood flow doesn’t get too low even in ‘Fight of Flight’ situations.

Question 13

What is Renal autoregulation?

Answer 13

These are local mechanisms within the kidney that keep GFR and renal blood flow constant over a range of systemic blood pressures.

Question 14

What is the myogenic mechanism of renal autoregulation?

Answer 14

This is the reflex response of Afferent arterioles to changes in blood pressure

Question 15

Discuss the myogenic response during high blood pressure

Answer 15

Smooth muscle cells stretch
CICR contraction occurs due to stretch
Afferent arterioles constrict due to smooth muscle contraction
Increased arteriolar resistance lowers blood pressure to normal

Question 16

What is the tubuloglomerular mechanism?

Answer 16

This is a feedback that links the GFR to the salt concentration in the tubules

Question 17

_____________ are specialized cells found in the distal convoluted tubule that serve as salt sensors

Answer 17

Macula Densa cells

Question 18

Discuss the tubuloglomerular mechanism as it occurs during high blood pressure

Answer 18

High blood pressure means high salt levels filtered into tubules
Macula Densa cells secrete adenosine in response to high salt levels
Adenosine acts on Afferent arterioles causing vasoconstriction
Increased arteriolar resistance causes low GFR and thus low salt levels filtered

Question 19

What effect does adenosine have on Juxtaglomerular cells?

Answer 19

Inhibits their renin secretion

Question 20

Macula Densa cells secrete ____________ in response to high salt levels

Answer 20

Adenosine

Question 21

Macula Densa cells secrete _______________ in response to low salt levels

Answer 21

Prostaglandin