renal 2

Question 1

what is filtration?

Answer 1

filtration of plasma from the glomerular capillaries into the kidney tubules is the first step in urine formation
-RBCs and plasma proteins remain in the blood, plasma and dissolved solutes make up filtrate
-of all the plasma that enters into the Bowman’s capsule, only 20% is filtered (filtration fraction), 80% continues on to the peritubular capillaries

Question 2

what is the equation for filtration?

Answer 2

Question 3

what is the renal corpuscle?

Answer 3

Question 4

what is the triple filtration barrier?

Answer 4

Question 5

what are mesangial cell?

Answer 5

-supportive and connective tissue cells
-can influence filtration by reducing surface area (by contracting)

Question 6

what are the three pressures govern filtration from glomerular capillaries into the renal tubules?

Answer 6

-hydrostatic pressure
-colloid osmotic pressure
-bowman’s capsule hydrostatic pressure

Question 7

what is hydrostatic pressure?

Answer 7

hydrostatic pressure of blood in the glomerular capillaries favors filtration (55mm Hg) (overall blood pressure)

Question 8

what is colloid osmotic (oncotic) pressure?

Answer 8

colloid osmotic pressure of the blood is the pressure gradient due to the presence of plasma proteins and opposes filtration (30 mmHg)

Question 9

what is bowmans capsule hydrostatic pressure?

Answer 9

(fluid pressure) opposes filtration (15mmHg)

Question 10

what is GFR?

Answer 10

glomerular filtration rate
-the volume of fluid that filters from the glomerular capillaries into the bowman’s capsules per unit time

Question 11

how much plasma does GFR in a day?

Answer 11

-normally 125 ml/min or 180L/day
-our plasma volume is about 3L meaning the kidneys filter our entire plasma volume approximately 60 times per day
-if it was not reabsorbed we would run out of plasma in about 24 minutes

Question 12

GFR is ____________

Answer 12

RELATIVELY CONSTANT
-relatively constant over a wide range of blood pressures

Question 13

what is GFR primarily regulated by ____________

Answer 13

renal arterioles (afferent and efferent)

Question 14

how does the GFR remain relatively constant?

Answer 14

-renal blood flow is dependent on overall resistance, which is determined by the resistance in both the afferent and efferent arterioles
-if afferent arteriole resistance decreased and efferent stayed the same then RBF would increase, hydrostatic pressure increase and GFR increase

REGULATION MAINLY OCCURS AT THE AFFERENT ARTERIOLES

Question 15

what happens for the GFR to decrease and increase?

Answer 15

Question 16

what is the GFR autoregulation?

Answer 16

two auto-regulatory mechanisms maintain a relatively stable GFR in the face of normal blood pressure fluctuations
-to protect the filtration barriers from high blood pressure that would cause damage

Question 17

what are the two mechanisms of autoregulation of GFR?

Answer 17

-myogenic response of the afferent arterioles (myogenic autoregulation)
-tubuloglomerular feedback

Question 18

what is myogenic autoregulation?

Answer 18

contraction in response to stretch of the vascular smooth muscle

Question 19

what is the graph of myogenic autoregulation?

Answer 19

Question 20

what is tubuloglomerular feedback?

Answer 20

-local control pathway in which fluid flow through the tubule portion of the nephron influences GFR

Question 21

what is the tubuloglomerular feedback graph?

Answer 21

increased NaCl transport in macula densa cells/increased cilia movement

Question 22

what other two factors can influence GFR? and how is it allowed?

Answer 22

-sympathetic neurons
-hormones

-integrating centers outside the kidneys are capable of overriding the local control mechanisms by altering resistance or filtration coefficient

Question 23

how can sympathetic neurons influence GFR?

Answer 23

-sympathetic neurons release norepinephrine that acts on a1 adrenergic receptors on both afferent and efferent arterioles leading to vasoconstriction
-sympathetic activation only really alters GFR when there is a sharp rapid drop in blood pressure (ex: hemorrhage or severe dehydration when water needs to be conserved)

Question 24

how do hormones influence GFR?

Answer 24

-two important hormones that modulate arterioles resistance are angiotensin II, which is a potent vasoconstrictor and prostaglandins, which act as vasodilators
-these hormones are also believed to alter the filtration coefficient by acting on podocytes and/or mesangial cells
-modulation of podocytes changes the size of the filtration slits altering permeability for filtration
-contraction of mesangial cells alters capillary surface area available for filtration