lecture 15 (T3): micturition and glomerular filtration

Question 1

how are sensory signals from bladder stretch receptors conduction to sacral region of spinal cord

Answer 1

via pelvic nerves

Question 2

how are sensory signals from bladder stretch receptor conducted reflexively back to bladder

Answer 2

via parasympathetic nerves

Question 3

what are the major functions of nephrons

Answer 3

get rid of waste materials (urea, creatinine, uric acid, bilirubin
regulate water, electrolyte balance, body fluid osmolarity
regulate arterial pressure
regulate acid-base balance
secretion, metabolism and excretion of hormones, gluconeogenesis

Question 4

how is arterial pressure regulated long term in nephrons

Answer 4

excrete variable amounts of sodium ions and water

Question 5

how is arterial pressure regulated short term in nephrons

Answer 5

secrete hormones and vasoactive factors such as renin

Question 6

what hormones are secreted, metabolized, and excreted from nephrons

Answer 6

erythropoietin

active form of vitamin D

Question 7

what are the 3 processes that determine the rates at which different substances are excrete in urine

Answer 7

filtration, reabsorption and secretion

Question 8

what is the mathematical expression of the urinary excretion rate

Answer 8

fitration rate-reabsorption rate+ secretion rate

Question 9

what is the first step in urine formation

Answer 9

filtration

Question 10

what are the components of the glomerular filtrate

Answer 10

water, ions, glucose, urea

Question 11

what is the equation for the filtration fraction

Answer 11

GFR/renal plasma flow

Question 12

what is the fraction of renal plasma flow that is filtered

Answer 12

20%

Question 13

why are some low-molecular weight substances not freely filtered

Answer 13

they are partially bound to proteins

Question 14

what are the 3 layers of the filtration barrier

Answer 14

endothelium (with fenestrae and negative charge)
basement membrane (with collagen and proteoglycan fibers and strong negative charges)
podocytes (with negative charges)

Question 15

what is GFR determined by

Answer 15

balance of hydrostatic and colloid osmotic forces acting across capillary membrane
capillary filtration coefficient

Question 16

what is the filterability of water

Answer 16

1.0

Question 17

what are some diseases that lower glomerular capillary filtration coefficient

Answer 17

chronic uncontrolled hypertension and diabetes mellitus

Question 18

define minimal change nephropathy

Answer 18

loss of negative charges on the basement membrane

Question 19

define hydronephrosis

Answer 19

distension and dilation of renal pelvis and calyces

Question 20

what is the numerical value for glomerular hydrostatic pressure

Answer 20

60 mm Hg

Question 21

what is the numerical value for bowman’s capsule hydrostatic pressure

Answer 21

18 mm Hg

Question 22

what is the numerical value for glomerular capillary colloid osmotic pressure

Answer 22

32 mm hg

Question 23

what is the numerical value for colloid osmotic pressure of bowman’s capsule

Answer 23

zero

Question 24

what is K1

Answer 24

capillary filtration coefficient= product of permeability and filtering surface area of capillaries

Question 25

what happens to GFR if K1 is increased

Answer 25

it increases

Question 26

what factors influence glomerular capillary colloid osmotic pressure

Answer 26

arterial plasma colloid osmotic pressure | filtration fraction

Question 27

what factors increase glomerular colloid osmotic pressure

Answer 27

increasing filtration fraction

Question 28

what variables determine GFR

Answer 28

arterial pressure (proportional) afferent arterial resistance (as it increases, GFR decreases) efferent arteriole resistance (proportional)

Question 29

what is the equation for renal blood flow

Answer 29

(renal artery pressure-renal vein pressure)/ (total vascular resistance)

Question 30

all blood vessels of the kidneys are richly innervated by _______________

Answer 30

sympathetic system

Question 31

what are strong activations of renal sympathetic nerves

Answer 31

constrict renal arterioles | decrease renal blood flow and GFR

Question 32

what is endothelia released by

Answer 32

damaged vascular endothelial cells of kidneys and other tissues

Question 33

what disease states lead to an increase in plasma level associated with vascular injury

Answer 33

toxemia of pregnancy acute renal failure chronic uremia

Question 34

what does endothelia contribute to

Answer 34

renal vasoconstriction leading to reduced GFR | hemostasis when a blood vessel is severed

Question 35

what does angiotensin II do in controlling GFR

Answer 35

constricts efferent arterioles | formed in situations associated with decreased arterial pressure or volume depletion

Question 36

why do afferent arterioles seem be protected against the effects of angiotensin II

Answer 36

due to release of prostaglandins and nitric oxide which are vasodilators

Question 37

what is the role of nitric oxide in controlling GFR

Answer 37

derived from endothelial cells | basic peel helps maintain renal vasodilation

Question 38

what do prostaglandins and bradykinin do in controlling GFR

Answer 38

they are vasodilators that may offset effects of sympathetic and angiotensin II vasoconstrictor effects

Question 39

define autoregulation

Answer 39

relative constancy of GFR and renal blood flow

Question 40

what is the primary function of autoregulation

Answer 40

maintain relatively constant GFR allow precise control of renal excretion of water and solutes prevent relatively large changes in GFR and renal excretion that would otherwise occur with changes in blood pressure

Question 41

what is normal GFR

Answer 41

180L/day

Question 42

what are the 2 components of the tubuloglomerular feedback mechanism for autoregulation

Answer 42

an afferent arteriolar feedback mechanism | an efferent arteriolar feedback mechanism

Question 43

where is the macula densa located

Answer 43

distal tubule

Question 44

where are juxaglomerular cells located

Answer 44

in afferent and efferent arterioles

Question 45

what happens to flow rate in loop of henle when GFR decreases

Answer 45

it slows increased reabsorption of sodium and chloride ions in ascending limb decrease in sodium chloride in macula densa

Question 46

what does a decrease in [NaCl] result in (signal from macula dense)

Answer 46

decrease resistance to blood in afferent arterioles | increase renin release from JG cells, angiotensin II and efferent arteriolar resistance

Question 47

what is the major storage site of renin

Answer 47

JG cells