HSF 4 - Unit 1 Physiology: Organization of the Urinary System

Question 1

what are the major functions of the kidney?

Answer 1

homeostatic, excretory, and endocrine

Question 2

what are the homeostatic functions of the kidney?

Answer 2

regulation of ECF blood pressure by volume control
regulation of ECF electrolyte composition by osmolality control
regulation of ECF acid-base balance

Question 3

what are the excretory functions of the kidney?

Answer 3

metabolic waste products like urea and creatinine

foreign substances and toxins like drugs and pesticides

Question 4

what are the endocrine functions of the kidney?

Answer 4

regulation of blood pressure with renin
EPO for RBC production
Vitamin D activity and gluconeogenesis (50%)

Question 5

what are the 2 types of nephrons? what are the differences?

Answer 5

cortical (7/8) shorter loops, juxtamedullary (1/8) longer loops and bigger glomeruli so can concentrate urine more

Question 6

what are the parts of the early nephron? what are the functions of each part?

Answer 6

glomerulus (filtration), PT (reabsorption of salts and drug secretion) LOH (DL, reabsorption of water)

Question 7

what happens if you lose nephrons? what is considered the ‘point of no return’?

Answer 7

they adapt to compensate, but if you lose over 50% you are pushed towards kidney failure/uremia

Question 8

what happens to nephrons as you age?

Answer 8

<10% lost per decade after 40 years of age, by age 80 are left with about 480k-720k

Question 9

how many nephrons do we have?

Answer 9

800k-1.2 mil per kidney

Question 10

what are the parts of the mid to late nephron? what are the functions of each part?

Answer 10

LOH (AL, NaCl reabsorption and adjusting salts)

DCT (adjusting salts), CD (adjusting water)

Question 11

what is the flow of fluid in nephrons to the rest of the kidney? how does it get moved into the rest of the urinary tract and what control is it under?

Answer 11

fluid from nephrons dumps into collecting ducts, connected to calyces that have a stretch induced pacemaker myogenic activity, which induces peristaltic contractions from calyces to the renal pelvis to the ureters; the lower ureter peristalsis pumps the fluid into the bladder; parasympathetic control increases peristalsis where sympathetic inhibits peristalsis

Question 12

what muscles control micturition?

Answer 12

detrusor (smooth muscle around the bladder), internal sphincter, external sphincter, ureter

Question 13

how does the detrusor muscle control micturition?

Answer 13

micturition reflex via gap junctions, contractions +40-60 cm H2O; deltaP = urination

Question 14

how does the internal sphincter muscle control micturition? what is is composed of?

Answer 14

involuntary tonic contraction; detrusor muscle + elastic tissue

Question 15

how does the external sphincter muscle control micturition?

Answer 15

voluntary skeletal muscle that the higher brain centers control to prevent urination

Question 16

how does the ureter control micturition?

Answer 16

high intraluminal pressure pushes on ureter to reduce reflux like a valve

Question 17

what is the micturition reflex?

Answer 17

an autonomic spinal cord reflex using self-regenerating contractions to raise bladder pressures

Question 18

what is the stretch reflex of the bladder?

Answer 18

it is initiated by sensory stretch receptors in the bladder wall, stretch is sent to the CNS via sensory afferent pelvic nerve fibers and comes back to bladder via efferent parasympathetic pelvic nerve fibers

Question 19

what nerves control the bladder?

Answer 19

hypogastric, pelvic, pudendal

Question 20

how does the hypogastric nerve control the bladder?

Answer 20

sympathetic, B3R on the bladder that is relaxed with NE, a1R on the internal sphincter that contracts with NE

Question 21

how does the pelvic nerve control the bladder?

Answer 21

parasympathetic, M3R on the bladder, contraction with Ach; cGMP on the internal sphincter that relaxes with NO

Question 22

how does the pudendal nerve control the bladder?

Answer 22

somatic, external sphincter has Nicotinic R that contracts with Ach

Question 23

what does a decrease in sympathetic activity cause?

Answer 23

relaxation of internal urethral sphincter

Question 24

what does an increase in parasympathetic activity cause?

Answer 24

contraction of the detrusor muscle

Question 25

what does a decrease in somatic motor neuron activity cause?

Answer 25

relaxation of external urethral sphincter

Question 26

what does an increased volume of fluid in the bladder cause?

Answer 26

expansion of the wall and activation of the stretch receptors, which cause variable effects on the spinal cord

Question 27

why does the kidney get ____% of the cardiac output?

Answer 27

20; because it filters the blood even though it is a fairly small organ

Question 28

what is the path of blood flow through the kidney?

Answer 28

arcuate a., interlobular a., afferent arteriole, glomerulus, efferent arteriole, peritubular capillaries, vasa recta, interlobular v., arcuate v.

Question 29

what is special about the afferent arteriole?

Answer 29

high pressure where hydrostatic pressure > oncotic pressure to drive filtration (water pushed out blood vessel)

Question 30

what is special about efferent arteriole and peritubular capillaries?

Answer 30

lower pressure as flows out in this direction with oncotic > hydrostatic (high concentration of unfiltered blood proteins) to allow reabsorption of fluid

Question 31

what is special about the vasa recta?

Answer 31

continuations of efferent arterioles that run parallel to the collecting tubules and the loops of henle to provide a counter-current, altered osmotic gradient for exchange

Question 32

what is TGF?

Answer 32

tubuloglomerular feedback; nephrons' intrinsic ability to increase GFR (during low Na+ delivery) or decrease it during high Na+ by dilating or constricting the afferent arterioles

Question 33

what composes the JGA?

Answer 33

macula densa cells, juxtaglomerular cells, extracellular mesangial cells

Question 34

what do macula densa cells do?

Answer 34

NaCl sensors, release adenosine to constrict AAs, located in the distal tubular region

Question 35

what do juxtaglomerular cells do?

Answer 35

aka granular cells, SMCs of the afferent arteriole and secrete renin due to low pressure, input from macula densa or sympathetic input

Question 36

what do extracellular mesangial cells do?

Answer 36

unclear function but could help transmit signals for TGF or alter glomerular flow by contraction

Question 37

what are the 4 mechanisms the kidney filters the blood, regulates the ECF, and produces urine?

Answer 37

filtration (glomerular capillary to bowman's space), tubular reabsorption (tubular lumen to peritubular capillary plasma), tubular secretion (peritubular plasma to tubular lumen), excretion (excreted urine = filtration - reabsorption +secretion)

Question 38

how does the kidney handle protein?

Answer 38

all stays in the vasculature

Question 39

how does the kidney handle inulin?

Answer 39

a portion moves through vasculature while some goes through the nephron for excretion

Question 40

how does the kidney handle K, Na, and urea?

Answer 40

a portion through vasculature, some through the nephron, some of this portion gets reabsorbed into vasculature

Question 41

how does the kidney handle glucose and bicarb?

Answer 41

some through vasculature and others through nephron but reabsorbed into vasculature

Question 42

how does the kidney handle PAH?

Answer 42

some through the vasculature and this gets secreted to nephron, other straight through nephron

Question 43

how does the kidney handle creatinine?

Answer 43

some through vasculature, some through nephron, of vasculature some secreted

Question 44

what are the aspects of the glomerular filtration barrier?

Answer 44

fenestrated capillary endothelium, glomerular basement membrane, podocyte with filtration slit diaphragm

Question 45

why is the charge of the basement membrane important?

Answer 45

negative, stops proteins from entering; if lost lose oncotic pressure so less force keeping water out of interstitial space and end up with edema

Question 46

what do the endothelial cells contribute to the barrier?

Answer 46

fenestrations that are size selective, 70 nm holes (RBCs, WBCs, no platelets)

Question 47

what do the podocyte cells contribute to the barrier?

Answer 47

visceral epithelial cells with foot processes (pedicels), overlie the BM, size selective with 40 nm slit pores

Question 48

what would mutations in the podocyte cause?

Answer 48

proteinuria/nephrotic syndrome

Question 49

what substances are freely filterable? which ones are not?

Answer 49

water, Na, glucose, inulin; myoglobin, albumin (very little for albumin); positive charged easier

Question 50

what is NFP?

Answer 50

(Pgc - Pbs) - (Pigc - Pibs)

Question 51

what is the major factor in filtration?

Answer 51

Pgc/glomerular capillary hydrostatic pressure; is proportional to filtration

Question 52

what is the difference between plasma and filtrate?

Answer 52

way more protein in the plasma

Question 53

what happens with LPS?

Answer 53

severe inflammatory signal that causes gut permeability

Question 54

what happens with EC swelling?

Answer 54

inhibits movement across the membrane

Question 55

what happens with diabetes?

Answer 55

thickening of the BM,, inhibition of movement across membrane

Question 56

what happens with minimal change disease?

Answer 56

proteinuria, protein molecules spill into the urine because of abnormalities in the capillary wall

Question 57

what happens with glomerulonephritis?

Answer 57

any renal disease where the immune cells destroy the glomerular barrier causing proteinuria