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Anatomy and Physiology II > Lecture 24 > Flashcards

Lecture 24 Flashcards

1
Q

Nephrons and collecting ducts perform 3 basic processes:

A
  1. glomerular filtration
  2. tubular reabsorption
  3. tubular secretion
    2 and 3 = both filtration happens once
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2
Q

glomerular filtration:

A

a portion of the blood plasma is filtered into the kidney

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3
Q

tubular reabsorption:

A

water & useful substances are reabsorbed into the blood

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4
Q

tubular secretion:

A

wastes are removed from the blood & secreted into urine

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5
Q

Rate of excretion of any substance =

A

rate of filtration + secretion - reabsorption

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6
Q

Blood pressure produces

A

glomerular filtrate

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7
Q

Filtration fraction is

A

20% of plasma

why? -circulating rate

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8
Q

Filtering capacity enhanced by:

A
  • thinness of membrane & large surface area of glomerular capillaries
  • glomerular capillary BP is high due to small size of efferent arteriole
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9
Q

Filtration Membrane: 3 Steps

A 
#1 Stops all cells and platelets - Endothial fenestration stops
#2 Stops large plasma proteins - basal lamina stops
#3 Stops medium-sized proteins, not small ones - slit membrane stops
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10
Q

NFP is

A

total pressure that promotes filtration

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11
Q

NFP equation =

A

GBHP - (CHP + BCOP) = 10mm Hg

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12
Q

Net Filtration Pressure Steps:

A
  1. GBHP Glomerular Blood Hydrostatic Pressure = 55mmHg major force
  2. CHP Capsular Hydrostatic Pressure
  3. BCOP Blood Colloid Osmotic Pressure
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13
Q

What if the concentration is lower than 55 mmHg?

A

no filtration

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14
Q

What if the concentration is more than 55 mmHg?

A

It increased/ more filtration

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15
Q

GFR:

A

Glomerular Filtration Rate

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16
Q

Amount of filtrate formed in

A

all renal corpuscles of both kidneys / minute

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17
Q

Homeostasis requires GFR that is

A

constant

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18
Q

Too high of GFR =

A

useful substances are lost due to the speed of fluid passage through nephron

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19
Q

Too low of GFR:

A

sufficient waste products may not be removed from the body

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20
Q

Changes in net filtration pressure does what?

A

affects GFR by:

  • filtration stops if GBHP drops to 45mm Hg
  • functions normally with mean arterial pressures 80-180
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21
Q

Renal Autoregulation of GFR:

A

Mechanisms that maintain a constant GFR despite changes in arterial BP:

  1. myogenic mechanism
  2. tubuloglomerular feedback
22
Q

myogenic mechanism:

A
  • systemic increases in BP, stretch the afferent arteriole

- smooth muscle contraction reduces the diameter of the arteriole returning the GFR to its previous level in seconds

23
Q

tubuloglomerular feedback: 1st step =

A
  1. elevated systemic BP raises the GFR so that fluid flows too rapidly through the renal tubule & Na+, Cl- and water are not reabsorbed
24
Q

tubuloglomerular feedback: 2nd step =

A
  1. macula densa detects that difference & releases a vasoconstrictor from the juxtaglomerular apparatus
25
tubuloglomerular feedback: 3rd step =
3. afferent arterioles constrict & reduce GFR
26
Neural Regulation of GFR: Blood vessels of the kidney are supplied by
sympathetic fibers that cause vasoconstriction of afferent arterioles
27
Neural Regulation of GFR: At rest, renal BV
are maximally dilated because sympathetic activity is minimal -renal autoregulation occurs
28
Neural Regulation of GFR: With moderate sympathetic stimulation =
Both afferent & efferent arterioles constrict equally | -decreasing GFR equally
29
Neural Regulation of GFR: With extreme sympathetic stimulation =
Vasoconstriction of afferent arterioles reduces GFR | -lowers urine output & permits blood flow to other tissues
30
Hormonal Regulation of GFR: Atrial natriuretic peptide (ANP)
increases GFR
31
Atrial natriuretic peptide (ANP) does what?
stretch heart = increase BP = hormonal release = normal BP
32
Hormonal Regulation of GFR: Angiotensin II
reduces GFR
33
Angiotensin II has and does what?
potent vasoconstrictor that narrows both afferent & efferent arterioles reducing GFR
34
Normal GFR is so high that volume of filtrate in capsular space in half an hour is
greater than the total plasma volume
35
Nephron must reabsorb
99% of the filtrate
36
PCT with their microvilli do
most of work with rest of nephron doing just the fine-tuning
37
Important function of nephron is tubular secretion:
-transfer of materials from blood into tubular fluid
38
2 Types of Reabsorption Routes:
Paracellular | Transcellular
39
Paracellular reabsorption:
-50% of reabsorbed materialmoves between cells by diffusion in some parts oftubule
40
Transcellular reabsorption
material moves throughboth the apical and basalmembranes of the tubulecell by active transport
41
Transport Mechanisms: 2 different membranes of tubule cells have different types of transport proteins?
Apical and basolateral membranes
42
What is the most important ion of reabsorption?
Na+ - several transport systems exist to reabsorb Na+ - Na+/K+ ATPase pumps sodium from tubule cell cytosol through the basolateral membrane ONLY
43
Water is only reabsorbed by
osmosis
44
Water follows
salt
45
Glucosuria: Renal symporters can not reabsorb glucose fast enough if blood glucose level is above
200 mg/mL
46
Unless urine has UTI, urine is
sterile | -some glucose remain in urine
47
***Common cause of Glucosuria =
is diabetes mellitis because insulin activity is deficient and blood sugar is too high
48
Reabsorption in the Prox. Con. Tubule: 1st step
Na+ symporters help reabsorb materials from the tubular filtrate
49
Reabsorption in the Prox. Con. Tubule: 2nd step
Glucose, amino acids, lactic acid, water-soluble vitamins and other nutrients are completely reabsorbed in the first half of the proximal convoluted tubule
50
Reabsorption in the Prox. Con. Tubule: 3rd step
Intracellular sodium levels are kept low due to Na+/K+ pump

Anatomy and Physiology II (26 decks)

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