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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
Q

tubuloglomerular feedback: 3rd step =

A
  1. afferent arterioles constrict & reduce GFR
26
Q

Neural Regulation of GFR: Blood vessels of the kidney are supplied by

A

sympathetic fibers that cause vasoconstriction of afferent arterioles

27
Q

Neural Regulation of GFR: At rest, renal BV

A

are maximally dilated because sympathetic activity is minimal
-renal autoregulation occurs

28
Q

Neural Regulation of GFR: With moderate sympathetic stimulation =

A

Both afferent & efferent arterioles constrict equally

-decreasing GFR equally

29
Q

Neural Regulation of GFR: With extreme sympathetic stimulation =

A

Vasoconstriction of afferent arterioles reduces GFR

-lowers urine output & permits blood flow to other tissues

30
Q

Hormonal Regulation of GFR: Atrial natriuretic peptide (ANP)

A

increases GFR

31
Q

Atrial natriuretic peptide (ANP) does what?

A

stretch heart = increase BP = hormonal release = normal BP

32
Q

Hormonal Regulation of GFR: Angiotensin II

A

reduces GFR

33
Q

Angiotensin II has and does what?

A

potent vasoconstrictor that narrows both afferent & efferent arterioles reducing GFR

34
Q

Normal GFR is so high that volume of filtrate in capsular space in half an hour is

A

greater than the total plasma volume

35
Q

Nephron must reabsorb

A

99% of the filtrate

36
Q

PCT with their microvilli do

A

most of work with rest of nephron doing just the fine-tuning

37
Q

Important function of nephron is tubular secretion:

A

-transfer of materials from blood into tubular fluid

38
Q

2 Types of Reabsorption Routes:

A

Paracellular

Transcellular

39
Q

Paracellular reabsorption:

A

-50% of reabsorbed materialmoves between cells by diffusion in some parts oftubule

40
Q

Transcellular reabsorption

A

material moves throughboth the apical and basalmembranes of the tubulecell by active transport

41
Q

Transport Mechanisms: 2 different membranes of tubule cells have different types of transport proteins?

A

Apical and basolateral membranes

42
Q

What is the most important ion of reabsorption?

A

Na+

  • several transport systems exist to reabsorb Na+
  • Na+/K+ ATPase pumps sodium from tubule cell cytosol through the basolateral membrane ONLY
43
Q

Water is only reabsorbed by

A

osmosis

44
Q

Water follows

A

salt

45
Q

Glucosuria: Renal symporters can not reabsorb glucose fast enough if blood glucose level is above

A

200 mg/mL

46
Q

Unless urine has UTI, urine is

A

sterile

-some glucose remain in urine

47
Q

***Common cause of Glucosuria =

A

is diabetes mellitis because insulin activity is deficient and blood sugar is too high

48
Q

Reabsorption in the Prox. Con. Tubule: 1st step

A

Na+ symporters help reabsorb materials from the tubular filtrate

49
Q

Reabsorption in the Prox. Con. Tubule: 2nd step

A

Glucose, amino acids, lactic acid, water-soluble vitamins and other nutrients are completely reabsorbed in the first half of the proximal convoluted tubule

50
Q

Reabsorption in the Prox. Con. Tubule: 3rd step

A

Intracellular sodium levels are kept low due to Na+/K+ pump

Anatomy and Physiology II (26 decks)

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