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Physiology 214 > Section 7: Renal Physiology > Flashcards

Section 7: Renal Physiology Flashcards

1
Q

Homeostatic roles of the kidney (6):

A

1.Fluid balance / plasma volume 2. regulation of osmolarity 3. electrolyte balance 4. plasma pH 5. waste excretion 6. hormone production

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2
Q

hormones produced in the kidney (2)

A

erythropoetin (EPO) calcitriol (active vitamin D3)

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3
Q

Yellow colour of urine comes from :

A

billirubin

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4
Q

typical total water composition of human body

A

0.6 (60%) (Male) 0.5 (50%) (Female)

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5
Q

Total body water (TBW) is distributed into 2 categories: ECF and ICF. What are the % distributions of the water ?

A

Extracellular fluid (ECF) is 1/3 total body water Intracellular fluid (ICF) is 2/3 TBW

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6
Q

ECF consists of 2 parts :

A

interstitial fluid (ISF) and plasma

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7
Q

water distribution of ECF into interstitial fluid and plasma

A

Extracellular fluid is 3/4 interstitial fluid and 1/4 plasma

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8
Q

osmolarity definition

A

concentration of particles in osmol/L

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9
Q

osmolality defintion

A

concentration of particles in osmol/kg

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10
Q

ECF osmolarity (typical)

A

300 mOsmol / L

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11
Q

osmolarity of 150 mM NaCl solution

A

300 osmol (NaCl dissociates into two particles)

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12
Q

type of solutes that do not contribute to osmotic pressure (do not affect osmolarity)

A

penetrating solutes eg EtOH, urea

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13
Q

If a cell is placed into a solution with a lower osmolarity than the cell, water will

A

enter the cell

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14
Q

Forces governing fluid movement between intersitial fluid and plasma (across capillaries)

A

capillary blood pressure osmotic pressure tissue pressure

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15
Q

Normal saline

A

150 mM NaCl

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16
Q

Renal process (4 steps)

A

Filtration
Re absorption
Secretion
Excretion

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17
Q

role of podocytes

A

epithelial cells that surround capillaries

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18
Q

What is GFR ?

A

glomerular filtration rate, volume of plasma filtred over time

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19
Q

What forms kidney stones ?

A

Calcium buildup in the kidney or uriter

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20
Q

intrinsic myogenic control of glomerular blood flow

A

high blood pressure activates stretch sensitive channels and lets calcium in, activating muscles that constrict blood vessels

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21
Q

intrinsic tubloglomerular feedback control system of glomular flow

A

macula densa senses paracrine constriction of afferent arteriole

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22
Q

extrinsic control of glomerular flow

A

sympathetic innervation (α1) decreases glomerular permiability and causes afferent arteriole constriction

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23
Q

role of mesangial cells

A

reduce permeability by constricting and bringing podocytes close together. Contract when stimulated by sympathetic NS and angiotensins

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24
Q

clearance

A

filtred volume from which a solute is excreted

(volume returns to blood without solute, so that volume is cleared)

25
Q

if 100 ml afferent blood is 50 mg/ml and 100 ml efferent blood is 40 mg/ml, how much is cleared ?

A

20 ml

26
Q

What substance is used to measure clearance ?

A

Insulin was once used, but creatine is more practical

27
Q

Substance used to measure renal plasma flow

A

P-aminohippuric acid (PAH)
is totally cleared, so it is used in renal plasma flow measurements

28
Q

Renal blood flow equation

A

RBF = RPF / (1-Hct)

where:
RBF = renal blood flow
RPF = renal plasma flow
Hct = haematocrit (% of blood that is RBC)

29
Q

Characteristics of the tubular epithelium

A
  • one cell thick-have polarity (luminar and basal sides)
  • brush borders
30
Q

Re absorption of glucose:

a) uses antiports
b) is transcellular
c) causes solvent decay
d) occurs down a gradient into a tubular cell

A

b) is transcellular

31
Q

solvent drag

A

when a solvent (water) is reabsorbed, small particles are dragged along with it (eg Na, K)

32
Q

solutes reabsorbed in the proximal tubule (6)

A

Na, Cl, K, glucose, amino acids, Bicarbonate (HCO3)

33
Q

Organic ion secretion

A

addition of COO- to an organic molecule in order to actively secrete into filtrate

34
Q

Na/K pump limitation

A

can only pump against 200 mM gradient (why we need countercurrent system)

35
Q

Permeability in the loop of Henle

A

descending loop is permeable to water, but not saltascending loop is permeaple to salt, but not water

36
Q

ADH role

A

ADH is a peptide hormone that makes membrane more permeable to water (more absorption)

37
Q

ADH mechanism of action

A

causes release of cAMP and promotes release of aquaporins

38
Q

ADH released from :

A

posterior pituitary gland

39
Q

potential cause of diabetes insipidus (ADH related)

A

absence or nonfunctional ADH/ADH receptors

40
Q

effects of angiotensin II (3)

A
  • arteriolar constrtiction
  • promotes Na reabsorption on proximal tubule
  • stimulates aldesterone release
41
Q

aldosterone effects (2)

A

increases Na reabsorption by distal tubule

regulates potassium

42
Q

Atrial natriuretic hormone (2)

A

-released by atrial muscle,

-inhibits Na reabsorption
(Natri -> sodium (Na))

43
Q

possible causes of ECF hypertonicity (6)

A
  • decreased water intake
  • sweating
  • vomiting, osmotic diarrhea
  • diabetes insipidus
  • diabetes mellitus
44
Q

possible causes of cellular hypotonicity (2)

A

excessive water ingestion (compulsive (?))

excessive vasopression (ADH)

45
Q

isotonic ECF disturbances (2)

A

loss: haemorrage, diarrhea
gain: isotonic IV saline

46
Q

Which IV solution would est correct a hypertonic ECF:

a) normal saline (.15M)
b) 1/2 normal saline (.075M)
c) 0.3 M glucose
d) a hypertonic solution
e) a hypotonic solution

A

a) is incorrect because very little will enter cell
b) only ~1/2 will go in
c) is correct2/3 will go into cell (see ECF/ICF distribution)

47
Q

Sweat 1L, drink 1L water, ECF will be :

A

hypotonic, as sweat contains electrolytes etc.Note the sweat is slightly hypotonic to interstitial fluid

48
Q

pH formula

A

pH = -log[H+] = log1/[H+]

49
Q

Average plasma pH

A

7.35 - 7.45

(7.4)

50
Q

Methods body uses to regulate pH (3)

A

1) buffers
2) H+ secretion
3) HCO- reabsorption

(#2 and 3 are done by the kidneys)

51
Q

buffers in blood (2)

A

bicarbonate / carbonic acid

Haemoglobin / Oxyhaemoglobin

(pKa 6.1)

52
Q

buffers in urine

A

phosphate (H2PO4- / HPO42-)

ammonium (NH4+/ NH3)

pKa = 6.8

53
Q

Henderson Hasselbach equation

A

pH = pK + log(products/reagents)

54
Q

in addition to buffering, these molecules can affect pH

A

CO2 / HCO3-

55
Q

urine pH

A

~6 (slightly acid)

56
Q

Can you judge H+ excretion from urine pH?

A

No, it is buffered, so H+ excretion has a minimal effect on urine pH

57
Q

Polarity of renal cells

A

Brush border faces the renal tubule (laminal side),
Basolateral side faces the bloodstream

58
Q

enzyme that combines carbonate with hydrogen

A

carbonic anhydrase catalyses

H+ + HCO3- –> CO2 + H2O

59
Q

How is H+ secreted into the proximal tubule ?

(5 steps)

A

1) Na+ concentration is created with a Na/K pump
2) H+ moved out of cell with Na/H antiport
3) H+ combines with bicarbonate to form water and CO2
4) CO2 diffuses back into cell and converted back into HCO3-
5) HCO3- is transported into bloodstream

Physiology 214 (8 decks)

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