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physiology Flashcards

1
Q

What is osmolarity?

A

The concentration of osmotically active particles present in a solution

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2
Q

What is needed to calculate the osmolarity?

A

The molar concentration of the solution
The number of osmotically active particles present

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3
Q

What is Tonicity?

A

The effect a solution has on cell volume

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4
Q

What happens to a cell in a hypotonic solution?

A

Too much water
Induces cell lysis

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5
Q

In which forms does total body water exist?

A

Intracellular fluid (67% of total body water)
Extracellular fluid (33% of total body water)

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6
Q

What are the components of extracellular fluid?

A

Plasma (20%)
interstitial fluid (80%)
Lymph and trans cellular fluid (negligible)

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7
Q

How are the fluid compartments measured?

A

TBW- 3H20
ECF- inulin
Plasma- labelled albumin

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8
Q

What is insensible loss of water?

A

Skin
Lungs

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9
Q

What is sensible loss of water?

A

Sweat
Faeces
Urine

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10
Q

What causes the biggest loss of water?

A

Urine

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11
Q

Are there always more Na and Cl ions outside the cell compared to inside?

A

Yes

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12
Q

What alters the composition and volume of ECF?

A

Kidneys

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13
Q

What is the primary function of the kidney?

A

Regulate the volume, composition and osmolarity of the body fluids
Controlled excretion of ions

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14
Q

What is the functional unit of the kidneys?

A

The nephron

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15
Q

What are the functions of nephrons?

A

Filtration
Reabsorption
Secretion

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16
Q

What is urine?

A

Modified filtrate of blood

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17
Q

What are the renal processes?

A

Glomerular filtration
Tubular reabsorption
Tubular secretion

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18
Q

How much of plasma that enters the glomerulus is filtered?

A

20%
80% is unfiltered and leaves through the efferent arteriole

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19
Q

is the diameter of the afferent arteriole bigger or smaller than the efferent arteriole?

A

bigger

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20
Q

what acts as a barrier to RBC in glomerular filtration?

A

the glomerular capillary endothelium

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21
Q

what acts as a barrier to plasma proteins in glomerular filtration?

A

the basement membrane

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22
Q

what is glomerular filtration rate?

A

rate at which protein free plasma is filtered from the glomeruli into the bowmans capsule per unit time

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23
Q

what is the major determinant of GFR?

A

glomerular capillary blood pressure

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24
Q

what is the intrinsic regulation of GFR?

A

myogenic mechanism
tubuloglomerular feedback mechanism

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25
Q

what is the extrinsic control of GFR?

A

sympathetic control via baroreceptor reflex

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26
Q

what affect does an increase in arterial BP have on glomerular capillary blood pressure?

A

increased glomerular capillary BP, therefore increased net filtration pressure and then increased GFR

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27
Q

what affect does a decrease in urine production have on arterial blood pressure?

A

it helps compensate for the drop in BP

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28
Q

what happens in myogenic autoregulation?

A

if vascular smooth muscle is stretched (arterial pressure is increased) it contracts, thus constricting the arteriole

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29
Q

what happens in tubuloglomerular feedback autoregulation?

A

involves the juxtaglomerular apparatus (mechanism remains unclear)
if GFR rises then more NaCl flows through the tubule leading to constriction of the afferent arterioles

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30
Q

what senses NaCl in the tubular fluid of the juxtaglomerular apparatus?

A

macula densa cells

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31
Q

what can cause an increase in bowmans capsule fluid pressure?

A

a kidney stone
results in a lower GFR

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32
Q

what can cause an increase in capillary oncotic pressure?

A

diarrhoea
results in a lower GFR

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33
Q

what can cause a decrease in bowmans capsule oncotic pressure?

A

severe burns
results in an increase in GFR

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34
Q

what is plasma clearance?

A

a measure of how effectively the kidneys can ‘clean’ the blood of a substance

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35
Q

what is inulin clearance equal to?

A

GFR

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36
Q

what are the features of inulin?

A

freely filtered at the glomerulus
neither absorbed nor secreted
not metabolised by the kidneys
not toxic
easily measured in urine and blood

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37
Q

what is used as the gold standard to clinically determine GFR?

A

inulin

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38
Q

what is the clearance for a substance that are filtered, completely reabsorbed and not secreted in urine eg. glucose?

A

0

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39
Q

what is the clearance in a substance that is filtered, partially reabsorbed and not secreted eg. urea?

A

clearance< GFR

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40
Q

what is the clearance for a substance that is filtered, secreted but not reabsorbed eg H?

A

clearance>GFR

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41
Q

what is used to measure renal plasma flow?

A

para-amino hippuric acid (PAH)

42
Q

what kind of fluid is reabsorbed in the proximal tubule?

A

iso-osmotic fluid with filtrate

43
Q

what is reabsorbed in the proximal tubule?

A

sugars
amino acids
phosphate
sulphate
lactate

44
Q

what is secreted in the proximal tubule?

A

H
hippurates
neurotransmitters
bile pigments
uric acid
drugs
toxins

45
Q

what is primary active transport?

A

energy is directly required to operate the carrier and move the substance against its concentration gradient

46
Q

what is secondary active transport?

A

the carrier molecule is transported coupled to the concentration gradient of an ion (usually Na)

47
Q

what is facilitated diffusion?

A

passive carrier-mediated transport of a substance down its concentration gradient

48
Q

where are sodium ions reabsorbed?

A

all areas of the nephron except the descending loop of henle

49
Q

what drives Na reabsorption in the proximal tubule?

A

the basolateral Na-k ATPase

50
Q

what drives Cl reabsorption?

A

Na reabsorption

51
Q

what is the function of the loop of henle?

A

generates a cortico medullary solute concentration gradient which enables the formation of a hypertonic urine

52
Q

what is counter current flow?

A

opposing flow in the two limbs of the loop of henle

53
Q

what are the features of the ascending limb of henle?

A

Na and Cl are being reabsorbed
relatively impermeable to water

54
Q

what is the feature of the descending limb of henle?

A

does not reabsorb NaCl and is highly permeable to water

55
Q

which drugs block the triple co transporter in the thick ascending loop of henle?

A

loop diuretics

56
Q

what are the features of the countercurrent exchange?

A

vasa recta runs alongside the long loop of henle of juxtamedullary nephrons
capillary blood equilibrates with interstitial fluid across the “leaky” endothelium
blood osmolality rises as it dips down the medulla (water loss, solute gained)
blood osmolality falls as it rises back up into the cortex (water gained, solute lost)

57
Q

true or false- all tubules empty into collecting ducts?

A

true

58
Q

what affect does ADH have on water?

A

increases reabsorption

59
Q

what affect does aldosterone have?

A

increase Na reabsorption
decrease H/K secretion

60
Q

what affect does atrial natriuretic hormone have?

A

decreases Na reabsorption

61
Q

what affect does PTH have?

A

increases Ca reabsorption
decreases PO4 reabsorption

62
Q

what has a low permeability to water and urea?

A

the distal tubule

63
Q

where is urea concentrated?

A

in the tubular fluid

64
Q

what happens in the early distal tubule?

A

Na-K-2Cl transport (NaCl reabsorption)

65
Q

what happens in the late distal tubule?

A

Ca reabsorption
H secretion
Na reabsorption
K reabsorption

66
Q

what are the features of the late collecting duct?

A

a low ion permeability
permeability to water (and urea) influenced by ADH

67
Q

where is ADH secreted from?

A

the posterior pituitary

68
Q

what happens when we are dehydrated?

A

ADH secretion is increased (leading to a high water permeability and a highly concentrated urine)

69
Q

what happens to the collecting duct in the presence of minimal ADH concentration?

A

impermeable to water so therefore there is no water reabsorption

70
Q

what are the symptoms of diabetes insipidus?

A

large volumes of dilute urine
constant thirst

71
Q

how is diabetes insipidus treated?

A

ADH replacement
(demsopressin)

72
Q

what is aldosterone?

A

a steroid hormone secreted by the adrenal cortex

73
Q

when is ADH secreted?

A

in response to rising K concentration or falling Na conc in the blood
also secreted after activation of the renin-angiotensin system

74
Q

what does aldosterone do?

A

it stimulates Na reabsorption and K secretion

75
Q

what is the affect of an increase in K concentration as a result of aldosterone?

A

directly stimulates the adrenal cortex

76
Q

what increases production of aldosterone?

A

angiotensin II

77
Q

what does angiotensin II do?

A

increase thirst
increase vasopressin
increase arteriolar vasoconstriction

78
Q

what can trigger the release of renin?

A

reduced pressure in afferent arteriole
macula densa cells sense the amount of NaCl in the distal tubule
increased sympathetic activity

79
Q

what can abnormal increases in the RAA system cause?

A

hypertension

80
Q

what is responsible for the fluid retention associated with congestive HF?

A

RAA system

81
Q

how is fluid retention associated with HF treated?

A

low salt diet
loop diuretics

82
Q

what does ANP promote?

A

excretion of Na and diuresis, decreasing plasma volume
lowers BP

83
Q

what affect does an increase in H ion conc have on pH?

A

reduces pH

84
Q

what affect can acidosis have on the nervous system?

A

depresses CNS

85
Q

what affect can alkalosis have on the nervous system?

A

overexcitability of the peripheral nervous system and the CNS

86
Q

where does H ions come from?

A

carbonic acid formation
inorganic acids produced during breakdown of nutrients
organic acids resulting from metabolism

87
Q

what is bodily pH equal to?

A

concentration of kidneys divided by lungs

88
Q

what is the rate of HCO3 filtration?

A

GFR x conc of HCO3
(4320mmol/day filtered by the kidneys)

89
Q

what is the result of H ion secretion by the tubule?

A

drives reabsorption of HCO3
forms acid phosphate
forms ammonium ion

90
Q

what is the purpose of excreting TA and NH4 simultaneously?

A

it rids the body’s acid load and regenerates buffer zones (alkalinizes the body)

91
Q

what is the normal acid base balance in the body?

A

plasma pH close to 7.4 (7.35-7.45)
conc of HCO3 close to 25 mmol/l
arterial PCO2 close to 40mmHg

92
Q

which condition can cause respiratory acidosis?

A

chronic bronchitis
chronic emphysema
airway restriction
chest injuries
respiratory depression

93
Q

what is the definition of uncompensated respiratory acidosis?

A

pH<7.35 and PCO2>45mmHg

94
Q

how does the renal system compensate for respiratory acidosis?

A

H secretion is stimulated
all filtered HCO3 is reabsorbed
H continues to be secreted and generates titratable acid and NH4
acid is excreted and new HCO3 is added to the blood

95
Q

what is respiratory alkalosis?

A

the excessive removal of CO2 by the body

96
Q

what are some causes of respiratory alkalosis?

A

low PO2 at altitude (hypoxia)
hyperventilation

97
Q

how does the renal system compensate for respiratory alkalosis?

A

H secretion is insufficient to reabsorb HCO3
HCO3 is excreted and the urine is alkaline
no TA and NH4 are formed so no new HCO3 is generated

98
Q

what are some causes of metabolic acidosis?

A

ingestion of acids
excessive metabolic production of H (eg lactic acidosis during exercise or ketoacidosis)
excessive loss of base from the body (eg diarrhoea)

99
Q

how does the renal system correct metabolic acidosis?

A

filtered HCO3 is very low and readily absorbed
H secretion continues and produces TA and NH4 to generate more new HCO3
the acid load is excreted (urine is acidic) and the conc of HCO3 is absorbed
ventilation can then be normalised

100
Q

what are some causes of metabolic alkalosis?

A

vomiting
ingestion of alkali
aldosterone hypersecretion

101
Q

how does the renal system compensate for metabolic alkalosis?

A

not all the filtered HCO3 is reabsorbed
no TA or NH4 is generated
HCO3 is excreted
conc of HCO3 falls backwards towards normal

renal (22 decks)

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