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Physiology Flashcards

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1
Q

define osmolarity

A

concentration of osmotically active particles in a solution

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2
Q

define osmolality

A

this is interchangeable with osmolarity for body fluids

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3
Q

osmolarity of body fluids?

A

300mosmol/L

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4
Q

define tonicity

A

effect a solution has on cell volume

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5
Q

define isotonic

A

no change on cell volume

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6
Q

define hypertonic

A

decreases cell volume, concentrated salt solution

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7
Q

define hypotonic

A

increases cell volume (lysis) due to dilute solution

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8
Q

what does tonicity also take into consideration?

A

ability of a solute to cross the cell membrane e.g. urea causes RBC lysis as water follows (sucrose is impermeable so has no effect)

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9
Q

two compartments of total body water

A

intracellular fluid

extracellular fluid

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10
Q

what does the extracellular fluid consist of?

A

plasma

interstitial fluid

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11
Q

tracer used to measure TBW

A

3H2O

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12
Q

tracer used to measure ECF

A

inulin

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13
Q

tracer used to measure plasma

A

labelled albumin

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14
Q

inputs in water homeostasis

A

fluid
food
metabolism

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15
Q

outputs of water homeostasis

A 
insensible losses (no sensible mechanism- skin and lungs)
sensible losses- sweat, faeces and urine
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16
Q

what separates plasma and interstitial fluid?

A

capillary wall

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17
Q

what separates interstitial fluid and intracellular fluid?

A

plasma membrane

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18
Q

main ions in ECF

A

Na+
Cl-
HCO3-

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19
Q

main ions in ICF

A

K+
Mg2+
-ve charged proteins

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20
Q

define fluid shift

A

movement of water between ICF and ECF in response to an osmotic gradient

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21
Q

is Na+ excluded from ICF?

A

yes so there is only water movement

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22
Q

what do the kidneys do to ECF

A

alter composition and volume

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23
Q

why is potassium balance important?

A

membrane potential (if leakages or increased uptake it can cause paralysis and cardiac irregularities)

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24
Q

why is sodium balance important

A

ECF concentration and volume

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25
kidney functions
``` water balance salt balance maintenance of plasma volume acid-base balance excretion of waste secretion of renin, erythopoietin and conversion of vit D ```
26
two types of nephron
juxtamedullary (glomerulus near corticomedullary border) | cortical (glomerulus in outer cortex)
27
glomerular filtration barriers
- endothelium (barrier to RBC) - basement membrane (basal lamina) - slit processes of podocytes (glomerular epithelium)
28
define glomerular filtration rate (GFR)
rate protein-free plasma is filtered from the glomeruli into Bowman's capsule per unit time
29
what is normal GFR?
125ml/min
30
extrinsic regulation of GFR
sympathetic control via baroreceptor reflex
31
intrinsic regulation of GFR
myogenic mechanism and tubuloglomerular feedback
32
define tubuloglomerular feedback
GFR rises then more NaCl flows through the tubule causing constriction of afferent arteriole
33
what senses NaCl concentration in the blood?
macula densa of DCT
34
calculi effect on GFR?
reduced
35
diarrhoea effect on GFR
reduced
36
burns effect on GFR
increases
37
example of a substance with clearance of 0 (completely reabsorbed)
glucose
38
example of substance that is partly reabsorbed (clearance < GFR)
urea
39
example of substance that is completely secreted (clearance > GFR)
H+
40
what marker can be used to measure renal plasma flow
para-amino hippuric acid (PAH)- exogenous organic anion
41
normal renal plasma flow
650ml/min
42
what happens to PAH
it is all secreted from peritubular capillaries
43
define filtration fraction
fraction of plasma flowing through the glomeruli that is filtered into the tubules
44
what does the PCT reabsorb?
``` sugars amino acids phosphate sulphate lactate ```
45
what does the PCT secrete?
``` H+ hippurates neurotransmitters bile pigments uric acids drugs toxins ```
46
what channel is used in the PCT for Na+ reabsorption?
Na+/K+ ATPase
47
define transport maximum (Tm)
point at which increases in concentration of a substance do not result in an increase in movement of a substance across a cell membrane
48
where is all glucose and amino acids reabsorbed in the nephron?
PCT
49
what is normal concentration of glucose entering filtrate and whats renal threshold
2mmol/min | 10-12mmol/L (consider diabetes)
50
define the counter-current multiplier
loop of Henle creates a solute gradient allowing formation of hypertonic urine
51
descending limb role of the nephron
does not reabsorb NaCl but is permeable to water
52
role of the ascending limb of the nephron
Na+ and Cl- are reabsorbed (thick limb is AT and thin limb it is passive) impermeable to water
53
what cycle also contributes to medullary osmolality?
urea cycle
54
is the DCT permeable to urea?
no
55
which part of the nephron absorbs urea
collecting duct
56
where does urea diffuse passively into?
loop of Henle
57
what is the counter-current exchanger?
vasa recta
58
what does the blood do in the vasa recta?
equilibrates with interstitial fluid
59
why are the vasa recta needed?
they provide nutrients for medulla and remove toxins but to minimise removal of needed NaCl and urea for the concentration gradient they have low blood flow and are freely permeable so passive exchange preserves gradient
60
what hormones influence DCT and collecting ducts?
ADH aldosterone ANH/P PTH
61
two segments of DCT
``` early= Na+/K+/2Cl- transporter late= aldosterone ```
62
define ADH
octapeptide that is synthesised in the hypothalamus and stored in the posterior pituitary
63
role of ADH
increases the number of aquaporins
64
most important stimulus for ADH release?
hypothalamic osmoreceptors
65
what secreted aldosterone?
adrenal cortex
66
why is aldosterone secreted
increased K+ or reduced Na+ | activation of RAAS
67
role of aldosterone
stimulates Na+ reabsorption and K+ secretion
68
what happens in the DCT when aldosterone is absent
rest of K+ is reabsorbed so there is none in the urine
69
what is renin released from?
granular cells in the JGA
70
processes that cause renin release
- reduced pressure in afferent arteriole - low NaCl sensed by macula densa - increased sympathetic activity in low BP
71
what produces atrial natriuretic peptides?
atrial cells
72
what causes ANP release?
atria stretching due to increased blood volume
73
role of ANP
promotes excretion of Na+ and diuresis
74
define water diuresis
increased urine flow but not increased solute excretion
75
define osmotic diuresis
increased urine flow as a result of increased salt excretion

Renal (54 decks)

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