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BMS242- Physiology and Pharmacology > core physiology > Flashcards

core physiology Flashcards

1
Q

what is the composition of the cell membrane?

A

Lipids - 42%
Proteins - 55%
Carbohydrates - 3%

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2
Q

what are the three types of transporter proteins?

A

Carriers, Pumps and Channels

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3
Q

which transporter requires ATP?

A

Pump

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4
Q

name the two methods of measuring membrane potential?

A

patch clamp and glass electrode

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5
Q

how would you go about using the glass electrode technique?

A

impale cell so the tip (filled with KCl) sits in the IC compartment - measure potential with respect to referee electrode

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6
Q

which technique would have the most specificity

A

small electrode as much smaller with very sharp tip and insoluble thin wire

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7
Q

what is the distribution of sodium

A

EC - 150 IC - 15

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8
Q

what is the distribution of potassium

A

EC - 5 IC - 150

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9
Q

what is the distribution of large organic anions

A

EC - 0 IC - 65

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10
Q

describe the key features of Na/KATPase

A

contributes 20% directly
electrogenic - 3 Na out, 2 K in - therefore lose 1 positive charge each time
indirect IC Na and K maintained
if blocked - instantly wipes out membrane potential

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11
Q

what does electrogenic mean

A

produces a change in electrical potential of cell - change in voltage plus a change in permeability of membrane

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12
Q

what do K+ channels contribute to membrane potential

A

-ve charge created when K+ moves
creates driving force for K+ to move into cell
equal - opposite movement of K+ means equilibrium

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13
Q

what do Na+ channels contribute

A

same as K+ - maintain equilibrium

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14
Q

what does the Nernst equation calculate

A

equilibrium potential of the cell

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15
Q

what is the predictive potential of Na and K

A

Na - +61.5mV K - -90.8mV

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16
Q

why are the predictive values not = -70mV

A

because there must be some leakage going on meaning Na can get into the cell and K can leave

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17
Q

what does the Goldman equation calculate

A

equilibrium potential of cell with more than one ion

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18
Q

what is the relationship between pH and [H+]

A

increase pH doubles/halves [H+]

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19
Q

how do we measure IC pH

A

using 2 microelectrodes - change in voltage = change in pH

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20
Q

what are the electrodes calibrated with

A

pH standards

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21
Q

what are the ideal cells for microelectrodes and why

A

nerves, muscles, Xenopus oocytes because they are large cells

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22
Q

what could you use to calculate pH of small cells i.e. epithelia

A

fluorescent indicators

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23
Q

how?

A

load cells with inactive form (so it can pass through the membrane)
inside cell it is converted to active form
excites a light with specific wavelength - amount at 2nd wavelength is measures
fluorescence = IC pH
indicator is calibrated inside cell and membrane is permeabilised and pH of bath solution is changed

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24
Q

what are the three factors in controlling IC pH

A

buffers
acid loading
acid extrusion

25
Q

what do buffers do

A

moderate effects of acid/alkali load by consuming/releasing protons
DO NOT PREVENT CHANGE pH!!!!

26
Q

what do buffers rely on

A

COOH group and NH2 group

27
Q

what exchanger is used for acid extrusion and hoe does it act

A

Na/H exchanger protein - exchanges one Na into cell for one H out

28
Q

what does it rely on

A

Na gradient set up by Na/K pump

29
Q

does high pH inhibit or activate exchanger

A

high pH inhibits - low pH activates

30
Q

what happens when allosteric modification occurs

A

a unused proton binds the the allosteric site increasing activity

31
Q

what is NHE1

A

housekeeping function with a primary role of regulating pH

32
Q

what inhibits NHE1

A

low conc of amiloride plus its analogue EIPA

33
Q

where is NHE1 found

A

basolateral membrane of epithelial cells

34
Q

what exchanger is involved in acid loading and what does it do

A

Cl/HCO3 exchanger - 1 Cl in and 1 HCO3 out

35
Q

is it inhibited by high or low pH

A

inhibited at low pH and activated at high`

36
Q

what family does this exchanger belong to and how many subtypes are there

A

the anion exchanger family (AE) - 4 subtypes

37
Q

what are they all inhibited by

A

DIDS

38
Q

do these exchangers rely on Na gradient

A

no they are independent of Na conc

39
Q

where is AE1 predominantly found and what shift is it responsible for

A

RBCs but also in kidneys - hamburger shift/chloride shift

40
Q

when is there no net proton flux

A

Je = Jl

41
Q

why is important to control IC Na+ - epithelial cells

A

creates gradients that allow uptake of other molecules

42
Q

excitable cells?

A

need high chemical gradient to create action potentials

43
Q

what is Na/K pump inhibited by

A

glucosides such as ouabain and digoxin

44
Q

what does Na/K pump do

A

maintains low IC Na snd high IC K

45
Q

what are the two roles Na/K pump has in membrane potential

A

electrogenic

accumulation of K inside cell -MAJOR FACTOR

46
Q

why is Na/K pump only found in physiologically significant pathways such as collecting duct and excitable cells

A

requires ALOT of energy

47
Q

what are normal compositions of Ca

A

EC - 1mM IC - 100nM

48
Q

why is Ca regulation important

A

important secondary messenger in important signalling pathways

49
Q

what are the two mechanisms in keeping low IC Ca

A

Na/Ca exchanger

Ca ATPase

50
Q

describe Na/Ca exchanger

A

usually exchanges EC Na for IC Ca

stoichiometry means effect of Na influx is magnified as 3Na:1Ca

51
Q

what family is Na/Ca exchanger

A

SLC8 family in mammals 3 forms exist

52
Q

what family is Ca ATPase

A

P-type ATPase family

53
Q

describe each type of Ca pump

A

PMCA - plasma membrane Ca pump - Ca out of cell
SERC - smooth endoplasmic reticulum Ca pump - pumps Ca into organelles for storage
SPCA - Golgi Ca pump - also transports Mn

54
Q

what are the 4 mechanisms of Ca signalling

A

VOCC
ROCC
MACC
SOCC

55
Q

VOCC

A

voltage operated calcium channel
found in excitable cells
activated by depolarisation

56
Q

ROCC

A

receptor operated calcium channel
found in secretory cells + synapses
activated by agonist binding e.g. NMDA

57
Q

MACC

A

mechanically activated calcium channel
stretch activated
found in cells that respond to deformation

58
Q

SOCC

A

store operated calcium channel

activated following depletion in Ca stores

59
Q

what are the two store pathways

A

IP3 receptors activate channel - ubiquitous
ryanodine receptors - low conc activates channel - high inhibits - also activated by caffiene - usually only in excitable cells

BMS242- Physiology and Pharmacology (2 decks)

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