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Semester 4 > Case 1 - epithelial solute and water transport > Flashcards

Case 1 - epithelial solute and water transport Flashcards

1
Q

how much of our body weight does fluid account for

A

60%

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2
Q

what makes up the extracellular fluid

A

the transcellular fluid, interstitial fluid, and the plasma

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3
Q

what separates the extracellular fluid form the outside world

A

the epithelial cells

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4
Q

what is considered outside of the body

A

anything on the apical side of the epithelium e.g GI tract, kidney tubules and salivary ducts

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5
Q

diagram showing the organisation of the body compartments

A
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6
Q

where does the apical membrane face

A

the outside

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7
Q

where does the basolateral membrane face

A

the inside

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8
Q

what do tight junctions do

A

separates the basolateral and apical membranes and also found between neighbouring cells

this allows for asymmetric expression of transport protiens

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9
Q

what provide support in epithelia structure

A

desmosomes and adhering junctions provide structure

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10
Q

what is tight junction permeability determined by

A

claudin family proteins

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11
Q

what are phospholipid bilayers

A

have hydrophilic head groups facing aqueous environments and hydrophobic lipid tails in the lipid bilayer

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12
Q

is the phospholipid bilayer permeable?

A

no, it is impermeable to ions and polar molecules

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13
Q

what is permeability provided by instead

A

membrane proteins (transporters)

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14
Q

what is sterol

A

provides structural integrity and provides precursors for fat soluble vitamins and steroid hormones

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15
Q

what does the integral protein spanning proteins include

A

all of the cell surface receptors, G proteins, and our membrane transporters

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16
Q

what are the three types of membrane transporters

A

ion pumps
ion channels
transporter

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17
Q

what do ion pumps do

A

they move ions against their concentration gradients

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18
Q

what do ion pumps use energy from

A

ATP hydrolysis

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19
Q

do ion pumps use active transport

A

yes

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20
Q

features of the sodium pump

A

2 K+ in, 3 Na+ out

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21
Q

what do ion pumps do

A

creates and maintains electrochemical gradients

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22
Q

what gradient generates the membrane potential and what is the membrane potential value

A

the K+ gradient and membrane potential is approx -60mV

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23
Q

what gradient drives other passive transporters

A

Na+ gradient = secondary active transport

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24
Q

what are ion channels

A

highly selective protein pores in the membrane (specifically dependent on protein structure)

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25
Q

what is ion flow driven by in ion channels

A

driven by concentration gradient and membrane potential: electrochemical gradient - passive transport

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26
Q

what may ion channels be gated by

A

intracellular or extracellular messengers, or by membrane potential changes

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27
Q

what are transporter (carrier) proteins

A

highly selective carrier protein in the membrane

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28
Q

is transport active or passive in carrier proteins

A

passive

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29
Q

what is transporter (carrier proteins) driven by and what is another name for it

A

driven by concentration gradient alone

facilitated diffusion!!!

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30
Q

what is secondary active transport

A

cotransporters and exchangers

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31
Q

what are the most common cotransporters

A

Na+, K+, Cl-

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32
Q

what does inwards movements of Na+ drive

A

uptake of Cl- against its gradient

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33
Q

what is the Na+/H+ exchanger

A

an anti porter

inwards movement of Na+ drives extrusion of H+ against its gradient

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34
Q

what is the composition values of intracellular fluid

A

low in Na+ and high in K+

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35
Q

what is the composition values of extracellular fluid

A

high in Na+ and low in K+

36
Q

what is passive transport

A

simple or facilitated diffusion

molecules move along the concentration gradient

high to low concentration

37
Q

what is active transport

A

moves molecules against the concentration gradient

hydrolysis of ATP - ion pumps

secondary active transport

38
Q

what is different about secondary active transport

A

the gradient has usually been established by another ion

39
Q

what are aquaporins

A

pore is highly selective to water

water flow is driven by osmosis

40
Q

what is osmosis

A

osmosis is the diffusion of water through a semi-permeable membrane

from a region of lower total solute concentration to one of higher total solute concentration

41
Q

diagram showing transcellular transport

A

mostly glucose and Cl-

42
Q

what is the only thing to mediate active transport

A

pumps

43
Q

how may transport occur

A

via transcellular or paracellular pathways

44
Q

what are the main salivary glands

A

parotid - the largest
submandibular
sunlingual

45
Q

what are the cells found in the parotid gland

A

mainly serous acinar cells

46
Q

what are the cells found in the submandibular gland

A

serous and mucous acinar cells

47
Q

what are the cells found in the sublingual gland

A

mainly mucous acinar cells

48
Q

how much saliva do humans secrete in a day

A

1L

49
Q

what technically determines the pH value of saliva

A

the higher the incidence of bicarbonate

50
Q

secretion as a two stage process diagram

A
50
Q

secretion as a two stage process diagram

A
51
Q

features of the acinus part of secretion

A

secretion of Na, Cl, and HCO3 by active transport

high water permeability

isotonic, plasma like primary secretion

52
Q

features of the duct part of secretion

A

reabsorption of NaCl

some secretions of K and HCO3

low water permeability

hypotonic final saliva

53
Q

where does the saliva become hypotonic

A

the duct

54
Q

what is primary secretion performed by and what pump is responsible for setting the ion gradient

A

primary secretion by acinar cells and the sodium pump sets the ion gradient

55
Q

what happens when chlorine moves into the lumen (negatively charged ion)

A

leads to a small negative charge building up within the lumen and that then draws positive ions like Na+, paracellularly, passively down its electrochemical gradient

56
Q

what do acinar cells express in the apical and basolateral membranes and what does this do

A

express aquaporin 5

this lets water move via osmosis

57
Q

primary secretion by acinar cells diagram

A
58
Q

summary of the Na+, K+, ATPase pump

A

maintains concentration gradients for Na+ and K+

small direct contribution to membrane potential

59
Q

summary of the Na+, K+, 2CL cotransporter

A

electrically neutral

uses inward gradient for Na+ to drive coupled uptake of Cl-

secondary active transport

60
Q

what are examples of the Na+, K+, 2Cl- cotransporter

A

NKCC1, SLC12A2

61
Q

summary of K+ channels

A

recycles K+ and maintains membrane potential

62
Q

examples of K+ channels

A

BK ans IK1

63
Q

summary of Ca2+ activated Cl- channels

A

allows Cl- efflux down its electrochemical gradient

64
Q

example of Ca2+ activated Cl- channel

A

TMEM16A

65
Q

what drives Na+ secretion via the paracellular pathway

A

small negative potential in the lumen

66
Q

summary of the aquaporin 5 water channel

A

allows H20 efflux driven by a small osmotic gradient

67
Q

example of an aquaporin channel

A

AQP5

68
Q

modification of primary saliva by salivary duct cells diagram

A
69
Q

what is the difference between acinar and salivary duct cells

A

salivary duct cells are impermeable to water

70
Q

what is the final saliva

A

more hypotonic

71
Q

how does Na+ enter the salivary duct cell

A

passively via ENaC channels

72
Q

how does Na+ leave the salivary duct channels

A

cross the basolateral membrane via Na+,K+ ATPase

73
Q

what draws Cl- through the cell via Cl- channels

A

small positive potential on the blood sie

74
Q

what is Cl- also taken up from the saliva in exchange for

A

HCO3- via apical Cl-/HC03- exchangers

75
Q

what is intracellular HC03- generated from

A

from CO2 and water by an enzyme called carbonic anhydrase

76
Q

what extrudes H+

A

basolateral Na+/H+ exchangers

77
Q

what ensures little water reabsoprtion

A

low water permeability

78
Q

what raises the amount of saliva produced

A

stimulation of parasympathetic nervous system

79
Q

parasympathetic nervous system stimulation

A

acetylcholine raises intracellular Ca2+

acetylcholine will bind to M1 and M3 muscarinic G protein coupled receptors

this activates a signalling cascade

we get activation of phosphoplipase C

leads to increase in inositol triphosphate

the binding of this to calcium channels then leads to:
triggers Ca2+ release from the endoplasmic reticulum
calcium then acts as a signalling molecule to activate other ion channels

80
Q

parasympathetic nerve stimulation diagram

A
81
Q

what effect does the sympathetic nervous system have

A

noradrenaline raises intracellular cAMP

82
Q

diagram showing this effect

A
83
Q

what does raised intracellular cAMP lead to

A

protein secretion

84
Q

diagram summing up parasympathetic and sympathetic nerve activation

A

Semester 4 (80 decks)

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