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nas > Memrane Physiology > Flashcards

Memrane Physiology Flashcards

1
Q

Function of cell membrane

A

Defines boundaries of cell
Enclose cell organelles
Enables cell to create an internal environment

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2
Q

Describe the compartment within confines of the cell membrane

A

Intracellular environment
Largely aqueous

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3
Q

Describe the compartment outside the cell membrane

A

Extracellular compartment:
Interstitial space
Largely aqueous

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4
Q

Examples of charge carrying particles in the intracellular environment

A

Organelles
Proteins
Anions or cations

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5
Q

Chemical gradient?

A

Concentration gradient of ions between the Intracellular and extracellular compartments of the cell

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6
Q

Electrical gradient?

A

Known as membrane potential
Electrical polarity between inside and outside of cells due to charged particles

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7
Q

Electrochemical gradient?

A

Combined electrical and chemical gradients
Standing electrochemical gradient because continuously present

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8
Q

What is Resting membrane potential?

A

Cells of different tissue have different resting potentials
Electrical gradient between inside and outside of the cell
Maintained via ion pump
Leak channels open

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9
Q

RMP of nerve cell?

A

-70 mv

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10
Q

Characteristic of electrically excitable tissues?

A

They able to momentarily discharge the standing electrical potential between the Intracellular and extracellular compartments

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11
Q

What is death in terms of electrically excitable tissue?

A

The permanent discharge of resting membrane potentials

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12
Q

Factors that decide what can cross cell membrane

A

Size
Polarity
Solubility in water
Ion channel/ protein

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13
Q

Types of ion channels

A

Selective
Leak

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14
Q

Transmembrane spanning proteins?

A

Protein assemblies that span the full thickness of the cell membrane

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15
Q

Common on ion channels

A

Voltage gated - generate AP
Ligand gated - generate Em at synapse with NT
Leak - set RMP
Mechanically gated

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16
Q

What is the function Ion pumps in nerve cells?

A

Maintain resting potential, dont set it up
Require ATP

they provide the starting point for the ability of the cell to generate electrical signals.

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17
Q

What is a Graded depolarisation?

A

Depolarisation is proportional to the strength of stimulation applied
Once threshold reached same AP always generated

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18
Q

What is level of membrane potential at which graded depolarisations become an action potential known as?

A

‘Threshold level’
Different neuronal cell types have different threshold levels
~ -55mV in neurones

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19
Q

Value of Resting membrane potential

A

-70mV

20
Q

Nerst equation used for

A

Calculates membrane potential at eqm for each of the ions in question

Need to know relative conc of ion intracellularly and extracellularly

21
Q

Epm potential of K+

A

-80mV

22
Q

Eqm potential of Na+

A

+60mV

23
Q

What is conductance of ion channels

A

Represents the activity of ion channels
Directly proportional to how many channels are opening in membrane
Each ion has its own conductance

24
Q

When are voltage gates channels open

A

RMP closed
Depolarisation Na+ open
Repolarisation K+ open

25
Q

Goldman Hodgkin Katz equation

A

Modification of the nerst equation
Takes into account relative permeabilities of ions in question

26
Q

What happens during depolarisation

A

Na+ enters the cell
Membrane depolarises
Depolarisation reaches threshold
More Voltage gated Na+ channels open

27
Q

Repolarisation events

A

K+ channels open - K+ efflux
Na+ channels closed - Na+ influx stopped

28
Q

Extracellular voltage?

A

Zero mV

29
Q

Channels that determine resting membrane potential?

A

Leak channels control permeability at rest

30
Q

Electrogenic?

A

Many active transport mechanisms are electrogenic
Produce change in voltage because there is net movement of anions/ cations to one side of membrane

31
Q

Chemical force

A

Differences in ion concentration

32
Q

Electrical force?

A

Due to electrical charge intracellularly/ extracellularly
Membrane potential of the cell

33
Q

What is eqm potential?

A

When chemical force = electrical force
Equal and opposite

34
Q

Resting membrane potential will be equal to eqm potential if membrane permeable to one ion only. True/ False?

A

True
Skeletal muscle cells/ glial cells only permeable to k+
So membrane potential = K+ eqm potential

35
Q

Ion composition of Na and K

A

• K+ concentration is high inside the cell, low outside
• Na+ concentration is low inside the cell, high outside

36
Q

Driving an ion across the membrane electrically requires:

A

• the membrane possesses channels permeable to that ion to provide conductance
• There is an electrical potential difference across the
membrane

37
Q

How does Em remain constant

A

Na influx = K efflux
- Driving force of K small and cell has large permeability to K
- Driving force of Na large but small permeability to Na

38
Q

Why is the Na driving force large at Em (resting membrane potential)

A

Na influx due to chemical and electrical force
Big electrical difference. Na eqm is +60mV and Em is -65mV.
More Na outside due to pump so steep Chemical gradient.

39
Q

What does resting potential depend on

A

Permeability of the ions
The ions driving forces

40
Q

What is a nerve cell more permeable to?

A

K
More K leak channels

41
Q

Why is there a small K driving force at RMP

A

Eqm potential of K+ is -80mV and Em is -65m. So small difference.
Chemical gradient (causing efflux) is greater than electrical force (causing influx)

42
Q

Which ion is resting membrane most permeable to

A

K+

43
Q

What are the permeabilities of ions during hyperpolarisation

A

Increased k+ permeability
Decreased Na+ permeability

44
Q

What is the conductance of ions during depolarisation

A

Sodium has higher conductance than potassium
So sodium influx

45
Q

What is refractory period caused by

A

Inactivation of na+ channels
Delayed closing of K+ channels

46
Q

Do AP spread backwards?

A

No

nas (17 decks)

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