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Bio /chem/cell > Membrane Potential W2 > Flashcards

Membrane Potential W2 Flashcards

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1
Q

Why are membrane dynamic (3)

A

Growth
Movement
Proteins have a finite lifetime

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2
Q

Why are membranes excitable (4)

A

Communication
Movement
Contraction
Respond to stimulus

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3
Q

What causes membrane potential

A

Regulation of ion movement which causes a difference in charge

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4
Q

The ….. of membrane in positive

A

Outside

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5
Q

The …. of the membrane is negative

A

Inside

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6
Q

What is the resting membrane potential

A

Charge difference across a cell at rest (unstimulated)

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7
Q

Muscle resting membrane potential …. mV

A

-85

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8
Q

Nerve testing membrane potential ….mV

A

70

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9
Q

Membrane is said to be …… at rest

A

Polarised

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10
Q 
Inside cell:
Lots of....
Not much....
Compared to outside 
AT REST
A

K+

Na+

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11
Q

To cross lipid rich membrane

Ions need

A

Transport proteins

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12
Q

Proteins responsible for maintaining membrane potential (2)

A

Ion channels

Membrane bound enzymes

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13
Q

Example of ion channel

A

Sodium channels

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14
Q

What do sodium channels do

A

Allow sodium ions to flow down concentration gradients

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15
Q

Example of membrane bound enzymes

A

Sodium - potassium ATPase

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16
Q

What does Sodium - potassium ATPase pump do

A

Uses atp to pump ions through membrane against concentration gradient

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17
Q

….. …… form the basis of cell communication

A

Ion channels

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18
Q

Two types of ion channels

A

Non gated

Gated

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19
Q

When do gated ion channels open

A

Randomly

20
Q

When do ligand gated ion channels open

A

Open in response to chemical stimuli

21
Q

When to voltage gated ion channels open

A

In response to chemical stimuli

22
Q

Two types of gated ion channels

A

Ligand gated

Voltage gated

23
Q

Ion channel structure

A

5 integral proteins joined together

24
Q

Which region of ion channels line inside of the protein

A

Hydrophilic

25
Q

Which region of ion channels line outside of the protein

A

Hydrophobic

26
Q

Ion Channels- what determines which ions may pass

A

The charge of the hydrophilic region of proteins that join together to make ion channel

27
Q

How to ligand gated ion channels open - what do they have and process

A

Exposed receptor site for binding specific ligand molecules

Molecule binds - changing shape of protein and allowing ions to flow through

28
Q

Example of ligand gated ion channel opening

A

Muscle contraction -Acetylcholine bonds to Ligan gated sodium channel on surface of muscle fibre
Sodium flows into cell causing depolarisation

29
Q

Example of voltage gated ion channels opening closing process (Na+/K+)

A

Na+ flows into nerve cell causing depolarisation

Voltage gated K+channels open causing repolarisation

30
Q

K+/Na+ ATPase - how many molecules of ….. does it pump out of the cell

A

3 Na+ molecules

31
Q

K+/Na+ ATPase - how many molecules of ….. does it pump into the cell

A

2K+

32
Q

What two factors maintain the resting membrane potential

A

Leakage ion channels

K+/Na+ ATPase pump

33
Q

Passive ion diffusion is up/down the chemical gradient

A

Down

34
Q

When ions move to a region of opposite charge they move ….. their electrical gradient

A

Along

35
Q

How does membrane potential change

Via ……… or ……… - ……. ion channels

A

Voltage or ligand gated

36
Q

Phases of ACTION potential

A

Initial stimulus - ligand gated ion channels open

Voltage - gated Na+ channels open

Voltage gated K+channels open

37
Q

1*Phases of ACTION potential -initial stimulus

Describe

Result

A

Ligand gated channels open allowing Na+ to flow into the cell down its concentration gradient

Depolarises local area of cell to threshold (about -50mV)

38
Q

2Phases of ACTION potential: Voltage - gated Na+ channels open

Describe

Result

A

Very brief Na+ rushes in down concentration gradient

Initiates propagated action potential

39
Q

3Phases of ACTION potential: Voltage - gated K+ channels open

Describe

Result

A

K+ rushes out of cell (slower rate than that of Na+rushing in before)
Voltage gated Na+ channels begin to close

Repolarisation

40
Q

Describe the process of action potential

A

Rest–>depolarisation–>repolarisation–>rest

RESTING MEMBRANE POT 
atlases pump maintaining rest 
Most ion movement via leakage channels 
DEPOLARISATION
stimuli(eg the opening of ligand gated Na+ ion channel)  opens a voltage gated Na+ channel, depolarising the membrane potential 
REPOLARISATION 
voltage gated Na+ channels inactivated 
Voltage gated K+ channels activated 
RESTORING MEMBRANE POTENTIAL 
Na+/K+ ATPase works to restore Reston membrane potential (more Na+ outside that's inside and more K+ inside rather than outside)
41
Q

Action potentials and skeletal muscle contraction process

Describe

A

An action potential arrives at neuromuscular junction

Causing aCh to be released
aCh binds to ligand gated sodium ion channels which initiates action potential in that cell
This travels along t tubules
And prompts the release of calcium ions
Calcium ions bind to troponin –> moving tropomyosin away

42
Q

Action potential and nerve conduction

Describe

A

In response to signal soma end of axon becomes depolarised

Depolarisation spreads down the axon, meanwhile whilst the soma depolarises

Action potential continues to travel down the axon

43
Q

What determines how quickly action potentials can be repeated

A

Refractory period

44
Q

Two types of refractory periods

A

Absolute

Relative

45
Q

What does absolute refractory period mean

Why is this so

A

Additional depolarising stimuli do not relish in new action potential

Because Na+ channels are inactivated during this time

46
Q

What does relative refractory period mean

Why is this so

A

Only strong enough stimuli will result in action potential

Because Na+ channels begin to recover but K+ channels have not closed yet
So and efflux of Na+ ions will be balanced out but he efflux of K+ions unless it’s big enough

Bio /chem/cell (13 decks)

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