DONE Action Potential Flashcards

1
Q

What is an increase in conductance?

A

An increase in the number of open channels for a particular ion

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2
Q

Absolute refractory period

A

during depolarisationMost sodium channels inactivated = can’t fire A.P. as clan only open again from closed state (go from inactive to closed during HYPERPOLARISATION)

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3
Q

Relative refractory period

A

Hyperpolarization = sodium channels recovering from inactivation, voltage gated potassium channels close

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4
Q

Sodium channel subunit

A

1 alpha subunit to form functional sodium channel

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5
Q

Potassium channel subunit

A

4 x alpha subunit to form 1 functional potassium channel

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6
Q

What is lidocaine?

A

Local anaesthetic = is membrane permeable in its unprotonated form
Blocks sodium channels = no A.P.

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7
Q

What is the length constant?

A

Distance it takes for the potential to fall to 37% of its original value
Longer length = faster conduction velocity

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8
Q

What is capacitance?

A

Ability to store charge = property of lipid bilayer

High capacitance = voltage changes more slowly in response to current injection

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9
Q

Membrane resistance

A

Lower resistance = more ion channels open = more loss of local current across membrane
High resistance = change in voltage spreads further along axon

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10
Q

How does a myelin sheath improve conduction?

A

Large increase in membrane resistance
Decrease membrane capacitance
Which both increase length constant

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11
Q

Acetylcholine esterase

A

Breaks down ACh

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12
Q

How is transmitter released?

A
Calcium enters through calcium channels 
Binds to synaptotagmin
Vesicle brought close to membrane 
Snare complex makes fusion pore
Transmitter released through pore
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13
Q

What does d-tubocurarine do?

A

Competitive block of nAChR = paralysis

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14
Q

What does succinylcholine do?

A

Depolarising block = adjacent sodium channels inactivated = no depolarisation

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15
Q

Myasthenia gravies

A

Autoimmune disease of nAChR by antibodies

Loss of functional nAChR = end-plate potentials fail to reach threshold = muscle weakness + fatigue

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16
Q

End plate potential

A

ACh binds to nAChR on muscle end-plate = open + cations flow = a depolarisation occurs

17
Q

Depolarisation

A

Decrease in size of mem potential from normal value, cell interior less -ve

18
Q

Ek for potassium

Ecl for chlorine

A
  • 95mV

- 96mV

19
Q

Ena

Eca

A

+70mV

+122mV

20
Q

Membrane potentials of different cells

A

Cardiac myocytes = -80mV
Neurones = -70mV
Skeletal muscle = -90mV
Smooth muscle = -50mV

21
Q

How does an action potential occur?

A

Depolarisation = Na in
Repolarisation = K out
Hyperpolarisation