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Principles Pharmacology > Action Potentials > Flashcards

Action Potentials Flashcards

1
Q

Does the inner surface of the cell membrane have a negative or positive potential with respect to the outer surface?

A

Negative

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2
Q

What is depolarization?

A

Membrane potential becomes less negative

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3
Q

What is hyperpolarization?

A

Where membrane potential becomes more negative

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4
Q

What 2 things does direction of change of potentional (hyper or depolarization) depend on?

A

Direction of ion movement and charge carried by ion

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5
Q

What drives passive movement through ion channels?

A

Electrochemical gradient

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6
Q

What is movement of sodium in response to?

A

Opening of cell membrane sodium-selective channels (sodium conductance)

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7
Q

What is the symbol for G? How can you rearrange Ohm’s law to fit it in?

A

G. V=1/G

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8
Q

What is Ohm’s law?

A

V=IR

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9
Q

In what direction does Sodium flow?

A

Inwardly

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10
Q

In what direction does Potassium flow?

A

Outwardly

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11
Q

What is the membrane potential for sodium ions?

A

+60mV

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12
Q

What is the membrane potential for potassium ions?

A

-100mV

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13
Q

What is the membrane potential for most neurones?

A

-70-80mV

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14
Q

What is the definition of an action potential?

A

Brief electrical signal in which the polarity of the nerve cell membrane is reversed.

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15
Q

In action potentials, what happens once depolarization reaches a critical value (threshold value)?

A

Voltage-gated sodium channels open very rapidly along the neurone, causing rapid depolarization (upstroke)

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16
Q

What causes the downstroke in action potentials?

A

Voltage gated potassium channels are opened, leading to rapid repolarisation

17
Q

Why does undershoot occur?

A

Voltage gated potassium channels are still open

18
Q

Do action potentials propagate along nerve cell axons with constant or varying magnitude and velocity?

A

constant (allowing signalling over long distances)

19
Q

What was discovered in the Hodgkin-Katz experiment?

A

Sodium ions cause upstroke, potassium ions cause downstroke

20
Q

What activates voltage-activated Na+ and K+ channels?

A

membrane depolarization

21
Q

Is activation of sodium channels self limiting (negative feedback) or self reinforcing (positive feedback)?

A

self reinforcing (positive feedback)

22
Q

Is activation of potassium channels self limiting (negative feedback) or self reinforcing (positive feedback)?

A

self limiting (negative feedback)

23
Q

During maintained depolarization, what do voltage-activated sodium channels enter?

A

non-conducting, inactivated state

24
Q

What is required for the channel to enter the closed state?

A

repolarization

25
Q

What is responsible for the refractory period?

A

Inactivation contributing to repolarizing phase

26
Q

Where are dorsal route ganglia?

A

bilateral on either side of the spinal column posteriorly

27
Q

How many processes do dorsal route ganglia have?

A

2 each

28
Q

What do action potentials progress along to the CNS?

A

whole length of axon

29
Q

Are the sensory fibres myelinated or non-myelinated?

A

non-myelinated

30
Q

What is the myelin sheat made up of?

A

Schwann cells

31
Q

How are Schwann cells situated around axon?

A

wrap around axon in concentric layers

32
Q

What do Schwann cells do?

A

protect, insulate electrically, carry out some phagocytosis

33
Q

What does the myelin sheath do?

A

Prevent any ion channels opening where it covers membrane

34
Q

The action potential jumps between gaps between adjacent Schwann cells: what is this type of conduction?

A

Saltatory conduction

35
Q

What are the gaps between Schwann cells called?

A

Nodes of Ranvier

36
Q

What is the difference between the absolute and relative refractory period?

A

Absolute: no stimulus can elicit second action potential
Refractory: Stronger than normal stimulus may elicit second action potential

Principles Pharmacology (6 decks)

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