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Pharmacology - Principles > Action Potentials - Lecture 6 > Flashcards

Action Potentials - Lecture 6 Flashcards

1
Q

What is the typical resting membrane potential of a cell?

A

-70mV

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2
Q

What is depolarisation?

A

Depolarization – the membrane potential becomes less negative (or even positive)

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3
Q

What is hyperpolarisation?

A

Hyperpolarization – the membrane potential becomes more negative

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4
Q

What is influx?

A

The direction of the movement of the ion into the cell

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5
Q

What is efflux?

A

The direction of the movement of the ion out of the cell

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6
Q

How does movement of ions occur?

A

Movement of ions across membranes requires ion channels

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7
Q

The movement of a positive ion into the cell causes what to the membrane potential?

A

This causes depolarisation of the cell

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8
Q

The movement of a negative ion into a cell causes what to the membrane potential?

A

This causes hyperpolarisation

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9
Q

What is passive movement of an ion through an ion channel driven by?

A

Driven by an electrochemical gradient

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10
Q

What is the movement of Na+ in response to the opening of cell membrane sodium-selective channels called?

A

Na+ Conductance

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11
Q

How can the “driving force” of an ion into/out of a cell be calculated?

A

Driving force = Membrane potential - Equilibrium potential

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12
Q

What is the definition of the “driving force” of an ion?

A

It is the energy from the concentration gradient of that ion and the energy from the electrical gradient of that ion

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13
Q

What are ion channels?

A

Ion channels are protein complexes that span the lipid bilayer to form a central pathway that allows rapid flow of selected ions

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14
Q

What are the types of ions channels that are open gated?

A

Membrane voltage – voltage-gated ion channels
Chemical substances – ligand-gated ion channels
Physical stimuli – e.g., mechanical, thermal

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15
Q

What voltage activate channels are responsible for depolarising?

A

Na+

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16
Q

What voltage activate channels are responsible for hyperpolarising?

A

K+

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17
Q

What is an action potential?

A

A brief change were the membrane changes polarity

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18
Q

Describe an action potential.

A

Sodium channels open causing sodium to enter and cause an extreme depolarising signal - This is called the upstroke

This causes voltage activated potassium to open and for potassium to leave - This is the downstroke

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19
Q

What occurs after the downstroke in an action potential?

A

An Undershoot

20
Q

What causes an undershoot in an action potential?

A

Caused by Potassium channels remaining open and Potassium continuing to leave the cell

21
Q

What occurs at the peak of an action potential?

A

It transiently changes polarity

22
Q

What triggers an action potential?

A

A depolarising stimulus

23
Q

How long does an action potential last for?

A

2 ms

24
Q

Describe how the action potential moves along the axon?

A

Constant Velocity

Constant Magnitude

25
Q

What must be overcome for an action potential to be sent?

A

A Threshold

26
Q

What is the stimulus that will not send an action potential?

A

Subthreshold depolarizing stimulus

27
Q

What is the stimulus that will send an action potential?

A

Threshold depolarizing stimulus

28
Q

Describe ion conductance at the rest, before the action potential is sent.

A

At rest there is Potassium Conductance out of the cell

29
Q

Describe ion conductance at the peak of the action potential.

A

Sodium channels open - causing depolarisation

30
Q

Describe ion conductance at the undershoot of the action potential.

A

Increased Potassium conductance out of the cell

31
Q

The activation of Sodium channels can be defined as what type of feedback system?

A

A Positive Feedback system

  • Depolarisation as sodium enters, causes more Na+ channels to open
32
Q

The activation of Potassium channels can be defined as what type of feedback system?

A

A Negative Feedback System

-Depolarisation cases the Potassium channels to open. Outward flow causes re polarisation, which shuts off Potassium channels

33
Q

What turns off the Sodium Selective Ion Channels?

A

Opening of Potassium Channels

  • Re polarisation
34
Q

There are two gates on ion channels - What are they?

A

The Activation Gate

The Inactivation Gate

35
Q

Describe the gates when an ion channel is closed?

A

The Activation Gate is closed

The Inactivation Gate is closed

36
Q

Describe the gates when an ion channel is depolarised?

A

The Activation Gate is Open

The Inactivation Gate is Open

37
Q

Describe the gates when an ion channel is re polarising?

A

The Activation Gate is Open

The Inactivation Gate is Closed

38
Q

What is the period of time when the neurone cannot transmit a signal called?

A

The Refractory period

39
Q

What are the two types of Refractory Periods?

A

Absolutely Refractory Period

Relative Refractory Period

40
Q

Can an action potential occur in a refractory period?

A

Yes.

Required a larger depolarisation however.

41
Q

What is an Absolute Refractory Period?

A

No stimulus can elicit an action potential

42
Q

What is a Relative Refractory Period?

A

A stronger than normal signal can elicit an action potential

43
Q

What cells are used in the peripheral nervous system to insulate the axon?

A

Schwann Cells

44
Q

What cells are used in the central nervous system to insulate the Axon?

A

Oligodendrocytes

45
Q

Describe Saltatory Conduction in Myelinated Axons?

A

The Action Potential jumps from one node of ranvier to the next

46
Q

What conducts better:

A Myelinated Axon or a Unmyelinated axon?

A

Myelinated

Pharmacology - Principles (6 decks)

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