Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Cellular And Molecular > Lecture 3 - Axons > Flashcards

Lecture 3 - Axons Flashcards

1
Q

What do nerve cells exhibit?

A

Excitability

Conductibility

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What do neurons have a threshold for?

A

Initialisation of an action potential of about -45 to -55mv

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What produces a large but transient flow of positive charge into the cell?

A

Increasing the voltage from -60 to 0mv

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is followed by a sustained flow of positive charge out of the cell?

A

The transient inward current

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Where are each action potential initiated in?

A

The initial portion of axon

Axon initial segment

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What does the initial segment of axon have?

A

Lowest threshold for action potential generation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Once a spike is initiated, where does the action potential propagate?

A

Down the axon to the synaptic terminal where it releases a transmitter to modulate intracellular processes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the refractory period?

A

Inactivation of Na+ channels

Activation of K+ channels

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is absolute refractory period?

A

Inactivation of Na+ channels

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is relative refractory period?

A

Occurs during the action potential afterhyperpolarisarion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is the implication of refractory period?

A

Action potential are not allowed to “reverberate”

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is critical for allowing impulses to propagate?

A

Local circuit

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Where does continuous conduction take place?

A

Unmyelinated fibres

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is continuous conduction?

A

The wave of depolarisation travels down the length of the axon

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

How does continuous conduction work?

A

Current flows when a patch of membrane is active

There is inward ionic current through sodium channels all around the circumference of the axon

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Why is the distribution of current slightly different?

A

Effect of the activation of voltage gated potassium channels following the activation of sodium channel

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

How does the sodium channel work?

A

Alters the amount of charge held on the membrane capacitance

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What flows in opposite direction?

A

Ionic current

Capacitance current

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

How does a sodium channel depolarise?

A

Passing ionic current inwards which is matched by a capacity current going outward

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Why can’t you change a membrane potential?

A

There is no capacity current

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What is Na+ current?

A

Inward and brief

Activate and inactivate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What is K+ current?

A

Outward and sustained

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

How do ionic currents contribute to action potential?

A

Na+ current generate upswing of action potential

Na+ channel inactivation and K+ channels activation underlie depolarisation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What does K+ channel activation generate?

A

Afterhyperpolarisation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

In squid axon, when does afterhyperpolarization occur?

A

After action potential

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

What happens when you excite a nerve somewhere along its length?

A

Impulses can be propagated away in both directions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

What happens when action potential is initiated naturally?

A

Propagates only in one direction because of the refractory period

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

Following an action potential, what happens when sodium channels are inactivated?

A

Another impulse cannot be generated

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

Not all nerve fibres are…

A

The same

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

What can be observed in a mixed nerve in a vertebrate (frog)?

A

Different fibre groups

31
Q

What is A alpha?

A

Largest motor axon

32
Q

What is A beta?

A

Largest sensory axon

33
Q

What is A Gamma?

A

Gamma motor neurons

34
Q

What has the highest conduction velocity?

A

Myelinated fibres

35
Q

What is B fibre?

A

Preganglionic synthesis

36
Q

What is C fibre?

A

Unmyelinated
Smallest diameter
Slowest conduction

37
Q

What is saltatory conduction?

A

A way of increasing conduction velocity in axon withoout having to make the diameter bigger

38
Q

What are 2 factors that determine conduction velocity?

A

Large diameter

Myelination

39
Q

What does large diameter show?

A

How far the potential can spread passively in axon

40
Q

What does efficient and rapid propagation of action potentials in myelinated axons?

A

Molecular specialisation of the nodes of Ranvier

41
Q

What does nodal regions have?

A

Unique set of ion channels
Cell adhesion molecule
Cytoplasmic adaptor proteins

42
Q

What are Schwann cells?

A

Satellite cells in the peripheral nervous system

43
Q

Why does sodium channel in the phase contrast image glow red?

A

Presence of selective antibody which is carrying fluorescent tag

44
Q

What does green fluorescence show?

A

Terminal loop of myelin attaching to the axon

45
Q

What is expressed where terminal loop of myelin touches the axon?

A

Casper

46
Q

What is the only place generating inward current?

A

Node of Ranvier

47
Q

What does current contour map show?

A

How a functionally isolated myelinated axons work

48
Q

What is present in the internode ?

A

Outward current (large capacity current)

49
Q

What is a nerve axon?

A

Series of element which have resistances and capacitance

50
Q

What is present outside the axon?

A

Resistance through the extracellular fluid

51
Q

What happens when current flow outside?

A

Potential difference occurring

52
Q

What is present inside the axon?

A

Axial resistance

53
Q

What is present across the membrane?

A

Resistance which can change

The ability to pass ionic currents

54
Q

What are properties of C fibre?

A

Very thin
High axial resistance
Space constant is short (0.5 micrometer diameter)

55
Q

A fibre

A

Local circuit is present all the way along the internode (10micrometer)

56
Q

What do large axons have?

A

Low R axial resistance

Easier to push a current along

57
Q

What did Ruston WAH calculate?

A

Small axons are not myelinated

Large axons are myelinated

58
Q

What is the relationship between myelinated and unmyelinated fibres?

A

As the diameter of the fibre is increased, myelinated axons will conduct faster

59
Q

What did Tasaki 1959 show?

A

Air is an insulator
Air gaps block any current flow
There is stimulator to initiate action potential
Action potential will propagate through nerve bath along axon

60
Q

What do air gap force?

A

The current flow outside the axon to go through Tasaki’s wire

61
Q

What does amplifier measure?

A

Potential changes across the resistor

V=I/R

62
Q

What is an example of outward current?

A

capacitance/capacity

63
Q

Conduction velocity in a large myelinated axon is around…

A

50 ms-1 (~ 60 ms-1)

64
Q

An action potential at a single point lasts close to …

A

0.5 milliseconds at body temperature

65
Q

What is a part of cytoskeleton?

A

anKg

66
Q

What is expressed in the paranode where there are terminal loops of myelin?

A

Caspr and Contactin

67
Q

What is Juxtaparanode?

A

Sodium channels expressed underneath the myelin

68
Q

What is an important cell adhesion molecule in the myelin?

A

P0

69
Q

Where is P0 expressed?

A

On extracellular faces of myelin membrane

70
Q

What is myelin made up of?

A

Turns of cell membrane

71
Q

Why is axon-satellite cell interaction crucial?

A

Formation of nodes of Ranvier

72
Q

What is important factor in Na+ channel clustering?

A

Interaction of gliomedin in Schwann cells and NF-186

73
Q

What does myelinated axon membrane incorporate?

A

Domain typically expressing certain ion channels and cell adhesion meolcules (CAMs)

74
Q

What does the sheath contain?

A

characteristic CAM
E.g. P0
P0 stabilise myelin

Cellular And Molecular (9 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions