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Neural Control of Movement > Lecture 3 > Flashcards

Lecture 3 Flashcards

1
Q

myelinated fiber

A

enclosed in a sheath made of nonneural cells (glial cells)

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2
Q

The ____________ has breaks (Ranvier nodes) where action potentials are generated

A

myelin sheath

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3
Q

Slow nerve conduction speed

A

0.5 m/s

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4
Q

Sprinter Speed

A

10.0 m/s

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5
Q

Speed Limit

A

30 m/s

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6
Q

Fast nerve conduction speed

A

100 m/s

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7
Q

Sound in air speed

A

330.0 m/s

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8
Q

Light or electromagnetic field

A

300,000,000 m/s

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9
Q

Conduction of an Action Potential

A
  1. Membrane depolarization to the threshold
  2. Generation of an action potential
  3. Local currents spread passively
  4. They depolarize adjacent areas of the membrane
  5. A new action potential is generated
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10
Q

Myelin increase what in local currents?

A

Myelin increases the effective distance of local currents

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11
Q

What is the velocity of conduction in myelinated fibers?

A

6*d (m)

velocity in m/s

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12
Q

Orthodomic Conduction

A

from soma to terminal branches

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13
Q

Anti-orthodomic conduction

A

from the end of the axon to the soma

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14
Q

Soma

A

body of the cell; the site of input signals

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15
Q

Dendrites

A

shot branches originating from the soma; sites of inputs

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16
Q

Axon

A

a long branch; transmits output signals

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17
Q

Axon Hillock

A

the site where the axon exits the soma; typically, the site of generation of action potentials

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18
Q

terminal branches

A

a “brush” at the end of the axon

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19
Q

myelin

A

a fatlike substance covering the axon; it increases the speed of conduction of action potentials

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20
Q

ranvier nodes

A

breaks in the myelin sheath; places where action potentials are generated

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21
Q

Nerve (peripheral) or neural tract (central)

A

many axons running together

22
Q

How many ion channels are there under the myelin sheath in a neuron?

A

there are virtually no ion channels under the myelin sheath.

23
Q

How many ion channels are there in the Ranvier nodes in neurons?

A

There are many ion channels in the Ranvier nodes.

24
Q

the importance of ______ for the generation of APs has gained prominence lately (steady depolarization) in neurons.

A

dendrites

25
Q

What is a PIC?

A

a depolarizing inward current that activates as long as the membrane potential is depolarized

26
Q

PIC’s allow for an increase _________________.

A

in the number of action potentials that are generated.

27
Q

Recent studies have reported that PIC’s are strong in ____________ during everyday tasks.

A

human alpha motorneurons

28
Q

PIC’s are likely strong enough to play a major role in defininf the patterns of ________________________.

A

recruitment and derecruitment of motor units

29
Q

PIC’s are very sensitive to ___________ inhibition, meaning they can be controlled?

A

postsynaptic

30
Q

What effect does the all or none law have on action potential generation?

A

Each action potential transmits 1 bit of information

31
Q

How can a neuron encode significant amounts of information?

A

By generating sequences of action potentials

  • by changing the frequency of firing
  • neurons take into account the timing and number of action potentials
32
Q

What does a synapse consist of?

A

A synapse consists of a presynaptic membrane, a synaptic cleft, and a postsynaptic membrane.

33
Q

What happens with an action potential in a presynaptic fiber?

A

An action potential in a presynaptic fiber makes synaptic vesicles move to the membrane, fuse with it, and release molecules of neurotransmitters into the cleft.

34
Q

What changes the potential of the postsynaptic membrane?

A

The neurotransmitters act at the postsynaptic membrane and change its potential.

35
Q

Obligatory synapse

A

AP on the presynaptic membrane always gives rise to an AP on the post synaptic membrane

36
Q

Nonobligatory Synapse

A

A single AP on the presynaptic membrane is typically unable to induce an AP on the postsynaptic membrane?

37
Q

A presynaptic action potential can induce either a depolarization or a hyperpolarization of the postsynaptic membrane. These eggects are called __________.

A

EPSP and IPSP

38
Q

Synaptic Transmission

A
  1. A presynaptic action potential arrives
  2. The presynaptic membrane lets vesicles with molecules of neurotransmitters pass though
  3. The vesicles release the neurotransmitters into the synaptic cleft
  4. The molecules diffuse across the cleft to the postsynaptic membrane and act at special sites (receptors).
  5. The postsynaptic membrane is either depolarized or hyperpolarized.
39
Q

How long does the synaptic transmission process take?

A

0.5 ms

40
Q

Gap junction channels in electrical synapses

A

Gap junction channels provide a low resistance pathway for the electrical current to flow between cells

41
Q

Current flow in Electrical synapses

A

current flows from the presynaptic cell into the postsynaptic cell, depositing a positive charge

42
Q

Depolarization in electrical synapses

A

If depolarization exceeds threshold, the postsynaptic cell will generate an action potential

43
Q

Synaptic delay in Electrical Synapses

A

Very little synaptic delay

44
Q

What kind of current can electrical synapses transmit?

A

can transmit both depolarizing and hyperpolarizing currents

45
Q

Where are electrical synapses located?

A

between glial cells and schwann cells in the brain

46
Q

What are electrical synapses likely to be involved in?

A

brain signaling and myelin formation

47
Q

temporal summation

A

occurs when several action potentials arrive at a presynaptic membrane at intervals that do not allow individual EPSPs to disappear. Their effects can sum up and induce an action potental

48
Q

spatial summation

A

spatial summation occurs when several action potentials arrive simultaneously synapses on the same presynaptic membrane so that their individual EPSPs sum up and can induce an action potential.

49
Q

temporal and spatial summation can occur for both _____.

A

EPSPs and IPSPs.

increases the amount of inhibition.

50
Q

The phenomenon of ________ does not allow an action potential to “backfire.” If an action potential comes to point 2 from point 1, it cannot go back. It can only travel forward to point 3.

A

inactivation of sodium channels

Neural Control of Movement (24 decks)

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