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EP 4703: Neural Control Of Human Movement > Test 1 (Lectures 1-7, 8a) > Flashcards

Test 1 (Lectures 1-7, 8a) Flashcards

1
Q

The five questions of neural science?

A
  1. How does the brain develop?
  2. How do nerve cells in the brain communicate with each other?
  3. How do different patterns of interconnections give rise to different perceptions and motor acts?
  4. How is communication between neurons modified by experience?
  5. How is that communication altered by disease?
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2
Q

How many individual nerve cells are in the human brain?

A

Over 100 billion

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3
Q

Reducing the elements of a system to a basic level of functioning elements?

A

Reductionism

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4
Q

Knowledge of the elements essential to understanding the system but greater emphasis is placed on investigating and understanding the system as a whole

A

Complex System Approach

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5
Q

This approach allows for a more succinct description of behavior and the interpretation

A

The Complex System Approach

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6
Q

Why are membranes partially permeable?

A

Helps them regulate the influx and efflux of ions

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7
Q

Three major types of substances that can cross membranes

A

Solvents
Electrolytes
Non electrolytes

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8
Q

Example of a solvent

A

Water

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9
Q

Example of an electrolyte

A

Ions

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10
Q

Example of a nonelectrolyte

A

Non-charged molecules

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11
Q

High pressure to low pressure

A

Convection

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12
Q

High concentration to low concentration

A

Diffusion

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13
Q

Movement of a solute based on a pressure

A

Convection

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14
Q

Movement of the concentration of particles within a solution.

A

Diffusion

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15
Q

Movement of a solvent (water) and solutes from an area of high pressure to an area of low pressure.

A

Convection

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16
Q

The movement of particles dissolved in a solvent from an area of high concentration to an area of low concentration

A

Diffusion

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17
Q

This creates a difference of potentials that induces a flow of charged particles

A

An electric field

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18
Q

Movement of a solvent (water) and solutes from an area of high pressure to an area of low pressure.

A

Convection

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19
Q

The movement of particles dissolved in a solvent from an area of high concentration to an area of low concentration

A

Diffusion

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20
Q

This creates a difference of potentials that induces a flow of charged particles

A

An electric field

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21
Q

The 2 forces that ion movement is influenced by

A

Concentration

Difference of potentials

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22
Q

Movement of charged particles (ions) under the action of a difference of potentials

A

Electric current

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23
Q

Movement of water (solvent) from an area of low solute concentration to an area of high solute concentration; the total concentration of particles matter

A

Osmosis

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24
Q

Low concentration to high concentration

A

Osmosis

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25
Q

Allow certain substances across, but not others

A

Membrane channels

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26
Q

Movements of all particles are counterbalanced in this state

A

Equilibrium

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27
Q

3 properties of ion channels

A
  1. They conduct ions
  2. They recognize specific ions
  3. They open and close in response to specific electrical, mechanical, or chemical signals
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28
Q

How many ions can pass through a channel per second

A

Up to 100 million ions

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29
Q

What is the difference in electrical potential across the membrane known as?

A

Resting membrane potential

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30
Q

Resting membrane potential of neurons are around

A

-60 mV to -70 mV

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31
Q

Regenerative electrical signal in which the amplitude does not attenuate as it moves up or down the axon

A

Action potential

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32
Q

This allows for a much more rapid pace than convection or diffusion

A

Action potential

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33
Q

Communication based on this is far greater than that of diffusion or convection

A

Membrane potential

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34
Q

Maintains ion concentration gradients across the membrane

A

Sodium-potassium pump

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35
Q

The three ions that play an active role in the electric capabilities of a system and influence neural communication

A

Sodium (Na+)
Potassium (K+)
Chloride (Cl-)

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36
Q

How can an electric potential emerge by itself?

A

If a membrane separates two areas with and without Na+ and Cl- ions, diffusion of the ions will occur from the area of high concentration to low concentration

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37
Q

Do different ions diffuse at the same rate?

A

No

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38
Q

These store electrical charges and electrical potentials

A

Capacitors

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39
Q

The membrane can be considered a

A

Capacitor

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40
Q

The dispersion of an electrical signal

A

Action potential

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41
Q

Small stimulus leads to

A

A small response

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42
Q

Medium stimulus leads to a

A

Medium response

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43
Q

Large stimulus leads to

A

A large response

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44
Q

An action potential can only occur when

A

The stimulus is strong enough to depolarize the membrane beyond the membrane potential

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45
Q

When the stimulus leads to depolarization of the membrane potential to the point of generating an action potential, an action potential will be generated. Increasing stimulus intensity will not lead to an increase in the generation of the action potential.

A

All or none principle

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46
Q

Negative movement away from the threshold

A

Hyperpolarization

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47
Q

Positive movement towards the threshold

A

Depolarization

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48
Q

The size and shape of every action potential is always

A

The same

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49
Q

Either the membrane doesn’t generate an action potential or it generates an action potential with a standard shape and magnitude.

A

All or none principle

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50
Q

A membrane’s resting potential will change somewhat in response to a small stimulus before

A

Returning to its resting level

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51
Q

The period after an action potential where the possibility of generating another action potential is reduced or not possible

A

Refractory period

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52
Q

The period following an action potential in which it is possible to generate another action potential

A

Relative refractory period

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53
Q

The period following an action potential in which it is not possible to generate another action potential

A

Absolute refractory period

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54
Q

This leads to a rapid amplification of the effect

A

Positive feedback

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55
Q

The leads to a restoration of the original state

A

Negative feedback

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56
Q

Depolarization

A

Positive feedback

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57
Q

Hyperpolarization

A

Negative feedback

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58
Q

This does not allow an action potential to “backfire”

A

Inactivation of sodium channels

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59
Q

In nerve fibers, larger diameters

A

result in signals traveling faster

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60
Q

An enclosed sheath of non-neural (glial) cells covering neurons

A

Myelinated fiber

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61
Q

Breaks in myelin sheath

A

Ranvier nodes

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62
Q

Where action potentials are generated in neurons

A

Ranvier nodes

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63
Q

5 steps of action potential conduction

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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64
Q

This increases the effective distance of local currents in neurons

A

Myelin

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65
Q

Velocity of conduction in myelinated fibers in m/s

A

6 x d(m)

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66
Q

These two things prevent action potentials from backfiring

A

Absolute refractory period

Inactivation of sodium channels

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67
Q

The biggest and fastest neurons in the body

A

Sensory types IA and IB

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68
Q

This type of neuron is not far behind the biggest and fastest neurons in the body

A

Motor type Aa.

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69
Q

Conduction from the soma to terminal branches

A

Orthrodromic conduction

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70
Q

Conduction from the end of the axon to the soma

A

Antidromic conduction

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71
Q

These neurons are orthrodromic

A

Motor neurons

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72
Q

These neurons are antidromic

A

Sensory neurons

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73
Q

Body of the cell; the site of input signals

A

Soma

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74
Q

Short branches originating from the soma; sites of inputs

A

Dendrites

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75
Q

A long branch; transmits output signals

A

Axon

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76
Q

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

A

Axon hillock

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77
Q

A “brush” at the end of the axon

A

Terminal branches

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78
Q

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

A

Myelin

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79
Q

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

A

Ranvier nodes

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80
Q

Many axons running together

A

Nerve (peripheral) or neural tract (central)

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81
Q

Are there ion channels under the myelin sheath?

A

No

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82
Q

Are there ion channels in the Ranvier nodes?

A

Yes, there are many ion channels

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83
Q

Each action potential transmits

A

1 bit of information

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84
Q

How can a neuron encode significant amounts of information?

A

By generating sequences of action potentials.

  • By changing the frequency of firing
  • Neuron take into account the timing and number of action potentials
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85
Q

What does a synapse consist of?

A

A presynaptic membrane, a synaptic cleft, and a postsynaptic membrane

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86
Q

These change the potential of the postsynaptic membrane

A

Neurotransmitters

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87
Q

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.

A

Conduction of a signal across the synapse

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88
Q

Types of synapses

A

Obligatory synapse

Non-obligatory synapse

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89
Q

1/1 ratio

A

Obligatory synapse

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90
Q

Not 1/1 ratio

A

Non-obligatory synapse

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91
Q

Action potential on the presynaptic membrane always give rise to an action potential on the postsynaptic membrane

A

Obligatory synapse

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92
Q

A single action potential on the presynaptic membrane is typically unable to induce an action potential on the postsynaptic membrane

A

Non-obligatory synapse

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93
Q

Excitatory Post Synaptic Potential (EPSP)

A

Depolarization

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94
Q

Inhibitory Post Synaptic Potential (IPSP)

A

Hyperpolarization

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95
Q

Synaptic transmission

A
  1. A presynaptic action potential arrives.
  2. The presynaptic membrane lets vesicles with molecules of neurotransmitters pass through.
  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.
  6. The whole process takes 0.5 ms.
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96
Q

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 potential.

A

Temporal summation

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97
Q

Several action potentials arrive simultaneously at different synapes on the same presynaptic membrane so that their EPSPs sum up and can induce an action potential.

A

Spatial summation

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98
Q

Temporal and spatial summation can occur for both

A

EPSPs and IPSPs

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99
Q

Components of skeletal muscle

A

Sarcolemma
Sarcoplasm
Myofilaments
Sarcoplasmic reticulum

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100
Q

Contains myofilaments and sarcoplasmic reticulum

A

Sarcoplasm

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101
Q

Contains the sarcoplasm

A

Sarcolemma

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102
Q

The two filaments that bind two form cross-bridges

A

Actin and myosin

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103
Q

Smallest functioning unit of skeletal muscle

A

Sarcomere

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104
Q

How is movement created?

A

A signal from the CNS is sent to the muscle to cause movement

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105
Q

How does the neuromuscular synapse work?

A

A presynaptic nerve action potential induces movement of vesicles with acetylcholine (ACh) to the presynaptic membrane, their fusion, and release of ACh into the cleft
ACh diffuses to the postsynaptic muscle membrane, depolarizers it, and induces an action potential.

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106
Q

The specialized region of muscle membrane that received the neurotransmitters

A

Motor end plate

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107
Q

The neurotransmitter of the neuromuscular synapse

A

Acetylcholine (ACh)

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108
Q

A synaptic potential is produced in the neuromuscular synapse of around

A

70 mV

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109
Q

Always excitatory

A

Neuromuscular synapse

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110
Q

Obligatory

A

Neuromuscular synapse

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111
Q

Does not have multiple innervations

A

Neuromuscular synapse

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112
Q

ACh in the synaptic cleft is destroyed by

A

AChesterase

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113
Q

Miniature excitatory postsynaptic potentials that spontaneously occur in the postsynaptic muscle membrane

A

Motor End Plate Potentials (MEPP’s)

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114
Q

Are around - 1 mV

A

Motor End Plate Potentials

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115
Q

Functional meaning is unclear

A

MEPP’s

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116
Q

This always reaches depolarization threshold and induces a muscle action potential

A

A presynaptic nerve action potential

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117
Q

How are Ca++ ions released

A

Muscle action potential travels along the sarcolemma, enters T-tubules, and leads to a release of Ca++ ions from the sarcoplasmic reticulum

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118
Q

Ca++ ions remove tropomyosin and frees a site for myosin to bind to troponin (this process uses energy from ATP). A ratchet motion occurs, moving the filaments with respect to each other.

A

Sliding Filament Theory

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119
Q

Muscle can only

A

Contract.

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120
Q

Muscle cannot

A

Flex or extend

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121
Q

The delay between the electrical signal and the production of force

A

Latent period

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122
Q

A single muscular contraction in response to a single stimulus

A

Muscle twitch

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123
Q

Time sensitive

A

Temporal

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124
Q

Two action potentials come at a short interval and induce two twitch contractions. Their mechanical effects are superimposed, leading to a higher level of muscle force

A

Temporal summation

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125
Q

A sequence of action potentials may lead to a smooth contraction.

A

Tetanus

126
Q

Encapsulates a single fascia

A

Endomysium

127
Q

Encapsulates the endomysiums

A

Perimysium

128
Q

Encapsulates the perimysiums

A

Epimysium

129
Q

The Y axis of the force-velocity curve

A

Represents the velocity of muscle shortening

130
Q

The muscle produces higher forces when it is

A

Lengthening

131
Q

Negative velocity

A

The muscle is lengthening

132
Q

Positive velocity

A

The muscle is shortening

133
Q

A muscle always works against

A

A load

134
Q

Three types of loads

A

Isometric
Isotonic
Elastic

135
Q

Prevents changes in “muscle plus tendon”

A

An isometric load

136
Q

Load does not change

A

Isotonic

137
Q

Load acts like a spring

A

Elastic

138
Q

Muscle develops force while shortening

A

Concentric

139
Q

A muscle develops force while lengthening

A

Eccentric

140
Q

The “muscle plus tendon” length does not change

A

Isometric

141
Q

The apparent external load does not change

A

Isotonic

142
Q

The load is a spring

A

Elastic

143
Q

External loads

A

Isometric
Isotonic
Elastic

144
Q

These allow dendrites to start generating action potentials and continue to do so without any external stimuli as long as the membrane potential stays above threshold

A

Persistent Inward Currents

145
Q

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

A

Persistent inward currents

146
Q

Allows for an increase in the number of action potentials that are generated

A

Persistent inward currents

147
Q

Very sensitive to postsynaptic inhibition

A

Persistent inward currents

148
Q

Likely strong enough to play a major role in defining the patterns of recruitment and derecruitment of motor units

A

Persistent inward currents

149
Q

Not all synapses are chemical

A

Some electrical

150
Q

Provide a low resistance pathway for the electrical current to flow between cells

A

Gap junction cells

151
Q

Current flows from presynaptic cell into the postsynaptic cell, depositing a positive or negative charge

A

Electrical synapse

152
Q

If deplorization in the postsynaptic cell exceeds threshold,

A

The postsynaptic cell will generate an action potential

153
Q

Very little synaptic delay

A

Electrical synapse

154
Q

Can transmit both depolarizing and hyperpolarizing currents

A

Electrical synapse

155
Q

Located between glial and Schwann cells in the brain

A

Electrical synapse

156
Q

Likely involved in brain signaling and myelin formation

A

Electrical synapse

157
Q

The three types of perception

A

Exteroception
Interoception
Proprioception

158
Q

Perception involving vision, hearing, smell, touch

A

Exteroception

159
Q

Perception involving internal objects and organs

A

Interoception

160
Q

Perception of the position of body parts

A

Proprioception

161
Q

The body of a sensory neuron is located in a

A

Ganglion near the spinal cord

162
Q

In a sensory neuron, one branch of the T-shaped axon goes to the _____ ______ ______, and another branch goes through the _______ ______ into the spinal cord

A

Peripheral sensory ending, dorsal roots

163
Q

Perceived sensation is _______ as it relates to stimulus intensity.

A

Logarithmic

164
Q

Logarithmic

A

The size of the stimulus = the size of the sensation

165
Q

Body is a long T-shaped axon, and sensory ending

A

Proprioceptor Neuron

166
Q

Body is in spinal ganglia or dorsal side

A

Proprioceptor Neuron

167
Q

Proprioceptor neurons conduct things primarily in this manner

A

Antidromic conduction

168
Q

No dendrites, no synapses on the body

A

Proprioceptor neurons

169
Q

How are muscle spindles oriented?

A

Parallel to extrafusal muscle fibers

170
Q

Where are primary endings of muscle fibers seen?

A

In virtually all intrafusal fibers

171
Q

Secondary endings of muscle spindle are not seen in

A

Dynamic bag fibers

172
Q

Efferent motor fibers are also called

A

Gamma motor neurons

173
Q

Three components if muscle spindles

A

Intrafusal muscle fibers
Efferent sensory fiber endings
Efferent motor fiber endings

174
Q

Th central region of these muscle fibers are non contractile

A

Intrafusal fibers

175
Q

These fibers spiral around the central region of the intrafusal fibers, and respond to stretching of the intrafusal fibers

A

Efferent sensory fibers

176
Q

These motor neurons are much smaller than alpha motor neurons

A

Gamma motor neurons

177
Q

These innervate the contractile polar region of the intrafusal fibers

A

Gamma motor neurons

178
Q

When a gamma motor neuron activates an intrafusal fiber, it will contract. What does this do?

A

It increases the intrafusal fiber’s sensitivity to stretch

179
Q

The three types of intrafusal fibers

A

Dynamic bag fibers
Static bag fibers
Chain fibers

180
Q

Innervated by a single primary (Ia) sensory ending. Also innervated by a dynamic gamma motor neuron

A

Dynamic bag fiber

181
Q

Innervated by a single primary (Ia) sensory ending and a secondary (II) ending. Also innervated by a static gamma motor neuron.

A

Static bag fibers and Chain fibers

182
Q

The primary ending of a muscle spindle response to stretching increases with

A

Muscle length and stretch velocity

183
Q

The spindle response to stretch concerning the secondary ending

A

The response increases with muscle length, but does not depend velocity

184
Q

The two types of small motor neurons that innervate intrafusal fibers in muscle spindles

A

Dynamic motor neurons

Static motor neurons

185
Q

These motor neurons innervate dynamic bag fibers and change the sensitivity of primary endings

A

Dynamic motor neurons

186
Q

These motor neurons innervate static bag fibers and chain fibers. They change the sensitivity of primary and secondary endings.

A

Static motor neurons

187
Q

Primary endings of muscle spindle are

A

Sensitive to length and velocity of muscle fibers

188
Q

Secondary endings of muscle fibers are

A

Sensitive only to length of muscle fibers

189
Q

These innervate intrafusal muscle fibers

A

Gamma motor neurons

190
Q

A system to modify sensitivity of the spindle endings

A

Gamma motor neurons

191
Q

Located in a series of extrafusal muscle fibers at their junction with the tendon

A

Golgi tendon organs

192
Q

Innervated with fast conducting Ib axons of sensory neurons in spinal ganglia

A

Golgi tendon organs

193
Q

Located in the junction between muscle fibers and the tendon

A

Golgi tendon organs

194
Q

Are considered to be in a series with a group of muscle fibers

A

Golgi tendon organs

195
Q

Sensitive to changes in muscle tension

A

Golgi tendon organs

196
Q

Are not sensitive to changes in length, only tension

A

Golgi tendon organs

197
Q

Not innervated by gamma motor neurons

A

Golgi tendon organs

198
Q

Provide feedback about joint position

A

Articular receptors

199
Q

Most fire in rather narrow ranges of joint angle, mostly close to the anatomical limits

A

Articular receptors

200
Q

Articular receptors increase their response when

A

An increase in muscle force leads to an increase in joint capsule tension

201
Q

A passive sensory ending sensitive only to tendon force

A

Golgi tendon organ

202
Q

Sensitive to joint angle close to the anatomical limits of joint rotation

A

Articular receptors

203
Q

Sensitive to joint capsule tension

A

Articular receptors

204
Q

Cutaneous and subcutaneous receptors

A

Merkel disks
Meissner corpuscles
Ruffini endings
Pacinian corpuscles

205
Q

This receptor measures vertical pressure

A

Merkel disks

206
Q

This receptor measures quickly changing pressure

A

Meissner corpuscles

207
Q

This receptor measures deformation of large skin areas

A

Ruffini endings

208
Q

This receptor measures rapidly changing mechanical deformation

A

Pacinian corpuscles

209
Q

Afferent nerves from the peripheral receptors go into

A

The spinal cord through the dorsal roots

210
Q

Once in the dorsal roots of the spine, synapses occur on

A

The interneurons and motor neurons (only primary spindle endings)

211
Q

After synapsing with the interneurons and motor neurons,

A

Signals are sent to the brain

212
Q

These induce changes in muscle activity that bypass consciousness

A

Proprioceptors

213
Q

Tell us where our arms and legs are and how heavy or light, or rough or soft the objects we handle are

A

Proprioceptors

214
Q

Help create an internal reference system the brain uses to plan and execute movements

A

Proprioceptors

215
Q

These motor neurons send their axons from the ventral roots of the spinal cord.

A

Alpha motor neurons

216
Q

The axons branch in a target muscle, and each axon innervates several muscle fibers

A

Alpha motor neuron

217
Q

What is a motor unit?

A

An alpha motor neuron and the muscle fibers it innervates

218
Q

The three main types of motor units

A
  1. Slow twitch, fatigue resistant (small)
  2. Fast twitch, fatigue resistant (larger)
  3. Fast twitch, fatigable (large)
219
Q

Fiber diameter of fast twitch, fatigable

A

Large

220
Q

Fiber diameter of fast twitch, fatigue resistant

A

Medium

221
Q

Fiber diameter of slow twitch

A

Small

222
Q

Size principle (Henneman Principle)

A

Small motor units are recruited first at low muscular forces. An increase in muscle force leads to recruitment of larger motor units

223
Q

How can the CNS increase muscle force?

A

By recruiting new motor units and/or increasing the firing frequency of already recruited motor units.

224
Q

Measures the electrical activity (action potentials) associated with muscle contraction

A

Eletromyography (EMG)

225
Q

Has uses both clinically and in research

A

EMG

226
Q

Beneficial for reflex testing

A

EMG

227
Q

Very useful for measuring reaction time or muscle latency, when muscles turn on and off

A

EMG

228
Q

Uses thin needle electrodes.

A

Intramuscular EMG

229
Q

The difference of potentials between the tip of the wire and the tip of the needle is amplified and recorded

A

Intramuscular EMG

230
Q

This form of EMG records the activity of individual motor units

A

Intramuscular EMG

231
Q

This form of EMG is uncomfortable

A

Intramuscular EMG

232
Q

Provides information about excitation of a small volume within a muscle

A

Intramuscular EMG

233
Q

Uses a pair of electrodes placed on a muscle belly with a third electrode (ground) to reduce noise.

A

Surface EMG

234
Q

How are action potentials recorded with surface EMG?

A

An action potential runs under a pair of electrodes. The difference of potentials recorded by the electrodes will change is sign (the upper record).

235
Q

Making all the values of the difference of potentials positive

A

Rectification

236
Q

Averages the activity of many (all) motor units

A

Surface EMG

237
Q

Causes no discomfort

A

Surface EMG

238
Q

Is not selective

A

Surface EMG

239
Q

Has a laminar structure

A

Spinal cord

240
Q

Forms a characteristic butterfly picture at each level of the spinal cord

A

Gray matter

241
Q

Toward the head

A

Rostral

242
Q

Toward the tail

A

Caudal

243
Q

Toward the back

A

Dorsal

244
Q

Toward the front

A

Ventral

245
Q

Toward the center of the body or point of attachment

A

Proximal

246
Q

Away from the center of the body or point of attachment

A

Distal

247
Q

Has a body and a spinous process

A

Vertebra

248
Q

Is sent through the dorsal roots of the spinal cord

A

Peripheral information

249
Q

Is sent through the ventral roots of the spinal cord

A

Efferent signals

250
Q

The numbering of the vertebrae

A

C1 to C7
T1 to T12
L1 to L5

251
Q

The numbering of spinal segments

A

C1 to C8
T1 to T12
L1 to L5
S1 to S5

252
Q

This spinal segment ends above the vertebrae

A

C1

253
Q

This spinal segment ends below vertebrae C7

A

C8

254
Q

From this spinal segment on, all spinal segments are lined up with the corresponding vertebra.

A

T1 on

255
Q

What does a synapse consist of?

A

A presynaptic membrane
A synaptic cleft
A postsynaptic membrane

256
Q

A decrease in the efficacy of the synapse

A

Inhibition

257
Q

May occur as a result of events on the presynaptic or postsynaptic membrane

A

Inhibition

258
Q

Leads to a depolarization of the postsynaptic membrane

A

An excitatory synapse

259
Q

Leads to a hyperpolarizatoin of the postsynaptic membrane

A

An inhibitory synapse

260
Q

When one neuron hyperpolarizes the cell body (or dendrites) of another cell body

A

Postsynaptic inhibition

261
Q

Will hyperpolarize the entire membrane, essentially shutting down that cell for a period of time to all incoming stimuli

A

Postsynaptic inhibition

262
Q

A more general type of inhibition

A

Postsynaptic inhibition

263
Q

This synapse hyperpolarizes the postsynaptic membrane and decreases it responsiveness to excitatory synapses

A

A postsynaptic inhibitory synapse

264
Q

Branch very close to the cell body and make excitatory synapses on Renshaw cells

A

Axons of alpha motorneurons

265
Q

Make inhibitory synapses on alpha motornuerons of the same pool and on gamma motorneurons

A

Renshaw cells

266
Q

Are inhibitory in nature

A

Renshaw cells

267
Q

Alpha motorneurons excite Renshaw cells that inhibit the same alpha motorneurons

A

Recurrent Inhibition

268
Q

Benefits of recurrent inhibition

A

Helps regulate the amount of force produced by the muscle

269
Q

Helps to stabilize the firing rate of motor neurons

A

Renshaw cells

270
Q

Renshaw cells are also innervated by

A

Descending signals

271
Q

These neurons are in the spinal cord

A

Interneurons

272
Q

Ia interneurons receive excitatory inputs from

A

Ia afferent neurons

273
Q

Make inhibitory synapses on motorneurons innvervating the antagonist muscle.

A

Ia interneurons

274
Q

Are inhibited by Renshaw cells and also receive descending inputs

A

Ia interneurons

275
Q

Inhibits motorneurons of the same pool

A

Recurrent inhibition

276
Q

Inhibits motorneurons of the antagonist muscle

A

Reciprocal inhibition

277
Q

The steps of recurrent inhibition

A
  1. Alpha-motorneurons of a pool fire.
  2. They send axon branches to Renshaw cells in the ventral horns of the spinal cord.
  3. Renshaw cells inhibit all motorneurons of the same pool.
278
Q

The steps of reciprocal inhibition

A
  1. Small (Ia) interneurons are activated by primary spindle (Ia) afferent fibers.
  2. The Ia interneurons inhibit motorneurons of the antagonist muscle.
279
Q

Ia interneurons can be inhibited by ______ _____ to stop reciprocal inhibition.

A

Renshaw cells

280
Q

When a neruon contacts the axon terminal, rather than the cell body, of another neuron.

A

Presynaptic inhibition

281
Q

This will reduce the amount of neurotransmitter released by the second neuron onto the third cell

A

Presynaptic inhibition

282
Q

This is a more specific or selective form of inhibition

A

Presynaptic inhibition

283
Q

Acts selectively on certain synapses

A

Presynaptic inhibition

284
Q

How does presynaptic inhibition work?

A

An excitatory synapse acts on the presynaptic membrane and induces a steady subthreshold depolarization. This decreases the amount of neurotransmitter released in response to one presynaptic action potential.

285
Q

Definition of a reflex

A

A muscle contraction induced by an external stimulus that cannot be changed by pure thinking

286
Q

Are highly adaptable to changes in behavior goals, mainly because several different circuits exist to connect sensory and motor neurons

A

Reflexes

287
Q

Cannot be directly controlled voluntarily

A

Reflexes

288
Q

Stereotyped responses to specific stimuli that are generated by simple neural circuits in the spinal cord or brain stem

A

Reflexes

289
Q

One central synapse

A

Monosynaptic

290
Q

A few central synapses, usually 2 to 3

A

Oligosynaptic

291
Q

Many central synapses

A

Polysynaptic

292
Q

Slow, steady-state, maintained

A

Tonic

293
Q

Fast, transient, in response to a change in stimulus

A

Phasic

294
Q

Have no higher brain involvement

A

Reflexes

295
Q

Value of studying reflexes

A

Can assist in diagnosis of certain conditions

Help localize injury or disease in CNS

296
Q

Often indicate a disorder in one or more of the components of the reflex arc

A

Absent or hypoactive reflexes

297
Q

Can cause both hyperactive and hypoactive reflexes

A

Lesions in the CNS

298
Q

Most common form of hyperactive reflexes

A

Spasticity

299
Q

results in increased muscle tone

A

Spasticity

300
Q

5 components of a reflex arc

A
  1. Sensory element (receptor)
  2. Afferent (sensory) nerve
  3. Central processing unit
  4. Efferent (command) nerve
  5. Effector (muscle)
301
Q

3 components of the reflex latency

A
  1. Afferent conduction delay
  2. Central processing delay
  3. Efferent conduction delay
302
Q

Involves one central synapse

A

Monosynaptic reflex

303
Q

Originates from Ia spindle afferents and induces a response in the same muscle or in muscles in the vincinity

A

Monosynaptic reflex

304
Q

Technique for examining monosynaptic reflexes developed in the 1950s by P. Hoffman

A

H-reflex

305
Q

Involves electrical stimulation of Ia afferents in a peripheral nerve and recording the motor (reflex) response in the same muscle

A

H-reflex

306
Q

Commonly assessed by stimulating the tibial nerve and measuring the response of the soleus

A

H-reflex

307
Q

In H-reflexes, the stimulation is applied to

A

both afferent and efferent fibers

308
Q

A further increase in the strength of the stimulation leads to

A

An increase in the M-response and suppression of the H-relfex

309
Q

How a H-reflex works

A

Afferent fibers are the first to react to a slowly increasing electrical stimulus. They induce a reflex muscle contraction (H-reflex). Later, efferent fibers become excited and induce a direct muscle contraction (M-response).

310
Q

The peak-to-peak amplitude of the H-reflex and the M-response depends on

A

The strength of the stimulation applied to a muscle nerve

EP 4703: Neural Control Of Human Movement (4 decks)

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