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Kin 3690: Motor Control > Midterm 1 > Flashcards

Midterm 1 Flashcards

1
Q

Motor control definition

A

How fluid and efficient movements are produced, regulated, and coordinated

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2
Q

What are the 8 essential components of motor control?

A

Volition
Coordination of signals
Proprioception
Postural adjustments
Sensory feedback
Compensation for the physical characteristics of the body
Unconscious processing
Adaptability

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3
Q

Who is Sir Charles Sherrington?

A

Father of motor control, neurophysiologist

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4
Q

Homonymous definition

A

Relating to the same muscle

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5
Q

Concentric vs eccentric

A

Concentric: contraction in the shortened position
Eccentric: contraction in the lengthened position

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6
Q

Main characteristic of a pseudounipolar neuron

A

A process emerges from the soma and then splits into two

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7
Q

Bipolar neuron characteristics (2)

A

2 processes directly from soma
Special sense organs

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8
Q

Multipolar neuron characteristics (2)

A

Single axon from soma
Motor neurons

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9
Q

What are the 3 types of synapses?

A

Axoaxonic
Axodendritic
Axosomatic

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10
Q

Which ions are found extracellularly and intracellularly?

A

Extracellular: Na+ and Cl-
Intracellular: K+ and negative ions

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11
Q

At resting membrane potential where is there a higher concentration of negative ions?

A

Inside the cell

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12
Q

Depolarization and hyperpolarization is directly related to the membrane permeability of which ion?

A

Na+

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13
Q

What is the threshold potential of a neuron and a muscle cell?

A

Neuron: -55mV
Muscle cell: - 75mV

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14
Q

Where is there a high density of Na+ channels?

A

Axon hillock

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15
Q

What does it mean that APs are dynamic?

A

They can regenerate along the axon for propagation

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16
Q

What characteristics of the neuron influence propagation speed?

A

Myelination
Diameter of the axon

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17
Q

Temporal summation

A

Summation from a single synapse in a certain period of time

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18
Q

Spatial summation

A

Summing the effects of EPSPs from different synapses at the same time

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19
Q

Motor neuron pool definition

A

All the (alpha) motor neurons that innervate a single skeletal muscle

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20
Q

Where are the cell bodies of alpha motor neurons found?

A

Ventral horn of the spinal cord

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21
Q

What are the 2 somatotopic arrangements of motor neuron pools?

A

Longitudinal arrangement: lower vs upper body (whole spinal cord)
Mediolateral arrangement: medial vs lateral section of the spinal cord

medial = axial m. lateral = distal m.

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22
Q

Motor unit definition

A

An alpha motor neuron and all the muscle fibres it innervates

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23
Q

What is the smallest functional unit of the neuromotor system?

A

Motor unit

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24
Q

What is the function of the motor unit?

A

Produces synchronized contraction of the innervates fibres

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25
Q

Motor end plate definition

A

Region of muscle fibre that receives ACh from NMJ
- produces EPSP that moves along muscle fibre

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26
Q

Motor unit action potential definition

A

An action potential that occurs within muscle cells to produce action/contraction

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27
Q

What is the prime difference b/w AP and MUAP?

A

AP is unidirectional and MUAP is bidirectional

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28
Q

Innervation ratio definition

A

Average number of muscle fibres the alpha motor neuron innervates

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29
Q

What does a smaller innervation ratio mean?

A

There is a higher degree of control

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30
Q

What are 3 ways that motor units differ?

A

Size of soma
Diameter of axon
Properties of the muscle fibres innervated

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31
Q

What are the 3 types of motor units?

A

Fast fatigable (FF) MU
Fast fatigue-resistant (FR) MU
Slow (S) MU

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32
Q

Characteristics of fast fatigable MU 3

A

Biggest soma
Biggest axon diameter
High force capacity of m. fibres = quickest fatigue

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33
Q

Characteristics of fast fatigue-resistant MU

A

Mid for everything

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34
Q

Characteristics of slow MU

A

Smallest everything
Most fatigue-resistant

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35
Q

What are the 4 events that occur in information processing?

A

Reception
Transduction
Coding
Awareness

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36
Q

Reception definition

A

Sensory receptors absorbing the physical energy of the stimulus

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37
Q

Transduction definition

A

Conversion of physical E into electrical E

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38
Q

Coding definition

A

Matching of stimuli parameters to the neuronal parameters that represent it, leading to awareness/perception

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39
Q

How are sensory receptors classified?

A

Based on the origin of the stimulation to which they respond

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40
Q

Exteroceptors

A

Respond to stimuli in the external environment

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41
Q

Proprioceptors

A

Respond to mechanical stimuli associated with configuration and movement of body and body segments

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42
Q

Interoceptors

A

Respond to stimuli within the body
(CO2 levels, etc.)

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43
Q

Photoreceptors

A

Respond to light

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44
Q

Mechanoreceptors

A

Respond to mechanical energy (touch, vestibular)

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45
Q

Chemoreceptors

A

Respond to chemical substances (gustatory and olfaction)

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46
Q

What is proprioception vs kinesthesia?

A

Proprioception: static positions, awareness of joint position
Kinesthesia: dynamic position sense

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47
Q

What are 4 attributes that form sensation together?

A

Modality: what is it
Intensity: amount of stimuli
Duration: start to end of stimuli
Location: where in body

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48
Q

What are the 2 types of adapting receptors?

A

Phasic responders (rapid): silent when a stimulus is maintained
Tonic responders (slow): continue to fire when stimulus is maintained

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49
Q

Where is the sensory cortex?

A

Post-central gyrus

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50
Q

What is two-point discrimination?

A

Ability to distinguish between closely spaced stimuli

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51
Q

What are the 2 reasons why there is a variance in tactile discrimination?

A

Varying receptor density throughout the body

Regional differences in receptive field size

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52
Q

Receptive field definition

A

Total area of the skin surface within which a correct stimulus will evoke a response in the afferent fibre

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53
Q

What do Meissner corpuscles respond to?

A

Pressure

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54
Q

What do Merkel disk receptive fields respond to?

A

Vertical pressure

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55
Q

What do Pacinian corpuscle receptors respond to?

A

Vibration

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56
Q

Where does the pseudounipolar neurons (sensory info) convey info to?

A

Dorsal root ganglion (outside of spinal cord)

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57
Q

What are the 2 branches of the pseudounipolar neuron?

A

Peripheral and central

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58
Q

Which branch of the pseudounipolar neuron has the sensory receptor?

A

Terminal of peripheral branch

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59
Q

Which branch of the pseudounipolar neuron leads to the spinal cord?

A

Central branch

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60
Q

What is the easiest way to identify ascending sensory motor tracts?

A

Begin with spino- because they start at the spine and ascend

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61
Q

Function of the 1st order neuron

A

From sensory receptor to the spinal cord

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62
Q

Function of the 2nd order neuron

A

Decussates in the spinal cord, ascends

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63
Q

Function of the 3rd order neuron

A

From thalamus to primary somatosensory cortex

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64
Q

What are the 3 sources of sensory feedback receptors that contribute to kinesthetic sense?

A

Articular receptors (joint capsule)
Muscle
Cutaneous
- all mechanoreceptors

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65
Q

What did the study by Adachi et al. show about the mechanoreceptors in the ACL?

A

Proprioceptive function of the ACL is related to the number of mechanoreceptors
- important surgical considerations

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66
Q

What are the 2 types of muscle proprioceptors?

A

Golgi tendon organs
Muscle spindles

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67
Q

What is the function of Golgi tendon organs?

A

Sense a change in tension/force due to their location in the tendon

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68
Q

What type of neuron innervates Golgi tendon organs?

A

1B afferents; large diameter & myelinated = fast

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69
Q

What occurs to the 1B afferent when muscle force occurs?

A

It is compressed and is then depolarize to produce AP

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70
Q

What is the relationship between muscle force and AP firing of 1B afferents?

A

When there is an increase in muscle force, there is also an increase in AP firing from the 1B afferents

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71
Q

How is muscle force increased? 2

A

Eccentric and concentric contraction

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72
Q

Does eccentric or concentric contraction have a bigger AP firing frequency of the 1B afferents?

A

Concentric

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73
Q

What are muscle spindles?

A

Muscle stretch detectors

74
Q

What are the 3 main components of a muscle spindle?

A

Intrafusal fibres
Sensory innervation
Motor innervation

75
Q

What are the 2 main types of intrafusal fibres found in muscle spindles?

A

Nuclear bag
Nuclear chain

76
Q

What are the 2 main sections of all intrafusal fibres? Which section is the contractile region?

A

Equatorial and polar
Polar is contractile region

77
Q

What are the 2 subcategories of nuclear bag intrafusal fibres?

A

Static nuclear bag
Dynamic nuclear bag

78
Q

What intrafusal fibre type do Ia afferents innervate? What fibre type do Ia and II innervate?

A

Ia innervates all intrafusal fibres
II (also Ia) innervates only nuclear chain and static bag

79
Q

In which region does the Ia afferent innervate on all intrafusal fibres?

A

The central/equatorial region

80
Q

Where does the II afferents innervate on the static nuclear bag and nuclear chain intrafusal fibres?

A

At the junction b/w the polar and equatorial/central region

81
Q

Does muscle stretch result in spindle loading or unloading?

What occurs to the intrafusal fibres when the muscle is stretched?

A

Spindle loading

If the muscle stretches the spindle stretches (it is within the muscle) and therefore loads the spindle

82
Q

What occurs to the AP firing frequency when spindle loading occurs?

A

Spindle loading, due to muscle stretch, results in increased AP firing frequency

83
Q

What is the difference in AP firing frequency between muscle spindles and Golgi tendon organs in response to muscle stretch?

A

Muscle spindles have a more robust (higher AP firing freq) than Golgi tendon organs

84
Q

In response to stretch, and therefore spindle loading, which afferent fibre (Ia or II) will have a more robust response and why?

A

Ia will have a more robust response.
Majority of stretching occurs in the equatorial region which is where the Ia afferents are

85
Q

What type of contraction (eccentric vs concentric) results in spindle unloading?

A

Concentric contraction, the muscle shortens

86
Q

What is observed in the AP firing frequency during spindle unloading and why?

A

There is decreased AP firing frequency, occurs because when the spindle is compressed the afferents that wrap around it are slacked and stimulated less

87
Q

What is the difference between a muscle spindle and Golgi tendon organ in response to concentric contraction?

A

Muscle spindle is unloaded, compressed, and therefore has decreased AP firing frequency
GTO is compressed within the tendon and has an increased AP firing frequency

88
Q

In spindle unloading, which afferent shows a greater decrease in AP firing frequency and why?

A

Ia afferent has a bigger decrease because of it’s location, slackened more when around the equatorial region

89
Q

What influence do the static and dynamic phases of muscle length have on Ia and II afferents firing frequency?

A

Static phase: Ia and II reach a similar steady firing rate
Dynamic phase: Ia has a more robust response than in the static phase and compared to II afferents. II afferents increase firing frequency slightly

90
Q

How does the velocity of stretch impact the AP firing frequency of Ia afferents?

A

Higher velocity of stretch increases the AP firing frequency

91
Q

What information do Ia afferents in muscle spindles provide? 3

A
  • static length (position)
  • dynamic length (movement)
  • rate of length change (velocity)
92
Q

What kind of motor neurons innervate muscle spindles and where do they innervate?

A

Gamma motor neurons; innervate at the polar regions

93
Q

What is the function of the gamma motor system in muscle spindles?

A

Regulate the sensitivity of muscle spindles for detecting stretch

94
Q

What are the 2 types of gamma motor neurons?

A

Static and dynamic

95
Q

Of the 2 types, what gamma motor neuron increases steady-state firing?

A

Static gamma motor neuron

96
Q

Of the 2 types of gamma motor neurons, which type increases firing rate during dynamic phase of stretch?

A

Dynamic gamma motor neurons

97
Q

What type of intrafusal fibre do dynamic gamma MN and static gamma MN innervate?

A

Dynamic gamma MN: innervates dynamic nuclear bag

Static gamma MN: innervates static nuclear bag and nuclear chain

98
Q

In muscle spindle unloading (concentric) the afferents do not produce an AP, how does the CNS get information on muscle length and rate of change?

A

Activation of gamma MNs; fusimotor system

99
Q

How does the muscle spindle remain taut to respond to muscle length change?

A

Alpha - gamma co-activation

Gamma activation leads to shortening of polar regions and stretching of equatorial region = taut spindle

100
Q

What is required for Ia afferents to fire during concentric contraction?

A

The firing of gamma MNs to keep the muscle spindle taut

101
Q

If gamma MNs activate before alpha MNs (in muscle spindle) what does it do to the intrafusal fibre?

A

It prestretches the equatorial region and alters their sensitivity

102
Q

What type of MN regulates the muscle spindle’s sensitivity to stretch?

A

Gamma MNs

103
Q

What type of gamma MN is activated in slow and predictable change in muscle length?

A

Static gamma MN

104
Q

What type of gamma MN is activated in rapid and unpredictable change in muscle length?

A

Dynamic MNs

105
Q

What type of MN (alpha or gamma) activity is increased as requirements for stretch sensitivity increases?

I.e Walking on ice

A

Gamma MN

106
Q

How is gamma MN bias adjusted to prime the spindles for impending stretch?

A

Upper motor neurons
Lower motor neurons

107
Q

Rootlets

A

Collection of axons entering or exiting the spinal cord

108
Q

Roots

A

Collection of 8-12 rootlets

109
Q

What forms a spinal nerve?

A

Anterior and posterior roots

110
Q

What type(s) of fibres (afferent, efferent) make up a spinal nerve?

A

Both, it is mixed

111
Q

What does the spinal nerve divide into?

A

Two rami (arms)

112
Q

What are the 2 rami that a spinal nerve divides into and what do they innervate?

A

Dorsal (posterior) ramus: deep muscles of back
Ventral (anterior): lateral & anterior torso, upper and lower limbs

113
Q

What is found in the grey matter of the spinal cord?

A

Cell bodies, dendrites, and unmyelinated axons

114
Q

What is found in the white matter of the spinal cord?

A

Myelinated axons - ascending and descending tracts

115
Q

What type of tract (ascending/descending) is the posterior funiculus? Therefore what kind of information (sensory/motor) is carried in this tract?

A

Ascending; sensory

116
Q

In which funiculus (posterior/lateral/anterior) is the dorsal column medial lemniscus pathway found?

A

Posterior

117
Q

What type of tract (ascending/descending) is found in the lateral funiculus?

A

Both, mixed

118
Q

What type of tract (ascending/descending) is the anterior funiculus? Does it carry sensory or motor info?

A

Descending; motor

119
Q

What structure connects the R and L grey matter of the spinal cord?

A

Grey commissure

120
Q

Where are the sensory nuclei found in the spinal cord? (Anterior/posterior/lateral horn)

A

Posterior horn of grey matter

121
Q

Where are the motor nuclei found in the grey matter of the spinal cord? (Anterior/posterior/lateral horn)

A

Anterior horn of grey matter

122
Q

What type of nuclei does the lateral grey horn of the spinal cord house?

A

Autonomic or visceral motor nuclei

123
Q

What are the 2 subsections of the posterior funiculus?

A

Fasciculus gracilis
Fasciculus cuneatus

124
Q

Where does the fasciculus gracilis carry info from?

A

Lower limbs (T6 or lower) to higher areas

125
Q

Where does the fasciculus cuneatus carry info from?

A

From upper limbs to higher areas

126
Q

What pathway are the fasciculus gracilis and cuneatus apart of?

A

Dorsal column medial lemniscus (DCML) pathway

127
Q

What are the 4 systems that contribute to motor output?

A
  • spinal cord & brainstem
  • descending systems
  • basal ganglia
  • cerebellum
128
Q

What is reciprocal inhibition?

A

Simultaneous contraction of the agonist relaxation of the antagonist muscles

129
Q

How can excitatory inputs be modulated to be less effective/strong? 2

A

Presynaptic inhibition
Postsynaptic inhibition

130
Q

What is presynaptic inhibition?

A

An inhibitory IN acts (GABA) on the presynaptic axon and dampens its response

131
Q

What occurs in postsynaptic inhibition?

A

Membrane hyperpolarization leads to less sensitivity to excitatory input

132
Q

Reflex definition

A

Rapid, involuntary and stereotyped motor response to a sensory stimulus

133
Q

Spinal reflex definition

A

Neural circuitry for motor response contained in the spinal cord

134
Q

How were spinal reflexes discovered?

A

Sherrington’s cats; decerebrate preparations

135
Q

What does decerebrate mean?

A

Lesions at the brainstem so the brain and spinal cord do not talk

136
Q

Reflex arc definition

A

Neural pathway involved in a reflex action

137
Q

What are the 3 components of a reflex arc?

A

Afferent neuron; central processing unit; efferent neuron

138
Q

How can reflex circuitry be categorized?

A

Based on the number of synapses; monosynaptic, oligosynaptic, polysynaptic

139
Q

Where are interneurons found in the spinal cord?

A

Dorsal and ventral horns, intermediate areas

140
Q

What is reflex latency?

A

The time delay between stimulus and reaction

141
Q

What are the 3 components of reflex latency?

A

Δta: time of afferent conduction
Δte: time of efferent conduction
∆tc: central delay

142
Q

What impacts the time of efferent conduction? 3

A

Neuron type
Length of fibre
Health of neuron

143
Q

What impacts the time of central delay?

A

Number of synapses

144
Q

What is the function of the monosynaptic stretch reflex?

A

Maintain muscle length at a desired set of values

145
Q

What locations in the body is the monosynaptic stretch reflex seen in?

A

Ankle, jaw, biceps, triceps, knee

146
Q

What are the components of the monosynaptic stretch reflex? 5

A

Homonymous muscle
Muscle spindle
Sensory cell body of pseudounipolar neuron
Synapse
Alpha MN

147
Q

What muscle is excited an inhibited in the MSR?

A

Homonymous and synergistic muscle is excited
Antagonist is inhibited

148
Q

How many collaterals does the Ia afferent axon split into in the spinal cord for the MSR? What does each do?

A

3 collaterals
2 excite the agonist and Synergist
1 inhibits the antagonist

149
Q

What is the reflex latency value of the MSR?

A

70ms

150
Q

What is reciprocal innervation?

A

Innervation of the agonist and antagonist comes from the same neuron source

151
Q

What is monosynaptic reflex gain?

A

The magnitude of motor response relative to the magnitude of sensory stimulus

152
Q

What is high gain vs low gain?

A

For the same input, high gain has a more effective reflex pathway that creates a stronger output than low gain

153
Q

What mechanisms are thought to account for reflex gain? 3

A

Fusimotor activity
Presynaptic modulation
Postsynaptic modulation

154
Q

What are 3 potential contributing factors to a hypoactive MSR?

A
  • disorder of reflex circuit
  • higher order issue
  • peripheral disorder (spindle)
155
Q

What is a possible explanation for hyperactive MSR?

A
  • higher order issue (lesions); no descending inhibition
156
Q

What is the purpose of the Hoffmann reflex?

A

It eliminates peripheral input (muscle spindle) and assesses the resulting motor response

157
Q

What occurs at low stimulus intensity in the Hoffmann reflex?

A

Large fibre axons are activated (Ia) which leads to a reflex-based motor response

158
Q

What is the reflex latency speed of the Hoffmann reflex?

A

30ms, eliminates the time from the muscle spindle

159
Q

What occurs as stimulus intensity increases in the Hoffmann reflex?

A

As stimulus intensity increases the recruitments of small neurons (alpha MN) occurs

160
Q

In increased stimulus intensity, what does the subsequent recruitment/activation of alpha MNs result in?

Hoffmann reflex

A

Causes a direct stimulation of muscle fibres

161
Q

What is the M-wave representative of?

A

Alpha MN recruitment

162
Q

As stimulus intensity increases, what occurs to the M-wave and H-reflex amplitude?

A

M-wave amplitude increases until all alpha MNs are recruited
H-reflex amplitude decreases due to electrical blockade

163
Q

Explain what the neuron types are involved in the electrical blockade

A

Antidromic (opposite) propagation of the efferent MN blocks the orthodromic propagation of the Ia axon and blocks AP

164
Q

What can the M-wave amplitude tell us?

A

There is an increase in stimulation intensity due to more alpha MNs recruited

165
Q

If M-wave (stimulus intensity) is constant, but there is a change in H-wave (increase or decrease), what causes this?

A

Change in reflex gain
Reflex modulation

166
Q

What is the H-reflex a clinical test of?

A

Integrity of central mechanisms in altering the excitability of an alpha MN pool

167
Q

What is modulation of reflex gain based on?

A

The functional demands of the task

168
Q

What is the effect of taping along the muscle fibres of the triceps surae?

A

Reduces motor neuron excitability; decrease in reflex gain

169
Q

What is the effect of taping across the muscle fibres of the triceps surae?

A

Had no effect on motor neuron excitability

170
Q

What are renshaw cells?

A

They are inhibitory interneurons in the grey matter of the spinal cord

171
Q

What does co-contraction allow for? 4

A

Direction reversals (flexion to extension)
Increase in joint stiffness
Precise movements
Joint stabilization

172
Q

Where do renshaw cells receive their input from?

A

Alpha motor neurons and descending commands

173
Q

What is the relationship between a renshaw cell and the alpha motor neuron it innervates?
What is this relationship called?

A

Renshaw receives excitatory info from alpha MN
Same alpha MN receives the same renshaw cell’s inhibitory inputs

Recurrent collateral

174
Q

Renshaw mediated co-contraction definition

A

Decreasing alpha MN agonist output and (inhibition) and increasing antagonist alpha MN output (disinhibition) via renshaw neuron

175
Q

Why is the decrease in alpha MN output via renshaw activation needed?

A

There needs to be periods of decreased MN output to allow for a change in direction

176
Q

What type of interneurons mediates the inverse stretch reflex?

A

Ib inhibitory interneurons

177
Q

How is the flexor reflex classified?

A

It is an interjoint multi-segmental reflex

178
Q

What is the outcome of the flexor reflex?

A

Elevation of the limb due to a noxious stimuli

179
Q

Which muscles are excited and inhibited on the ipsilateral side in response to the flexor reflex?

A

Flexors are excited
Extensors are inhibited

180
Q

What is the flexor/crossed extensor reflex?

A

Same as the flexor reflex, but it involves both sides; contralateral

181
Q

What muscles are excited and inhibited on the contralateral side during the flexor/crossed extensor reflex?

A

The extensors are excited
The flexors are inhibited
- allows for the planting of the foot

Kin 3690: Motor Control (3 decks)

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