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Neurobiology > Motor 1 and 2 > Flashcards

Motor 1 and 2 Flashcards

1
Q

Motor system is made up of which 2 parts?

A

Brain and spinal cord.

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2
Q

Purpose of motor system

A

For coordinated motor movements

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3
Q

What is succinylcholine made up of ? What does it do ?

A

It is made from 2 acetylcholine. It stimulates muscle contraction.

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4
Q

What is the inhibitor of acetylcholine?

A

Acetylcholinesterase

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5
Q

List out the types of motor neurons and its functions

A
  1. Upper motor neuron (passes sensory information down to interneurons)
  2. Lower motor neuron
    - Alpha MN = innervate extrafusal fibers
    - Gamma MN = innervate intrafusal fibers
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6
Q

What is 1 motor unit

A

1 alpha motor neuron to a few muscle fibers

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7
Q

What is a motor neuron pool

A

A few alpha motor neurons to a muscle group

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8
Q

What is the origin of lower MN?

A

Ventral horn of spinal cord

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9
Q

What is mixed spinal nerve?

A

Contains the info from sensory and lower motor neuron

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10
Q

How many pairs of spinal nerves are there?

A

31

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11
Q

Which part of spinal cord innervates the distal and proximal limbs?

A

Cervical - for upper limb
Lumbar and sacrum - for lower limb

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12
Q

Acetylcholine is stimulated by which neuron?

A

Alpha motor neuron

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13
Q

How does acetylcholine cause muscle to contract?

A

Generates AP -> EPSP -> PSAP -> muscle twitch

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14
Q

What is the relationship between AP and muscle contraction?

A

More AP, longer maintained muscle contraction

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15
Q

What is size principle?

A

Recruitment of motor unit will start from the smallest to the largest

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16
Q

Where is the location of alpha MN and gamma MN in a muscle spindle?

A

Alpha MN is located outside of muscle spindle, Gamma MN is located inside of muscle spindle

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17
Q

What is the function of muscle spindle?

A

Detect muscle length change

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18
Q

What is the function of golgi tendon?

A

To detect muscle tension

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19
Q

Alpha MN receives how many inputs?

A

Receives input from
1. Spinal interneurons
2. Muscle spindles (Sensory input)
3. Upper motor neuron in brain

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20
Q

What is the function of spinal interneurons ?

A

Facilitate motor, sensory and autonomic functions in CNS

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21
Q

What are the 2 common causes of injury to Alpha MN

A
  1. Poliovirus - kills cells in ventral horn
  2. Amyotrophic lateral sclerosis (ALS) - neurodegenerative disease that targets motor neurons controlling voluntary muscles.
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22
Q

Damage to alpha MN will cause ?

A
  1. Muscle weakness
  2. Atrophy (wasting)
  3. Fasciculations (visible twitches)
  4. Fibrillation potentials (twitches only detected by EMG)
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23
Q

Will change of Alpha MN type affect a muscle phenotype?

A

Yes! Based on the crossed- innervation, change in Alpha MN type will change muscle phenotype accordingly (e.g. Slow Alpha NM will cause slow twitch in muscles. (vice versa))

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24
Q

Which part of the brain influence voluntary motor activity ?

A

Neocortex, basal ganglia = Strategy
Motor cortex, cerebellum = Tactics
Brain stem, spinal cord = Execution

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25
Q

Which motor pathway controls conscious control of muscles? Where does this pathway originate from?

A

The pyramidal pathway. It originates from the cerebral cortex and outputs to the muscles in the body and face.

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26
Q

Which motor pathway controls unconscious, reflexive or responsive control of muscles? Where does it originate from and to where?

A

The extrapyramidal pathway. It originates from the brain stem to postural or anti gravity muscles.

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27
Q

Pyramidal tracts are named as such because? It can be divided into ?

A

They are named as such as they pass through the pyramids of the medulla oblongata.

It can be divided into 2 tracts:
1. Corticospinal tract
2. Corticobulbar tract

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28
Q

Which tract carries information from cerebral cortex to spinal cord ?

A

Corticospinal tract

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29
Q

What is Corticospinal tract main source and other sources of input ?

A

Main: Primary motor cortex
Others: premotor and supplementary motor

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30
Q

Corticospinal tract mainly innervates muscles of?

A

Distal muscles of hands and feet

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31
Q

Explain the decussation of Corticospinal tract

A

85% decussates at the pyramids in medulla and continues down spinal cord via lateral Corticospinal tract

15% does not decussate, and just continue down via medial Corticospinal tract

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32
Q

Where does Corticospinal tract terminates ?

A

55% at cervical level
25% at sacral level
20% at thoracic level

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33
Q

Damaged upper motor neuron is also known as?

A

Upper motor neuron lesion

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34
Q

In Corticospinal tract, lesion cranial to decussation would lead to deficits on which side?

A

Contralateral side

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35
Q

In Corticospinal tract, lesion caudal to decussation would lead to deficits on which side?

A

Ipsilateral side

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36
Q

What is Corticobulbar tract composed of?

A

Motor neurons of cranial nerves

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37
Q

Where does Corticobulbar tract start and terminates?

A

Originate: cerebral motor cortex
Terminates: Motor nuclei of brain stem

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38
Q

What muscles does Corticobulbar tract control?

A

Face, head, neck

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39
Q

Corticobulbar tract control muscles of ?

A

Face, head, neck

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40
Q

How many extrapyramidal tract are there? List them out

A
  1. Reticulospinal tract
  2. Vestibulospinal tract
  3. Rubrospinal tract
  4. Tectospinal tract
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41
Q

Where do extrapyramidal tract originates and terminates? Do they pass through the pyramids ?

A

Originate from brain stem.
Terminates at spinal cord.
Does not pass through the pyramids.

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42
Q

What does reflexive or responsive movement of muscles help with ?

A

They will help to control balance, locomotion, posture and tone.

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43
Q

Which of the extrapyramidal tract decussates and which side do they innervate?

A

Does NOT decussates = provide ipsilateral innversations:
- Reticulospinal tract
- Vestibulospinal tract

DOES decussates = provides contralateral innervations:
- Rubrospinal tract
- Tectospinal tract

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44
Q

The reticulospinal tract is made up of? and where does it end?

A

Made of Pontine reticular nuclei (in pons) + Medullary reticular nuclei (in medulla)

Inserts: Spinal cord

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45
Q

Reticulospinal tract controls which part of the body?

A
  • Trunk for posture
  • Antigravity muscles of limbs
46
Q

Functions of reticulospinal tract

A
  1. Motor activity
  2. Posture maintenance*
  3. Control of autonomic functions -> by controlling sym (F or F etc) and parasym (rest, digest etc) outflow
  4. Locomotion* (ability to move from one place to another)
47
Q

Lesion in reticulospinal tract can lead to?

A

Decreased postural control

48
Q

Function of vestibulospinal tract

A
  1. Reflexes*
  2. Upright posture maintenance
49
Q

Origin and termination of vestibulospinal tract

A

Origin: Vestibular nucleus in medulla

Terminates: Both Ventral horns of spinal cord

50
Q

Vestibulospinal tract divides into ?

A

Medial (to medial of spinal cord) and lateral (to lateral of spinal cord)

51
Q

Lesion at vestibulospinal tract leads to?

A
  1. Ataxia
  2. Posture instability
52
Q

Rubospinal tract originates and terminates? and where does it decussates?

A

Origin: Red nucleus at midbrain

Decussates: midbrain level

Terminates: spinal cord

53
Q

Function of rubospinal tract

A
  1. Modulate flexor muscle tone
  2. Modulate reflex activity
  3. Inhibit anti-gravity muscles to allow better coordination of limbs like better movements between the joints
54
Q

Tectospinal tract originate and terminates? Where does it decussates?

A

Origin: Superior colliculus of midbrain

Decussates: Midbrain level

Terminates: Spinal cord

55
Q

Function of tectospinal tract

A

Mediates reflexes of eyes and head in response of visual input by superior colliculus

56
Q

Electromyogram (EMG) detects what?

A

Proportional Muscle strength (small activation = small activity in EMG etc)

57
Q

EMG can be used for?

A
  1. Biofeedback for voluntary control
  2. Gamification
58
Q

Motor cortex is made up of which areas ?

A
  1. Area 6 = Supplementary area (SMA) + Pre motor area (PMA)
  2. Area 4 = Primary motor area (M1)
59
Q

Stimulation of area 6 allows…?

A

more complex motor functions as it lies anterior to area 4

60
Q

Function of area 6 (SMA and PMA)

A

SMA - innervates distal motor units (more complex movements)

PMA - innervates proximal motor units (coordinate larger body parts)

61
Q

Damage to area 4 will cause damage to which side of the body?

A

Contralateral side

62
Q

What is the function of Posterior parietal cortex, and what will happen if there is a lesion?

A

Posterior parietal cortex helps to keep track of body position and spatial awareness.

Lesion here will cause individual to move weirdly due to incorrect judgement of of distances/ unable to execute smooth movements

63
Q

Prefrontal cortex is also known as area? and when is it activated?

A

AKA area 8.

Activates during planning and decision-making stages, just before execution of movement

64
Q

Posterior parietal cortex is made up of area? Where does these areas receive their input?

A

5 and 7.

Area 5 receives input from somatosensory cortex (S1)

Area 7 receives input from higher order visual cortex.

65
Q

Order of area activation in cerebral cortex during movement planning

A
  1. S1 and Posterior Parietal Cortex: These areas provide sensory input and spatial awareness, helping form a movement plan.
  2. Area 8: Involved in higher-level planning and initiation of eye and head movements.
  3. Area 6: Important for motor planning and coordination of movements.
  4. Area 4: Executes the planned movement by sending signals to muscles.
66
Q

Purpose of mirror neurons, and when are they active?

A

To learn new things through observation. Important for understanding, identifying and imitating other people.

They are active when watching and preparing to perform the movement

67
Q

Mirror neurons are mainly found in?

A

Area 6

68
Q

Mirror neurons activates more strongly and less strongly when…why?

A

MN activates more strongly when performed by the same/ similar species.

MN actives less strongly if same task is done differently

This is because MN cells has very specific preferences

69
Q

Does direction of movement affects firing rate of M1 neurons?

A

Yes

70
Q

The Babinski sign, a reflex response, occurs when there is damage to ?

A

the corticospinal tract

71
Q

In the 6 pathways from pyramidal and extrapyramidal, which ones are lateral and medial?

A

Lateral: Corticospinal, corticobulbar, rubospinal

Medial: Reticulospinal, Vestibulospinal, Tectospinal

72
Q

Major structures of cerebellum

A
  1. Folia and Lobules (x10) - to increase S.A.
  2. Deep cerebellar nuclei - Relay its output to brain stem
  3. Vermis - Separates the 2 hemi. Contributes to medial pathways
  4. Cerebellar hemispheres - Contribute to lateral pathways
73
Q

Function of cerebellum, and does it trigger movement when stimulated?

A

Function: Initiate sequence of muscle contraction

It does not initiate any movement if stimulated. AKA silent area of brain

74
Q

Cerebellum has how many lobes and what are their names

A
  1. Posterior, anterior and flocculonodular
75
Q

Lateral zone of cerebellum controls?

A

Planning and coordinating voluntary movements of the distal limbs.

76
Q

Intermediate zone of cerebellum controls?

A

Controls proximal limb muscles for large movements

77
Q

What is the motor loop through the lateral cerebellum ?

A

Premotor cortex + sensory cortex -> Pontine nuclei in pons -> lateral cerebellum -> ventrolateral caudalis in thalamus -> Primary motor cortex

78
Q

Afferent (input pathways) of cerebellum from other pars of brain

A
  1. Cerebropontile tract
    - Origin: motor, premotor and sensory areas in cerebral cortex
    - Terminates: Pons*
  2. Pontocerebellar tract
    - Origin: Pontine nuclei in pons
    - Terminates: Lat. hemi. cerebellum
  3. Vestibulocerebellar tract
    - Origin: Vestibular nuclei in brain stem
    - Terminates: flocculonodular lobe
  4. Olivocerebellar tract
    - Origin: Olivary nucleus in medulla
    - Terminates: cerebellar cortex (outer layer of cerebellum)
  5. Reticulocerebellar tract
    - Origin: Reticular info from brain stem
    - Terminates: Cerebellar cortex and vermis
79
Q

What are the pathways for Denate nuclei and what does it do?

A

Cerebellar cortex -> denate nuclei -> thalamus -> cerebral cortex

It does fine motor planning and coordination

80
Q

What is the pathway for fastigial nuclei? What does it do?

A

Vermis -> fastigial -> brain stem

It maintain posture, balance and influence proximal limbs

81
Q

What is the pathway for interposed nuclei?

A

Intermediate zone -> interposed nuclei -> thalamus <-> cerebral cortex

OR

Cerebral cortex -> thalamus -> red nucleus in brainstem

To cerebral cortex - For controlling proximal limbs

To red nucleus - For adjustment of motor execution

82
Q

1 function unit of cerebellum has ?

A

A large purkinje cell and deep nuclear cell

83
Q

What excites and inhibits the deep nuclear cell?

A

Excites: Afferent input from brain and peripheral

Inhibited by GABA neurotransmitters by purkinje cells

84
Q

Vestibulocerebellum helps with?

A

Balance movements

85
Q

Spinocerebellum helps with?

A

Movement of distal limbs

86
Q

Cerebrocerebellum helps with?

A

Planning voluntary movements (aka motor imagery)

87
Q

Clinical abnormalities if there is damage to cerebellum

A
  1. Dysmetria - inability to control the distance, speed, or force of a movement –> 2. past pointing
  2. Ataxia - uncoordinated movement
  3. Cerebellar nystagmus - eyeball tremor
  4. Hypotonia - decreased muscle tone
88
Q

Striatum is made up of ?

A

Caudate nucleus + Putamen

89
Q

Internal capsule is what kind of structure and what does it do?

A

It is a white matter structure and helps transmit information to and fro cerebral cortex, brain stem and spinal cord

90
Q

Explain the basal ganglia circuitry

A

Initiate movement (direct):
Excited motor cortex -> excite striatum -> inhibit globus pallidus -> less suppressed thalamus* -> excite cortex -> more movement

Inhibit movement (indirect):
Excited motor cortex -> excite striatum -> inhibit globus pallidus -> excite subthalamic nucleus* -> stimulate globus pallidus -> inhibit thalamas -> inhibit cortex -> less movement

Both happen together.
If one is more than the other, it is abnormal (e.g. in parkinson, subthalamic nucleus is overactive -> less movement, rigidity )

91
Q

Purpoose of basal ganglia circuitry

A

Modulate voluntary movements

92
Q

Putamen works with what structures to refine complex patterns of motor activity?

A
  1. Subthalamic
  2. Ancillary circuits
  3. Substantia nigra
93
Q

Lesion in subthalamic will cause what?

A

Hemiballismus - violent large movements on one side of the body

94
Q

Lesion in putamen will cause what?

A

Chorea - random uncontrolled jerks/ twitches

95
Q

Lesion in striatum will cause what?

A

Athetosis - Uncontrolled slow continuous movements

96
Q

Lesion in substantia nigra will cause?

A

Parkinson’s diesease - rigidity, tremor

97
Q

What is caudate circuit for? What does it act on?

A

Cognitive control of motor movements (Subconscious, happens within seconds)

It acts on all lobes of cerebrum

98
Q

Lesion in caudate circuit will lead to?

A

Unable to store knowledge, always have to relearn

99
Q

State the caudate circuit pathway

A

Area 6, M1, S1 -> caudate -> internal globus pallidus -> ventroanterior (VA) and ventrolateral (VL) nuclei of thalamus -> area 8 and 6

100
Q

How many neurotransmitters are in the basal ganglia?

A
  1. Dopamine
  2. GABA
  3. Acetylcholine
101
Q

Dopamine comes from and goes to?

A

Comes from substantia nigra, goes to caudate and putamen

102
Q

GABA comes from and goes to?

A

comes from caudate and putamen, goes to substantia nigra and globus pallidus

103
Q

Acetylcholine comes from, and goes to?

A

Comes from cerebral cortex and goes to caudate and putamen

104
Q

Damage to basal ganglia can cause symptoms called?

A

Parkinsonism (problems with speech, movement , posture)

105
Q

What is hyperkinesia ?

A

Motor overactivity (e.g. Huntington’s disease)

106
Q

What is hypokinesias?

A

motor underactivity (e.g. Parkinson’s)

107
Q

Symptoms of Parkinson’s disease

A
  • tremor, bradykinesia (posture instability), rigidity
108
Q

In PD, how many % dopamine producing neurons are destroyed?

A

> 70% = Super low dopamine levels

In normal, about 4% loss only

109
Q

How is dopamine made?

A

Tyrosine -> (tyrosine hydroxylase) -> DOPA (dopa decarboxylase) -> dopamine

110
Q

How PD affects neurotransmission?

A

Loss of dopamine release in striatum -> acetylcholine higher -> overstimulates target neurons -> abnormal signaling -> abnormal mobility

111
Q

Treatment of PD

A
  1. I-Dopa (only useful in early stage of PD as in the end, there wont be enough dopamine still. Body will convert I-Dopa into dopamine.)
  2. Monoamine oxidase inhibitors (inhibits break down of dopamine)
  3. Transplanted fetal dopamine cells (replace dead dopamine producing neurons into new fetus ones)
  4. Deep brain stimulation (DBS) (If not responding to drugs)

Neurobiology (2 decks)

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