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ALHT210 > Motor Control Concepts & Motor Cortex > Flashcards

Motor Control Concepts & Motor Cortex Flashcards

1
Q

where is the primary motor cortex located?

A

pre central gyrus (frontal lobe)

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2
Q

what does the prim motor cortex house?

A

UMN’s

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3
Q

what does the primary motor cortex do?

A

execute commands to motor neurons

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4
Q

what does stimulation of the prim motor cortex do?

A

elicits simple movements of single jts

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5
Q

what is the somatotropic organisation of the prim motor cortex called?

A

motor homunculus

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6
Q

secondary motor areas
what does the pre-motor cortex do?

A

receives input from sensory areas

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7
Q

pre-motor cortex role

A

planning movement

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8
Q

what is the pre-motor cortex related to?

A

sensory input / sensory guidance of movement
- spatial guidance of movement

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9
Q

role of the supplementary motor cortex?

A

sequencing movement

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10
Q

what does the supplementary motor cortex do?

A

feeds correct motor instructions in correct sequence to the primary motor cortex

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11
Q

when is the supplementary motor cortex active?

A

during mental rehearsal of coordinated movements

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12
Q

what are the 3 classes of movement?

A
  1. reflexes
  2. rhythmic motor patterns
  3. voluntary
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13
Q

what is a reflex?

A

involuntary, rapid, stereotyped movements

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14
Q

what is a reflex intiated by?

A

an eliciting stimulus

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15
Q

What is a rhythmic motor pattern?

A

combination of voluntary & reflexive acts e.g.chewing

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16
Q

is initiation & termination voluntary in a rhythmic motor pattern?

A

yes

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17
Q

what happens to the movement of a rhythmic motor pattern once intiated?

A

repetitive & reflexive

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18
Q

what types of actions are voluntary movements?

A

complex actions e.g. writing

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19
Q

voluntary movements are…

A

purposeful , goal-oriented

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20
Q

voluntary movements can be …

A

learnt & improved with practice

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21
Q

where is voluntary movement intiated?

A

cerebral cortex level

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22
Q

what is needed to generate a desired movement / action?

A
  • motor command = configured which involves the integration of sensory information, the selection of approprtiate sets of muscles and joint activations, and the determination of the required forces needed
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23
Q

what is planning a movement?

A

formulating the strategy of action by specifying motor GOALS

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24
Q

what is programming (sequencing) a movement?

A

procedure orientated; constructing the actual sub parts of the movement

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25
Q

what is executing a movement?

A

getting the commands to the muscles by descending pathways and modulated by sensory feedback and higher subcortical centres

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26
Q

Define motor control?

A

ability to regulate / direct the mechanisms essential to movement

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27
Q

UPPER MOTOR NEURONS (UMN)
where are the UMN cell bodies found?

A

either in primary motor cortex / brainstem

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28
Q

What are the pathways originating from the cortex? (2)

A
  • corticospinal tract
  • corticobrainstem (corticobulbar) tract
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29
Q

What pathways originate from the brainstem? (4)

A
  • vestibulospinal
  • reticulospinal
  • rubrospinal
  • tectospinal
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30
Q

what is a LMN?

A

transmits the signal from the uppoer motor neuron to the effector muscle to perform movement (in the SC)

31
Q

What is the origin of the corticospinal tract?

A

primary motor cortex (& supplementary, premotor area, and somatosensory cortex)

32
Q

Course of the corticospinal tract

A
  • axons of UMN descend via internal capsule (in posterior limb)
  • descend in the cerebral peduncle of mid-brain, pons, and pyramids of the medulla
33
Q

what happens to 85% of axons in the corticospinal tract?

A

decussate descend through centrally as lateral corticospinal tract (leg axons = lateral & arm axons = medial)

34
Q

what happens to 10% of axons?

A

remain & descend as anterior corticospinal tract & decussate in the SC at levels close to exit

35
Q

Where does the corticospinal tract terminate?

A

on lower motor neurons (alpha motor neurons) in anterior (ventral) horn of SC

36
Q

functions of the CST? (3)

A
  1. voluntary control of precise movements of the distal muscles of the limbs (lateral CST)
  2. control of less precise movements of the trunk and prox muscles of the limbs (anterior CST)
  3. small % of CST axons project to the dorsal horn of the SC to modify sensory information. brain can filter/ suppress stimuli –> pay attention to other things
37
Q

what is the origin of the corticobrainstem pathway?

A

lateral aspect of the primary motor cortex (homunculus area representing face & head)

38
Q

course of the corticobrainstem pathway

A
  1. descend via the internal capsule (medial to CST)
  2. most cranial nerve nuclei receive bilateral UMN innervation except VII (only lower half of face) and XII
  3. contralateral fibres decussate at the level of brainstem where cranial cell bodies are
39
Q

function of the CBT

A
  • serves as UMNs to all motor cranial nerves
  • facilitates volunatry control of Cranial nerves (LMNs) (V, VII, IX, X, XI, XII)
40
Q

what are the other brainstem pathways? (3)

A
  • tectospinal
  • rubrospinal
  • vestibulospinal
41
Q

Function of the tectospinal tract

A

reflexive head movement response to visual / auditory input

42
Q

function of the vestibulospinal tract

A

arises from vestibular nucleus to help controlling neck & upper back muscles
- aids in balance

43
Q

rubrospinal tract function

A

arises from red nucleus in the midbrain but has minimal contribution to UL extensor muscles

44
Q

LOWER MOTOR NEURON (LMN)
what do they do?

A

transmit signals directly to the skeletal muscles –> contraction of muscle fibres that move the UL & fingers

45
Q

LMN
where are the cell bodies?

A

CNS
- anterior horn of the SC (CST speaks to this) – axons travel within peripheral nerves (to peripheral limbs)
- brainstem (talk to cranial nerves with motor output) –> axons travel within cranial nerves (to other motor areas)

46
Q

what are the 2 types of LMN?

A

alpha, gamma

47
Q

what are the characteristics of an ALpha LMN?

A

large cell bodies, large myelinated axons & project to EXTRAFUSAL muscle fibres

48
Q

what are the characteristics of a gamma LMN?

A

medium sized myelinated axons, project to INTRAFUSAL muscle fibres in the muscle spindles

49
Q

what is a motor unit?

A

1 alpha LMN and the muscle fibres it innervates

50
Q

what happens when 1 neuron fires?

A

all the muscle cells which are stimulated by that alpha neuron, will contract

51
Q

what do alpha motor neurons release so that the muscle fibres contract?

A

acetylcholine (Ach)

52
Q

what is the strength of a muscle contraction determined by?

A

size & number of motor units being stimulated

53
Q

large motor unit

A

increased muscle fibres for gross control

54
Q

small motor unit

A

decreased muscle fibres for precise control

55
Q

what is the relationship between motor units and cortical tissue?

A

inverse

56
Q

larger cortical tissue …

A

= small motor unit (more precise) (more of the motor units - more precise)

57
Q

smaller cortical tissue…

A

= large motor unit (less precise) (less UMN cell bodies going to the LMN then to the muscle group – less precise)

58
Q

what causes decerebrate rigidity?

A
  • severe midbrain lesions
  • rigid extension of the limbs, trunk, interal rot of UL & PF
59
Q

what causes decorticate rigidity?

A
  • severe lesions above the midbrain
  • rigid flexed UL, extended neck & LL & PF
60
Q

can a reflex be protective?

A

yes

61
Q

reflexes can…

A

integrate motor movements so they function in a coordinated manner e.g. postural adjustments to external stimuli while wlaking

62
Q

what else can a reflex involve?

A

be polysnaptic circuit involving interneurons & several levels of spinal cord e.g. withdrawal reflex

63
Q

what are spinal reflexes facilitated by?

A

descending pathways from cortex & brainstem and damage to them will = absence

64
Q

phasic stretch reflex

A

muscle contraction is response to quick stretch e.g. quad tendon reflex

65
Q

cutaneous reflex

A

afferent info from skin, muscles, and/or joints can elicit a variety of withdrawal movements, even before the patient is consciously aware of the pain

66
Q

gag reflex

A

protective mechanism to prevent unwanted entry of foreign objects in to the respiratory passage = choking

67
Q

where does the gag reflex get sensory innervation from?

A

CN IX (soft palate, pharynx)

68
Q

how does the gag reflex respond to stimuli?

A

muscular from CN X to close glottis, elevate palate, & gag

69
Q

abnormal reflexes (4)

A
  1. babinski
  2. hyperreflexia
  3. areflexia
  4. hyporeflexia
70
Q

babinski’s sign

A

extension of the great toe & fanning of other toes
- firmly stroke lateral sole of the foot from heel to ball of foot then across the ball of the foot

71
Q

areflexia

A

absence of reflexes

72
Q

hyperreflexia

A

increased / overactive reflexes

73
Q

what happens with hyperreflexia?

A
  • loss of inhibitory corticospinal input combined with LMN and interneuron development of enhanced excitability = excessive LMN response to afferent input from stretch receptors
  • excessive muscle contraction occurs when spindles are stretched as a result of excessive firing from the LMNs
74
Q

hyporeflexia

A

ALHT210 (7 decks)

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