Motor Control

Question 1

Neuromuscular Junction

Answer 1

> Specialized synapse between the nervous system and muscle fibres

Question 2

Muscle composition

Answer 2

Muscles are made up of muscle fibres
— electrical impulse from motor neurons makes these fibres contract
—– Motor neuron soma resides in the ventral spinal cord
One motor neuron innervates ~2-3 muscle fibres for fine motor control (up to >100 for large muscles)

Question 3

Lateral Corticospinal Motor Tract

Answer 3

Involved in the fine movement of distal (distant) limb muscles
»» arms, hands, fingers, lower legs, feet
Tract is contralateral- it crosses from one side of the brain to the opposite side of the body
»> this crossover occurs in the medulla

Question 4

Medial Motor Tract

Answer 4

Involved in control of trunk and proximal (nearby) muscles
Involved in posture and bilateral movements
Both contralateral and ipsilateral

Question 5

The Cerebellum and motor control

Answer 5

1. Coordinating timing of movement
2. Planning movement
3. Learning motor skills
   Three main divisions that each receive a distinct type of info and sends output to distinct parts of the nervous system
   Information flowing through cerebellar loops allows it to modulate motor processing

Question 6

3 Divisions of the Cerebellum

Answer 6

1. Vestibulocerebellum
2. Spinocerebellum
3. Cerebrocerebellum

Question 7

Vestibulocerebellum

Answer 7

Receives information from vestibular nuclei in the brainstem
Damage causes difficulty with balance and postural instability

Question 8

Spinocerebellum

Answer 8

Receives input from somatosensory and kinesthetic information from the spinal cord
Damage causes difficulty with smooth movement control of movement and movement of proximal (near) muscles

Question 9

Cerebrocerebellum

Answer 9

Receives input from regions of the cortex including motor and association cortices
Damage causes difficulty with regulation of highly skilled movement that requires sensorimotor learning

Question 10

Cerebellar Ataxia

Answer 10

Difficulties in coordination of movement after cerebellar damage
– spinocerebellar?
Dysarthria when speech output is involved
Traditional test: patient touches their nose then the neurologist’s movement
» occurs when the activity of agonist and antagonist muscles are not coordinated
» disrupts coordination of multi-joint movements (must be moved one join at a time to compensate)
Difficulties with sensory-motor learning after damages to lateral parts of the cerebellum (Cerebrocerebellar?)

Question 11

Agonist muscles

Answer 11

Muscles that contract during movement

Question 12

Antagonist Muscles

Answer 12

Muscles that relax/ lengthen during movement

Question 13

Forward Model Theory of Cerebellar Function

Answer 13

> The cerebellum helps to predict the sensory consequences of motor plans
» Forward models not influenced by feedback from the periphery (spinocerebellar)
Makes the cerebellum important for ballistic movement (occurs rapidly over a short period of time, with no opportunity for modification)

Question 14

The Basal Ganglia

Answer 14

Collection of subcortical nuclei:
- Caudate Nucleus
- Putamen
- Nucleus Accumbens
- Globus Pallidus
- Substantia nigra
- subthalamic nucleus

Question 15

The roles of the basal ganglia

Answer 15

Multiple roles in motor actions:
»> Setting the motor system (in regard to posture)
»> Preparing the nervous system to accomplish a voluntary motor act
»> acting as autopilot for well-learned sequential movements
»> controlling the timing of and switching between motor acts
Recieves both motor and nonmotor information, thought to assist in motor planning and learning too

Question 16

Basal Ganglia vs. Cerebellum

Answer 16

Cerebellum: movements that cannot be modified once started (ballistic)
Basal Ganglia: movements that take time to initiate or stop

Question 17

Theories of Basal Ganglia Function