Motor Control

Question 1

Each lower motor neuron innervates…

Answer 1

The fibres of just one muscle

Question 2

Upper motor neurons of the cortex…

Answer 2

• Initiate complex voluntary movements

- Project mainly contralaterally via corticospinal tract

Question 3

Upper motor neurons of the brainstem…

Answer 3

• More concerned with maintenance of posture and balance
• Located in several nuclei including: reticular formation, vestibular nucleus, superior colliculus
• Project ipsilaterally mainly to lower motor neurons controlling axial muscles (posture)

Question 4

Upper motor neurons always synapse on _____, whereas lower motor neurons always synapse on _____

Answer 4

• Lower motor neurons

- Muscle fibres

Question 5

Upper motor neurons in the cortex influence spinal cord circuits by…

Answer 5

• Anticipated by indirect projection via reticular formation to muscles
• Activation of voluntary movement direct to spinal cord via corticospinal tract

Question 6

Motor neurone disease (ALS)

Answer 6

• Can affect either upper or lower MNs
• Does not affect intellect
• Most die within 5 years of diagnosis

Question 7

Lower motor neuron disease

Answer 7

• Muscle paresis (weakness) or paralysis
• Loss of muscle tone due to loss of stretch reflexes
• Leads to severe muscle atrophy
• Patients usually die from lung dysfunction (atrophy of intercostal muscles)

Question 8

Upper motor neuron disease

Answer 8

• Muscle weakness
• Spasticity due to increased muscle tone (no modulation of stretch reflex)
• Hyperactive refelxes
• Loss of fine voluntary movement
• Patients usually die from bulbar (tongue and pharynx) involvement

Question 9

Basal ganglia and cerebellum on motor control

Answer 9

Influence movement indirectly by regulating the function of upper motor neurons

Question 10

Motor loop - basal ganglia

Answer 10

• Basal gangla is connected to motor cortex
• Feedback to premotor area via ventrolateral complex of the thalamus
• This controls initiation of movement

Question 11

Basal ganglia components

Answer 11

• Caudate
• Putamen
• Globus pallidus

Question 12

Huntington’s disease is due to

Answer 12

The degeneration of the striatum

Question 13

Huntington’s disease leads to

Answer 13

Hyperkinesis (rapid and jerky movements)

Question 14

Parkinson’s disease is due to

Answer 14

Degeneration in the substantia nigra

Question 15

Parkinson’s disease leads to

Answer 15

Hypokinesis (suppressed initiation of movement)

Question 16

Cerebellum

Answer 16

Required for the proper execution of planned, voluntary, multijoint movements

Question 17

Cerebellar ataxia

Answer 17

Poorly integrated movement

Question 18

Cerebellum motor loop

Answer 18

• Cerebellum receives massive input from many areas of cortex
• Projects back to the motor cortex via the thalamus
• No direct output to the spinal cord
• Primary function is to detect and correct differences between the intended movement and the actual movement