Sensorimotor control

Question 1

Pathways and n___ within the brainstem (and midbrain) connect s____ input to m____ output in quite direct ways, providing an evolutionarily ancient but still very important control system.

Answer 1

Nuclei
Sensory
Motor

Question 2

Motor Cortex

Primary motor cortex exerts quite d___, t__ d____ control over muscular activity, with as few as one synapse (in the s___) between a cortical neuron and innervation of muscle cells

Answer 2

Direct
Top Down
Spine

Question 3

Where does motor command originate from?

Answer 3

In motor cortex, in pyramidal cells (layer 5-6 of grey matter)

Question 4

Most cortical projection innervate c_____ motor units

Answer 4

contralateral

Question 5

Few motor commands require isolated activation of a single m___ u____.

Answer 5

motor unit

Question 6

Dorsolateral corticospinal tract

Answer 6

From cortex, through medullary pyramid to spinal cord, then LMNs take to contralateral muscle.
Can have indirect route via brainstem nuclei (i.e. red nucleus)
Innervate contralateral side of one segment of spinal cord
Sometimes directly to alpha motor neuron
Project to distal muscles e.g. fingers

Question 7

Corticorubrospinal tract

Answer 7

Has a synapse at the red nucleus

Question 8

Ventromedial corticospinal tract

Answer 8

Direct route and indirect route via brainstem nuclei (tectum, vestibular nuclei, reticular formation and cranial nerve nuclei).
Project to both sides and multiple segments of spinal cord
Innervate proximal muscles of the trunk and limbs.

Question 9

basal ganglia

Answer 9

A group of structures beneath the cortex that act as a ‘gate-keeper’ for control of the motor system (muscles)

Question 10

Pathway of basal ganglia

Answer 10

Receives excitatory input
output to cortex via thalamus
Output mainly inhibitory (GABA)
5 principle nuclei (substantia nigra, caudate, putamen, globus pallidus and subthalamic nucleus)

Question 11

Basal ganglia in selection

Answer 11

Receives many input, sorts through competing inputs.

Question 12

Cerebellum

Answer 12

A large brain structure that acts as a ‘parallel processor’, enabling smooth, co-ordinated movements. It may also be very important in a range of cognitive tasks.

Question 13

The cerebellum, like b__ g___, no direction projection to the lower motor neurons - instead modulate activity of upper motor neurons.

Answer 13

basal ganglia

Question 14

Cortical inputs and outputs of cerebellum

Answer 14

Mostly from motor cortex (copies of motor commands)

Also somatosensory and visual areas of parietal cortex

Question 15

Spinal inputs and outputs of cerebellum

Answer 15

Proprioceptive information about limb position and movement (muscle spindles, other mechanoreceptors)

Question 16

Vestibular inputs and outputs of cerebellum

Answer 16

Rotational and acceleratory head movement (semi-circular canals / otoliths in inner ear)

Question 17

The cerebellum computes motor e___ and adjusts cortical m___ commands accordingly

Answer 17

error
motor