Descending Motor Pathways

Question 1

Describe the location of the motor cortex and name its three sub areas

Answer 1

Located anterior to central cortical sulcus. 3 sub areas; Primary motor cortex, premotor area and supplementary motor area and some specialised areas within them.

Question 2

Describe some features of the primary motor cortex

Answer 2

-Topographical representation - Half or the cortex controls hands and muscles of speech - Excitation results in pattern of muscle movement

Question 3

Describe some of the features of the premotor area

Answer 3

-It has similar topographical representation as primary motor cortex - Nerve signals give rise to more complex patterns of movement

Question 4

Describe some features of the Supplemental motor area

Answer 4

• Contractions elicited are often bilateral (using both hands) - Usually functions together with premotor area (gives background movement)

Question 5

Describe some features of the corticospinal tract (what it does, travel of neurons)

Answer 5

• Carries signals from cortex to spinal cord - Neurons travel from cortex to pyramids of medulla and the majority cross in lower medulla. They then travel in lateral corticospinal tracts before terminating on interneurons. - Those neurons that do not cross travel in ventral corticospinal tracts

Question 6

Describe the features of the lateral pathways

Answer 6

• controlled via cerebral cortex via 2 corticospinal tracts - General control of voluntary movement - Mainly associated with control of distal muscles

Question 7

Describe some of the features of the ventomedial pathway (where ventral corticospinal pathway is found)

Answer 7

-Controlled in brainstem - Control of posture and rhythmic movements associated with locomotion - Control of axial and proximal muscles

Question 8

What are the extra pyramidal tracts and their features?

Answer 8

Reticulopsoinal tract - Posture, locomotion and autonomic function Vestibulospinal tract - Balance and posture Rubrospinal tract - From red nucleus and excitatory to flexors Tectospinal tract - head and neck movement for visual tracking.

Question 9

Posture is adjusted by? and controlled by?

Answer 9

Involuntary movement driven by both predicatively (postural set) and reactively (compensation). It is controlled and driven by brainstem

Question 10

To maintain posture sensory information is integrated from what?

Answer 10

• Muscle proprioceptors (changes in length or tension) - Sense of balance derived from movements of head relative to earths gravitational feild. - Visual inputs

Question 11

What are the different nuclei within the brainstem?

Answer 11

Pontine and medullary (mainly counteract each other) and the vestibular nuclei

Question 12

Describe some of the features of pontine reticular system

Answer 12

• Nuclei transmit excitatory signals down into the cord via pontine reticulospinal tract in anterior column. - Sends high degreee of excitatory signals to extensor muscles and axial muscles

Question 13

Describe some of the features of the medullary reticular system

Answer 13

• Nuclei transmit inhibitory signals to same anterior motor neurons via medullay reticulospinal tract in lateral column. - Receives strong inputs from corticospinal tract, rubrospinal tract and other motor pathways.

Question 14

Describe some of the features of the vestibular nuclei

Answer 14

• Function in association with poutine reticular nuceli to control antigravity muscles - Transmit excitatory signals to antigravity muscles via lateral and medial vestibulospinal tracts

Question 15

What are Upper motor neurons and Lower motor neurons

Answer 15

UMN - Originate in cortex and brainstem nuclei, do not contact muscle LMN - Found in brainstem and spinal cord, motor control to muscles

Question 16

Describe the features of upper motor neuron lesions

Answer 16

Increased tone, spasticity, increased deep tendon reflexes and clonus (repeated rhythmic contraction)

Question 17

Describe the features of lower motor neurons

Answer 17

Flaccid paralysis, decreased tendon reflexes, fasciculations and atrophy

Question 18

Draw out the spinal cord tracts

Answer 18