2.2 Descending Control and Movement

Question 1

What are the 2 types of motor neuron that voluntary movement in the skeletal muscle relies on

Answer 1

upper motor neurons and lower motor neurons

Question 2

What are the neuron pathways for vountary motor control and involuntary motor control

Answer 2

voluntary motor control is via the pyramidal pathway

but involuntary motor control is via the extrapyramidal pathway

Question 3

What is the part of the pyramidal pathway controlling voluntary movement of the trunk and limbs

Answer 3

The corticospinal tract

Question 4

Where do the upper motor neurons origniate from in the corticospinal tract

Answer 4

Upper motor neurons originate in the cerebral cortex, most of the axons leave the cerebral cortex from either the primary motor cortex, supplementary motor cortex or pre-motor cortex (with a few leaving from the sensory cortex)

Question 5

What are the 2 subdivisions of the corticospinal tract

Answer 5

the lateral tract and the anterio tract

Question 6

Describe the journey of the corticospinal tract from the cortex to the medulla

Answer 6

The corticospinal tract travels down through ceberal white matter called the corona radiata. The tract then descends through the internal capsule and the cerebral crus/peduncles. The tract then travels down the hemispheres and brain stem, with the lateral and anterior tracts still together. The tract continues through the mid brain and pons, but then at the medulla, 85% of the fibres cross over (decussate) at the pyramids of the medulla and form the lateral tract whilst the remainder are uncrossed and form the anterior tract. Both the tracts then separately move into the spinal cord

Question 7

Where does crossing over take place for the anterior tract

Answer 7

At the segmental level of the spinal cor

Question 8

Where do the upper motor neurons synapse with the lower motor neurons

Answer 8

In the ventral horn of the spinal cord

Question 9

How can lesions of the corticospinal tract be differentiated

Answer 9

-either on the upper or lower motor neurons
-either rostral or caudal in the CNS
-be ipsilateral (motor deficit is on the same side as the lesion) or contralateral (on the opposite side)
-the lesion can be mono (just affect one limb), hemi (arm and leg), para (both legs), quadra (all limbs)

Question 10

Give a possible effect of upper motor neurone lesion

Answer 10

Stroke

Question 11

Give a possible effect of lower motor neurone lesions

Answer 11

Trauma or poliomyeletis