Upper Motor Neurons

Question 1

What is apraxia?

Answer 1

Difficulty in using a body part to perform voluntary actions

Question 2

What is contralateral apraxia caused by?

Answer 2

A lesion to the premotor cortex or posterior parietal cortex

Question 3

What is the main distinction between upper and lower motor neurons?

Answer 3

Lower: directly innervate skeletal muscle
Upper: innervate LMNs directly or via interneurons

Question 4

How can we test for apraxia?

Answer 4

Asking a patients to perform a complex voluntary action: grabbing a pencil, buttoning

Question 5

What do LMNs innervate from the medial ventral horn? What actions do they control?

Answer 5

Proximal/axial limb muscles: posture/balance

Question 6

What do LMNs innervate from the lateral ventral horn? What actions do they control?

Answer 6

Distal limb muscles: skilled movements

Question 7

What does the motor cortex code for?

Answer 7

movements, NOT muscles

Question 8

What is clonus?

Answer 8

Occurs with hyper-reflexia - 5-7Hz oscillation when muscle rapidly stretched and held at constant length