4.1.3 Decussation and Peripheral Nervous System

Question 1

How are the primary motor cortex and peripheral nervous system connected?

Answer 1

Pain on right side is caused by the part of the brain on the contralateral side (opposite)

Therefore a right-sided pain is due to a lesion on left primary cortex vive. This is the same for the primary somatosensory cortex

This is for spinal nerves only

Question 2

At what level do pathways conencting primary cortex with spinal nerves cross over?

Answer 2

Decussate (cross) to opposite side at lower level of medulla

These then synpase with motor neurones

Question 3

What type of control do spinal nerves have?

Answer 3

Uni-cortical control
Supplied by a primary motor cortex on one hemisphere

Question 4

How does the motor control of cranial nerves differ from spinal nerves?

Answer 4

Cranial nerves have both contra & ipsilateral control

Cross from contral-lateral side at the level of the nuclei they communicate with

Question 5

What side is more dominant in cranial nerves?

Answer 5

Contralateral

Question 6

When might the ipsilateral motor control of cranial nerves be used?

Answer 6

During a stroke or injury, the contra-lateral side is dominant so when an injury occurs on this side the ipsilateral side has the ability to compensate