NB17 Descending pathways

Question 1

Cortical representation somatosensation:

Answer 1

termination of thalamocortical pathway

topographical map of sensory info, homunculus (lower body top bit, hand middleish, tongue lateral/bottom)

Question 2

Which descending motor pathway is responsible for voluntary control of the body and limbs?

Answer 2

corticospinal tract

Question 3

Which descending motor pathway has it’s origin in the red nucleus of the brainstem?

Answer 3

rubrospinal tract

Question 4

What is the corticobulbar tract responsible for innervating?

Answer 4

Motor nuclei of cranial nerves V, VII, XI, and XII

Question 5

What is the ‘babinski sign’, and what does it indicate when present in adults?

Answer 5

There is damage to the direct pathway - upper motor neurons (corticospinal and corticobulbar tracts)
flexing toes upwards on stroking of base of foot

Question 6

Define indirect pathway - Upper motor neurons.

2) effect of damadge

Answer 6

Tracts that originate in the brainstem nuclei (not motor cortex) and relay directly with lower motor neurons
2) spastic paralysis, its role is to intergrate supporting musculature during voluntary movement so without movements are spastic.

Question 7

How does the function of the lateral vestibulospinal tract differ from the medial vestibulospinal tract?
2) What do both these tracks pass through?

Answer 7

6. 1. Lateral Vestibulospinal tract - maintaining of balance and posture
7. 2. Medial vestibulospinal tract - maintaining of head position and fixation of gaze
      2) the internal capsule which can be damdge by stroke

Question 8

lateral corticospinal vs anterior corticospinal tract

Answer 8

lat= voluntary control of distal musculature ( 8% of fibres cross over at pyramidal decussation)
ant.= voluntary control of proximal musculature (20% of fibres cross over at segmental level in spinal cord)

Question 9

function of tectospinal tract:

Answer 9

orientation of head towards visual stimuli

Question 10

function of vestibulospinal tracts

Answer 10

balance, lat= antigravity muscle control

mes= head movement

Question 11

function of reticulospinal tract

Answer 11

regulate flexor mm. and initiates patterned activity

Question 12

function of rubrospinal tract

Answer 12

motor control, excitation of flexor mm.