Motor tracts

Question 1

Describe the Lateral corticospinal tract pathway

Answer 1

• Originates in motor cortex
• Fibres form bulge on ventral surface of medulla – pyramids
• Fibres decussate at medulla-spinal cord junction
• Fibres pass down spinal cord and innervates motor neurons in ventral horn of spinal cord

Question 2

Describe the function of the Lateral corticospinal tract

Answer 2

• Controls muscles of distal limbs
• Essential for fine movement of limbs
• Controls VOLUNTARY movements

Question 3

Describe the Anterior corticospinal tract pathway

Answer 3

• From motor cortex to motor neurons in spinal cord

* They do not decussate at the medulla

Question 4

Describe the function of the Anterior corticospinal tract

Answer 4

• Controls muscles of trunk

* Controls POSTURE

Question 5

Describe the Corticobulbar fibres pathway

Answer 5

• From motor cortex to brainstem nuclei of cranial nerves

* Most nuclei receive bilateral innervation from cortex except:

Question 6

What are the nuclei that do not recieve bilateral innervation from the corticobulbar fibres

Answer 6

o Motor nucleus controlling facial muscles below the eye – contralateral only
o Hypoglossal nucleus controlling tongue movements – contralateral only

Question 7

Describe the function of the Corticobulbar fibres

Answer 7

•Control VOLUNTARY motor functions of face, head and neck

Question 8

Describe the Rubrospinal tract pathway

Answer 8

• Originates in red nucleus in the midbrain
• Decussates immediately in the midbrain
• Travels alongside lateral corticospinal tract in the spinal cord

Question 9

Describe the function of the Rubrospinal tract

Answer 9

• Involved in VOLUNTARY movement – upper limbs only

* Exact function unclear – muscles of shoulders/upper arms? Some control of hands?

Question 10

Describe the Vestibulospinal tract pathway

Answer 10

• Vestibular nuclei in the pons and medulla receives information from vestibulocochlear nerve about head orientation
• Travel down spinal cord in anterior portions
• Bilateral innervation of muscles

Question 11

Describe the function of the Vestibulospinal tract

Answer 11

•Motor information sent from vestibular nuclei controls muscles of:
o Neck
o Trunk
o Some leg muscles
•Maintenance of upright POSTURE and head stabilisation

Question 12

Describe the Tectospinal tract pathway

Answer 12

• Originates from superior colliculus in midbrain
• Superior colliculi receive information from eyes and visual cortex
• Fibres from superior colliculi decussate ventral to the mesencephalic duct and innervate contralateral motor neurons of the spinal cord
• Fibres also project Ipsilateral to the motor neurons of the spinal cord

Question 13

Describe the function of the Tectospinal tract

Answer 13

• Coordinates head, neck and eye movements primarily inresponse to visual stimuli
• Involved in maintaining POSTURE

Question 14

Describe the Reticulospinal tract pathway

Answer 14

• Originates from reticular formation in pons and medulla

* Ipsilateral innervation of motor neurons in spinal cord

Question 15

Describe the function of the Reticulospinal tract

Answer 15

• Modulates voluntary movements
• Aids with locomotion and POSTURE
• Influences muscle tone