Descending Motor Pathways (Task 3)

Question 1

Origin point and function of pyramidal tracts

Answer 1

Originate in cerebral cortex

Responsible for the voluntary control of the musculature of the body and face

Question 2

Origin point and function of extapyramidal tracts

Answer 2

Originate in brainstem
Responsible for the involuntary and automatic control of all musculature (e.g., muscle tone, balance, posture and locomotion)

Question 3

Synapse point of upper motor neurons

Answer 3

Synapse only once with a LOWER motor neuron in the brain stem or spinal cord
Therefore all neurons in the descending motor pathways are considered upper motor neurons

Question 4

Divisions of pyramidal tracts

Answer 4

Corticospinal - supplies muscles of body and divides into lateral and anterior parts in the medulla

Corticobulbar - supplies muscles of head and neck

Question 5

Parts of cerebral cortex inputting info to corticospinal tracts

Answer 5

Primary motor cortex
Premotor cortex
Supplementary motor area
Somatosensory area

Question 6

Pathway of neurons in corticospinal tracts up until medulla

Answer 6

Originate in cortex
Pass through internal capsule 
Pass through crus cerebrei of midbrain
Pass through pons 
Enter medulla 
Divide into lateral and anterior tracts in medulla

Question 7

Pathway of corticospinal neurons from medulla onwards

Answer 7

Anterior corticospinal division remains ipsilateral, travels down spine, decussates and then terminates in ventral horn of cervical and upper thoracic segments

Lateral corticospinal division decussates in medulla, passes down contralateral spinal cord and terminate at ventral horn of segments at all levels

Question 8

Pathway of corticobulbar neurons

Answer 8

Originate in primary motor cortex
Travel through internal capsule
Enter brain stem
Synapse on nuclei of cranial nerves

Question 9

Most corticobulbar fibres provide bilateral innervation apart from two exceptions which are:

Answer 9

Facial nerve - upper motor neurons will only provide contralateral innervation to the lower face

Hypoglossal nerve - upper motor nuerons will only provide contralateral innervation

Question 10

Divisions of extrapyramidal tracts and side of innervation

Answer 10

Vestibulospinal - Ipsilateral
Reticulospinal - Ipsilateral
Rubrospinal - Contralateral
Tectospinal - Contralateral

Question 11

Vestibulospinal tract origin and function

Answer 11

Vestibular nuceli in lower pons and upper medulla
Control balance and posture via ‘anti-gravity’ muscles
IPSILATERAL

Question 12

Components of ‘anti-gravity’ muscles

Answer 12

Flexors of arms

Extensors of legs

Question 13

Reticulospinal tract origin and function

Answer 13

Medial division originates in pons
Facilitates voluntary movement and increases tone

Lateral originates in medulla
Inhibits voluntary movement and decreases tone

IPSILATERAL

Question 14

Rubrospinal tract origin and function

Answer 14

Red nucleus of midbrain
Fine control of hand movements
CONTRALATERAL

Question 15

Tectospinal tract origin and function

Answer 15

Superior colliculus of the midbrain
Superior colliculus receives input from the optic nerves
Coordination of head in response to visual stimuli
CONTRALATERAL

Question 16

Descending pathways impacted by a posterior spinal nerve blockage

Answer 16

Lateral Corticospinal (Pyramidal)
Rubro and Reticulospinal (Extapyramidal)

Question 17

Descending pathways impacted by an anterior spinal nerve blockage

Answer 17

Anterior Corticospinal (Pyramidal)
Reticulo and Vestibulospinal (Extapyramidal)