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Flashcards in Descending motor pathways Deck (31):

Lower motor neuron lesions has what 5 clinical effects?

1) Muscle wasting (Atrophy as not stimulated)
2) Muscle weakness/ reduced power
3) Hypotonia - reduced resting muscle tone
4) Absent tendon reflexes
5) Fasciculation/ fibrillation


What are the 3 roles of UMNs?

1) Influence LMN activity
2) Modify local reflex activity
3) Superimpose more complex patterns of movement


Other than corticospinal/corticobulbar, what are the 3 other motor pathways?

1) Reticulospinal
2) Vestibulospinal
3) Rebrospinal


Corticospinal pathway is mainly involved in what movement?

Voluntary fine precision movements


What are the initial effects of selective damage to the corticospinal pathway? 2

1) Flaccid paralysis of contralateral limbs
2) Loss of tendon reflexes


After several days following selective damage to the corticospinal tract and initial paralysis what occurs?

Motor function recovers but with hypertonia


What are the 3 long terms effects of selective damage to the corticospinal pathway?

1) Spasticity
2) Hypereflexia
3) Permanent inability to carry out fine movements of hands and feet


Corticobulbar fibres go from where to where?

Pre central gyrus to cranial nerve nuclei


Cranial nerve motor nuclei are located where within the brainstem?

The floor of the 4th ventricle (pons)


Corticobulbar fibres travel from the pre central gyrus to the cranial nerve nuclei via what?

Genu of the internal capsule


Corticospinal fibres travel from where to where?

Pre central gyrus to the ventral grey horn of the spinal cord


Are corticospinal and corticobulbar fibres UMNs or LMNs?



Are cranial nerves UMNs or LMNs?



Corticospinal fibres pass from pre central gyrus to brain stem via what?

Posterior limb of internal capsule


What is the root of corticospinal fibres to the ventral grey horn?

From pre central gyrus via posterior limb of internal capsule
Descend through cerebral peduncles and ventral pons to pyramids
85% of fibres decussate at pyramids and descend through spinal cord in contralateral lateral corticospinal tract
15% of fibres descend in ipsilateral pyramids and ipsilateral anterior corticospinal tract through spinal cord


The right pre central gyrus controls which side of the body?

The left


Where do corticospinal neurones decussate?

85% within the medulla at decussation of pyramids
15% at level of exit through the spinal cord via the anterior white commissure


Where do corticospinal neurones and LMNs synapse?

Contralateral ventral grey horn


Where do corticospinal fibres descend within the spinal cord?

85% in contralateral lateral corticospinal tract
15% in ipsilateral anterior corticospinal tract


The posterior limb of the internal capsule is somatotypically mapped, which lies most posterior, the arm of leg?

leg most posteriorly
(Arm most anteriorly and trunk in the middle)


The cerebral peduncles are somatotypically mapped, which part of the body lies closest to the interpeduncular fossa and which furthest away?

Leg furthest away
Then trunk then arm
Then face closest to interpeduncular fossa


The lateral corticospinal tract is somatotypically mapped, does the arm or leg lie most anterior?

arm lies most anterior
Leg lies most posterior


How do LMNs leave the spinal cord?

Via the ventral grey horn as ventral rootlets to form spinal nerve


Name the 8 cranial nerve motor nuclei?

1) CN3 - occulomotor
2) CN4 - trochlear
3) CN5 - trigeminal
4) CN6 - abducens
5) CN7 - facial
6) CN9 and 10 - glossopharyngeal and vagus
7) CN11 - accessory
8) CN12 - hypoglossal


Corticobulbar fibres to all motor cranial nerve nuclei except hypoglossal and facial take what path?

From pre central gyrus via genu of internal capsule
Give some fibres to contralateral and some to ipsilateral nucleus


Corticobulbar fibres synapse with LMNs where?

Motor cranial nerve nuclei


How are hypoglossal motor nuclei served?

By contralateral corticobulbar fibres


How does the facial motor nuclei differ to other cranial nerve nuclei?

Split into upper and lower part
Upper part sends fibres to muscles of upper face
Lower part sends fibres to muscles of lower face


How is the upper part of facial motor nucleus served?

Served by bilateral corticobulbar fibres
So upper face is served bilaterally


How is the lower part of facial motor nucleus served?

Served only by contralateral corticobulbar fibres
Lower face is served contralaterally


How do LMN from the facial motor nucleus pass to the facial muscles?

Via the facial nerve
Passes out of skull via internal acoustic meatus
Passes through facial canal
Out of stylomastoid foramen
Branches into 5 branches within the substance of the parotid gland