Descending motor pathways Flashcards
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?
UMNs
Are cranial nerves UMNs or LMNs?
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
