Motor III Flashcards
Describe the corticonuclear fibers to TRIGEMINAL MOTOR NUCLEUS (V)
- Origin = motor cortex
- Descend along with corticospinal fibers to brainstem
- At PONTINE LEVEL, corticonuclear fibers TERMINATE BILATERALLY on interneurons in reticular formation next to the V motor nucleus
What is the function of the Trigeminal Motor nucleus
- innervates the mucles of masticiation = moves the jaw up and down and from side to side during chewing and speaking
describe corticonuclear fibers to FACIAL NUCLEUS
- Origin = motor cortex
- SUPERIOR HALF VII = BILATERAL upper motoneurons (UMN) projections to SUPERIOR HALF of the facial nucleus
- INFERIOR HALF VII = CONTRALATERAL UMN projections to inferior half of facial nucleus
Function of facial nucleus
- Motor nucleus
- SUPERIOR HALF = cotnain LMN that innervate muscles of UPPER HALF of face
- INFERIOR HALF = contain LMN that innervate the muscles of LOWER HALF of FACE
What is the result of a UNILATERAL UMN lesion involving corticonuclear fibers terminating in facial nucleus?
- Upper half of facial nucleus recieves BILATERAL corticonuclear (UMN) projections = if one side is damaged there is backup of corticonuclear projections to the facial nucleus from OPPOSITE SIDE
- Lower half of face will show WEAKNESS/PARALYSIS CONTRALATERAL to side of lesion = lower half of facial nucleus receives contralateral corticonuclear (UMN) projections
**UPPER FACE + IPSILATERAL side of lesion is SPARED!**
Why are more deficits apparent in the body on the SAME SIDE as the FACIAL weakness in a unilateral corticonuclear tract lesion
- CORTICONUCLEAR FIBERS travel close to CORTICOSPINAL fibers in the INTERNAL CAPSULE, BASIS PEDUNCULI of midbrain and BASILAR PONS and PYRAMID of medulla
- lesion that damages corticonuclear fibers will most likely damage corticospinal tract = weakness of thumb, fingers and tongue on SAME SIDE of facial weakness
describe the corticonuclear fibers to NUCLEUS AMBIGUUS
- Origin = Motor cortex
- Descend BILATERALLY
Function of Nucleus Ambiguus
- contains cell bodies of LMN’s that run the branches of GLOSSOPHARYNGEAL (IX), and VAGUS (V)
- innervate muscles of SOFT PALATE (SWALLOWING), LARYNX (SPEAKING), AND PHARYNX (SWALLOWING)
- Unilateral lesion on the right side = Uvula deviates to the side of lesions
Describe the corticonuclear fibers to ACCESSORY NUCLEUS (spinal portion?)
- Origin = Motor cortex
- Descends IPSILATERALLY to accessory nucleus
- UMN synapse with LMN’s in accessory nucleus of the CERVICAL SPINAL CORD
**Innvervate sternocleidomastoid and trapezius muscles**
Descrive Corticonuclear fibers to HYPOSGLOSSAL NUCLEUS
- Origin = motor cortex
- Descends BILATERALLY to neurons in hypoglassal nucleus
- Hypoglossal nucleus innvervae ALL the muscles of the tongue
–> hypoglossal nucleus that innervate GENIOGLOSSUS MUSCLES (protrudes tongue) RECEIVES mainly CONTRALATERAL INPUT
Result of a UNILATERAL lesion to corticonuclear fibers to the XII nucleus
- No deficits in MOST TONGUE MUSCLES (bilateral projections)
- GENIOGLOSSUS CONTRALATERAL TO LESION WILL BE WEAK = causes tongue to deviate to the WEAK SIDE upon protrusion (AWAY FROM LESION)
describe the Projections to the Oculomotor, Trochlear and Abducens nuclei
- NO PROJECTIONS FROM CORTICONUCLEAR FIBERS DIRECTLY
1) Fontal and parietal motor eye fields sends BILATERAL projections to:
2) Midbrain reticular formation and paramedian pontine reticular formation (PPRF) send projections to:
3) Motor nuclei of oculomotor, trochlear and abducent nerves to produce CONJUGATE EYE MOVEMENTS CONTRALATERAL to side of origin of cortical input
Describe the tract of the Corticonuclear takes through the brain
- descends in the genu of internal capsule and then shifts posteriorly descending in the anterior part of posterior limb of the internal capsule
- cerebral peduncles
- basal pons and medullary pyramids
what is blood supply to caudal pons (facial nuclei)
- AICE and Basilar artery supply facial nucleus and fascicles
