Neuro Exam 4 Pathways

Where does the parasympathetic nervous system arise from?

From the cranial spine/brain stem

Edinger-westphal nucleus (in midbrain) → CN III (to ciliary ganglion for pupillary reflex)

Salivatory nuclei (upper medulla) → CN VII (facial nerve) + CN IX (saliva + tears)

Dorsal motor nucleus of vagus + Nucleus ambiguus (cardiac, larynx, pharynx) → CN X (HR, lung constriction)

And from the sacral spine (S1-S5) - intermediate gray zone b/t horns like the sympathetic nervous system - leaves spine to enter pelvic splanchnic nerve to synapse at ciliary ganglion

Colliculospinal/Tectospinal tract

Involuntary control of neck (turn head to sight/sound)

Superior (vision) + inferior (sound) colliculus (midbrain) → DEUSSATE in midbrain → down cervical spinal cord → branch bilaterally when synapse onto medial motor neuron in cervical spine

Reticulospinal tract

Colliculus → deussate in midbrain → synapse at pontine reticular formation → synapse bilaterally at target for alertness/broader posture

Vestibulospinal tract

Begin in lateral and medial vestibular nuclei (medulla and pons) → synapse bilaterally at target for maintaining balance

Anterior/ventral corticospinal tract

Voluntary control of posture

Upper motor neurons in medial motor cortex → internal capsule → cerebral peduncle (midbrain) → pontine fiber bundles (middle pons) → synapse bilaterally (branch bilaterally at pyramidal deussation in spine) at lower motor neuron

Corticorecticulospinal tract

Involuntary, feed-forward posture - shift weight for movement before it happens

Primary motor cortex + medial + lateral premotor cortex → synapse bilaterally at reticular formation → synapse at lower motor neurons bilaterally

Lateral corticospinal tract

Voluntary movement of limbs

Movement planned in medial (internal cues) or lateral (external cues) premotor cortex → primary motor cortex → upper motor neurons → internal capsule → cerebral peduncle (midbrain) → pontine fiber bundles (middle pons) → pyramidal DECUSSATION at caudal medulla → synapse at ventral horn onto lower motor neurons

Corticobulb tract

Voluntary face + neck movement

lateral portion of precentral gyrus → primary motor cortex → internal capsule → cerebral peduncle (midbrain) → middle pons →

synapse at contralateral trigeminal motor nucleus of CN V (jaw) or CN VII (face) (middle pons)

OR

pontine fiber bundles → middle medulla → synapse contralaterally at hypoglossal nucleus CN XII (tounge) or CN XI (trapezius + sternocleidomastoid muscles)

Facial expressions tract

Lower face:

Facial representation in primary motor cortex → pons → contralateral facial nucleus → facial nerve (VII)

Upper face:

Both sides of cortex have two paths

1 path: face representation in cingulate motor area → synapse ipsilaterally at facial nucleus

2nd path: face representation in cingulate motor area → synapse contralaterally at facial nerve

So damage on one side won’t affect upper face unless after facial nerve

Cerebellum input pathways

Info from primary, pre, and supplementary motor, and somatosensory cortex (to pontine nuclei → deussates and enters through middle peduncle)

info from clarke’s nucleus (leg proprioception) and cuneate nucleus (arm proprioception) (through inferior peduncle) to coordinate timing

Info from sensory motor association cortex (to pontine nuclei → deussates and enters through middle peduncle) to refine movement

Info from vestibular nuclei (through inferior peduncle) for balance

Info from inferior olive (through inferior peduncle) for motor learning

Vestibulocerebellum

Floccus + nodulus

Bottom, vestibular input for posture and eye movement

Spinocerebellum

Midline = vermis = trunk, some eye movement in coordination w verstibulocerebellum

Outter part of midline = intermediate hemisphere = gross coordination of limbs

Cerebrocerebellum

Newest part of cerebellum, outter hemispheres

Learning

Coordinates info from motor cortex for refined mvmt

Coordinates ongoing visual mvmt w/ premotor cortex

Deep cerebellar nuclei

Relay outputs from cerebellum

Fastigial (vermis → vestibular nuclei + reticular formation), interposed (lateral to fastigial → red nucleus), dentate (more lateral to interposed (cerebrocerebellum) → red nucleus + VA thalamus)