Neuro Pathways
Pain/temperature:
Body: Lissauer’s tract substantia gelatinosa contralateral spinothalamic tract VPL posterior internal capsule postcentral gyrus
Head: trigeminal n. spinal trigeminal tract spinal trigeminal nucleus contralateral spinothalamic tract VPM posterior internal capsule postcentral gyrus
- Note: The homunculus of the facial tract has the midline structures in the superior brainstem with lateral in the inferior brainstem; it also has the superior (V1) structures in the anterior tract and the inferior (V3) in the posterior tract.
Touch/position:
Arm: fasciculus cuneatus nucleus cuneatus contralateral medial lemniscus VPL posterior internal capsule postcentral gyrus
Leg: fasciculus gracilis nucleus gracilis contralateral medial lemniscus VPL posterior internal capsule postcentral gyrus
Face: trigeminal n. main sensory nucleus contralateral medial lemniscus VPL posterior internal capsule postcentral gyrus
Visual:
retina optic n. optic chiasm bilateral optic tract LGN
retrolenticular/sublenticular internal capsule occipital lobe
superior brachium pretectal area (posterior commisure) Edinger-Westphal nucleus eye muscles
Oculomotor:
Saccades: frontal eye field (superior colliculus) contralateral PPRF abducens nucleus
abducens n. lateral rectus (ends contralaterally)
contralateral MLF oculomotor nucleus oculomotor n. medial rectus (ends ipsilaterally)
Pursuit: frontal eye field and visual association cortex pontine nucleus contralateral flocculus vestibular nuclei contralateral abducens nucleus
abducens n. lateral rectus (ends ipsilaterally)
contralateral MLF oculomotor nucleus oculomotor n. medial rectus (ends contralaterally)
Olfactory:
olfactory n. bundles olfactory bulb uncus/amygdala
- Note: This pathway doesn’t relay in the thalamus or cross the midline
Gustatory:
taste buds solitary tract nucleus of the solitary tract anterior insula
- Note: This pathway doesn’t relay in the thalamus or cross the midline
Vestibular:
vestibulocochlear n. vestibular nuclei
medial vestibulospinal tract (in MLF) head posture
lateral vestibulospinal tract (in MLF) body posture
oculomotor pathway
inferior cerebellar peduncle flocculonodular lobe
thalamus cortex (regions not specified)
Motor output:
precentral gyrus posterior internal capsule cerebral peduncle basal pons pyramid pyramidal decussation contralateral corticospinal tract lower motor neuron ventral root output
Basal ganglia(speed of movement, involuntary and abnormal postures):
(Direct pathway):
cortex (glutamate +)
compact substantia nigra (dopamine, D1 receptors +)
striatum (caudate, nucleus accumbens, putamen)(GABA -)
globus pallidus internal segment
(Indirect pathway):
compact substantia nigra (dopamine, D2 receptors +)
globus pallidus external segment (+)
subthalamic nucleus (+)
globus pallidus internal segment
globus pallidus internal segment (also reticular substantia nigra)(GABA -) ansa lenticularis, lenticular fasciculus VA/VL (glutamate +) posterior internal capsule precentral gyrus, premotor cortex (voluntary movement planning), supplementary motor areas (complex, self-paced movements)
Cerebellum (uncoordinated ataxia, tremor, dysmetria):
Intermediate: cortex, periphery interposed nuclei
superior cerebellar peduncle red nucleus spinal cord
VA/VL posterior internal capsule precentral gyrus, premotor cortex, supplementary motor areas
Lateral: cortex
inferior olive inferior cerebellar peduncle
pons middle cerebellar peduncle
dentate nucleus
red nucleus inferior olive inferior cerebellar peduncle loop back to dentate nucleus
superior cerebellar peduncle VA/VL posterior internal capsule precentral gyrus, premotor cortex, supplementary motor areas
Vermis: spinocerebellar input fastigial nucleus
vestibular nuclei
reticular formation
Hypothalamus:
Temperature: preoptic/anterior sensitive to high temperatures cooling
posterior sensitive to low temperature heating
Osmotic thirst: preoptic/anterior (OVLT) anterior pituitary (supraoptic, paraventricular)
Volumetric thirst: serum angiotensin SFO
Eating: high fat, high glucose
inhibit LH
excite VMH (energy regulator)
stop eating
low fat, low glucose
excite LH
inhibit VMH
eat
Hippocampus:
Papez circuit: hippocampus
fornix mammilary bodies mammilothalamic tract → anterior nucleus cingulate, parahippocampal gyri loop back to hippocampus
fornix → hypothalamus prefrontal cortex association cortex loop back to hippocampus
amygdala septal areas and loop back to hippocampus
Amygdala:
amygdala
stria terminalis hypothalamus, septal area
amygdalofugal
DM thalamus
brainstem
cingulate, parahippocampal gyri
Sleep:
rostral medulla/caudal pons reticular formation inhibits ARAS causes sleep
tubermammilary nucleus (histamine) REM sleep
- Note: the preoptic/anterior hypothalamus blocks histamine
Pain modulation:
pain afferent periaqueductal grey nucleus Raphe magnus output
Micturition:
Storage: T11-L2 inhibit parasympathetic detrusor relaxation
S2 (Onuf’s nucleus) stimulates sphincter
Elimination: detrusor stretch pontine micturition center
S2-S4 stimulates parasympathetic detrusor constriction
inhibition of S2 (Onuf’s nucleus) relaxes sphincter
Neuro Reflex Arcs
Stretch: afferent → dorsal root → spinal cord → ventral root → efferent
Flexor: stretch reflex ascending/descending to multiple levels
Near/light: light on retina → optic n. → optic chiasm → optic tract → LGN → superior brachium pretectal area (posterior commisure) Edinger-Westphal nucleus → MLF → oculomotor n.
→ ciliary ganglion → short ciliary n. → ciliary contraction/papillary sphincter contraction
→ medial recti muscle contraction
Dark: hypothalamus → intermediolateral cell column → superior cervical ganglion → dilator contraction
Blink: cornea touch → spinal trigeminal nucleus → bilateral facial motor nuclei → orbicularis oculi
Vestibuloocular: vestibular n. → vestibular nuclei → abducens nucleus → eye muscles
Vesicovesical: detrusor stretch → S2-S4 → parasympathetic stimulation → detrusor contraction