Ascending and descending pathways Flashcards
Properties of medial leminiscus
Ascending pathway
Epicritic sensibility
Nerve endings: Meissner corpuscle, pacinian corpuscle, Golgi, Muscle spindle
Brodman area: 3,1,2
Cuneate: cervical and upper thoracic
Gracile: sacral, lumbar, lower thoracic
1st order neuron: Abeta type, thick, myelinated
Pathway of medial leminiscus
Nerve ending - dorsal root ganglion - gracile/cuneate fasciculus - synapse in gracile/cuneate nucleus in medulla(multipolar) - cross in lower medulla - internal arcuate fibers - VPL - post. limb of internal capsule - post central gyrus
Properties of spinothalamic tract
Ascending
Protophatic sensibility
Receptors: free nerve ending: mechano-, thermo-, chemo-, nocireceptors
1st order neuron: fine myelinated A delta/ unmyelinated C
Pathway of spinothalamic tract
Receptor- dorsal root ganglion - dorsolateral tract of Lissauer -synapse in Lamina 1,2 and 5 - Several interneurons - cross to anterior and lateral tract - spinal leminiscus with spinotectal - VPL - Post central gyrus
- some slow fibers to intralaminar nuclei and reticular formation
- some fibers from VPL to cingulate gyrus= emotion
- small pain fibers to insula=autonomic respons
Pain decrease
Light touch to pain area - medial leminiscus (faster) - connector neuron inhibit spinothalamic neuron - periventricular grey matter, periaqueductal grey matter, other midline nuclei - releases morphine, enkephalins, endorphins
Posterior spinocerebellar tract
Ascending
Proprioception
Golgi tendons, muscle spindle, pressure receptor
1st order neuron - Dorsal root ganglion - Clarke’s column - 2nd order neuron - lateral funiculus - Medulla - Inferior cerebellar peduncle - Cerebellum
Anterior spinocerebellar tract
Ascending
Exteroception, proprioception
Golgi tendons, muscle spindle, pressure receptor
1st order neuron - dorsal root ganglion - synapse in intermediate zone - 2nd order neuron - cross to lateral funiculus - midbrain - superior cerebellar peduncle - recross - cerebellum
Minor ascending tracts
Spinotectal:
- spinal leminiscus with spinothalamic tract
- visual
- to tectum- superior colliculus
Spinoolivary:
- proprioception, touch, pressure
- to inferior olive
Spinoreticular tract:
- ipsilateral
- to reticular formation
Corticospinal tract
Descending
Axial and limb motor
Pyramidal tract
Precentral gyrus (brodmann 4, 5th layer) - internal capsule - corticobulbar tract - 90% cross by pyramids(lateral corticospinal) and 10% continue(ant. corticospinal) - anterior corticospinal cross in spinal cord - both to Aalpha and Agamma motoneurons - ventral root - muscle
Tectospinal tract
Descending
Regulated optic tectal reflexes
Extrapyramidal tract
Superior colliculus - cross in midbrain - anterior funiculus - intermediate zone and ventral horn - terminate in cervical spinal cord - synapse with internuncial neurons - head and upper limb
Reticulospinal tract
Descending
Regulate movement: activate or inhibit voluntary movement or reflex activities
Extrapyramidal tract
Reticular formation in pons - uncrossed - pontine-reticulospinal tract - anterior white column - extensor m.
Reticular formation in medulla - crossed and uncrossed - medullary reticulospinal tract - lateral white column - flexor m.
Rubrospinal tract
Descending
Regulates movement: activate flexor and inhibit extensor
Extrapyramidal tract
Red nucleus - cross in tegmentum - dorsal contralateral lateral funiculus - intermediate zone and ventral horn - flexors
Vestibulospinal tract
Descending
Regulates body balance: activate extensors, inhibit flexors
Extrapyramidal tract
Lateral vestibular nucleus - uncrossed - anterior white column - terminate and synapse with internuncial neurons of ant. grey column - extensors
Olivospinal tract
Descending
Regulates body balance
Extrapyramidal tract
Inferior olivary nucleus - lateral white column - motor neurons in anterior grey column
