ascending and descending pathways Flashcards by Mavis Mawuena

tracts in the conscious pathway get to the

cerebral cortex

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tracts in unconscious pathway

do not get to the cerebral cortex

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an ascending neurone carrying conscious information will pass through

thallamus

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general types of nerve fibres in white matter

long ascending fibres to thallamus,cerebellum,brainstem nuclei
Descending fibres from cerebral cortex,brainstem nuclei to spinal gray matter

3, propiospinal fibres connecting various spinal cord levels

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ascending pathways function

conducts information from soma and viscera to higher centers

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an unconscious pathway usually ends up in

cerebellum

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conscious pathway must fulfill 3 processes including

pass through thallamus
dessucate
Go to somatosensory cortex

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1st order neurones arise from

posterior root ganglion

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Ascending tracts

found in all funiculi and include

lateral spinothalamic
ventral spinothalamis
dorsal spinocerebellar
ventral spinocerebellar
spino olivary
posterior colum/fasciculus

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posterior or dorsal column function

conscious propioception which include

2 point discriminatory touch
vibration
fine touch
joints and muscle sensation

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input into posterior column

pacini corpuscles
meissners corpuscles
joint receptors
muscle spindles
golgi tendon organ

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first order neurones enter posterior white matter on what side

on same side

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first order neurones divide into

2 fibres

long ascending
short descending branches

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descending branches of first order neurones terminate on

posterior grey horn cells

internuncial neurones

anterior grey horn cells

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ascending fibres of first order neurones synapse on

anterior grey horn
posterior grey horn
internuncial neurones

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Most ascending first order neurones travel in white column as

fasciculus gracialis

fasciculus cuneatus

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Faciculus gracialis location in spinal cord

located at all levels

has long ascending fibres from lower regions ie sacral,lumbar, and lower thoracic

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Fasciculus cuneatus location in spinal cord

Not present at all levels. it exists and recieves ascending fibres from upper thoracic(T1-T6) and cervical regions

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2nd order neurones of posterior column found in

gracile and cuneate nuclei in medulla

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how is medial lemniscus formed

gracile and cuneate nucleus->Internal arcuate fibres->dessucation of IAF->medial lemniscus->ascends through contralateral brainstem->terminates in ventral posterolateral nucleus of thallamus

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3rd order neurones of posterior column located in

ventral posterolateral nucleus in thallamus

project via posterior corona radiata and internal capsule to somatosensory cortex

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posterior spinocerebellar tract function

unconscious propioception of muscle,joint sense,pressure.

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2nd order neurones of posterior spinocerebellar tract found in

nucleus dorsalis of clarke in T1-L3

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posterior spinocerebellar tract begins from

upper lumbar

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posterior spinocerebellar is

uncrossed, ascends on ipsilateral side

posterior spinocerebellar tract exits through

inferior cerebellar peduncle to cerebellum

the ventral spinocerebellar tract function

unconscious propioception to cerebellum from trunk ,upper and lower limb

the ventral spinocerebellar tract has first order neurones entering from

the dorsal root ganglia

first order neurones of ventral spinocerebellar tract terminate

on nucleus dorsalis

2nd order neurones of ventral spinocerebellar tract

cross over twice nd terminate ipsilateral to its origin

2nd order neurons of ventral spinocerebellar tract terminate at

cerebellum through superior cerebellar peduncle

posterior section of ascending tracts include

posterior column ventral spinocerebellar dorsal spinocerebellar

lateral section or funiculus of ascending tracts include

lateral spinothalamic dorsal spinocerebellar ventral spinocerebellar spinoolivary tract

lateral spinothalamic tract mediates

pain and temperature

first order neurones of lateral spinothalamic tract arise from

dorsal root ganglion

how is lateral spinothalamic tract formed

from dorsal root ganglion->passes through lissauers fasciculus->climbs 2 vetebrae higher->deccusates->synapses on lateral spinothalamic tract->ascends through brainstem to contralateral thallamus

pain and temperature felt on what side of body

contralateral side. somatotopic organization present

function of anterior spinothallamic tract

crude touch and pressure

first order neurones of anterior spinothalamic tract present in

posterior root ganglion

first order neurones of anterior spinothalamic tract present in

posterior root ganglion

second order neurones of anterior spinothalamic tract in

posterior grey horn i.e nucleus propius prescence of somatotopic organization

cuneocerebellar tract

upper extremity equivalent of spinocerebellar tract

first order neurons of cuneocerebellar tract are in

posterior root ganglion of c2-T7

how is cuneocerebellar tract formed

dorsal root ganglion->fasciculus cuneatus->assecory cuneate nucleus(a homologue of nucleus dorsalis of clarke) ->2 order neurones project to cerebellum via inferior cerebellar peduncle

spino olivary tract pathway

originates in spinal grey matter->crosses over->terminates in olivary nucleus in medulla->cerebellum via inferior cerebellar peduncle

neurones in anterior grey horn of spinal cord innervate

skeletal muscles

neurones in anterior grey horn of spinal cord are

lower motor neurones controlled by nerves descending from brainstem and cortex

major descending pathways include

``` lateral corticospinal tract ventral corticospinal rubrospinal tectospinal vestibulospinal reticulospinal autonomic ```

descending pathways general organization

first order neurones in cortex,brainstem->synapse on second order neurones in anterior grey column->synapse on 3rd order neurones in lower motor neurones

function of corticospinal tracts

voluntary,discrete,skilled movement

reticulospinal tract

facilitate or prevent reflex activity

tectospinal tract function

reflex postural movement in response to visual stimuli

rubrospinal tract function

facilitates flexor muscle action | prevents extensor muscle action

vestibulospinal tract function

facilitates extensor action and prevents flexor action

autonomic

controls visceral activity

corticospinal tract composition

axons of pyramidal cells in 5th layer of cerebral cortex 2/3 from precentral gyrus 1/3 from post central gyrus mostly originate from betz cells in primary motor cortex

in internal capsule corticospinal tracts have

somatic organization, where cervical fibres are close to genu posterior fibres are associated with lower limb

descending of corticospinal tract pathway

descend in middle 3/5 of crus cerebri through to pons and medulla

in medulla corticospinal tract

decussate in spinomedullary junction and continue caudally as lateral corticospinal tract-3/4 1/4 that dont decussate continue as ventral corticospinal tract

lateral corticospinal tracts synapse on

intermediate grey horns

pathway of ventral corticospinal tracts

passes through anterior white matter->terminates in ventral horn of cervical and thoracic segments

rubrospinal tract arises from

red nucleus. crosses in ventral section of midbrain tegmentum

tectospinal tracts arise from

superior colliculus

pathway for tectospinal tract

decussates in dorsal tegmentum of midbrain and descends contralaterally and terminates upper cervical cord sements associated with head and neck movements

vestibulospinal tract origin

arise in vestibular nuclei at floor of 4th ventricle uncrossed all spinal cord segments

upper motor neurones acute lesion causes

spinal shock compromising flaccid paralysis areflexia hypotonia

upper motor neurone lesion-chronic

spastic paralysis(muscle stiffness) hypertonia loss of superficial abdominal or cremasteric reflexes babinski sign clonus-involuntary,repetitive muscle contraction

lower motor neurones found in

ventral horns of spinal cord and cn 3,4.7.9.12

LMN lesion results in

flaccid paralysis areflexia muscle atrophy fasciculation and fibrillations