ascending and descending pathways Flashcards
tracts in the conscious pathway get to the
cerebral cortex
tracts in unconscious pathway
do not get to the cerebral cortex
an ascending neurone carrying conscious information will pass through
thallamus
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
ascending pathways function
conducts information from soma and viscera to higher centers
an unconscious pathway usually ends up in
cerebellum
conscious pathway must fulfill 3 processes including
pass through thallamus
dessucate
Go to somatosensory cortex
1st order neurones arise from
posterior root ganglion
Ascending tracts
found in all funiculi and include
lateral spinothalamic ventral spinothalamis dorsal spinocerebellar ventral spinocerebellar spino olivary posterior colum/fasciculus
posterior or dorsal column function
conscious propioception which include
2 point discriminatory touch
vibration
fine touch
joints and muscle sensation
input into posterior column
pacini corpuscles meissners corpuscles joint receptors muscle spindles golgi tendon organ
first order neurones enter posterior white matter on what side
on same side
first order neurones divide into
2 fibres
long ascending
short descending branches
descending branches of first order neurones terminate on
posterior grey horn cells
internuncial neurones
anterior grey horn cells
ascending fibres of first order neurones synapse on
anterior grey horn
posterior grey horn
internuncial neurones
Most ascending first order neurones travel in white column as
fasciculus gracialis
fasciculus cuneatus
Faciculus gracialis location in spinal cord
located at all levels
has long ascending fibres from lower regions ie sacral,lumbar, and lower thoracic
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
2nd order neurones of posterior column found in
gracile and cuneate nuclei in medulla
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
3rd order neurones of posterior column located in
ventral posterolateral nucleus in thallamus
project via posterior corona radiata and internal capsule to somatosensory cortex
posterior spinocerebellar tract function
unconscious propioception of muscle,joint sense,pressure.
2nd order neurones of posterior spinocerebellar tract found in
nucleus dorsalis of clarke in T1-L3
posterior spinocerebellar tract begins from
upper lumbar
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
