Ascending an Descneding pathways Flashcards
what type of neurons does the ventral column contain
motor
what type of neurons does the dorsal column contain
sensory
what are the ascending pathways
SENSORY
dorsal column/medial leminiscus system
spinothalamic tract
what are the descending pathways
MOTOR
pyramidial and extra-pyramidial tracts
what are the extra-pyramidial tracts
tectospinal tract
reticulospinal tract
vestibulospinal tract
what sensory modalities are controlled by dorsal column medial leminiscus tract
fine touch
proprioception
what sensory modalities are controlled by spinothalamic tract
pain, temperature and deep pressure
how do first order axons enter spinal cord for DCML
through dorsal root and travel up dorsal column
where do first order neurons terminate in DCML tract
medulla oblongata - nucleus gracilis and nucleus cutaneous
where do fibres for DCML cross the midline and where do they go
medulla oblongata - 2nd order neurons
travel up medial leminiscus tract (pons)
what are 2nd order neurons in DCML called
internal arcuate fibres
where do 2nd order neurons from DMCL terminate
ventral posterolateral thalamus
where do 3rd order DCML project to
parietal cortex in somatotopic arrangement
how do PNS sensory fibres enter spinothalamic tract
through dorsal root to dorsal column
terminate in posterior aspect of dorsal horn (substantia gelatinosa)
what happens to 2nd order neurons in spinothalamic tract
they decussate in spinal cord (cross midline)
travel up spinothalamic tract (anterior column)
then through lateral/spinal leminiscus (pons)
terminate at thalamus (posterolateral nucleus)
where do 3rd order neurons in spinothalamic tract project to
ipsilateral primary sensory cortex
what are the function of the pyramidial tracts
voluntary movement of musculature of face and body
what are the function of extra-pyramidial tracts
involuntary control of all musculature: posture balance tone locomotion
where do pyramidial tracts originate
cerebral cortex
where do extra-pyramidial tracts originate
brain stem
where are upper motor neurons found
CNS
cell body in brain stem or cerebral cortex
axons remain in CNS
what are the 2 pyramidial tracts
corticospinal
corticobulbar
where do fibres of corticospinal tract originate from and travel to
originate from pre-motor cortex, primary motor cortex and somatosensory area
travel through internal capsule
where is internal capsule
between basal ganglia and thalamus
what is internal capsule susceptible to and what is the clinical relevance of this
compression from haemorrhagic bleed
may cause lesion of descending pathway
where does the corticospinal tract divide into 2, and what are the 2 divisions called
medulla
lateral and anterior
what happens to lateral corticospinal tract
decussates in medulla (crosses midline)
descends in spinal cord terminating in ventral horn
LMN supplies muscles of body
what happens to anterior corticospinal tract
remains ipsilateral when travelling down spinal cord
decussate (cross midline) and terminate in ventral horn of CERVICAL and UPPER THORACIC segments
where do upper motor neurons of corticobulbar tract terminate
on motor fibres of cranial nerves
from the extra-pyramidial tracts, which one does decussate (cross midline)
tectospinal
where does tectospinal originate
midbrain - superior colliculus
what does superior colliculus receive input from
optic nerve
what is the function of the tectospinal tract
control movements of head and neck in relation to visual stimulus
where do UMN from tectospinal tract decussate and terminate
decussate in midbrain
terminate in cervical segment of spinal cord
where does vestibulospinal tract originate
vestibular nuclei of pons and medulla
where do vestibular nuclei receive input from
organs of balance
what is the function of vestibulospinal tract
controls anti-gravity muscles to maintain posture and balance
what are the anti gravity muscles
flexors of arms
extensors of legs
what are the two reticulospinal tracts and where do they originate
medial - pons
lateral - medulla
function of medial reticulospinal tract
facilitates voluntary movements
increases muscle tone
function of lateral reticulospinal tract
inhibits voluntary movements
decreases muscle tone
