ascending tracts Flashcards
what is the function of the ascending tracts?
neural pathways
sensory info from peripheral nerves is transmitted to cerebral cortex
functionally, what can the ascending tract be divided into?
into type of info they trasmit:
conscious
unconscious
what are the conscious tracts comprised of?
- dorsal column-medial lemniscal pathway
- anterolateral system
what are the unconscious tracts comprised of?
spinocerebellar tracts
what modalities does the DCML carry?
sensory modalities of fine touch, vibration and proprioception
where does the name, DCML come from?
- in spinal cord, info travels via dorsal columns
- in brainstem travels via medial lemniscus
what are the first order neurones in the DCML?
2 different pathways which first order neurones take:
- signals from upper limb (T6 and above): travel in fasciculus cuneatus, synapse in nucleus cuneatus of medulla
- signals from lower limb (below T6): travel in fasciculus gracilis, synapse in nucleus gracilis of medulla
describe the passage of the second order neurones
- begin in cuneate nucleus or gracilis
- deliver info to 3rd order neurones in thalamus
- within medulla, these fibres decussate
- travel in contralteral medial lemniscus to reach thalamus
describe the passage of the third order neurones
- transmit sensory signals from thalamus to ipsilateral primary sensory cortex of brain
- ascend from ventral posterolateral nucleus of thalamus
- through internal capsule
- terminate at sensory cortex
what 2 tracts is the anterolateral system made up of?
- anterior spinothalamic tract
- lateral spinothalamic tract
what modalities does the anterior spinothalamic tract carry?
sensory
crude touch, pressure
what modalities does the lateral spinothalamic tract carry?
sensory
pain and temp
describe the first order neurones of anterolateral system
- arise from sensory receptors in periphery
- enter spinal cord
- ascend 1-2 vertebral levels and synpase at tip of dorsal horn (substantia gelatinosa)
describe the passage of the second order neurones
- substantia gelatinosa to thalamus
- synpase w/ first order neurones
- fibres decussate within spinal cord
- then form 2 distinct tracts (anterior and lateral)
describe the passage of the third order neurones
- thalamus to ipsilateral primary sensory cortex of brain
- ascend from ventral posterolateral nucleus of thalamus
- travel through internal capsule
- terminate at sensory cortex
what is the function of the spinocerebellar tracts ?(unconscious)
help our brain co-ordinate and refine motor movements
transmit info from muscles to cerebellum
within the spinocerebellar tract, what are the 4 individual pathways?
- posterior spinocerebellar tract
- cuneocerebellar tract
- anterior spinocerebellar tract
- rostral spinocerebellar tract
what is the function of the posterior spinocerebellar tract?
carries proprioceptive info from lower limbs to ipsilateral cerebellum
what is the function of the cuneocerebellar tract?
carriers proprioceptive infro from upper lumbs to ipsilateral cerebellum
what is the function of the anterior spinocerebellar tract?
carries proprioceptive infro from lower limbs
fibres decussate twice so terminate in ipsilateral cerebellum
what is the function of the rostral spinocerebellar tract?
carriers proprioceptive info from upper limbs to ipsilateral cerebellum
what would happen if there was a lesion of the DCML pathway?
- loss of proprioception and fine touch
- but there is a small number of tactile fibres in anterolateral system so pt is still able to perform tasks in tactile info
if the lesion occurs in the spinal cord, what side will the sensory loss be?
ipsilateral
what would injury to the anterolateral system produce?
impairment of pain and temp sensation
what side will the sensory loss be?
contralteral
spinothalamic tracts decussate within spinal cord
what is Brown-Sequard syndrome?
- hemisection (one sided lesion) of spinal cord
- most often due to traumatic injury
- involved both anterolateral sytem and DCML pathway
- DCML - ipsilateral loss of touch, vibration, proprioception
- AL system - contralteral loss of pain and temp sensation
what will lesions of the spinocerebellar tract present with?
ipsilateral loss of muscle co-ordination
