Pathways Flashcards
what are the ascending tracts responsible for
carrying sensory information from the peripheral nerves to the cerebral cortex
what are the 3 ascending pathways
Dorsal Column-Medial Lemniscal (DCML)
Anterolateral Spinothalamic system
Spinocerebellar tract
what is the unconscious tract
spinocerebellar
what are the conscious tracts
DCML
Anterolateral Spinothalamic system
what is the DCML pathway responsible for
fine touch
vibration
proprioception
why is the DCML named as such
in the spinal cord, the sensation travels via the DORSAL COLUMNS
in the brainstem, it is transmitted through the MEDIAL LEMNISCUS
what is the role of the first order neurones in the DCML pathway
carry sensory information from touch/proprioceptive receptors to the medulla oblongata
how do signals from the upper and lower limb differ in the DCML pathway
signals from upper limb (to T5) travel in fasciculus coneatus
signals from lower limb (T6 and below) travel in fasciculus gracilis
where is the fasciculus coneatus located in the dorsal column
laterally
where is the fasciculus gracilis located in the dorsal column
medially
where does the signal travelling via the fasciculus coneatus synapse
cuneate nucleus of the medulla oblongata
where does the signal travelling via the fasciculus gracilis synapse
gracile nucleus of the medulla oblongata
what begins in either the cuneate nucleus or gracilis
second order neurones
where are the third order neurones found in the DCML pathway
thalamus
where do the fibres decussate in the DCML pathway
medulla oblongata
what does decussate mean
when the fibres cross over to the other side
how to the second order neurones travel to the thalamus in the DCML pathway
they travel in the contralateral medial lemniscus
where do the third order neurones in the DCML pathway take the sensory signals to
primary sensory cortex of the brain ascending through the ventral posterolateral nucleus
what two tracts comprise the anterolateral system
anterior spinothalamic tract
lateral spinothalamic tract
what sensory modalities is the anterior spinothalamic tract responsible for
crude touch
pressure
what sensory modalities is the lateral spinothalamic tract responsible for
pain
temperature
what is the tract of first order neurones in the anterolateral system
arise in sensory receptors in the periphery»_space; enter spinal cord»_space; ascend 1-2 levels»_space; terminate at the tip of dorsal horn
where do the neurones decussate in the anterolateral system
at the synapse of the first and second order neurones
where do the second order neurones synapse with the third
thalamus
how do third order neurones reach the primary sensory cortex from the thalamus
ventral posterolateral nucleus
the spinocerebellar tracts are a collection of 4 pathways, what are they
Posterior spinocerebellar
Cuneocerebellar
Anterior spinocerebellar
Rostral spinocerebellar
what would a lesion of the DCML pathway cause
loss of proprioception and FINE touch
if the lesion occurs in the spinal cord, what the sensory loss be (contra or ipsilateral) and why
ipsilateral
fibres decussate at the medulla oblongata
what will damage to the anterior and lateral spinothalamic tract cause
loss of pain and temperature sensation
where would the sensory loss be in the anterolateral system and why
contralateral
as fibres decussate within the spinal cord
what is Brown-Sequard syndrome
hemisection of the spinal cord
one sided lesion
what symptoms are seen in Brown-Sequard syndrome
ipsilateral loss of tactile sensation and proprioception (due to damage to DCML)
contralateral loss of pain and temperature sensation
(due to damage to anterolateral)
what does injury to the spinocerebellar tract but why is this rarely seen
ipsilateral loss of muscle co-ordination
spinocerebellar pathways are unlikely to be damaged in isolation
what normally accompanies injury to the spinocerebellar tract
injury to the descending motor tracts
what are the descending tracts responsible for
pathways by which motor signals are sent from the brain to LMN
what are the two major groups for descending pathways
pyramidal tracts
extrapyramidal tracts
where do pyramidal tracts originate and where do they carry motor fibres to
- cerebral cortex
- spinal cord and brain stem
what are pyramidal tracts responsible for
voluntary control of the musculature of the body and face
where do extrapyramidal tracts originate and where do they carry motor fibres to
- brain stem
- spinal cord
what are extrapyramidal tracts responsible for
involuntary and automatic control of all musculature
e.g. muscle tone, balance, posture
what are there none of in the descending pathways which are seen in the ascending
synapses
what are all neurones within the descending motor system called and why
Upper Motor Neurones
as the neurones synapse with a Lower Motor Neurone
where are the cell bodies of the UMN found
in the cerebral cortex or brain stem and their axon remain within the CNS
what do the pyramidal tracts pass through
the medullary pyramids of the medulla oblongata
what are the two pyramidal tracts
corticospinal tracts
corticobulbar tracts
what is the corticospinal tract responsible for
supplying the musculature of the body
fine, precise movement of distal limb muscles
what is the corticobulbar tract responsible for
supplying the musculature of the head and neck
where does the corticospinal tract originate and where does it descend too
- cerebral cortex
- internal capsule
what is the internal capsule
white matter pathway located between the thalamus an the basal ganglia
what is the internal capsule susceptible to
compression from haemorrhage bleeds
= known as “capsular stroke”
what differs between the lateral and anterior (ventral) corticospinal tract
lateral decussates in the medulla
anterior (ventral) decussate and terminate in the ventral horn of the cervical/upper thoracic segmental levels
where does the corticobulbar tract arise from
lateral aspect of the primary motor cortex
where do the fibres in the corticobulbar tract travel to
the brainstem
where do the extrapyramidal tracts originate
in the brainstem
what are the extrapyramidal tracts responsible for
involuntary/automatic control
muscle tone, balance, posture, locomotion
what are the 4 extrapyramidal tracts
vestibulospinal
reticulospinal
rubrospinal
tectospinal
what are the signs of a lesion in the upper motor neurones
hypertonia hyperreflexia clonus babinski sign muscle weakness
where does the primary motor cortex sit
in the pre central gyrus
what symptoms are seen in Brown-Sequard’s Syndrome
ipsilateral spastic paralysis
ipsilateral hyper-reflexia and extensor plantar reflex
ipsilateral loss of vibration and proprioception
contralateral loss of pain and temperature
where are the 1st 2nd and 3rd order neurone located in the Trigeminal system
1st - trigeminal sensory ganglion
2nd - chief sensory nucleus (general tactile stimuli) or spinal nucleus (pain, temp, info)
3rd - ventroposteriomedial (VPM) nucleus of the thalamus
