L13 - ascending pathways Flashcards
dermatome
A specific region of skin of the body innervated by the sensory fibres of a single segmental spinal nerve
general sensory pathways
Carry information of different types or modalities from: Skin, mucus membranes, joints and muscles to the brain
modalities
pain temperature touch, pressure proprioception vibration
dorsal columns
ascending:
fine touch
vibration
pressure
joint position sense
components of DCML pathway
gracile fascicles above T6
cuneate fascicles if below T6
DCML
dorsal column medial lemniscus
ventral corticospinal tract
descending fibres
lateral coricospical tract
descending motor neurones - autonomic
- mainly sympathetic
spinothalamic tract
ascending
crude touch
pain
temperature
how many neurones in sensory pathway
3
first order sensory neurones
from PNS to CNS
what type of neurones are first order sensory neurones
pseudounipolar
location of first order sensory neurones
dorsal root ganglion
location of second order neurones
CNS ipsilateral grey mater
where do second order sensory neurones terminate
VPL nucleus of thalamus
location of third order sensory neurones
in the thalamus
where do third order sensory neurones terminate
primary somato-sensory cortex
first synapse of spinothalamic pathway
at the dorsal cord
route of second order neurone in spinothalamic pathway
- sends axon and crossing over occurs at the ventral white commissure
- travels contra laterally to entrance
- reach VLP of thalamus
second synapse of spinothalamic pathway
thalamus
route of third order neurone in spinothalamic pathway
from thalamus to primary somato-sensory cortex
lamina
where there are synapses from the spinothalamic tract
spinal lemniscus
spinothalamic tract as soon as it leaves the medulla
DCML amove T6
cuneate fascicle
DCML below T6
gracile fascile
medial dorsal column
gracile
lateral dorsal column
cuneate
first order neurone in DCML
enters at dorsal aspect of cord and ascends ipsilaterally, jumping out to the fascicles
dorsal column medial lemniscus
discriminative touch, vibration, proprioception, pressure
first synapse of DCML
closed medulla
- cuneate / gracile nucleus
route of second order neurones of DCML
- send axons to cross the midline at the level of the medulla
- travel in medial meniscus to enter the thalamus on the contralateral side
where do axons cross the midline in the spinothalamic pathway
dorsal cord
where do axons cross the midline in DCML
closed medulla
medial lemniscus
ascending white matter fibres
arcuate fibres
2nd order fibres which arch out the cuneate / gracile nucleus to reach the medial lemniscus
second synapse of DCML
thalamus and axons travel to primary sensory cortex
which ascending pathway travels contralaterally
spinothalamic
which ascending pathway travels ipsilaterally
dorsal column medial lemniscus
in which region of the cerebral cortex does the spinothalamic and DCML pathway terminate
primary sensory / post-central gyrus
internal capsule
bundle of white matter fibres between brain and CNS which connects the brain to lower centres
what type of fibres are located in the internal capsule
projection
ascending and descending
how to ascending fibres reach the brain
travel within the internal capsule, specifically in the posterior limb
location of posterior limb of internal capsule
between thalamus and lentiform nuclei
which cranial nerves carry general somatic sensation to the head
CN5 - trigeminal
CN7 - facial
CN9 - glossopharyngeal
CN10 - vagus
somatic sensation from CN5
face
nose
scalp
dura
somatic sensation from CN7
external ear
somatic sensation from CN9
post 1/3 tongue
pharynx
middle ear
somatic sensation from CN10
auditory canal
larynx
pharynx
oesophagus
location of somatic sensory cranial nerve fibres
run within the trigeminal sensory nucleus to the thalamus
location of motor nuclei in relation to sensory nuclei
motor = medial sensory = lateral
spinal tract
collection of descending white matter axons
spinal nucleus
collection of cell bodies
3 divisions of sensory nuclei from trigeminal nuclei
mesencephalic
pontine
spinal
pontine nucleus
- discriminative touch
- largest located in the pons
mesencephalic nucleus
- proprioception
- extends to midbrain
spinal nucleus
- touch and pressure (more rostral)
- pain and temperature (bottom)
trigeminothalamic pathway for pain and temperature
- enter pons via trigeminal ganglion
- white matter fibres start to descend
- synapses with second nucleic in the caudal spinal nucleus
- secondary nucleus ascends contralaterally in the trigeminothalamic tract to VPM in the thalamus
trigeminothalamic pathway for crude touch and pressure
- enter pons via trigeminal ganglion
- white matter fibres start to descend
- synapses with second nucleic in the rostral spinal nucleus
- secondary nucleus ascends contralaterally in the trigeminothalamic tract to VPM in the thalamus
Sensory consequences of a lesion affecting the lateral medulla
sensation from face:
- loss of pain, temperature, touch and pressure on ispilateral side
sensation from body
- loss of pain, temperature, touch and pressure on contralateral side
fibres carrying pain and temperature pathways from body
spinothalamic pathway
fibres carrying pain and temperature pathways from head
trigeminothalamic pathway
trigeminothalamic pathway
- descends through medulla to spinal nucleus
- cross below entry
trigeminothalamic pathway for discriminatory touch
- Primary sensory neuron with cell body in trigeminal ganglion
- Synapse with 2nd order neuron occurs at the pontine / chief nucleus in the pons
- Axon crosses the midline to go to the oposite VPM of the thalamus
trigeminothalamic pathway for proprioception
- Cell bodies are not in the trigeminal ganglion (ONLY EXEPTION TO THE RULE)
- They are instead located in the mesencephalic nucleus directly
- From there, they make contact with another cell body of a second order neuron just beside it in the brainstem
- This axon crosses the midline to go to the VPM in the thalamus
