ascending pathways Flashcards
draw a diagram of major ascending and descending pathways
see page 26 of control notes
what sensations are involved in the spinothalamic pathway
pain, temperature, crude touch, pressure
what sensations are involved in dorsal column pathway
fine touch, vibration, pressure and position
where do the spinothalamic and dorsal column pathways terminate
primary somatosensory cortex
what is the role of general sensory pathways
skin, mucous membranes, joints and muscles send info to the brain
what is a dermatome and what is an example disease which follows these rules
region of skin innervated by sneezy fibres of a single segmented spinal nerve
herpes zoster hits dorsal root ganglia and shingles present in dermatomes
describe the 3 neuron chain in general sensory pathways
1st neurone - pseudo unipolar - cell body in sensory ganglion (DRG or CN ganglion)
2nd neurone - axon crosses midline (in spinal cord), ascends to ventral posterior thalamus
3rd neurone - axon projects to post central gyrus (parietal lobe)
what is convergence and divergence
many to one
one to many
describe the route of the spinothaalmic tract
through dorsal root into dorsal horn - either travels up cord slightly (lissauers tracts) or connects with secondary neuron in dorsal grey horn
axon 2 crosses midline in ventral white commissure
ascend from spinal lemiscus in the brain stem and enter the VPL of thalamus then via 3rd neurone to primary somatosensory cortex
what are the different sensations using lissauers tract in the spinothalamic pathway
pain and temp synapse in substantial gelatinosa and don’t use tract
crude touch ascend lissauers tract before synapsing in SC - allows differentiation
how are the areas in the spinothalamic tract organised
somatotopically
arm is medial
trunk is central
leg is lateral
describe a brief summary of the dorsal column pathway
through dorsal root into dorsal horn
2nd neurone axons cross midline (internal arcuate fibres) which then ascend in medial menisnus
enter VPL of thalamus and then to primary somatosensory fibres via end neurone fibres
in the DCML pathway what is the difference in travel routes above and below T6
below T6 - primary neurone from leg enters gracilis fascicle
above T6 - primary sensory neurone enters cuneate fascicle
what’s the difference between the anterior STT and the lateral
anterior is crude touch and pressure
lateral is temperature and pain
at what level in the dorsal column pathway does the primary neurones synapse to secondary
closed medulla and cross midline into medial leminscus
what is the somatotopic organisation in the dorsal column pathway
fibres ascending the medial leincus
arm in ventral, trunk is central leg is dorsal
general sensation in the head is carried by which cranial nerves
5
7
9
10
what are the somatic sensation roles for cranial nerve 5, 7, 9, 10
5 - trigeminal - face nose scalp dura
7 - facial - external ear
9 - glossopharnegela - posterior 1/3 tongue, pharynx middle ear
10 - vagus - auditory canals larynx and oesophagus
general sensation from their respected areas of cranial nerve, 5, 7, 9, 10 travel through which pathway
trigeminal sensory pathway
in the trigeminal nuclei what are the sensory nuclei divided into
mesencephalic - proprioception
pontine (chief sensory) - discriminative touch
spinal nucleus - simple touch pressure, pain and temp
describe the process of pain and temperature pathway of trigeminal pathway
1 neurone cell bodies in trigeminal ganglion which then run in spinal tract of trigeminal
synapse with 2 neurone in caudal spinal nucleus
2 neuron axon crossed midline and ascends in the trigeminothelamic tract (trigeminal leminscus) to VPM of thalamus
describe the process of crude touch and pressure pathway in the trigeminal nuclei
1 neurones cell bodies sin trigeminal ganglion - run in spinal tract of trigeminal
synapse with 2 neurone more rostrally in the spinal nucleus - axon crosses midline and ascends in trigeminothalamic tract
to VPM of thalamus
what what a lesion to the lateral medulla on either side cause
affet sensation
of the face on the ipsilateral side
but of the body from the contralateral side
describe the trigeminal pathway of discriminatory touch via the pons (chief sensory)
1 neuone cell bodies in the trigeminal ganglion
synapses with 2 neurones in the pontine nucleus
these axons then cross the midline in the pons and ascend in the trigeminothalamiac tract to the VPM of thet thalamus
describe the route and pathway of the proprioception sensation
exception to having the general first order cell bodie sin the peripheral ganglia
afferent primary axons have their cell bodie sin the mesencephalic nucleus (not trigeminal) they then synapse adjacent to the mesencephalic nucleus
2 neurons crosses and ascend to the thalamus in the trigeminothaalmic tract to the VPM thalamus
(some fibres skip the mesencephalic and synapse with the trigeminal motor nucleus for the jaw jerk reflex)
