somatosensory pathways Flashcards
Second order afferents
cells in dorsal horn. Axons cross the spinal cord, project up the contralateral spinal cord
largest tracts in the spinal cord
dorsal funiculi
which afferents are in the fasciculus gracilis
lower limb and genitals
what tracts are in the Fasciculus Cuneatus
upper limb
which is more medial in the spinal cord, the gracile or cuneate fasciculus
gracile
where do the dorsal fasciculi project to
cuneate and gracile nuclei in the lower medulla of the brainstem
Medial Lemniscus
large ascending bundle of heavily myelinated axons that goes to the brain stem
what is the start of the medial lemniscus
Fibres leaving the base of cuneate and gracile nuclei
where do Fibres leaving the base of cuneate and gracile nuclei go
cross midline, ascend to ventro postero lateral nucleus of contralateral thalamus, project to somatosensory cortex
internal arcuate fibres
medial lemniscus fibres that cross the midline in the lower medulla
where do internal arcuate fibres terminate
ventro postero medial nucleus
where is the somatosensory cortex
posterior to central sulcus
which tracts lead to somatosensory cortex
DCML
spinothalamic
what info is carried by the spinothalamic tract
pain, temp, crude touch
what info is carried by the DCML
fine touch, vibration, pressure, two-point discrimination and proprioception
rombergs test
Patient stands upright, closes eyes. If they wobble: positive sign
Asses proprioception from muscles and joint
what test Asses proprioception from muscles and joint
rombergs
what receptors detect pain
nocioceptors
what types of nerve fibres are nocioceptors at the end of
a delta and C
which nerve types trigger withdrawal reflexes
a delta
do nocioceptors have free nerve endings
yes
what type of pain do nociceptors pick up
normal pain
what are components of normal pain
chronic and acute
how do nociceptors detect pain
special Na channels open causing tonic depolarisation
what triggers a nociceptor
pro inflammatory chemicals
where do nocioceptors project to
anterior spinothalmic tract
where does the spinothalmic tract project to
venteroposterolateral nucleus of thalamus, then on to somatosensory cortex
what is the difference in pain info from the anterior and lateral spinothalamic tracts
anterior localises pain
lateral sensation and unpleasantness
where is pain from internal organs felt
region with afferent input in same dermatome
what information does the post and ant spinocerebellar pathways convey
proprioception to regulate balance
inputs to spinocerebellar tract
joint receptors
muscle spindles
does the spinocerebellar tract cross the midline
no
