Exam 3 somatosensory pathways part 1- Michaels Flashcards
What sensations does dorsal column-medial lemniscus pathway deal with?
Fine touch, vibration, proprioception
What sensations does the spinothalamic tract deal with?
Pain and temperature (monitory changes in temperature)
where does sensory information go to in the cortex
S1 of the somatosensory cortex (post central gyrus)
When does the Dorsal column-medial lemniscus pathway decussate?
2nd order neuron crosses over after the dorsal column nuclei (caudal medulla) up to the thalamus
When does the spinothalamic pathway decussate?
the 2nd order neuron crosses midline at the same level or along lissauer’s tract
what type of neurons are involved in the pain pathway?
A-delta and C fibers (which are much slower)
Where does the corticospinal pathway decussate?
upper motor neuron decussates within the pyramids of the medulla
what happens when lower motor neurons are injured?
muscle atrophies
What happens when upper motor neuron is injured?
hyperreflexia
As a general rule, do axons of primary sensory neurons cross the midline?
nope
Where are the cell bodies of sensory neurons located in the dorsal root ganglia
Medial part of DRG
What part of spinal cord section does spinal nerves ascend toward brain?
Dorsal column (gracile and cuneate fasciculi)
Where are local branches of primary afferent sensory neurons terminating in the spinal cord?
Terminate in dorsal horn in Lamina V with interneurons that contribute to reflexes
T/F: primary afferent neurons cross the dorsal column and ascend to the brain contralaterally?
False, don’t decussate until medulla
What is convergence?
Neurons that supply a large area in terms of sensory feed back to a single secondary nerve
Where are the cervical nerves located in the ventral posteriolateral nucleus in the thalamus? Sacral?
Cervical is more medial than sacral.
Where do sensory neurons from the thalamus pass to?
Pass laterally through internal capsule and project to the postcentral gyrus of ipsilateral cortex (S1)
What sensations does the spinothalamic tract deal with?
Pain and temperature
What kinds of receptors provide input to the STT neurons?
nociceptors, thermoreceptors and mechanoreceptors
T/F: damage to the STT results in deficits in pain and temp sensation but not touch
true
At what level does the STT cross?
second order neuron cell bodies in the substantia gelatinosa of the dorsal horn can cross at the same level to the STT via the white commissure and ascent in the ventrolateral funiculus, or move up 1 or 2 segments via lissauer’s tract and then cross at that level
Does a lesion at a specific level cut out all pain and temperature below that level?
No, 1 or 2 segments below it can move around the lesion via lissauer’s tract and still report pain receptor activity
When is it certain that an axon of the STT has crossed?
within two spinal segments up the spinal cord
What is syringomyelia?
a hole or cyst develops in the center of the cord and expands out rostral/caudally up to several inches, usually caused by CSF block, and blocks crossing STT fibers
What results from a syringomyelia?
bilateral loss of pain and temperature sensation
Where does the primary nociceptor neuron synapse with the secondary neuron NOT using the lissauer’s tract?
Within the substantia gelatinosa
Where does the STT tract drop information off to awaken an individual in pain?
Reticular formation (leads to depolarization of cortical neurons and desynchronization of EEG)
Besides thalamus, where does the reticular formation send information?
Central lateral nucleus synapsing to third order nuclei that sends information to limbic system of cortex, leading to the “suffering” of pain
What do lesions of the VPL result in?
difficulty localizing pain
Where is reticular formation located?
brainstem
What is Brown séquard syndrome?
half of spinal cord is lesioned leading to hemiplegia
