The Sensory System Flashcards
What fibers carry pain?
thinly myelinated A-delta fibers
What fibers carry temperature?
unmyelinated C fibers
What tract carries pain and temp signals?
spinothalamic
Where do the pain and temp signal decusate?
anterior white commisure, so ascend contralaterally
What fibers carry proprioception, vibration and light touch?
heavily myelinated A-alpha and A-beta fibers
What tract carries proprioception, vibration and light touch?
dorsal columns
Where do the dorsal columns decussate?
in the medulla (nuclei gracilis and cuneatus) (so ascend ipsilaterally)
after they decussate they ascend further in the medial lemniscus
Describe the somatotopic arrangement of fibers in the spinothalamic tract.
sacral segments are located laterally and cervical segments medially (so your feet stick out)
Describe the somatotopic arrangement of fibers in the dorsal columns.
opposite of the spinothalamic because they don’t decussate until higher up, so sacral segments are medial and cervical (arm) segments are lateral
then after they decusate and continue on as the medial lemniscus, it’s the same as the STT so that the feet are lateral and the arms are medial
Where does the STT terminate?
in the ventroposterolateral (VPL) lobe of the thalamus
Where does the trigeminal tract terminate?
in the ventroposteromedial (VPM) of the thalamus
What is a paresthesia?
a paresthesia is an abnormal sensation described as tingling, prickling, pins and needs, etc.
What is a dysesthesia?
a dysesthesia is an unpleasant sensation triggered by painful stimuli
What is hyperesthesia?
an increased sensitivity to sensory stimuli (but you still feel it as the appropriate sensation - pain is just more painful)
What is allodynia?
this is pain provoked by a normally innocuous stimuli
