Michaels

Question 1

chordotomy

Answer 1

sugical cutting of the anterolateral funiculus.

Sometimes performed bilaterally in terminally ill patients to releave pain

produces bilateral analgesia and athermia

Question 2

analgesia

Answer 2

the inabilty to feel pain

Question 3

syringomyelia

Answer 3

“hole” develops (cyst) in the center of the cord and expands out and rostral/caudally (up to several inches). May be related to blockage of CSF.

Initially it blocks crossing fibers from second order nociceptive and thermoreceptive neurons

Results in bilateral loss of pain and temperature sensation

Question 4

Brown-Séquard syndrome

also known as Brown-Séquard’s hemiplegia and Brown-Séquard’s paralysis,

Answer 4

loss of sensation and motor function due to lateral hemisection (cutting) of the spinal chord

Question 5

Sensory pathways

**Primary (first order) neuron **

Answer 5

receives the information

Question 6

Sensory pathways

**Second order neuron **

Answer 6

projects to the thalamus

Question 7

Sensory pathway

**Third order neuron **

Answer 7

projects from thalamus to cortex

Question 8

Convergence and receptive field overlap

Answer 8

Receptive fields of 2nd order neurons in the dorsal column nuclei are several times larger than those of primary afferent fibers (several neurons converge on one 2nd order neuron)

Receptive fields of 2nd order neurons often overlap producing a population response. Therefore stimulation of a small area of skin (point of convergence) could activate multiple 2nd order neurons

Question 9

primary somatosensory cortex

Answer 9

(S1), postcentral gyrus in the pariteal lobe; Brodmann’s areas 3, 1 and 2 – forms homunculus

Question 10

Spinothalamic Tract (STT)

Answer 10

Primary pathway for pain and temperature sensation

Input to STT neurons include nociceptors, thermoreceptors and mechanoreceptors

Damage to the tract results in reduced pain and temperature sensation but not touch