3. Somatosensory system

Question 1

other modality of dorsal column system

Answer 1

2 point discrimination (good at fingertip, poor at elbow)

Question 2

sensory encoding

Answer 2

intensity of stimulus encoded by frequency of action potentials along primary sensory neurone

Question 3

example of a rapidly adapting sensory receptor

Answer 3

mechanoreceptor

Question 4

benefit of nociceptors being slowly adapting

Answer 4

you don’t ‘get used to’ pain so you’ll fix the problem causing you pain

Question 5

define receptive field

Answer 5

area of skin supplied by one primary sensory neurone (overlaps=fuzzy dermatomal boundaries)

Question 6

cell body location for secondary sensory neurones

Answer 6

dorsal horn or medulla

Question 7

DCML pathway cell body of secondary sensory neurone

Answer 7

cuneate nucleus: UPPER BODY, T6 and above

gracile nucleus: LOWER BODY, T7 downwards

Question 8

in the spinothalamic pathway, are upper portions of the body more lateral>

Answer 8

no, more medial

Question 9

in brown-sequard syndrome, contralateral loss of spinothalamic modalities may be a couple of segments higher/lower than the lesion. why?

Answer 9

lissauer’s tract (primary afferents ascend)

Question 10

what is Syringomyelia?

Answer 10

cystic dilatation of central canal, midline lesion

bilateral, cape like, spinothalamic

Question 11

an expanding Syringomyelia could affect…?

Answer 11

ventral white commissure affected early, then:

if grows laterally:
-progressivley lower body areas for spinothalamic modalities
-ventral horns and so get lower motor neurone paralysis in upper limbs

if grows dorsally:
-progressivley higher body areas for dorsal column modalities