Somatic sensation

Question 1

A-alpha fibers

Answer 1

Unconscious propioception

Question 2

Meissner’s corpuscles nerve fiber and function

Answer 2

A-beta nerve fibers
Dynamic touch (rapidly adapting)

Question 3

Cool receptor nerve fiber

Answer 3

A-delta

Question 4

Warm receptor nerve fiber

Answer 4

C fiber

Question 5

Nociceptors nerve fiber

Answer 5

A-delta (mechanical thermal) = sharp prickling pain
C fibers (Polymodal thermal) = slow burning pain

Question 6

Nociceptors nerve fiber

Answer 6

A-delta (mechanical thermal) = sharp prickling pain
C fibers (Polymodal thermal) = slow burning pain

Question 7

Nociceptors nerve fiber

Answer 7

A-delta (mechanical thermal) = sharp prickling pain
C fibers (Polymodal thermal) = slow burning pain

Question 8

Merkel cell nerve fibers and fxn

Answer 8

A-beta nerve fibers
Static touch (slowly adapting)

Question 9

Pacinian corpusle nerve fibers and fxn

Answer 9

A-beta nerve fibers
Vibration (RA, rapidly adapting)

Question 10

Ruffini endings nerve fibers and fxn

Answer 10

A-beta nerve fibers
Skin stretch (SA, slowly adapting) AKA pressure

Question 11

Pressure and how heavy an object is is felt by…

Answer 11

Ruffini endings

Question 12

Indentation and grip force is felt by

Answer 12

Merkel cells

Question 13

Shape/surface is felt by

Answer 13

Meissner corpuscle

Question 14

Fingertips mechanoreceptor distribution

Answer 14

Best of: Merkel cells, Meissner corpuscles

Remark: Ruffini endings and Pacinian corpuscles have a uniform distribution

Question 15

The shallower a receptor is, the more __

Answer 15

Sensitivity for responding.

Meissner and Merkel are shallower than Pacinian corpuscles and Ruffini endings.

Question 16

Grasp & release of objects use __ mechanoreceptors

Answer 16

Meissner
Pacinian

Question 17

How does our body feel dynamic temperatures?

Answer 17

At sudden colder environments,
1. Cold receptors signals shoot up transiently, and then plateau at a greater frequency than before.
2. Warm receptors are silent (inhibited) transiently and then fire at a lesser frequency than before.

Question 18

Range of cold fibers

Answer 18

5-40 C
Preferred: 25 C

Question 19

Range of warm fibers

Answer 19

29-49 C
Peak: 45 C

Question 20

Fine touch tract

Answer 20

Ventral spinothalamic tract

Question 21

Astereognosis (Tactile agnosia)

Answer 21

Inability to identify an object by active touch of the hands without other sensory input – lesions of the dorsal column or parietal lobe or parieto-temporo-occipital lobe

Sensory ataxia – Tarbes dorsalis (neurosyphilis), pernicious anemia (vitamin B12 anemia), multiple sclerosis

Question 22

Romberg’s test

Answer 22

 Ask subject to stand erect with feet together – unable to balance even with eyes open = cerebellar ataxia
 Ask subject to close his/her eyes (30 sec) – swaying and unable to balance = Romberg’s test positive = sensory ataxia (propioception impairment) or vestibular dysfunction
 Pseudoathetosis (Choreaform of distal muscle) confirms severe sensory ataxia induced by lesion of dorsal column or polyneuropathy

Question 23

Dissociated sensory loss

Answer 23

Syringomyelia – a cyst or cavity (syrinx) forms within the spinal cord – suspended hyp(o)algesia (bilateral loss of sensation in pain and temperature)

Question 24

Pseudoathetosis

Answer 24

Choreaform of distal muscle

Pseudoathetosis refers to a movement disorder characterised by involuntary, slow, writhing movements resulting from loss of proprioception.