Processing of somatosensory input

Question 1

What is the somatosensory system?

Answer 1

A system containing different receptor types distributed throughout the body

Question 1

What sensory modalities are mediated by the somatosensory system?

Answer 1

Fine discriminatory touch (light touch, pressure, vibration, flutter and stretch)
Joint and muscle position sense (proprioception)
Temperature (thermosensation)
Pain (nociception)
Itch (pruriception)

Question 2

What are motor neurons divided into?

Answer 2

1st, 2nd and 3rd order neurons

Question 3

1st order neurons?

Answer 3

Upper motor neurons, arising from the brain and travelling down the spinal cord to synapse in the anterior grey horn.

Question 4

2nd order neurons?

Answer 4

Lower motor neurons. Usually located in brainstem or spinal cord. Travels from the spinal cord to innervate the muscles.

Question 5

3rd order neurons?

Answer 5

Carry signals from the thalamus to the primary sensory cortex.

Question 6

What do Pacinian (lamellar) corpuscles do?

Answer 6

Located deep in the dermis layer of the skin. Responding to transient pressure and high frequency vibration.

Question 7

What do Meissner’s (tactile) corpuscles do?

Answer 7

Located in the epidermis layer of the skin. Responds to touch and low frequency vibration.

Question 8

What are Ruffini’s endings?

Answer 8

Small, spindle shaped, slowly adapting receptors. Respond to pressure, stretching and angle change.

Question 9

What are Merkel’s discs?

Answer 9

Present in the outer layer of hairless skin. It is a touch receptor.