Somatosensation

Question 1

What are the three Somatosensory Systems?

Answer 1

-Exteroceptive system: Cutaneous sense and Information about
outside of the body

-Interoceptive system: Organic sense and Information about
inside of the body

-Proprioceptive system: Kinesthesia and Information about
the position of the body

Question 2

What are the five layers of Somatosensory receptors? (Skin receptors)

Answer 2

Free nerve endings: Temperature & Pain

Meisner Corpuscles: Light touch, edge contour, brail-
like (only in glabrous skin)

Merkel’s Disk: Precise information about touch, skin indentation

Ruffini Corpuscles: stretches, finger position

Pacinian Corpuscles: Skin vibration

Question 3

How do we detect pain?

Answer 3

• Mediated by free nerve endings

• Poorly localised information

• Temperature gated ion
channels

• Can be activated by ligands:
capsaicin for heat receptors/menthol for cold receptors

Question 4

How do we detect temperature?

Answer 4

• Mediated by free nerve endings

• Poorly localised information

• Nociceptors

• Respond to intense pressure
or extreme temperatures

Question 5

What is Tactile Agnosia (disorder of the Somatosensory System)?

Answer 5

Disorders of the somatosensory
association cortex

Cannot verbally identify object by touch alone

Can draw objects from touch alone

Question 6

What is phantom limb (disorder of the Somatosensory System)?

Answer 6

Sensation of pain coming from a limb that has been amputated

The somatosensory cortices is confused by noisy signals from the axons that have been cut