Somatosensory System (Touch)

Question 1

Sensory Homunculus

Answer 1

1. Mapping of body on somatosensory cortex
2. Neurons dedicated to perceiving sensory information from those parts of the body
   - Almost half dedicated to hand
   - Can be rearranged, very plastic

Question 2

Touch Receptors

Answer 2

1. Ruffini Ending: stretch
2. Pacinian Corpuscle: vibration
3. Merkel’s Disc: fine touch
4. Meissner Corpuscle: light touch
5. Pain Receptors: free nerve endings

Question 3

Adaptation

Answer 3

1. Progressive loss of response to maintained stimulus
   - Neurons reduce firing rates to constant stimulus over prolonged period of time

Question 4

Piezo Proteins

Answer 4

• Mechanically-gated Ion Channel
  1. Membrane is stretched, proteins pull apart
  2. Ion channel opens
  3. Na+ ions flow into the cell
  4. Depolarization

Question 5

Receptive Field

Answer 5

1. Only On-center receptive fields
   - Touch in-center depolarizes

Question 6

Top-down Processing

Answer 6

1. Higher brain centers suppress some sensory inputs and amplify others
   - Brain can change the way it receives information
   - Increase or decrease sensitivity to certain sensory systems

Question 7

Touch Pathway

Answer 7

1. Touch receptors on skin sends signals along dorsal part of spinal cord
2. Crosses over before reaching thalamus