(WIP) Lecture 3: The Somatosensory System: Touch and Proprioception 2

Dermatomes

The territory innervated by each spinal nerve

Maps of innervation arising from each dorsal root ganglion and its spinal nerve.

• Defined in patients suffering from shingles or after surgical interruption

• Individual differences

• Some overlap (more precise for pain)

• Helpful in determining area of spinal damage

Ia, Ib, II afferents

largest and fastest somatic afferents, supply sensory receptors to muscles for proprioception

Aβ afferents

smaller somatic afferents that convey touch

Aδ and C afferents

small and slow afferents that convey pain and temperature

Receptive fields

The area of skin surface over which stimulation results in a significant change in the rate of action potentials

Slowly adapting afferents

• Generate sustained discharge during ongoing stimulus

• Provide spatial info: size and shape of stimulus

Rapidly adapting afferents

• Fire rapidly when a stimulus is first presented

• Fall silent with continual stimulation

• Convey changes (stimulus movement)

Sensory transduction

Process of converting energy of stimulus into an electrical signal