touch and pain

Cortical Magnification

Body parts with more cortical space have higher sensitivity (fingertips, lips).

Somatosensory Cortex

Processes touch and pain; determines location and intensity of sensation.

Anterior Cingulate Cortex (ACC)

Region that processes emotional pain and distress.

Insula

Region that processes unpleasantness and emotional quality of pain.

Receptive Field

Area of skin a neuron responds to; determines resolution.

Small Receptive Field

High resolution; found in fingertips and lips.

Large Receptive Field

Low resolution; found in arms, back, etc.

Meissner’s Corpuscle

Small receptive field; fast adapting; detects light touch and low-frequency vibration.

Merkel’s Disk

Small receptive field; slow adapting; detects form, edges, and roughness.

Pacinian Corpuscle

Large receptive field; fast adapting; detects high-frequency vibration and deep pressure.

Ruffini Ending

Large receptive field; slow adapting; detects stretch and sustained pressure.

Fast Adapting

Neurons respond quickly but stop if stimulus continues (Meissner, Pacinian).

Slow Adapting

Neurons continue firing during stimulus (Merkel, Ruffini).

A-beta Fibers

Fast, thick, myelinated fibers that carry painless touch.

A-alpha Fibers

Largest, fastest fibers for proprioception.

A-delta Fibers

Thinly myelinated fibers carrying sharp, fast pain.

Releases glutamate in spinal cord

C-Fibers

Unmyelinated fibers carrying dull, slow, burning pain.

Substance P

Neurotransmitter released by C-fibers; increases dull pain (bad pain)

What is released by pituitary gland to block pain perception?

Endorphins, they bind to opiates on presynaptic membrane and block release of substance P

glycine

Initiatory neurotransmitter in spinal cord; reduces activity caused by substance p and glutamate

Cutaneous Senses

Skin senses including touch, vibration, heat, cold, and pain.

Proprioception

Sense of body position and movement.

Sensory Transduction

Converting physical stimuli into electrical signals the brain can understand.

Place Code

How the brain maps “where” touch occurs on the body.

Parallel Pathways

Touch and pain travel separate pathways into the brain.

TRPV1

Receptor for heat above 43°C; activated by capsaicin.

TRPM8

Receptor for cold below 25°C; activated by menthol.

TRPV2

Receptor for painfully hot temperatures above 52°C.

TRPA1

Receptor for extreme cold below 18°C.

Glabrous Skin

Hairless skin (fingertips, palms).

Mechanoreceptor

Sensory receptor responding to touch or physical pressure.

Two-Point Threshold

Minimum distance needed to feel two separate touches; smaller threshold = small receptive fields.

Which pathway carries touch?

Dorsal Column

Which pathway carried pain?

Spinothalamic

What receptors are located in hairy, glabrous skin?

Merkles and Pacinian

What receptors are located in glabrous skin?

Meissners and Ruffini