Somatosensation and Cutaneous Receptors (Video Notes)

Vocabulary flashcards extracted from the video notes on sensory systems, somatosensation, cutaneous receptors, and pain processing.

Sensory transduction

Process by which physical stimulus energy is converted into neural signals (electrical language) that the brain can understand.

Receptive field

Region of sensory space where a stimulus will alter the firing of a given neuron.

Place code

Topographic mapping that represents sensory input in the brain; location on the body corresponds to a specific brain area.

Parallel pathways

Separate neural streams that process different aspects of a sensory input simultaneously (e.g., touch vs pain).

Somatosensation

Senses that convey information about the body and its contact with the environment, including touch, proprioception, and pain.

Cutaneous senses

Skin-based senses including pressure, vibration, temperature, and pain.

Proprioception

Perception of body position and posture.

Stimuli for cutaneous senses

Skin stimuli such as pressure, vibration, heating, cooling, and tissue damage (pain).

Mechanoreceptors

Sensory receptors that transduce mechanical energy into neural signals.

Mechanotransduction

Conversion of mechanical stimuli into receptor potentials that can trigger action potentials.

Adaptation

Change in a receptor's response with sustained stimulation; fast adapting respond briefly, slow adapting continue.

Ruffini corpuscles

Large, slowly adapting mechanoreceptors that respond to skin stretch and sustained pressure.

Pacinian corpuscles

Large, fast-adapting receptors that detect high-frequency vibrations and rapid changes in pressure.

Meissner's corpuscles

Small receptive field, fast-adapting receptors in glabrous skin; sensitive to light touch and low-frequency vibrations; dense in fingertips and lips.

Merkel's disks

Small, slowly adapting receptors that detect edges, form, and texture, especially via fingertips.

Hair follicle endings

Receptors around hair follicles that detect movement of hairs.

Free nerve endings

Nerve endings that detect temperature, noxious stimuli, itch.

A-beta fibers

Thick, myelinated fibers that rapidly convey touch information to the spinal cord.

A-alpha fibers

Very thick, myelinated fibers that convey proprioceptive information.

Nociceptors

Pain receptors (free nerve endings) that detect potentially damaging stimuli.

A-delta fibers

Thinly myelinated fibers carrying fast, sharp (acute) pain signals.

C fibers

Unmyelinated fibers carrying slow, dull, lingering pain signals.

Temperature receptors (overview)

Skin receptors that detect warmth and cold, located at different depths; transmit via TRP channels.

TRP channels overview

Family of temperature-sensitive ion channels transducing thermal stimuli and irritants (e.g., capsaicin).

TRPV1

Heat-activated channel responsive to ≥43°C and capsaicin; initiates heat pain.

TRPV2

Activated by hotter temperatures beyond TRPV1 thresholds (extremely hot).

TRPV3

Warm-temperature sensor active around 31–39°C.

TRPV4

Warm sensor active around 27–34°C.

TRPM8

Cold sensor activated by cool temperatures (<25°C) and menthol.

TRPA1

Cold sensor activated by very cold temperatures (<18°C) and irritants.

Nociception

Neural processes encoding and processing noxious stimuli into pain perception.

Substance P

Neuropeptide released by C fibers signaling dull, ongoing pain and promoting inflammation.

Glutamate

Neurotransmitter released by A-delta fibers signaling acute pain in the spinal cord.

Glycine

Inhibitory neurotransmitter in the spinal cord that reduces pain signaling.

Mu opioid receptors

Receptors that bind endogenous opioids and morphine to inhibit pain signaling.

Endorphins

Endogenous opioids that modulate pain by activating mu receptors.

Enkephalins

Endogenous opioid peptides involved in pain modulation.

VTA dopamine neurons

Dopaminergic neurons in the ventral tegmental area linked to reward and addiction; involved in mu receptor effects.

Locus coeruleus (NA)

Norepinephrine-producing region implicated in arousal and withdrawal symptoms; pain modulation involved.

ACC (anterior cingulate cortex)

Brain region involved in the emotional aspects of pain; activity linked to pain unpleasantness.

Insula

Brain region associated with the subjective experience of pain.

Pain perception components

Pain has sensory-discriminative, immediate emotional, and long-term emotional components.

Hypnosis and pain

Mental modulation can reduce pain unpleasantness and ACC activity without changing primary somatosensory cortex.

Place code and cortical magnification

Mapping of body surface to cortex with larger representations for sensitive areas (e.g., fingertips).

Homunculus

Distorted cortical map showing body part representations in the somatosensory cortex.

Cutaneous receptor distribution (skin)

Different receptors and densities in hairy vs. glabrous skin across epidermis and dermis.

Skin layers

Epidermis (outer), dermis (middle), subcutaneous fat (beneath).

Glabrous vs. hairy skin

Glabrous skin is hairless (palms/soles); hairy skin contains hair follicles.

Two-point threshold determinants

Spatial resolution determined by receptive field size and overlap.

Pain pathways parallel

Touch and pain pathways run in parallel with distinct neural routes to brain regions.