Touch

Somatosensory System

Provides information about touch, pressure, vibration, pain, temperature, and proprioception.

Discriminative Information

Information that can be located and identified with fine features, such as fine touch and pressure.

Non-discriminative Information

Information that cannot be precisely located or identified, such as pain and temperature.

Exteroception

Information about the external world.

Mechanoreception

Detection of pressure or touch (tactile sensitivity).

Thermoreception

Detection of temperature (thermal sensitivity).

Nociception

Detection of noxious (damaging or potentially damaging) stimuli.

Proprioception

Awareness of the position and movement of the body in space.

Introception

Information about internal organs.

Specialised Endings

Receptors in the somatosensory system that detect specific stimuli types without specialized receptor cells.

Accessory Structures

Connective tissue and fluid surrounding nerve endings that modify stimulus energy arrival.

Free Nerve Endings

Nerve endings without accessory structures, detecting temperature and pain.

Direct Pathway

Activation of sensory receptors through mechanical displacement by the stimulus.

Indirect Pathway

Activation of sensory receptors through molecules acting on the cell membrane.

Afferent Fibres

Nerve fibres transmitting sensory information to the brain; often classified by diameter and myelin.

Fine Touch Dimensions

Three dimensions of fine touch: FORM, TEXTURE, and VIBRATION.

Form (Fine Touch)

Ability to identify shapes based on touch, such as reading braille.

Texture (Fine Touch)

Ability to discriminate the smoothness or roughness of objects.

Vibration (Fine Touch)

Ability to distinguish between fluttering and vibrating stimuli.

Adaptation Rate

The ability of receptors to tell if a stimulus is changing and how fast.

Receptive Field Size

Determines the precision of identifying where the stimulus occurs on the skin.

Touch Sensitivity

Varies across the body; best at fingertips, tongue, and lips.

Fingertips Sensitivity

Highest sensitivity due to exploration and detailed tactile feedback.

Accessory Sheaths

Surround nerve endings and modify how stimulus energy acts on the nerve terminal.