Week 7

Receptor Cell

A specialized cell that responds to a particular energy or substance in the internal or external environment and converts this energy into a change in the electrical potential across its membrane.

Stimulus

A physical event that triggers a sensory response.

Labeled Lines

The concept that each nerve input to the brain reports only a particular type of information.

Receptor potential

also called generator potential; a local change in the resting potential of a receptor cell in response to stimuli, which may initiate an action potential

Sensory Transduction

The process in which a receptor cell converts the energy in a stimulus into a change in the electrical potential across its membrane.

Pacinian Corpuscle

Also called lamellated corpuscle. A skin receptor cell type that detects vibration and pressure.

Threshold

Here, the stimulus intensity that is just adequate to trigger an action potential in a sensory cell.

Meissner's Corpuscle

Also called tactile corpuscle. A skin receptor cell type that detects light touch, responding especially to changes in stimuli.

Merkel's Disc

A skin receptor cell type that detects light touch, responding especially to edges and isolated points on a surface.

Ruffini Corpuscle

A skin receptor cell type that detects stretching of the skin.

Free nerve ending

an axon that terminates in the skin and has no specialized cell associated with it; free nerve endings detect pain or itch, or changes in temperature

somatosensory system

A set of specialized receptors and neural mechanisms responsible for body sensations such as touch and pain.

receptive field

The stimulus region and features that affect the activity of a cell in a sensory system.

sensory adaptation

The progressive loss of receptor response as stimulation is maintained.

phasic receptor

A receptor in which the frequency of action potentials drops rapidly as stimulation is maintained.

tonic receptor

A receptor in which the frequency of action potentials declines slowly or not at all as stimulation is maintained.

central modulation of sensory information

The process in which higher brain centers, such as the cortex and thalamus, suppress some sources of sensory information and amplify others.

dorsal column system

A somatosensory system that delivers most touch stimuli to the brain via the dorsal columns of spinal white matter.

dermatome

A strip of skin innervated by a particular spinal nerve.

thalamus

The brain regions at the top of the brainstem that trade information with the cortex.

primary sensory cortex

For a given sensory modality, the region of cortex that receives most of the information about that modality from the thalamus (or, in the case of olfaction, directly from the secondary sensory neurons).

nonprimary sensory cortex

Also called secondary sensory cortex. For a given sensory modality, the cortical regions receiving direct projections from primary sensory cortex for that modality.

primary somatosensory cortex

Also called somatosensory 1 or S1. Primarily the postcentral gyrus of the parietal lobe, where sensory inputs from the body surface are mapped.

polymodal neuron

A neuron upon which information from more than one sensory system converges.

synesthesia

A condition in which stimuli in one modality evoke the involuntary experience of an additional sensation in another modality.