PSYC 304 - Chapter 8: Sensory Processing, Touch, and Pain

Pain

The discomfort normally associated with tissue damage.

Congenital Insensitivity to Pain

The condition of being born without the ability to perceive pain.

Nociceptor

A receptor that responds to stimuli that produce tissue damage or pose the threat of damage.

Free Nerve Ending

An axon that terminates in the skin without any specialized cell associated with it and that detects pain and/or changes in temperature.

Capsaicin

A compound synthesized by various plants to deter predators by mimicking the experience of burning.

Transient Receptor Potential Vanilloid Type 1 (TRPV1)

Also called vanilloid receptor 1; a receptor that binds capsaicin to transmit the burning sensation from chili peppers and normally detects sudden increases in temperature.

Transient Receptor Potential Type M3 (TRPM3)

A receptor, found in some free nerve endings, that opens its channel in response to rising temperatures.

A Delta Fiber

A moderately large, myelinated, and therefore fast-conducting axon, usually transmitting acute pain information.

C fiber

A small, unmyelinated axon that conducts pain information slowly and adapts slowly.

TRPM8

Also called cool-menthol receptor 1 (CMR1); a sensory receptor found in some free nerve endings, that opens an ion channel in response to a mild temperature drop or exposure to menthol.

SCN9A

Also called NAv1.7; a voltage-gated sodium channel used almost exclusively by nociceptors to initiate action potentials.

Anterolateral System

Also called spinothalamic system; a somatosensory system that carries most of the pain and temperature information from the body to the brain.

Glutamate

An amino acid transmitter; the most common excitatory transmitter.

Substance P

A peptide transmitter implicated in pain transmission.

Migraines

Intense headaches, typically perceived from one half of the head, that recur regularly and can be difficult to treat.

Natriuretic Polypeptide B (Nppb)

A peptide neurotransmitter used by neurons reporting itch to the spinal cord.

Neuropathic Pain

Pain caused by damage to the peripheral nerves. It is often difficult to treat.

Epidermis

The outermost layer of skin, over the dermis.

Dermis

The middle layer of skin, between the epidermis and hypodermis.

Hypodermis

Also called subcutaneous tissue; the innermost layer of skin, under the dermis.

Tactile

Of, or relating to touch.

Meissner’s corpuscle

A skin receptor cell type that detects light touch.

Merkel’s disc

A skin receptor cell type that detects fine touch.

Piezo

A family of two proteins that respond to mechanical stretch by opening channels to let cations in to depolarize the cell.

Ruffini’s ending

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

Dorsal Column System

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

Dorsal Column Nuclei

Collection of neurons in the medulla that receive somatosensory information via the dorsal columns of the spinal cord. These neurons send their axons across the midline and to the thalamus.

Dermatome

A strip of skin innervated by a particular spinal nerve.

Coding

The rules by which action potentials in a sensory system reflect a physical stimulus.

Range Fractionation

A hypothesis of stimulus intensity perception stating that a wide range of intensity values can be encoded by a group of cells; each of which is a specialist for a particular range of stimulus intensities.

Somatosensory

Referring to body sensation, particularly touch and pain sensation.

Adaptation

Here, the progressive loss of receptor sensitivity 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.

Phasic Receptor

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

Top-Down Process

A process in which higher-order cognitive processes control lower-order systems, often reflecting conscious control.

Sensory Pathway

The chain of neural connections from sensory receptor cells to the cortex.

Thalamus

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

Receptive Field

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

Primary Sensory Cortex

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

Secondary Sensory Cortex

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

Primary Somatosensory Cortex (S1)

Also called somatosensory 1. The gyrus just posterior to the central sulcus, in the parietal lobe, where sensory receptors on the body surface are mapped; primary cortex for receiving touch and pain information.

Attention

A state or condition of selective awareness or perceptual receptivity, by which specific stimuli are selected for enhanced processing.

Cingulate Cortex

Also called cingulum; a region of medial cerebral cortex that lies dorsal to the corpus callosum.

Polymodal

Involving several sensory modalities.

Synesthesia

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

Sensory Receptor Organ

An organ (such as the eye or ear) specialized to receive particular stimuli.

Stimulus

A physical event that triggers a sensory response.

Receptor Cell

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

Adequate Stimulus

The type of stimulus for which a given sensory organ is particularly adapted.

Specific Nerve Energies

The doctrine that the receptors and neural channels for the different senses are independent and operate in their own special ways and can produce only one particular sensation each.

Labeled Lines

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

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.

Receptor Potential

Also called generator potential; a local change in the resting potential of a receptor cell that mediates between the impact of stimuli and the initiation of action potentials.

Pacinian corpuscle

Also called lamellated corpuscle; a skin receptor cell that detects vibration.

Threshold

The stimulus intensity that is just adequate to trigger an action potential.

Cannabis

Also called marijuana; dried leaves and flowers of the plant Cannabis sativa, typically smoked to obtain THC for a psychoactive effect.

Analgesia

Absence of or reduction in pain.

Opiates

A class of compounds that exert an effect like that of opium, including reduced pain sensitivity.

Endogenous Opioids

A class of peptides produced in various regions of the brain that bind to opioid receptors and act like opiates. Three kinds, endorphins, enkephalins, and dynorphins, that reduce pain perception.

Opioid Receptor

A receptor that responds to endogenous and/or exogenous opioids.

Periaqueductal Grey

The neuronal body-rich region of the midbrain surrounding the cerebral aqueduct that connects the third and fourth ventricles. It is involved in pain perception.

Placebo

A substance that is known to be ineffective or inert but that, when administered like a drug, can sometimes bring relief.

Naloxone

A potent antagonist of opiates that is often administered to people who have taken drug overdoses. It blocks receptors for endogenous opioids.

Nocebo

An inert substance that causes discomfort due to the patient’s expectations.