Sensory Processing (Pain and touch)

These flashcards extensively cover the general principles of sensory principles like touch and pain, with definitions and examples of detailed structures, according to chapter 8 of Behavioral Neuroscience (Breedlove & Watson, 2023). Created as a study guide for Exam 2 in PSYCH 384: Behavioral Neurobiology at BYU-I.

Stimulus

Any event that triggers a sensory response by affecting a sensory organ

Sensory receptor organ

An organ specialized to detect particular stimuli

Receptor cells

A specialized cell that responds to an energy or substance and converts energy into a change in the electrical potential across its membrane

Labeled lines

The concept that each nerve input to the brain only reports a particular type of information - preceded by Müller’s doctrine of “specific nerve energies”

Adequate stimulus

A type stimulus for which a sensory organ is adapted to detect

Sensory transduction

The process whereby a receptor cell coverts energy of a stimulus into a change in electrical potential across its membrane

Receptor potentials

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

A skin receptor cell type that detects vibration, resembling an onion for its layers of membrane

Piezo

A family of proteins that are stretch-sensitive and open channels in response to mechanical stretch

Coding

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

Range fractionation

A method of perceiving stimulus intensity in which intensity values are encoded by an array of cells, each specialized to detect specific ranges of intensities

Somatosensory system

The system referring to body sensation, particularly touch and pain

Phasic receptors

Receptors that display adaptation, rapidly decreasing the frequency of action potentials when stimulus is maintained

Tonic receptors

Sensory receptors that show little or no decrease in the frequency of action potentials as stimulation is maintained - relatively little sensory adaptation

Modality

One aspect of a stimulus or what is perceived after a stimulus (touch, vision, etc.)

Sensory pathways

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

Receptive field

A stimulus region in which a stimulus will alter a cell’s activity in a sensory system

Primary somatosensory cortex (S1)

The primary cortex for receiving touch and pain information where sensory receptors on the body surface are mapped (postcentral gyrus in the parietal lobe)

Secondary somatosensory cortex (S2)

The region of cortex that receives direct projections from primary somatosensory cortex, mapping both sides of the body

Attention

The process by which we select or focus on one or more specific stimuli for enhances processing and analysis

Top-down processing

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

Posterior parietal lobe

A cortical region that plays a special role in attention of sensory processes - cells here are especially responsive when a stimulus is expected

Cingulate cortex

The portion of cortex above the corpus callosum that seems to mediate the emotional, discomforting aspect of pain

Hypodermis (subcutaneous tissue)

The innermost layer of skin that contains Pacinian corpuscles, providing an anchor for muscles and helping shape the body

Dermis

The middle layer of skin containing a rich web of nerve fibers in a network of connective tissue and blood vessels

Epidermis

The outermost, thinnest layer of skin

Meissner corpuscles

Fast-adapting skin receptor cell type that detects light touch, densely distributed in skin regions with fine detail (fingertips, tongue, lips)

Merkel discs

Slow-adapting, oval skin receptor cell type that detects fine touch, densely distributed in skin regions with fine detail (fingertips, tongue, lips)

Ruffini endings

A slow-adapting skin receptor cell type that detects stretching of the skin with large receptive fields

Proprioception

Sense of body position and movements

Muscle spindles

Receptor that detects muscle stretch to provide proprioception

Free nerve endings

An axon ending in the skin without any specialized cell associated with it, detecting pain and/or changes in temperature

What are the four main sensory functions of somatosensory receptors?

Proprioception, touch, pain/temperature, temperature/pain/itch

Which functional sensory receptor type have the largest diameters and fastest conduction speeds?

Muscle spindles (for proprioception)

Dorsal root ganglia (DRGs)

The location near the spine where the four tactile receptors store their cell bodies

Dorsal column system

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

Dorsal column nuclei

Collection of neurons in the medulla that receive somatosensory information from the dorsal column system, sending their axons across the midline to the thalamus

Nociceptors

Peripheral receptors and nerve fibers specialized to respond to pain

Anterolateral (spinothalamic) system

A somatosensory system that carries most pain and temperature information from the body to the brain

Transient receptor potential (TRP) ion channels

A family of proteins that act as ion channels in response to certain somatosensory stimuli

Transient receptor potential vanilloid type 1 (TRPV1) ion channels

A receptor activated by capsaicin to transmit the spicy sensation, normally detects sudden increases in temperature

C fibers

Small, unmyelinated axons that conduct information slowly and adapt slowly, often possessing TRPV1 receptors (hence the slow burn of spice)

Transient receptor potential type M3 (TRPM3) ion channels

A receptor, found in some free nerve endings, that opens its channel in response to rising temperatures - higher than TRPV1

A-delta fibers

Large-diameter, myelinated axons that conduct action potentials quickly, possessing TRPM3 receptors

TRPM8

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

Natriuretic peptide B (Nppb)

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

Neuropathic pain

Pain caused by damage to peripheral nerves - occurring from inappropriate pain signaling of neurons rather than tissue damage

Phantom limb pain

Continued perception of chronic pain coming from a missing limb

Migraines

Intense headaches that typically affect one side of the head and recur at regular intervals - a type of neuropathic pain

How does damaged tissue trigger pain signaling in the periphery?

Damaged tissue releases chemicals that activate pain fibers in the skin

Nav1.7 (SCN9A)

A voltage-gated sodium channel used almost exclusively by nociceptors in free nerve endings to initiate action potentials

Congenital insensitivity to pain (CIP)

The condition of being born without the ability to perceive pain, resulting from mutation of SCN9A gene that prevents opening of the channel it encodes

Nav1.8

A voltage-gated sodium channel used almost exclusively by nociceptors in free nerve endings to sustain pain-signaling neuronal firing

Anterior cingulate cortex

Part of the cingulate cortex that plays a role in the pain associated with social rejection (and perhaps emphasized pain)

Opiates

Drugs derives from (or related to) opium

Opioids

Endogenous ligands that work similarly to opiates (on opioid receptors as painkillers)

What are the four main approaches to control chronic pain?

Psychogenic, pharmacological, surgical treatment, stimulation

Psychogenic approach to chronic pain (examples)

Placebo, hypnosis, stress, cognitive (learning, coping strategies)

Pharmacological approach to chronic pain (examples)

Opiates, spinal block, anti-inflammatory drugs, cannabinoids

Surgical treatments for chronic pain (examples)

Cutting peripheral nerve cord, rhizotomy (cutting dorsal root), cord hemisection, frontal lobotomy

Stimulation for chronic pain (examples)

Acupuncture, electrical stimulation of central gray

Placebo

An inert treatment with no obvious direct physiological effect that can sometimes bring relief when administered

Nocebo

An inert substance that causes discomfort due to the patient’s expectations - side effects of a placebo

Rhizotomy

The cutting of a dorsal root - a surgical treatment to control chronic pain

(Sensory) adaptation

The progressive loss of response when stimulation is maintained (usually through phasic receptors)

Light touch is detected by what four tactile receptors?

Pacinian corpuscles, Meissner corpuscles, Merkel discs, Ruffini endings

Stimulating the _______ of a receptive field often creates a(n) ________ effect to allow more _______ resolution

surrounding, inhibitory, spatial

What are some various substances that may be chemical mediators of pain?

Neuropeptides, serotonin, histamine, proteolytic (protein-metabolizing) enzymes, and prostaglandins

Stimulation of a Pacinian corpuscle causes the opening of _________-gated ______ channels

Mechanically; sodium

What brain region is especially active in tests that require spatial attention, and believed to play a significant role in an "executive" attention system?

Cingulate cortex

Which fast-adapting tactile receptors mediate most of our ability to perceive form?

Meissner corpuscles

Dermatome

An area of skin innervated by a single spinal nerve

Among monkeys trained to maintain one-finger contact with a moving object, cortical areas associated with the _______ finger would ________

trained; expand

Anti-inflammatory painkillers may help in what way?

Physiological, emotional, and social pain

What substance signals mast cells to release histamine in response to capsaicin, causing lips to swell?

Substance P

Which area of the brain is associated with the analgesic effects of painkillers (and electrical stimulation)?

Periaqueductal gray of the brainstem

Stimulation of the ________ area can induce ________

periaqueductal gray, analgesia

Descending fibers from the brainstem directly _______ dorsal horn cells that transmit _____ information

inhibit, pain