Sensory, Motor, Hearing, Balance, Taste, Olfaction, and Vision Neuroscience Review

Complete set of 176 vocabulary flashcards covering touch, temperature, pain, motor systems, hearing, vestibular function, gustation, olfaction, and vision from the course materials.

Free nerve endings

Sensory receptors that detect pain and temperature.

Merkel's discs

Sensory receptors that detect sustained touch.

Meissner's corpuscles

Sensory receptors that detect brief-burst touch and vibrations. Detect stimulus from light touch

Pacinian (lamellated) corpuscles

Sensory receptors that detect vibration and pressure.

Ruffini corpuscles

Sensory receptors that detect stretch.

Tonic receptors vs. phasic receptors

Tonic receptors show a slow or small decline in firing during continued stimulation; phasic receptors adapt quickly, with firing decreasing rapidly.

Receptive field

The part of the sensory world to which a sensory neuron responds.

Range fractionation

The mechanism by which different sensory neurons respond over different ranges of stimulus intensity, recruiting additional neurons as intensity increases.

Lateral inhibition (touch)

The process where neighboring sensory responses inhibit one another, sharpening spatial contrast and helping distinguish nearby stimuli.

Somatosensory cortical map

The cortical representation of sensory input from different body regions, in which the amount of cortex devoted to a region is not proportional to its physical size.

Somatosensory homunculus: hands and face

Body regions that occupy a disproportionately large amount of cortical space because they possess dense sensory representation and require fine discrimination.

Cortical reorganization after limb loss

The ability of the somatosensory cortical representation to reorganize when input from a body region is lost, allowing neighboring representations to expand into the altered territory.

TRP channels

A family of membrane ion channels used by sensory nerve endings to detect temperature and chemicals; TRP stands for transient receptor potential.

TRPV1, TRPM8, and TRP2 classification

Channel types or membrane proteins involved in detecting specific stimuli at sensory endings, rather than whole nerves or axons.

Sensory transduction (temperature/TRP)

Converting energy from a stimulus into a change in the sensory cell or neuron; temperature or a chemical activates a channel, altering membrane potential and producing a neural signal.

Activated TRP channel opening

The process where ions pass through the open membrane channel, resulting in membrane potential changes that depolarize the sensory ending and increase neural signaling.

TRPV1

A channel associated in Unit 2 materials with moderate heat and capsaicin.

Capsaicin

The chemical associated with the heat of chili peppers that activates TRPV1 channels, linking a chemical stimulus to heat- and pain-related sensory signaling.

TRPM8

A channel associated with moderate cold and methanol.

TRP2

A channel associated with high temperatures and signals carried by A-delta fibers.

Numbers in TRPV1, TRPM8, and TRP2

Names or identifiers for channel types rather than temperature values measured in degrees.

TRP channels vs. A-delta and C fibers

TRP channels detect and transduce stimuli at the sensory ending, whereas A-delta fibers (myelinated; fast, sharp pain) and C fibers (unmyelinated; slow, dull pain) carry signals toward the nervous system.

Nociceptors

Sensory receptors that detect potentially damaging stimuli and contribute to pain signaling.

A-delta fibers vs. C fibers

A-delta fibers are large, myelinated fibers carrying fast, sharp first pain; C fibers are small, unmyelinated fibers carrying slower, dull or aching pain.

Receptor for capsaicin and moderate heat

TRPV1.

Capsaicin (pain & modulation)

The substance associated with the heat of peppers that activates TRPV1 channels.

TRPM8 (pain & modulation)

A receptor associated with the detection of moderate cold and methanol.

TRP2 (pain & modulation)

A receptor associated with high temperatures, with signals carried by A-delta fibers.

Substance P

A neurotransmitter released during pain signaling.

Gate-control theory of pain

The model where activity in large-diameter touch fibers engages inhibitory spinal circuitry to reduce pain transmission from C fibers, subject to modulation by attention and emotional or cognitive factors.

TENS (transcutaneous electrical nerve stimulation)

A technique delivering electrical pulses to the skin to engage spinal gating mechanisms and reduce pain transmission.

Periaqueductal gray (PAG)

A midbrain region involved in pain processing and modulation that contains opioid receptors.

Anterior cingulate cortex (pain role)

The brain region emphasized for processing the emotional component and unpleasantness of pain.

Prefrontal cortex (pain role)

Contributes to the cognitive component of pain—how we think about, interpret, attend to, and evaluate pain. Cognitive factors, such as expectations and attention, can influence how pain is experienced.

Congenital insensitivity vs. congenital hypersensitivity to pain

Insensitivity is associated with loss-of-function sodium-channel mutations leading to an inability to feel pain; hypersensitivity is associated with gain-of-function changes causing excessive pain sensitivity.

Chronic pain

Pain that persists even after an injury has healed.

Neurogenic pain

Pain associated with nerve damage or inappropriate pain signaling by neurons.

Reflex sympathetic dystrophy (RSD)

A pain condition described as neurogenic pain associated with overactive sympathetic input.

Phantom limb pain

Pain perceived in a limb that has been lost, associated with cortical plasticity.

Synesthesia

A phenomenon in which a stimulus in one sensory modality evokes an experience in another modality, such as 'tasting blue' or associating a sound with a color.

Reflex

A brief, relatively automatic response, such as an eyeblink or finger twitch.

Motor plan

A set of muscle commands established before an action occurs.

Acts

Complex, sequential movements.

Ballistic movements vs. ramp movements

Ballistic movements are rapid and completed without ongoing sensory feedback corrections; ramp movements are slower, sustained motions guided by feedback.

Motor unit

One motoneuron's axon and all the muscle fibers it innervates.

Proprioception

The sense of body position and movement—where the body or its parts are and how they are moving.

Muscle spindles

Sensory receptors that detect muscle stretch or changes in muscle length.

Golgi tendon organs

Sensory receptors that detect muscle tension.

Classic stretch reflex (biceps)

The reflex where a muscle spindle detects stretch and sends afferent signals that excite motoneurons for the stretched biceps to contract while inhibiting the antagonist triceps.

Golgi tendon organ motor modulation

Increased activity from Golgi tendon organs that inhibits motoneurons, helping reduce excessive muscle tension.

Innervation ratio (motor control)

The number of muscle fibers controlled by a motoneuron; smaller motor units with fewer fibers per motoneuron support finer, more precise control.

Pyramidal system two-neuron chain

A motor pathway where upper motor neurons descend from primary motor cortex and cross at medullary pyramids before reaching spinal motoneurons, from which lower motor neurons carry commands to muscle.

Primary motor cortex

A motor area in the frontal lobe that issues commands involved in voluntary action.

Supplementary motor area (SMA)

A motor cortical area associated with initiating preplanned movement sequences and encoding sequences of movements.

Premotor cortex

A cortical area associated with planning movements guided by external events, whose neurons can fire shortly before an action.

Mirror neurons

Neurons described in the premotor cortex that discharge both when an action is performed and when a similar action is observed.

Basal ganglia structures

Caudate nucleus, putamen, and globus pallidus. The substantia nigra and subthalamic nucleus are closely connected structures that participate in basal ganglia circuits. Together, these circuits help initiate and regulate voluntary movement. (Located deep inside the brain, beneath the cerebral cortex.)

Basal ganglia functions

Structures that modulate movement initiation, amplitude, and direction; essential for movements performed from memory rather than guided purely by sensory feedback.

Cerebellar Purkinje cells

Cerebellar neurons that send inhibitory messages; critical for guiding movement through modulation, coordination, and inhibition.

Extrapyramidal system

A system contributing to movement modulation, coordination, initiation, and muscle tone, whose impairment affects motor control.

Central pattern generator

A neural circuit located in spinal circuits capable of generating rhythmic behaviors, such as walking.

Myasthenia gravis

An autoimmune disorder in which antibodies attack acetylcholine receptors at the neuromuscular junction, causing muscle weakness.

ALS (Amyotrophic lateral sclerosis)

Or Lou Gehrig's disease; degeneration of motor neurons. Associated with fasciculations.

Ataxia

Impaired coordination of movement associated with cerebellar damage.

Apraxia

Difficulty performing learned or sequenced movements despite having the basic motor capacity to move.

Parkinson's disease vs. Huntington's disease

Parkinson's disease involves degeneration of dopaminergic neurons in the substantia nigra with tremor and slowed movement; Huntington's disease involves caudate and putamen degeneration with excess involuntary chorea.

Frequency and amplitude (sound)

Frequency is sound-wave cycles per second ($\text{Hz}$) perceived mainly as pitch; amplitude represents sound intensity and loudness.

Human hearing range and conversation range

Hearing range is approximately $15\text{--}20{,}000\,\text{Hz}$; the conversation range is approximately $1{,}000\text{--}4{,}000\,\text{Hz}$.

Mechanical route of sound into the cochlea

Pinna and ear canal -> tympanic membrane (eardrum) -> ossicles (malleus, incus, stapes) -> oval window -> cochlear fluids and structures.

Ossicles

Three middle-ear bones ordered from eardrum to oval window: malleus, incus, and stapes.

Tensor tympani and stapedius muscles

Middle-ear muscles that stiffen the ossicular linkage to dampen sound transmission.

Oval window

The opening through which vibrations from the stapes reach the inner ear and cochlea.

Tip links

Fine links between stereocilia on hair cells that mechanically open ion channels when stereocilia bundles deflect.

Excitatory deflection of auditory hair-cell stereocilia

Mechanically gated channels open, hair cells depolarize, and calcium influx at the base triggers glutamate release onto auditory nerve fibers.

Hair cell action potentials

Auditory hair cells lack axons and do not generate action potentials; they transmit signals by depolarizing and releasing neurotransmitter onto auditory nerve fibers.

Inner hair cells vs. outer hair cells

Inner hair cells are primary sensory transducers conveying auditory information; outer hair cells serve as mechanical amplifiers within the inner ear.

Place theory of pitch

The coding principle stating that hair-cell location on the basilar membrane encodes frequency: high frequencies peak near the base and low frequencies near the apex.

Frequency coding (hearing)

The principle where the firing rate of an auditory neuron directly encodes pitch.

Volley principle

A mechanism where groups of auditory neurons coordinate their firing to represent sound wave cycles when a single neuron cannot fire rapidly enough for every cycle.

Ascending auditory pathway

Auditory nerve -> cochlear nuclei -> superior olivary complex/nucleus -> inferior colliculus -> medial geniculate nucleus -> auditory cortex.

Superior olivary nucleus

The first major auditory pathway structure to receive bilateral input; critical for sound localization.

Medial superior olive (MSO)

An auditory structure that encodes interaural timing or arrival-time differences, especially for low-frequency sound localization.

Lateral superior olive (LSO)

An auditory structure that encodes interaural intensity or loudness differences, especially for high-frequency sound localization.

Conductive hearing loss

A problem in the outer or middle ear that prevents sound from reaching the cochlea efficiently.

Sensorineural hearing loss

Hearing loss associated with damage to the cochlea or auditory nerve.

Central hearing loss

Hearing impairment caused by lesions in the brain's auditory processing systems, sometimes associated with auditory hallucinations.

Tinnitus and presbycusis

Tinnitus is persistent perceived sound without an external sound source; presbycusis is hearing loss associated with aging.

Dorsal auditory stream vs. ventral auditory stream

The dorsal stream is a frontoparietal 'where' pathway involved in sound location; the ventral stream is a temporal-lobe 'what' pathway analyzing sound identity and components.

Vestibular system

The sensory system for balance composed of three semicircular canals and two otolith organs (utricle and saccule).

Semicircular canals

Vestibular organs that detect angular head movement and rotational acceleration as endolymph deflects hair cells in the ampullae.

Utricle and saccule

Otolith organs that detect linear acceleration and head orientation relative to gravity.

Cranial nerve VIII

The vestibulocochlear nerve; carries both auditory signals from the cochlea and vestibular signals for balance.

Five basic tastes

Salty, sour, sweet, bitter, and umami.

Cranial nerves for taste

Cranial nerves VII (facial), IX (glossopharyngeal), and X (vagus).

Gustatory pathway

Taste receptor cells -> cranial nerves VII, IX, and X -> solitary tract/nucleus -> thalamus -> gustatory cortex in the insula and adjacent frontal operculum.

Tongue taste zones (neuromyth)

The disproven idea that distinct tongue regions exclusively detect specific tastes; all tongue regions can detect all five basic tastes.

Olfactory receptors and initial trajectory

Receptors located in the nasal cavity lining and olfactory epithelium whose axons project through the olfactory bulb.

Olfactory bulb projection targets

Direct projections reach the prepyriform cortex (primary olfactory cortex) and the amygdala in the limbic system.

Olfactory thalamic bypass

The unique property of olfaction where the primary sensory pathway reaches the cortex without first relaying through the thalamus.

Visible-light wavelength range

The electromagnetic spectrum range visible to humans, spanning approximately $380\text{--}740\,\text{nm}$.