Sensory, Auditory, Gustatory, and Motor Systems

Vocabulary practice flashcards covering sensory, visual, auditory, gustatory, and motor systems based on the lecture review transcript.

Ventral Posterior Nucleus (VPN)

The subregion of the thalamus (including VPL and VPM) that relays somatosensory and pain information from the body and face to the cerebral cortex.

Hemispatial Neglect

A condition resulting from damage to the right parietal cortex in which an individual has difficulty perceiving or attending to the left visual field, often unaware of the deficit.

Nociceptors

Free nerve endings in the skin that function as touch and pain receptors responding to mechanical injury, extreme temperatures, or chemical burns.

A-Delta Fibers

Myelinated sensory nerve fibers that transmit signals for fast, sharp, and intense pain.

C Fibers

Unmyelinated sensory nerve fibers that transmit signals responsible for slow, dull, aching, or burning pain.

Anterior Cingulate Cortex (ACC)

A brain region involved in processing cognitive and emotional responses to pain, as well as pain anticipation.

Periaqueductal Gray (PAG)

A brainstem structure densely populated with opioid receptors whose stimulation produces pain reduction.

Spinothalamic Pathway Midline Crossing

The anatomical decussation where pain and temperature information crosses to the opposite side within the spinal cord.

Dorsal Root

The sensory branch of the spinal nerve located in the dorsal part of the spinal cord that transmits incoming sensory signals from peripheral nerves into the central nervous system.

Medulla Oblongata (Touch Pathways)

The brainstem region where sensory pathways transmitting fine, non-painful touch cross the midline.

SCN9A Gene

The gene encoding the voltage-gated sodium channel NaV1.7; mutations in this gene cause congenital insensitivity to pain.

Lateral Geniculate Nucleus (LGN)

The thalamic subregion that receives visual inputs from retinal ganglion cells and relays visual information to the primary visual cortex.

Prosopagnosia

A visual agnosia characterized by the inability to recognize familiar faces based on visual input alone, typically resulting from brain injury.

Cortical Modules

Organized groups of cortical neurons that specialize in processing distinct types of visual information.

Rods

Retinal photoreceptors specialized for vision in dim light (night vision) that provide lower visual acuity and do not differentiate colors.

Cones

Retinal photoreceptors that function optimally in bright light, detect color, and provide sharp visual acuity.

Scotoma

A localized area of blindness or reduced vision within an otherwise intact visual field, often caused by a stroke.

Red-Green Color Blindness

A common visual impairment that follows a sex-linked pattern of inheritance.

Dorsal Visual Stream

The visual processing pathway that projects to the posterior parietal cortex, involved in spatial awareness and movement guidance.

Ventral Visual Stream

The visual processing pathway that projects to the inferior temporal cortex, responsible for object identification and recognition.

Fovea Centralis

The central retinal area devoid of large blood vessels that contains a high concentration of cones and provides maximum visual acuity for fine detail.

Optic Disc

The site on the retina where ganglion cell axons exit to form the optic nerve, creating a physiological blind spot due to the absence of photoreceptors.

Visual Agnosia

A neurological condition characterized by an inability to recognize or identify objects despite preserved visual acuity.

Superior Colliculus

A midbrain structure that coordinates reflexive eye and head movements toward sudden visual stimuli.

Hypercolumns

Functional processing units within the primary visual cortex (V1) that combine ocular dominance columns and cytochrome oxidase blobs to integrate visual inputs into coherent images.

Sensation vs. Perception

Sensation is the physical detection of a stimulus (such as light striking the retina), whereas perception is the psychological interpretation of that sensory input.

Light Wave Properties

Physical dimensions of light where wave amplitude encodes brightness and wavelength encodes color (hue).

Antagonistic Center-Surround Organization

A receptive field arrangement where light falling on the center produces an effect opposite to that of light falling on the surround, enhancing edge and contrast detection.

Retinal Ganglion Cells

Neurons in the retina that integrate incoming photoreceptor signals and project their axons via the optic nerve to the brain.

Binocular Disparity

The slight geometric difference between the images projected onto the two retinas, which increases as an object approaches and provides depth cues.

Phototransduction (in Rods)

The biochemical pathway in which light activates rhodopsin, triggering transducin and phosphodiesterase to decrease cGMP, close cGMP-gated ion channels, hyperpolarize the rod cell, and reduce glutamate release.

Dark Adaptation

The gradual visual adjustment occurring over approximately $30\,\text{minutes}$ in low-light environments as rhodopsin regenerates within rods to restore sensitivity.

Ossicles

Three tiny bones of the middle ear that mechanically transmit sound energy from the air to the fluid of the inner ear.

Tympanic Membrane

The eardrum, which forms the anatomical boundary between the outer ear and the middle ear.

Pinna

The visible external cartilaginous structure that constitutes the outer ear.

Organ of Corti

The specialized sensory receptor structure in the inner ear containing rows of hair cells that convert mechanical sound vibrations into neural signals.

Oval Window

The membrane-covered opening that establishes the boundary between the middle ear and the inner ear.

Ascending Auditory Pathway

The synaptic sequence relaying auditory signals: Cochlea $\rightarrow$ Cochlear nuclei $\rightarrow$ Superior olivary complex $\rightarrow$ Inferior colliculus $\rightarrow$ Medial geniculate nucleus (MGN) $\rightarrow$ Primary auditory cortex.

Medial Geniculate Nucleus (MGN)

The auditory subregion of the thalamus that relays acoustic information to the primary auditory cortex.

Stereocilia

Microscopic hair-like projections on cochlear hair cells that deflect within endolymph to alternatingly depolarize and hyperpolarize the cell, controlling glutamate release.

Gustatory Pathway

The ascending neural circuit for taste: Taste buds $\rightarrow$ Cranial nerves VII, IX, and X $\rightarrow$ Nucleus of the solitary tract $\rightarrow$ Ventral posteromedial (VPM) nucleus of the thalamus $\rightarrow$ Primary gustatory cortex.

OR6A2 Gene

An olfactory receptor gene whose genetic variants increase sensitivity to specific aldehydes, causing cilantro to taste like soap.

Taste Cranial Nerves

The facial (VII), glossopharyngeal (IX), and vagus (X) cranial nerves that transmit taste signals from taste receptor cells to the brainstem.

Five Basic Tastes

The fundamental perceptual taste modalities detected by taste receptor cells: sweet, sour, salty, bitter, and umami.

Primary Gustatory Cortex

The cortical region located primarily within the insula and frontal operculum (with additional processing in the parietal operculum) dedicated to identifying primary taste qualities.

Orbitofrontal Cortex (OFC)

The prefrontal area that integrates olfactory, gustatory, and visual signals to generate the unified perception of flavor.

Motor Unit

A functional neuromuscular unit composed of a single motor neuron and all the skeletal muscle fibers innervated by its axon.

Autonomic Nervous System (Motor Control)

The division of the nervous system responsible for the involuntary control and regulation of smooth muscle tissue.

Duchenne Muscular Dystrophy

A sex-linked genetic movement disorder that leads to progressive skeletal muscle weakness and degeneration.

Basal Ganglia

A group of subcortical forebrain nuclei responsible for selecting, initiating, and regulating voluntary movements while inhibiting unwanted movements.

Alpha Motor Neurons

Large lower motor neurons located in the ventral horn of the spinal cord whose axons directly innervate and stimulate contraction in skeletal muscle fibers.

Contralateral Motor Control

The anatomical organization whereby motor cortex damage in one hemisphere results in paralysis or weakness on the opposite side of the body.

Sarin

A toxic nerve agent that irreversibly inhibits the enzyme acetylcholinesterase, producing uncontrolled muscle contractions, loss of motor control, and death.

Actin

The structural contractile protein that forms the thin filaments of myofibrils in muscle tissue.

Monosynaptic Stretch Reflex

A simple reflex arc, such as the patellar tendon (knee-jerk) reflex, featuring direct monosynaptic excitation of an alpha motor neuron by a sensory afferent.

Golgi Tendon Organs

Proprioceptive sensory receptors located at the junction of muscles and tendons that detect and monitor changes in muscle tension.

Autogenic Inhibition

The protective Golgi tendon reflex initiated by excessive muscle tension to suppress contraction of the affected muscle and prevent injury.

Striatum (Huntington's Disease)

The basal ganglia structure composed of the caudate nucleus and putamen that sustains severe neurodegeneration in Huntington's disease, impairing voluntary movement control.

Acetylcholine (ACh)

The principal excitatory neurotransmitter released by alpha motor neurons at the neuromuscular junction to trigger muscle fiber contraction.

Lateral Corticospinal Pathway

The primary descending tract in the lateral spinal cord that mediates fine, voluntary movements of distal limbs.

Myasthenia Gravis

An autoimmune motor disorder caused by antibodies targeting and degrading nicotinic acetylcholine receptors, leading to extreme muscle weakness and fatigue.

Huntington's Disease Inheritance

An autosomal dominant pattern of transmission yielding a $50\%$ likelihood of disease inheritance when an affected individual is heterozygous and the other parent is unaffected.

Muscle Spindles

Proprioceptors embedded within skeletal muscles that detect changes in muscle length and trigger reflex contraction via alpha motor neurons during the stretch reflex.