3200 exam 4 online, specific anatomy parts

Sensory Receptors

Specialized cells or nerve endings that convert physical or chemical energy into graded receptor potentials via sensory transduction.

Sensory Unit

An individual afferent neuron including all its peripheral receptor branches its axon processes and its central terminals in the CNS.

Receptive Field

The physical area of the body where a stimulus triggers electrical activity in a specific afferent neuron.

Dorsal Column Pathway

A spinal somatosensory pathway processing fine touch proprioception vibration and two-point discrimination that ascends on the same side and decussates in the brainstem.

Anterolateral Pathway

A spinal somatosensory pathway processing pain and temperature whose neurons synapse in the spinal gray matter and immediately cross to the opposite side to ascend.

Somatosensory Cortex

A parietal lobe region with a somatotopic body map where densely innervated high-acuity areas occupy the largest real estate.

Stretch-Activated Ion Channels

Membrane channels in mechanoreceptors that pull open in response to physical deformation allowing sodium influx to depolarize the cell.

Meissner’s Corpuscle

A rapidly adapting skin mechanoreceptor responsible for detecting light touch and pressure changes.

Pacinian Corpuscle

A rapidly adapting skin mechanoreceptor deeply situated to detect high-frequency vibrations and deep pressure.

Merkel’s Corpuscle

A slowly adapting skin mechanoreceptor providing continuous signaling for sustained touch and pressure.

Ruffini Corpuscle

A slowly adapting skin mechanoreceptor specialized for monitoring skin stretch.

Free Nerve Endings

Small-diameter unencapsulated axon terminals serving as the structural receptors for temperature pain and itch.

Alpha Motor Neurons

Large motor neurons exiting the CNS to innervate force-generating extrafusal skeletal muscle fibers.

Muscle Spindle

An encapsulated length-monitoring structure embedded inside skeletal muscle containing specialized intrafusal fibers wrapped by stretch receptors.

Nuclear Chain Fibers

Muscle spindle stretch receptors that respond to the absolute magnitude of muscle stretch providing info about static muscle length.

Nuclear Bag Fibers

Muscle spindle stretch receptors that respond to both the magnitude and rate of stretch detecting dynamic changes in length.

Gamma Motor Neurons

Small motor neurons that contract the ends of intrafusal fibers to prevent spindle slackening during voluntary muscle shortening.

Alpha-Gamma Coactivation

The simultaneous firing of alpha and gamma motor neurons that preserves length-monitoring sensitivity during contraction.

Basal Nuclei

Paired subcortical structures that interact with the cortex to establish automated program sequences for intended motor actions.

Substantia Nigra

A midbrain structure containing dopaminergic neurons projecting to the basal nuclei whose degeneration causes Parkinson's disease.

Cerebellum

A major motor center providing timing signals for smooth muscle cycles and correcting errors by comparing ongoing movement with the intended program.

Corticospinal Pathway

Nerve tracts originating in the sensorimotor cortex that decussate in the medulla to control rapid fine voluntary movements of distal extremities.

Corticobulbar Pathway

Direct motor tracts traveling from the cortex to the brainstem to synapse with cranial nerves controlling head face tongue and neck muscles.

Brainstem Pathways

Descending direct tracts controlling axial trunk muscles essential for posture balance and walking that primarily remain uncrossed.

Sclera

The tough fibrous white outer capsule that maintains eyeball shape and anchors external eye muscles.

Cornea

The non-adjustable clear front window of the sclera responsible for the greatest amount of light refraction entering the eye.

Choroid

The deeply pigmented middle eye layer that functions to absorb stray light and prevent internal glare.

Iris

The colored circular muscular diaphragm containing the pupil that adjusts its size to regulate light entry.

Pupil

The central anterior opening of the eye that allows light to pass inward.

Ciliary Muscle

A ring-like smooth muscle that contracts under parasympathetic control to relax zonular fibers allowing the lens to round up for near focus.

Zonular Fibers

Connecting strands that pull the lens flat when the ciliary muscle is relaxed for distant vision.

Lens

The adjustable crystalline eye structure that determines the precise focal point of incoming light rays.

Macula Lutea

A central retinal zone relatively free of blood vessels optimized for highly detailed visual processing.

Fovea Centralis

A specialized central pit within the macula packed with a high density of cones providing the highest visual acuity.

Optic Disc

The exit point on the nasal retina where ganglion cell axons gather to form the optic nerve creating a natural blind spot.

Optic Nerve

The structural bundle of ganglion cell axons carrying visual action potentials to the brain.

Rods

Retinal photoreceptors with discrete stacked intracellular discs that are highly light-sensitive for dim gray-scale night vision.

Cones

Retinal photoreceptors with continuous membrane infoldings optimized for bright-light color vision and high visual acuity.

Opsin

A membrane-bound protein component of visual photopigments whose varying structure dictates the specific light wavelengths absorbed.

Retinal

A light-sensitive chromophore derived from Vitamin A that acts as the universal light-absorbing molecular component of photopigments.

Transducin

The visual G-protein activated by light-struck opsin that initiates the phototran