Sensory Physiology - Key Terms (Vision, Hearing, Receptors, Reflexes, SI Units)

A comprehensive set of vocabulary flashcards covering eye and ear anatomy, vision and hearing processes, neural reflexes, sensory receptors, pain pathways, and SI unit prefixes from the notes.

Refraction

Bending of light as it passes between media of different densities, causing light rays to change direction.

Principal focus

The point at which refracted rays converge after passing through a lens.

Diopter

Unit of refractive power; equal to the reciprocal of focal length in meters.

Accommodation

The eye's adjustment of lens shape via the ciliary muscle and suspensory ligaments to focus objects at different distances.

Emmetropic

Normal eye with proper refractive power and accommodation for clear vision at all distances.

Myopia (nearsightedness)

Condition where distant objects are blurry; corrected with concave (negative) lenses.

Hyperopia (farsightedness)

Condition where near objects are blurry; corrected with convex (positive) lenses.

Astigmatism

Irregular curvature of the cornea or lens causing blurred vision; corrected with a toric lens.

Macula lutea

Yellow central retina region rich in cones, providing the clearest vision.

Fovea centralis

Center of the macula with the highest visual acuity; contains only cone photoreceptors.

Cornea

Transparent outer layer that contributes most to the eye's refractive power.

Sclera

White, protective outer layer of the eye.

Iris

Colored part of the eye that controls pupil size and light intake.

Ciliary body

Structure that supports the lens and contains the ciliary muscle; produces aqueous humor.

Choroid

Vascular layer between the retina and sclera supplying blood to the eye.

Lens

Biconvex structure that refracts light; changes shape during accommodation.

Suspensory ligaments (Zonule of Zinn)

Fibers that suspend the lens and change its shape when the ciliary muscle contracts or relaxes.

Aqueous humor

Clear fluid in the anterior chamber that maintains intraocular pressure.

Vitreous humor

Gel-like substance filling the posterior eye cavity behind the lens.

Retina

Innermost neural tunic containing photoreceptors that transduce light into neural signals.

Oval window

Membrane boundary between middle and inner ear; movement initiates waves in the inner ear fluids.

Ossicles

Malleus (hammer), Incus (anvil), Stapes (stirrup) that amplify sound vibrations.

Tympanic membrane

Eardrum; vibrates in response to sound waves.

Endolymph

Fluid within the cochlear duct that moves with basilar membrane vibrations.

Perilymph

Fluid in the scala vestibuli and scala tympani surrounding the endolymph.

Basilar membrane

Membrane in the cochlea whose movement deflects hair cells, initiating auditory signals.

Tectorial membrane

Gel-like membrane over auditory hair cells that interacts with their stereocilia.

Organ of Corti

Sensory organ on the basilar membrane containing the hair cells for hearing.

Vestibulocochlear nerve (CN VIII)

Cranial nerve carrying hearing and balance information to the brain.

Semicircular canals

Three canals that detect rotational movement and contribute to dynamic equilibrium.

Utricle and Saccule

Otolith organs that detect linear acceleration and gravity; contain otoliths.

Otoliths

Calcium carbonate crystals in the otolithic membrane that respond to gravity.

Nociceptors

Pain receptors that include C fibers (slow pain) and A-delta fibers (fast pain).

A-delta fibers

Thinly myelinated fibers that transmit fast, sharp pain.

C fibers

Unmyelinated fibers that transmit slow, dull pain.

Mechanoreceptors

Receptors sensitive to mechanical stimuli such as touch, pressure, and vibration.

Pacinian corpuscles

Mechanoreceptors for deep pressure and vibration; fast adapting.

Meissner's corpuscles

Mechanoreceptors for light touch; fast adapting.

Merkel's discs

Mechanoreceptors for light touch and texture; slow adapting.

Ruffini endings

Mechanoreceptors for skin stretch; slow adapting.

Hair follicle receptors

Nerve endings surrounding hair follicles that detect light touch; fast adapting.

Proprioceptors

Receptors that monitor body position and movement; include muscle spindles, Golgi tendon organs, and joint receptors.

Muscle spindle

Proprioceptor detecting muscle stretch, essential for stretch reflexes.

Golgi tendon organs

Proprioceptors sensing muscle tension at tendons.

Joint receptors

Proprioceptors in joints that monitor position and movement.

Exteroceptors

Receptors that sense stimuli from the external environment (skin surface).

Visceral receptors

Receptors arising from internal organs.

Two-point threshold

A measure of tactile receptor density and discrimination ability in the skin.

Spinothalamic tract

Anterolateral pathways carrying temperature, pain, and crude touch to the brain.

Dorsal columns

Pathways carrying fine touch and proprioception to the brain.

Dermatome

Skin region innervated by a single spinal nerve; explains referred pain patterns.

Referred pain

Pain perceived at a site distant from the actual source due to shared spinal pathways.

Babinski sign

Upgoing great toe in response to lateral sole stimulation; indicates upper motor neuron involvement in adults (normal in newborns).

Reflex arc

Neural circuit of a reflex: receptor, afferent neuron, integrating center, efferent neuron, and effector.

Autonomic reflex

Reflexes mediated by the autonomic nervous system (e.g., pupillary reflex); not under conscious control.

Somatic reflex

Reflexes involving skeletal muscles (e.g., stretch, knee-jerk, corneal, gag, plantar reflex).

Stretch reflex

Monosynaptic reflex where muscle stretch activates a rapid contraction via muscle spindle.

Knee jerk (patellar) reflex

Stretch reflex testing L2-L4 through tapping the patellar tendon.

Ankle (Achilles) reflex

Stretch reflex testing S1-S2 via tapping the Achilles tendon.

Biceps reflex

Reflex testing C5-C6 via the musculocutaneous nerve.

Triceps reflex

Reflex testing C7-C8 via the radial nerve.

Corneal reflex

Somatic reflex mediated by CN V; blinking in response to corneal stimulation; absence indicates brainstem damage.

Gag reflex

Somatic reflex involving CN IX and X; stimulation of the oropharyngeal mucosa triggers a gag.

Plantar reflex

Superficial cord reflex; normal plantar flexion of toes; a Babinski sign indicates UMN pathology.

Pinna

Outer ear projection that channels sound into the ear canal.

Osmolarity

Total concentration of osmotically active particles per liter of solution.

Molarity (M)

Moles of solute per liter of solution.

Osmolality (Osm/L; mosm/L)

Osmolar concentration expressed as osmoles per kilogram (or liter) of solvent; mosm/L is milliosmoles per liter.

Prefixes (SI units)

Scale multipliers such as kilo (10^3), deci (10^-1), centi (10^-2), milli (10^-3), micro (10^-6), nano (10^-9), pico (10^-12), etc.