Chapters 23 & 24: General and Special Senses

Vocabulary flashcards covering key terms and definitions from Chapters 23 and 24: General and Special Senses.

General senses

Somatic senses including touch, pressure, temperature, pain, and proprioception; distributed throughout the body rather than in localized organs.

Receptors

Cells or processes that respond to stimuli by converting them into nerve impulses.

Receptor response

The process by which receptors respond to stimuli by converting them into nerve impulses.

Receptor potential

A local potential in the receptor’s membrane produced when an adequate stimulus acts on the receptor.

Adaptation

Decrease in receptor potential over time in response to a continuous stimulus.

Exteroceptors

Receptors on or near the body surface that provide information about the external environment.

Visceroceptors (interoceptors)

Located internally, often within body organs; provide information about the internal environment.

Proprioceptors

Special type of visceroceptor in skeletal muscles, joints, and tendons; provide information on body movement and position, with tonic and phasic types.

Tonic

A proprioceptor that provides a relatively constant rate of information about body position.

Phasic

A proprioceptor that adapts quickly and signals changes in position or movement.

Mechanoreceptors

Receptors that respond to mechanical stimuli such as touch, pressure, vibration, and stretch.

Chemoreceptors

Receptors that respond to chemical stimuli (e.g., odors, tastes, and chemical changes in the internal environment).

Thermoreceptors

Receptors that respond to changes in temperature.

Nociceptors

Pain receptors; respond to potentially damaging stimuli.

Photoreceptors

Light-detecting receptors in the retina (rods and cones).

Osmoreceptors

Receptors that detect osmotic pressure or osmolarity in body fluids.

Free nerve endings

Widely distributed sensory endings; many function as nociceptors for pain and temperature.

Merkel disks

Tactile receptors for discriminative touch located in the epidermis.

Meissner corpuscles

Encapsulated tactile receptors in hairless skin, abundant in fingertips, lips, and nipples; detect light touch.

Pacinian corpuscles (Lamellar)

Encapsulated deep-pressure and high-frequency vibration receptors in deep dermis and joints; adapt quickly.

Root hair plexuses

Nerve endings surrounding hair follicles that detect hair movement.

Muscle spindle

Proprioceptive receptor with Ia and II fibers that detects changes in muscle length.

Golgi tendon organ

Ib sensory receptors that detect muscle tension; when stimulated, cause muscle relaxation.

Olfactory receptors

Olfactory sensory neurons that detect odorants.

Olfactory cilia

Hair-like projections on olfactory receptor cells that detect odor molecules.

Olfactory epithelium

Olfactory tissue containing olfactory receptor cells.

Olfactory pathways

Odor detection leads to receptor potential, then action potential; signals travel to olfactory bulb, tract, thalamus, and olfactory cortex for interpretation and memory.

Gustatory cells

Taste-sensing cells within taste buds.

Taste buds

Taste receptor structures; each bud responds best to one of five basic tastes.

Facial nerve (CN VII) anterior 2/3 of tongue

Carries taste impulses from the anterior two-thirds of the tongue.

Glossopharyngeal nerve (CN IX) posterior 1/3 of tongue

Carries taste impulses from the posterior one-third of the tongue.

External ear

Outer part of the ear that collects sound; includes the auricle/pinna and the external acoustic meatus.

Auricle (pinna)

External, cartilaginous structure that collects sound.

External acoustic meatus

Ear canal leading to the tympanic membrane.

Malleus

Hammer; one of the three auditory ossicles of the middle ear.

Incus

Anvil; middle ear ossicle.

Stapes

Stirrup; smallest middle ear ossicle; fits into the oval window.

Tympanic membrane

Eardrum; boundary between outer and middle ear that vibrates with sound.

Oval window

Membrane-covered opening in the middle ear; stapes fits here and transmits vibrations to the inner ear.

Round window

Membrane-covered opening in the inner ear that allows fluid movement within the cochlea.

Auditory (Eustachian) tube

Tube linking middle ear with the nasopharynx to equalize pressure.

Bony labyrinth

Rigid outer casing of the inner ear housing the cochlea and vestibular apparatus.

Membranous labyrinth

Membranous sacs inside the bony labyrinth containing endolymph.

Cochlea

Coiled, hearing portion of the inner ear that converts vibrations into neural signals.

Endolymph

Fluid inside the membranous labyrinth.

Perilymph

Fluid between the bony and membranous labyrinth.

Vestibule

Inner ear region containing the utricle and saccule; important for static balance.

Utricle

Membranous sac in the vestibule that senses horizontal acceleration.

Saccule

Membranous sac in the vestibule that senses vertical acceleration.

Semicircular canals

Three canals oriented at right angles that detect rotational movement; contain semicircular ducts.

Ampulla

Swollen region at the base of each semicircular canal housing hair cells.

Otoliths

Ear stones in the macula of the utricle and saccule that respond to head position.

Macula

Sensory area in the utricle and saccule containing otoliths for static equilibrium.

Cupula

Gelatinous structure in semicircular ducts moved by endolymph; detects dynamic rotation.

Vestibular nerve (CN VIII)

Vestibulocochlear nerve; transmits balance information to the brain.

Static equilibrium

Balance maintenance when the head is stationary; mediated by otoliths in the macula.

Dynamic equilibrium

Balance maintenance during movement; detected by the cupula in semicircular canals.

Iris

Colored part of the eye; controls the size of the pupil.

Pupil

Opening in the iris that admits light into the eye.

Lens

Transparent structure that focuses light on the retina; changes shape during accommodation.

Ciliary muscle

Muscle that changes lens shape to alter focus (accommodation).

Retina

Inner layer of the eye containing photoreceptors; beginning of the visual pathway.

Optic nerve (CN II)

Second cranial nerve; transmits visual information from the retina to the brain.

Refraction

Bending of light rays to focus images on the retina.

Accommodation

Adjustment of the lens shape by the ciliary muscle to focus on near objects.

Near reflex

Pupil constriction accompanying lens accommodation for near vision.

Photopupillary reflex

Pupil constriction in response to bright light.

Convergence

Movement of the eyes toward each other to maintain focus on a near object.

Conjunctiva

Mucous membrane lining the eyelids and surface of the eyeball.

Palpebral fissure

Opening between the upper and lower eyelids.

Canthus

Corner where the upper and lower eyelids meet.

Extrinsic eye muscles

Six external muscles that move the eyeball: four rectus and two obliques.

Intrinsic eye muscles

Intraocular muscles: iris (pupil size) and ciliary muscle (lens shape).

Hyperopia

Farsightedness; difficulty focusing on near objects.

Myopia

Nearsightedness; difficulty seeing distant objects.

Cataracts

Clouding of the lens reducing vision.

Glaucoma

Increased intraocular pressure affecting the optic nerve.

Retinal detachment

Separation of the retina from underlying tissue, risking vision loss.

Diabetic retinopathy

Bleeding in retinal vessels with new, abnormal vessel growth.

Otosclerosis

Impaired conduction in the stapes often with tinnitus.

Otitis

Inflammation of the outer or middle ear.