Chapter 16: Sense Organs Lecture Flashcards

Vocabulary-style flashcards covering the anatomy, physiology, and sensory processes of the human sense organs based on Chapter 16 lecture notes.

Sensory receptor

A structure specialized to detect a stimulus, ranging from bare nerve endings to true sense organs with accessory tissues.

Sensation

A physical process involving intensity and the subjective awareness of a stimulus; most sensory signals are filtered in the brainstem and produce no conscious sensation.

Perception

The physiological and mental processing of sensory information to make sense of its significance and allow conscious awareness of the environment.

Transduction

The fundamental purpose of any sensory receptor: the conversion of one form of energy, such as light or heat, into nerve signals.

Receptor potential

A small local electrical change on a receptor cell brought about by a stimulus, resulting in the release of neurotransmitter or action potentials.

Absolute Threshold

The minimum stimulus required to cause a change in signal transduction.

Weber’s law

States that the ‘just noticeable difference’ for a stimulus is proportional to the magnitude of the original stimulus, and this proportion remains constant.

Modality

The type of stimulus or sensation produced, such as vision or hearing, determined by labeled line code pathways.

Receptive field

The specific area within which a sensory neuron detects stimuli; smaller fields in locations like fingertips allow for fine two-point touch discrimination.

Sensory adaptation

A property where the firing frequency of a neuron gets slower over time if a stimulus is prolonged.

Phasic receptors

Receptors that adapt rapidly, generating a burst of action potentials when first stimulated and then quickly stopping, such as those for smell or hair movement.

Tonic receptors

Receptors that adapt slowly and generate nerve signals steadily throughout the presence of a stimulus, such as proprioceptors.

Proprioceptors

Receptors that sense body position, muscle tension, and joint movements.

Exteroceptors

Receptors that detect external stimuli.

Interoceptors

Receptors that detect internal stimuli.

Tactile (Merkel) discs

Unencapsulated nerve endings found in the basal layer of the epidermis used for light touch and texture.

Lamellar (pacinian) corpuscles

Phasic encapsulated nerve endings that detect deep pressure, stretch, tickle, and vibration.

Nociceptors

Receptors for pain; fast pain travels via myelinated fibers at $12$ to $30\,m/s$, while slow pain travels via unmyelinated fibers at $0.5$ to $2\,m/s$.

Bradykinin

The most potent pain stimulus known; an injured tissue chemical that makes us aware of injury and promotes healing.

Referred pain

Pain in the viscera mistakenly thought to come from the skin due to the convergence of neural pathways in the CNS.

Lingual papillae

Surface bumps on the tongue including filiform (no taste buds), foliate, fungiform (tips/sides), and vallate (rear).

Gustation

The sensation of taste beginning with the action of chemical stimulants called tastants on taste buds.

Olfaction

The sense of smell; a response to chemicals called odorants detected by olfactory cells in the olfactory mucosa.

Glomeruli

Spherical clusters where olfactory cells synapse with dendrites of mitral and tufted cells, each dedicated to a single odor.

Pitch

The sense of a sound being ‘high’ or ‘low,’ determined by frequency in hertz ($Hz$); the human range is $20$ to $20,000\,Hz$.

Loudness

The perception of sound energy or intensity, expressed in decibels ($dB$).

Auricle

The outer ear funnel made of elastic cartilage that directs sound down the auditory canal.

Tympanic membrane

The eardrum; vibrates in response to sound and separates the outer ear from the middle ear.

Auditory ossicles

The three small bones of the middle ear: the malleus, incus, and stapes.

Cochlea

The snail-shaped organ of hearing in the inner ear that converts vibrations into nerve impulses.

Spiral organ (Organ of Corti)

The acoustic organ within the cochlear duct composed of hair cells with stereocilia and a tectorial membrane.

Static equilibrium

The perception of the orientation of the head when the body is stationary.

Dynamic equilibrium

The perception of motion or acceleration, divided into linear and angular acceleration.

Macula

A patch of hair cells and supporting cells in the saccule and utricle for equilibrium; contains otoliths (calcium carbonate granules).

Crista ampullaris

A mound of hair cells in the ampulla of each semicircular duct that detects rotary movements.

Tunica fibrosa

The outer fibrous layer of the eyeball consisting of the white sclera and the transparent cornea.

Aqueous humor

Serous fluid secreted by the ciliary body into the posterior chamber and reabsorbed by the scleral venous sinus.

Fovea centralis

The center of the macula lutea in the retina providing high-resolution color vision; contains only cone cells and no rods.

Cataract

The clouding of the lens caused by darkening lens fibers and debris accumulated with age or injury.

Glaucoma

Elevated pressure in the eye due to obstruction of the scleral venous sinus, leading to retinal cell death and optic nerve damage.

Emmetropia

The state in which the eye is relaxed and focused on an object more than $6\,m$ ($20\,ft$) away.

Accommodation

A change in the curvature of the lens by the ciliary muscle to focus on nearby objects.

Rhodopsin

The visual pigment in rods responsible for night (scotopic) or monochromatic vision.

Photopsin

The visual pigment in cones responsible for color (photopic) vision, with three types sensitive to different wavelengths (S, M, and L).