Chapter 15: Special Senses Vocabulary

Flashcards covering key terms from Chapter 15 Lecture Notes on Special Senses, including olfaction, gustation, vision, and hearing and equilibrium.

Sensation

The conscious or subconscious awareness of an internal or external stimulus.

External Stimulus

Light rays striking the retina of the eye, sound waves impinging on the tympanic membrane of the ear, molecules in the air and food transmitting smells and tastes to the chemical sensors in the nose and on the tongue, and the force of gravity acting on equilibrium receptors in the inner ear which sense changes in inertia

General Senses

Include somatic sensations (tactile, thermal, pain, and proprioceptive) and visceral sensations and are scattered throughout the body with relatively simple structures.

Special Senses

Include smell, taste, vision, hearing and equilibrium, are concentrated in specific locations in the head, are anatomically distinct structures and form complex neural pathways.

Olfaction

The process of perceiving smells through the interpretation of chemicals present in the environment.

Olfactory Epithelium

Located in the superior part of the nasal cavity, covering the surface of the cribriform plate of the ethmoid bone and extending along the superior nasal concha.

Olfactory Receptor

Bipolar neuron with cilia (called olfactory hairs) that respond to odorant molecules.

Methyl Mercaptan

Added to natural gas to provide olfactory warning of gas leaks because natural gas has no odor.

Nerve Impulses

Travel through the two olfactory nerves, olfactory bulbs, olfactory tract, and primary olfactory area in the temporal lobe of the cortex.

Olfactory sensory pathways

Impulses travel not only to the cerebral cortex, but also to the limbic system (the emotional brain) and are rapidly adapting.

Gustation

Much simpler than olfaction in that only five primary tastes can be distinguished: sour, sweet, bitter, salty, and umami (“meaty” or “savory”).

Umami

Believed to arise from taste receptors that are stimulated by monosodium glutamate (MSG), a substance naturally present in many foods and added to others as a flavor enhancer

Taste Buds

Located on the tongue, soft palate, pharynx, and larynx and is composed of about 50 gustatory receptor cells, surrounded by a number of supporting cells.

Gustatory Microvilli (Hairs)

Project from each receptor cell to the surface through the taste pore.

Basal Cells

Located near the CT base multiply and differentiate, first to become the supporting cells around the bud, then the gustatory receptor cells inside the taste bud

Papillae

Elevations on the tongue which provide a rough texture.

Anterior 2/3 of the tongue

The facial (VII) nerve serves taste buds in this location.

Posterior 1/3 of the tongue

The glossopharyngeal (IX) nerve serves taste buds in this location.

Throat and epiglottis

The vagus (X) nerve serves taste buds in this location.

Gustatory nucleus in the medulla oblongata

Taste signals project from here to the hypothalamus, limbic system, and thalamus

Vision

Possible because of photoreceptors that are able to “catch” photons of EM radiation in the 400-700 nm wavelengths.

Accessory structures of the eye

Include the extraocular muscles, Palpebra(eyelids), conjunctiva, and the lacrimal glands and ducts.

Conjunctiva

Clear mucous membrane that covers the white (avascular) part of the eye

Lacrimal Glands

Produce tears that contain a bactericidal enzyme to fight infection and are each about the size an almond, situated superolateral to the eyeball.

Lacrimal Puncta

Two openings on the nasal side of the extreme edge of the eyeball where tears drain into.

Vascular tunic: Sclera

The outer layer of the eyeball composed of the sclera (“white” of the eye) and the cornea (transparent epithelium that protects the front of the eye.

Vascular Tunic: Choriod

The middle layer of the eyeball composed of the ciliary body, the iris (colored) and choroid.

Nervous Tunic

The inner retinal layer of the eyeball.

Cornea

Transparent epithelium that covers the anterior eye and helps focus light onto the retina.

Sclera

Forms the tough, white part of the eye giving the eye it’s shape and protecting the inner anatomical parts

Ciliary Processes

Secretes aqueous humor

Ciliary Muscle

Changes the shape of the lens to adapt to near and far vision.

Iris

Colored portion of the choroid consisting of circular and radial smooth muscle fibers regulating the amount of light entering the eye through the pupil.

Melanin Pigmented Epithelium

Allows light to be absorbed rather than scattered.

Fovea Centralis

Small depression in the macula lutea with a high concentration of cones, giving us the sharp central vision necessary in any activity where detail is of primary importance.

Optic Disc

Where the optic nerve and retinal vessels enter and exit the eyeball, creating a necessary defect on the retina – an area where there are no cones or rods.

Lens

Avascular refractory structure situated posterior to the pupil and iris consisting of a capsule with crystallin proteins arranged in layers like an onion.

Vitreous Body

Transparent jellylike substance that holds the retina flush against the choroid, giving the retina an even surface for the reception of clear images within the vitreous chamber.

Aqueous Humor

Flows through the anterior cavity of the eye and is replaced every 90 minutes.

Glaucoma

Condition that results from blockage to aqueous humor flow, or overproduction at the ciliary body leading to degeneration of eye function because of pressure on the retina and optic nerve.

Shrinkage of the Vitreous Body

May lead to a detachment of the retina from the choroid (medical emergency).

Pupil

Composed of a radial muscle (dilator) and a circular muscle (sphincter) that regulates the amount of light entering the eyeball through the pupil.

Refraction

The process of bending light rays in which the cornea and the lens refract light rays.

Accommodation

An increase in the curvature of the lens for near vision (the minimum distance from the eye that an object can be clearly focused).

Convergence

The inward movement of the eyes so that both are directed at the object being viewed - becoming a little cross-eyed when viewing things close up

Emmetropic Eye

Normal eye

Myopia

Nearsightedness; only close objects can be seen clearly: Light rays coming in from distant objects are naturally focused in front of the retina and appear blurry

Hyperopia

Farsightedness; only distant objects can be seen clearly: Light rays coming in from nearer objects are naturally focused behind the retina

Astigmatism

Either the lens or the cornea has an irregular curvature

Rods

Photoreceptor cells abundant in the periphery of the retina whereas

Cones

photoreceptors are found more frequently in the central areas

Rods

Adapted for a low light threshold (high sensitivity) - they produce low resolution, black and white images (allow us to see in dim light)

Cones

Function in bright light produce high resolution color images

Cones 3 types

Results from different colors of light selectively activating the 3 different cone photopigments

Photopigment

Colored protein (red, green, blue) that undergoes structural changes when it absorbs light in the outer segment of a photoreceptor

Opsin

A glycoprotein and a derivative of vitamin A, called retinal; the light- absorbing part of all visual photopigments

Bleaching

Conformational change in the retinal molecule in response to light (trans-retinal detached from opsin)

Color Blindness

Inherited inability to distinguish between certain colors

Night Blindness or Nyctalopia

Prolonged vitamin A deficiency and the resulting below- normal amount of rhodopsin

Slight differences in the timing of nerve impulses arriving from the two ears at the superior olivary nuclei in the pons

Allow us to locate the source of a sound.

Static Equilibrium

Refers to a state of balance relative to the force of gravity (tilting head and linear acceleration and deceleration).

Dynamic Equilibrium

Involves the maintenance of balance during sudden movements (rotational acceleration).

Otolithic Membrane

Responds to gravity when head position is changed in the utricle and saccule

Crista

Small elevation in the ampulla of the semicircular canals containing hair cells.

Cupula

Mass of gelatinous material covering hair cells and supporting cells

Cataract

Opaque defect in the cornea or lens of the eye – most cataracts are in the lens caused by injury, medications, and diseases like diabetes (common in old age).

Conjunctivitis

Inflammation of the conjunctival membrane which covers part of the front of the eye caused most frequently by viral infections (pink eye) and allergy (can also result from bacterial infections and many other irritants)

Age Related Macular Degeneration

Results in a loss of vision in the center of the visual field (the macula) because of damage to the retina making it impossible to recognize faces.

Myringitis / Otitis Externa

Inflammation of the ear drum or a dermatitis of the epithelium of the outer ear (infectious and noninfectious).

Meniere’s Disease

Disorder of the inner ear that can affect hearing and balance due to increased pressure in the cochlea and semicircular canals (extra endolymph) resulting in episodes of vertigo (the room spinning) and ringing in the ears (tinnitus)

Audition

Process of hearing.

External Ear

Uses air to collect and channel sound waves.

Middle Ear

Uses a bony system to amplify sound vibrations.

Internal Ear

Generates action potentials to transmit sound and balance information to the brain.

Auricle (Pinna)

Flap of elastic cartilage covered by skin and containing ceruminous glands which secrete cerumen (earwax).

External Auditory Canal

Curved 1” long canal situated in the temporal bone leading from the meatus to the tympanic membrane (TM) – (ear drum) separates outer ear from the cavity of the middle ear.

Middle Ear

Air-filled cavity in the temporal bone lined with epithelium and contains 3 auditory ossicles (bones).

Eustachian (Auditory) Tube

Connects the middle ear with the nasopharynx (upper portion of the throat) which opens to equalize pressures on each side of the TM (allowing it to vibrate freely).

Internal Ear

Labyrinth with bony and membranous divisions including the cochlea, vestibule, and semicircular canals.

Cochlea

Contains the hearing apparatus.

light adaptation

dark to light (quickly)

dark adaptation

dark to light (slowly)

Rhodopsin

Only photopigment in rods

Astigmatism

irregular shape of cornea or lenstra

transduction

converting electromagnetic light energy into receptor potentials