Chapter 9: The Senses

Incus

"Anvil"

Optic Disc

"Blind spot" with no rods or cones.

Malleus

"Hammer"

How Temporal Bones are Connected

"Handle" of Malleus attaches to tympanic membrane, "head" of malleus attaches to incus. Incus attaches to stapes.

Presbyopia

"Oldsighted-ness"-> lens loses elasticity, can't focus on near objects (bifocals).

Stapes

"Stirrup"

Four Primary Taste Sensations

(1) Sweet, (2) Sour, (3) Bitter, (4) Salty.

Cornea

(Covers Iris) "Window"-> Clear front part of eye; has no blood vessels or lymphatics- makes laser eye surgery possible.

Acoustic Nerve

(Cranial Nerve VIII) Formed by the Vestibular and Cochlear nerves-> leads to auditory cortex in brain.

Tympanic Membrane

(Ear drum) Separates external ear from middle ear.

Muscle Spindles

(Found in Skeletal Muscle) Detects muscle length.

Golgi Tendon Organs

(Found in tendons) Detects muscle tension.

Chemoreceptors

(Gustatory Cells) Generate nerve impulses, in response to chemicals dissolved in saliva, that are interpreted in brain as taste.

Auricle

(Pinna) Appendage on side of head.

Ruffini Corpuscles

(Skin) Detects touch and pressure.

Membraneous Labyrinth

(within perilymph) Filled with endolymph.

Olfactory Receptors

Are chemoreceptors found in the small area of upper nasal cavity.

External Ear

Auricle, External Auditory Canal, and Tympanic Membrane.

Inner Ear

Bony labyrinth filled with perilymph (watery fluid) has 3 parts; vestibule, semicircular canals, cochlea, and organ of corti.

Characteristics of Cone Cells

Bright light (daytime vision), allow for distinguishing between colors.

Papillae

Bumps where most taste buds are located.

Special Sense Organ

Characterized by a dedicated organ (eye, ear, etc.), local group of special receptors.

Converting a Stimulus into a Sensation

Common functional characteristics of all sense organs are that they (1) detect particular stimulus, (2) convert to nerve impulse, and (3) nerve impulse is perceived as a sensation in the brain.

Aqueous Humor (cont.)

Constantly formed, drained and replaced.

Circular Fibers

Constrict pupil (less light).

Bright Light

Constricts.

Semicircular Canals

Contain mechanoreceptors for balance and equilibrium.

Crista Ampullaris

Contained in the ampulla of semicircular canals; receptor for balance and equilibrium, contains cells with hairlike extensions suspended in endolymph.

External Auditory Canal

Curved, 2.5 cm long; goes through temporal bone to tympanic membrane (ear drum); ceruminous glands produce cerumen (wax).

Meisnner Corpuscles

Detects fine touch and low-frequency vibration.

Proprioception

Detects muscle tension, and muscle length.

Pacini(an) [Lamellar] Corpuscles

Detects pressure and high-frequency vibrations.

Krause('s) End Bulbs [Bulboid Corpuscles]

Detects touch.

Radial Fibers

Dilate pupils (more light).

Dim Light

Dilates.

Characteristics of Rod Cells

Dim light (night vision), black and white vision, more sensitive than cone cells.

Otitis media

Ear infection that spreads from throat.

Divisions of Ear

External, Middle, and Inner.

Four Special Sense Organs

Eye, ear, nose, and taste buds.

Eyefluids

Fluid shapes eyeball and refracts light.

Vestibular Nerve

Formed by the nerves from receptors in the vestibule and semicircular canals.

Lacrimal Gland

Forms tears to keep conjunctiva moist.

Unencapsulated General Sense Organs

Free nerve endings; detect crude touch, pain, temperature, itch, and tickle.

Fovea Centralis

Greatest concentration of cores.

Visual Acuity

Greatest in good light.

Olfactory Cells

Have cilia that sense different chemicals that have dissolved in watery mucus that lines nasal cavity and generate a nerve impulse; are sensitive but adapt easily to odors and lose ability to respond to them.

Functions of the Ear

Hearing, balance, and equilibrium.

Lens

Immediately behind pupil, held in place by ligaments attached to ciliary muscle. See far-> muscles relax and lens curves. See close-> muscles contract and lens bulges, curves.

Auditory Cortex

In brain where impulses are interpreted as sound.

General Sense Organ

Individual cells or groups of cells, widely distributed throughout the body-microscopic, and found in skin (many)-> pain, temperature, pressure, vibration, touch, single cell receptors most common.

Conjunctivitis

Inflammation of the conjunctiva-"pink eye".

Retina

Inner most layer of eye.

Glaucoma

Internal pressure increases due to lack of drainage, cause damage and possible blindness.

Iris

Involuntary muscle.

Vitreous Humor

Jellylike fluid behind the lens.

Cataracts

Lens loses transparency (appears cloudy) due to UV exposure. Lens transplant or artificial lens can correct cataracts.

Pupil

Lets light in, prevent light from scattering.

Visual Pathway

Light is the stimulus; enters eye through pupil, refracted and focused on retina. Refraction occurs due to cornea, aqueous humor, lens and vitreous humor.

Organ of Corti

Located in membranous labyrinth of cochlea is surrounded by perilymph.

Unami

Meaty flavor.

Examples of Encapsulated General Sense Organs

Meissner Corpuscles, Ruffini Corpuscles, Pacini(an) Corpuscles, Krause End Bulbs, Golgi Tendon Organs, and Muscle Spindles.

Other Tastes

Metallic taste and meaty flavor.

Choroid

Middle layer; pupil, lens, and iris.

Flavors

Most flavors results from a combination of gustatory and olfactory stimulation (Cranial Nerves VII and IX-> Brain).

Conjunctiva

Mucous membrane that lines eyelids and covers sclera.

Encapsulated General Sense Organs

Nerves in a capsule.

Vestibule

Next to oval window, contains specialized mechanoreceptors for balance and equilibrium.

Cochlea

Organ of hearing.

Middle Ear

Ossicles, Oval Window, and Auditory tube.

Rods and Cones

Photoreceptors of eye. Produce nerve impulse in response to light stimulus, receptor cells synapse with neurons in bipolar and ganglionic layers of retina.

Receptors

Rod cells and cone cells (named by shapes).

Three Layers of the Eye

Sclera, Choroid, Retina.

Colored

See through cornea.

Taste Buds

Sense organs of taste.

Oval Window

Separates inner and middle ears. Is covered by a membrane that is being pressed by the stapes.

Ossicles

Smallest bones in body.

Memory and Emotion

Smells are closely associated with areas of brain important in memory and emotion.

Where hearing takes place

Sound waves vibrate membrane of oval window, causing perilymph within bony labyrinth to move. Movement of perilymph causes movement of endolymph in membranous labyrinth to move. Movement of endolymph causes hair cells on Organ of Corti to bend, generating nerve impulse. Vestibular and Cochlear nerves join to form the acoustic nerve, which leads to auditory cortex in brain where impulses are interpreted as sound. (Membrane of Oval Window-> Perilymph-> Endolymph-> Organ of Corti-> Auditory Cortex in Brain).

Sense Organs

Special and General Sense Organs.

Sclera

The outermost white layer of fibrous tissue; cornea, conjunctiva, and lacrimal gland.

Endolymph

Thick fluid found within semicircular canals.

Color Vision

Three kinds; sensitive to red, green, or blue.

Invisible Light

UV, radio, microwaves, infrared (hot), x-rays, gamma rays, etc.

Examples of General Sense Organs

Unencapsulated, and Encapsulated.

Function of the Eye

Uses visible light portion of electromagnetic spectrum (400-700 nm).

Sound Waves

Vibrate tympanic membrane; amplified through ossicles, moving the oval window-> fluid in inner ear moves.

Aqueous Humor

Watery fluid in front of the lens (anterior chamber).

"Seeing"

What impulses are interpreted as; optic nerve travels to visual cortex of occipital lobe.

Endolymph (cont.)

When head is moved, the endolymph moves, moving the hairlike extensions which generates a nerve impulse.

Circumvallate Papillae

Where most taste buds are actually located on tongue.

Olfactory Bulb

Where nerve impulse travels through to enter the brain (Brain interprets odors).

Optic Nerve

Where signals leave retina.

Macula Lutea

Yellowish area near center of retina, surrounds fovea centralis.