Chapter 17 Quiz

The Special Senses Include:

The Special Senses Include:

smell (olfaction), taste (gustation), vision, hearing, and equilibrium (balance)

Sense of smell

Called olfaction, is a chemical sense

Smell is linked to the...

cerebral cortex and limbic system

Olfactory epithelium

has 10-100 million receptors per square inch located in the superior part of the nasal cavity

Odorants

chemicals that can stimulate the olfactory apparatus

Olfactory epithelium is made up of:

1. olfactory receptors

2. supporting cells

3. basal (stem) cells

Olfactory receptors

receive stimulation, live about one month are bipolar (axon and dendrite) have olfactory hairs projecting from a dendrite into the air path

Supporting (olfactory) cells

columnar epithelial cells provide support, nourishment, electrical insulation, and detox

Basal (stem) cells

located between supporting cells produce new olfactory receptors (replaced monthly)

Olfactory (Bowman's) glands

throughout olfactory epithelium produce mucous which dissolves odor-ants so that transduction can occur and maintains a moist surface

Facial Nerve (cranial nerve VII)

when stimulated can set off olfactory glands and cause a runny nose or watery eyes

Transduction

ANY special sense has to transduce

Olfactory Transduction

occurs at or on the olfactory hair

Basic Olfactory Pathway

1)Odorant causes chemical reaction 2)sodium enters cytosol 3)depolarization of olfactory receptor cell membrane occurs 4)nerve impulse is triggered 5)axons carry impulse through the cribiform plate 6)then terminate in the brain and synapse with dendrites of the olfactory bulb 7)olfactory bulb axons form the olfactory tract and go to the primary olfactory area of the cerebral cortex 8) some also go to the limbic system and hypthalamus

Primary Olfactory area of the Cerebral Cortex

where the conscious awareness of smell begins

Frontal Lobe

odor identification area

Olfactory Adaptation

1. Low threshold- we can detect odors down to the 1/25 billionth of a milligram per milliliter of air.

2. Olfactory adaptation is RAPID- 50% after one second/ complete after one minute

Hyposmia

reduced ability to smell affects about half of those over 65 and 75% over 80 caused by neurological changes, drugs, and smoking

Gustation

Sense of Taste and is a Chemical sense

Five Primary Tastes

sour, sweet, bitter, salty, and umami (meaty/savory)

Umami

reported by Japanese scientist arises from monosodium glutamate (MSG)

Taste Bud Anatomy

10,000 in the oral area Location: tongue, soft palate, pharynx, and epiglottis

Taste bud Structure

oval body located mainly on the dorsal side of the tongue

Taste bud: Has 3 kinds of epithelial cells

Supporting cells, gustatory receptor cells, and basal cells

Supporting (gustatory) cells

surround and support about 50 gustatory receptor cells per taste bud

Gustatory receptor cells

the working cell of the taste bud Lifespan: 10 days have gustatory hairs the extend through the taste pore to contact food particles

Gustatory hairs

One hair for each receptor cells

Basal cells: (gustatory)

produce supporting cells which become receptor cells

Taste bud papillae

elevated areas on the tongue

Papillae with taste buds

vallate, fungiform, and foliate

Papillae without taste buds

filiform

Vallate Papillae

Wall-like, form inverted V-shaped row at the back of the tongue, consists of 12 papillae each with 100-300 taste buds

Fungiform Papillae

mushroom-like, contain 5 taste buds each, scatted over entire surface of tongue

Foliate Papillae

leaf-like, located in small trenches on the lateral edge of tongue, most of their taste buds degenerate after childhood

Filiform Papillae

thread-like, lack taste buds, have tactile receptors, increase friction during chewing

Gustatory Adaptation

occurs in 1-5 minutes depending on the taste Most sensitive- bitterness Least sensitive- sweet and salty

Vision

important to human survival cerebral cortex processes visual information

The Eye

over half of the sensory receptors in the human body are in the eye

Light

is electromagnetic radiation which is an energy in the form of waves that radiate from the sun

Visible Light

Range: 400-700 nanometers (wavelength) The eye can only detect visible light

Reflected VS. Absorbed

Our eyes see reflected light from an object not absorbed light

Accessory structures of the Eye

eyelids, eyelashes, eyebrows, lacrimal apparatus, and extrinsic eye muscles

Eyelids (Palpebrae) Functions

shade, protection, and lubrication

Eyelid Structure

Upper and Lower Composed of: epidermis, dermis, subcut layer, orbicularis oculi muscle, tarsal glands, tarsal plate, palpebral fissure, and conjunctiva

Orbicularis Oculi Muscle

Part of the eyelid (palpebrae) used for opening and closing (blinking)

Tarsal glands and Plate

Tarsal glands (meibomian)- lubricant between lids; keeps them from sticking together Tarsal Plate- gives form and support to the eyelids

Palpebral Fissure

gap between the eyelids

Conjunctiva

thin mucous membrane that lines and protects the inner aspect of the eyelids and passes onto the anterior surface of the eyeball

Eyelashes and Eyebrows Functions

Protection from foreign objects, perspiration, and rays of sunlight

Lacrimal Apparatus Components in Order:

1. lacrimal gland

2. lacrimal duct 3)lacrimal canal-- into the superior or inferior lacrimal puncta

3. lacrimal sac

4. nasal cavity

Lacrimal gland

produce and drain lacrimal fluid (tears)

Lacrimal Apparatus Pathway

Lacrimal gland drain through lacrimal ducts, then through the lacrimal canals into the lacrimal puncta and then into the lacrimal sac of the nasal cavity

Lacrimal fluid consists of:

water, salts, mucus, and lysozyme(protective bacteriocidal enzyme)

Extrinsic Eye Muscles other name

also called "extraocular muscles " meaning=(outside the eyeball)

Extrinsic eye muscles

Extend from the bony orbit of the eye onto the exterior surface of the eyeball at the sclera Six move each eye 4 rectus, 2 oblique innervated by cranial nerves III, IV, or VI

Extrinsic Eye Muscle Types

4 rectus: superior, inferior, lateral, and medial 2 oblique: inferior and superior

Adult eyeball diameter

1 inch (2.5 cm) 1/6 exposed, 5/6 protected by orbit

Eyeball wall's 3 layers

Called Tunics

1. fibrous tunic

2. vascular tunic

3. nervous tunic (retina)

Fibrous Tunic:

superfical (outer) layer consists of: the cornea and the sclera

Cornea

Part of the fibrous tunic the transparent coat over the iris which HELPS focus light onto the retina Composed of: non-keratinized stratified sq. epithelium, collagen fibers, fibroblasts, and simple sq. epithelium

Sclera= hard

the hard layer of dense connective tissue covering the eye the "white" of the eye covers entire eye (except the cornea) gives rigidity, shape, support and attachment points for extrinsic muscles to the eye posteriorly pierced by the optic nerve (cranial nerve II)

Sclera Vinous Sinus

Also called the canal of Schlemm opening at the junction of the cornea and sclera aqeuous humor drains into from the eye to the bloodstream

Vascular Tunic

middle layer Composed of: choroid, ciliary body, iris, and pupil

Choroid

highly vascular posterior part of vascular tunic lines internal surface of sclera it's blood vessels nourish the posterior retina contains melanocytes which produce melanin the melanin absorbs light rays and prevents the scattering of light throughout the eyeball

Ciliary body

anterior part of vascular tunic, contains melanin Contains: ciliary processes and ciliary muscles

Ciliary processes

folds on the internal surface of the ciliary body which secrete aqueous humor

Ciliary muscles

circular band of smooth muscle which contracts or relaxes to adjust tightness of suspensory ligaments which are attached to the lens

Suspensory ligaments

attached to the lens focus the lens for you

Lens

the refractive medium of the eye transparent and avascular Function: focus light rays onto the retina made of layers of proteins called crystallins

Presbyopia

lens loses elasticity and thus it's ability to focus

Iris= means rainbow

colored portion of the eye Main function: regulate the amount of light entering the eye through the pupil lays between the cornea and the lens contains circular and radial muscle fibers attached to the ciliary processes for constriction and dilation contains melanin- gives eyecolor

Pupil

hole in the center of the eye appears black because you're actually seeing the choroid and retina in the back of the eye

Pupil diameter

regulated by the response of autonomic reflexes determined by constrictor pupillae and dilator pupillae

Constrictor Pupillae

circular muscle fibers contract in bright light to SHRINK the pupil innervated by the parasympathetic fibers

Dilator Pupillae

radial muscle fibers contract in dim light to dilate the pupil (enlarge) innervated by the sympathetic fibers

Nervous Tunic (Retina)

the starting point of the visual pathway

Retina

the inner layer of the posterior 2/3 of the eyeball

Pigmented epithelium

part of the retina, no vision, absorbs stray light to help keep the image clear

Retinal layers include

Neural layer--- 1) photoreceptor layer 2) bipolar cell layer 3) the ganglion cell layer

Neural layer

a multilayered outgrowth of the brain

Photoreceptor layer

with rods and cones: transduces light into action potentials which travel through the outer synaptic layer to the bipolar cell layer

Bipolar cell layer

contains horizontal and amacrine cells which modify nerve impulses receives impulses from the photoreceptor layer and sends them through the INNER synaptic layer to the ganglion cell layer

Ganglion cell layer

it's axons form the optic nerve leaving the eyeball at the optic disc(blind spot)-- impulses travel from here to the thalamus and primary visual cortex

Optic disc

the blind spot, where there is no vision since no images can be formed there(no rods or cones)

Central retinal artery and vein

nourish and drain blood from the retina exit through the optic disc

Macula lutea

the exact center of the posterior portion of the retina corresponding to the visual axis of the eye-- fovea is located in the middle

Fovea

fovea centralis is a small depression in the center of the macula latea sharpest vision occurs here Contains ONLY cones for color vision area of highest visual acuity or resolution

Photoreceptors

Rods & Cones specialized cells that begin the process by which light is converted to a nerve impulse and sent to the brain

Rods

rod-shaped/ over 120 million per retina allow us to see in dim light & discriminate between dark and light permit us to see shapes and movement (motions) absent from fovea and macula lutea dense at periphery of retina

Cones

6 million per retina allow us to see color in brighter light for color vision and sharpness (acuity) concentrated in the fovea

Opthalmoscope

used to examine the retina

Detached retina

caused by head trauma fluid accumulates between layers of the retina causes distorted vision or blindness

Age-Related Macular Disease

macular degeneration degeneration of the retina and macula lutea in older people Effects: keep peripheral vision but lose ability to look straight ahead

Lens divides the interior of the eye into

1. the anterior cavity &

2. the vitreous chamber

Anterior cavity

the space anterior to the lens has two chambers: anterior and posterior

Anterior Cavity/ Anterior Chamber

the space between the cornea and the iris

Anterior Cavity/ Posterior Chamber

between the iris and the lens

Aqueous humor

fills both the anterior and posterior chambers of the anterior cavity nourishes the lens and cornea produced by the ciliary body replaced every 90 minutes

Flow of aqueous humor

flows from posterior chamber into the anterior chamber through the pupil

Vitreous chamber

large space between the lens and the retina contains the vitreous body