THE SPECIAL SENSES

Ch. 17

PART 1 OBJECTIVES Describe the olfactory receptors.

PART 1 – OLFACTION: SENSE OF SMELL Anatomy

3 types of cells Olfactory receptors – detect the smell and

initiate the signal to the brain Supporting cells – provide physical support,

nourishment, and insulation for receptors Basal cells – make supporting cells

Bowman’s glands Secrete mucus that moistens olfactory area

(boogers)

HYPOSMIA Reduced ability to smell Affects half of people over age 65 and

75% of people over age 80

Women smell better than men, especially during ovulation

Smoking can impair the sense of smell

PART 2 OBJECTIVES Describe the gustatory receptors.

PART 2 – GUSTATION: SENSE OF TASTE Only 5 primary tastes

Sour, sweet, bitter, salty, umami (meaty or savory)

all flavors are combinations of these tastes

Olfactory and gustatory senses are closely linked – like when you have a cold and food doesn’t taste the same It is your smell that actually isn’t working

properly

GUSTATION ANATOMY – P. 470 Taste bud – oval body consisting of cells Papillae – covered in taste buds

Vallate papillae – 12 very large, circular areas

Fungiform papillae – mushroom-shaped elevations scattered over area of tongue

Foliate papillae – small trenches on tongue – most taste buds are gone by childhood

Filiform papillae – no taste buds – just add friction to tongue making chewing and moving food easier

TASTE

PART 3 OBJECTIVES List and describe the accessory

structures of the eye and the structural components of the eyeball.

Discuss image formation by describing refraction and accommodation.

Describe vision abnormalities.

ACCESSORY STRUCTURES OF EYE Eyelids Eyelashes Eyebrows Lacrimal apparatus Extrinsic eye muscles

ACCESSORY STRUCTURES OF EYE Eyelids – palpebrae

Functions: Shade eyes during sleep Protect eyes from light Protect eyes from foreign objects Spread lubrication over eyeballs

upper eyelid is more moveable – levator palpebrae superioris muscle

Where eyelids meet is called commissure – lateral and medial

Lacrimal caruncle – reddish bump in medial commissure that secretes oil and sweat – causes “sleep” in your eyes

INFECTIONS Sty – infection in oil gland of eyelash

follicle Chalazion – infection in tarsal glands of

eyelidTarsal glands secrete fluid onto eye for

lubrication

ACCESSORY STRUCTURES OF EYE Lacrimal apparatus

Produces and drains lacrimal fluid or tears

Eye muscles

ANATOMY OF THE EYEBALL 2.5 cm in diameter 3 anatomical layers

Fibrous tunicVascular tunicRetina

TUNIC LAYERS Outer layer – fibrous

Cornea – transparent, focuses light raysSclera – white of the eyeOptic nerve – transmits info to brain

Middle layer – vascularChoroid coat – contains blood vesselsCiliary body – holds the lens in placeLens – focusingAqueous humor – fluid surrounding lensPupil – opening for light to enter

TUNIC LAYERS Inner layer

Retina – visual receptor cells

Vitreous humor – fluid supports internal structures

EYE

STRUCTURES OF EYEBALL

RETINA Made of cells that are light receptors –

photoreceptors Rods and cones

Rods – black and whiteCones - color

Color blindnessLack of cones

COLORBLINDNESSA genetic trait that affects boys more than girls. The location of the gene is on the X chromosome

IMAGE FORMATION Seeing is like taking a picture The object must be focused on a “film” –

retina The correct amount of light must be

present – pupil

Light bends - refraction

REFRACTION When light bends as it moves

between two mediums – air and water

Images on the retina are upside-down and have right-to-left reversal

IMAGE FORMATION PROCESS Light hits the cornea and is bent Light leaves the cornea and is bent

again Light enters the lens where it is focused

on the retina So why don’t we see everything upside-

down?Very early on the brain “learns” how to

coordinate the images and make them correct

ACCOMMODATION Most of the focusing is

done by the cornea 25% must be done by the

lens Our lens is convex on both

sides in order to produce clear images

The lens will increase its curvature in order to focus all images exactly

ANIMATIONS http://www.bbc.co.uk/science/humanbod

y/body/factfiles/sight/sight_animation.shtml

http://www.biologymad.com/resources/eye.swf

ABNORMALITIES AND CHANGES Presbyopia – lens loses elasticity with age

Around age 40 the lens can’t focus near images and people need glasses

Normal eye – emmetropic – can reflect images perfectly of objects 20 ft away

Myopia - near-sightedness Eyeball is too long for the focusing power of

the lens or lens is thicker than normal Hyperopia – far-sightedness

Eyeball is too short for the focusing power of the lens or lens is thinner than normal

ABNORMALITIES

PART 4 OBJECTIVES Describe the anatomy of the structures

in the three main regions of the ear. List the major events in the physiology

of hearing.

PART 4 – HEARING Anatomy of the ear

External ear Collects sound waves and

channels them inwardMiddle ear

Conveys sound vibrations to the oval window

Inner ear Houses the receptors for hearing

and equilibrium

EAR ANATOMY

OUTER EAR Auricle (pinna) – flap of elastic cartilage

shaped like a trumpet External auditory canal – curved tube that

lies in the temporal bone and leads from the auricle to the eardrum

Eardrum (tympanic membrane) – thin, semitransparent partition between the external auditory canal and the middle ear

Ceruminous glands – produce wax to protect ear from dust and foreign objects

OUTER EAR

MIDDLE EAR Small, air-filled cavity Contains 3 smallest bones in the body

Auditory ossicles Malleus, incus, and stapes

contains auditory tube (eustachian tube) – connects middle ear to the throat and nasal cavitiesHelps maintain air pressureCan lead to ear pain during sore throats

MIDDLE EAR

INNER EAR Labyrinth – communicating chambers

and tubes Contains

Semicircular canals – sense of equilibriumCochlea – sense of hearingOrgan of Corti – contains hearing receptors,

hair cells detect vibrations

INNER EAR

HEARING Pinna directs sound waves into auditory

canal Sound waves strike ear drum and it

vibrates Auditory ossicles amplify vibrations to

cochlea Organs of Corti contain receptor cells

(hair cells) that deform the vibrations Impulses sent to nerves Temporal lobe interprets sensory

impulses

HEARING

PART 5 OBJECTIVES Identify the receptor organs for

equilibrium, and describe how they function.

PART 5 - EQUILIBRIUM Balance – 2 types

Static – maintenance of body relative to gravity

Dynamic – maintenance of body in response to sudden movements like rotation, acceleration, and deceleration

Organs that control this are called the vestibular apparatus – all lined with hairsSaccule and utricleSemicircular ducts (canals)

EQUILIBRIUM The hair cells send

signals to the brain that tell it the position of the head

As the hair cells move, the brain can interpret and fix balance