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WARM-UP #1

Welcome Back!!!•Describe the steps used in a reflex arc. •Make sure to turn in your CONCUSSION movie questions.

UNIT 8- SPECIAL SENSES

• OBJECTIVES:• Identify structures and functions of the special• senses.• Explain the processes of vision, hearing, balance,

taste, and smell.• Summarize disorders of the special senses.

THE SENSES

• Special structures of the nervous system that collect information about the surrounding environment in order for your body to maintain homeostasis.• Smell• Taste• Sight• Hearing• Equilibrium

SENSE PATHWAYS

• Stimulus- stimulates receptor (transmits to the CNS)

• Receptors provide feedback about environment• In the senses, these receptors are very specific.

(most only respond to one type of stimulus)• Examples: Photoreceptors, chemoreceptors,

mechanoreceptors.

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SPECIAL SENSES - EYE

• 70 percent of all sensory receptors are in the eyes. (photoreceptors)

• Each eye has over a million nerve fibers• Protection for the eye• Bony orbit• Cushion of fat• Accessory structures

ACCESSORY STRUCTURES OF THE EYE

• Eyelids • Eyelashes• Conjunctiva- membrane covers outer surface, secretes

lubricating mucus (conjunctivitis= pink eye)

• Glands• Tarsal glands- oily secretions • Ciliary glands- modified sweat glands between lashes.• Lacrimal glands- secretes tears

• secretions also contain antibodies and lysozyme (enzyme that destroys bacteria)

• Secretions clean, protect, moisten, and lubricate the eye

• Extrinsic eye muscles

Figure 8.2a

Lacrimalgland

(a)

Conjunctiva

Anterioraspect

Eyelid

Eyelashes

Eyelid

Excretory ductof lacrimal gland

Figure 8.2b

LacrimalglandExcretory ductsof lacrimal gland

Nostril

(b)

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Figure 8.3c

EXTRINSIC EYE MUSCLES

• Six muscles attach to the outer surface of the eye producing movement

Figure 8.3a

Superioroblique muscle

Superioroblique tendon

Superiorrectus muscle

Conjunctiva

Lateral rectusmuscle

Opticnerve

Inferiorrectusmuscle

Inferiorobliquemuscle

(a)

STRUCTURE OF THE EYE STRUCTURE OF THE EYE

• Three layers (tunics) forming the wall of the eyeball• Sclera- fibrous layer (Outside layer)• Choroid- vascular layer (Middle

layer)• Retina- sensory layer (Inside layer)

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STRUCTURE OF THE EYE:SCLERA

• Tough fibrous tissue--white of the eye

• Cornea• Transparent, central

anterior portion• Allows for light to pass

through• Repairs itself easily• One of the only tissues

that can be transplanted without fear of rejection. (very rare…why might that be?)

STRUCTURE OF THE EYE: CHOROID

Vascular--blood-rich nutritive layer in the posterior of the eye

• Pigment prevents light from scattering

• Modified anteriorly into two structures1. Ciliary body—smooth muscle

attached to lens that helps regulate the thickness and shape of the lens.

2. Iris—Colored, muscular layer that regulates amount of light entering eye. (dilation)

• Pupil—rounded opening in the iris.

PHOTO PUPILLARY REFLEX…LENS

• Special tissue that focuses and directs light. • Biconvex crystal-like structure• Held in place by a suspensory ligament attached to

the ciliary body• Shape can change to accommodate near and far

vision (accommodation)

• As we age, the lens can become hard and opaque leading to cataracts.

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Figure 8.7

CATARACT STRUCTURE OF THE EYE: RETINA

• Innermost layer• Very fragile, thin layer• Contains millions of receptor cells (photoreceptors)

• Rods (gray tones in dim light; peripheral vision)• Cones (color and details)

• Cells are distributed over entire retina except where optic nerve leaves eyeball• Site is called optic disc, or blind spot

• Fovea Centralis - an area of the retina containing many cone cells• the area of sharpest vision

Figure 8.5a

RodCone

(a)

Pathwayof light

Pigmentedlayer of retina

STRUCTURE OF THE EYE: SENSORY LAYER

• Cone sensitivity • Three types of cones• Different cones are

sensitive to different wavelengths (red, green, blue)

• Color blindness is the result of the lack of one cone type

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EX:http://www.nlm.nih.gov/medlineplus/ency/imagepages/9962.htm

TWO SEGMENTS, OR CHAMBERS, OF THE EYE

• Anterior (aqueous) segment• Anterior to the lens• Contains aqueous

humor, which drains to the blood.

• Glaucoma could occur if this drainage is blocked.

• Posterior (vitreous) segment• Posterior to the lens• Contains vitreous

humor, gel-like substance that prevents the eye from collapsing.

CRASH COURSE- VISION

• https://www.youtube.com/watch?v=o0DYP-u1rNM

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REVIEW DO YOU UNDERSTAND?

1. Name 3 things that give protection to your eye.2. What are tears? Function?3. What are the 3 layers of the eye?4. What are the intrinsic muscles? Functions?5. Describe the photopupilary reflex?6. Compare rods and cones.

ACTIVE CLOSURE

• Develop a twitter post (less than 140 characters) describing what you learned about the eye today.

WARM-UP #2

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PATHWAY OF LIGHT THROUGH THE EYE AND REFRACTION

• Light must be focused to a point on the retina for optimal vision

• This is influenced by:• Shape of lens• Cornea thickness• Consistency of humors

• The eye is set for distance vision (over 20 feet away)

• Accommodation—the lens must change shape to focus on closer objects (less than 20 feet away)

Figure 8.9

Retina

Focal pointLight from distant source

(a)

Light from near source Focal point

Retina

(b)

PATHWAY OF LIGHT THROUGH THE EYE

1. Cornea2. Aqueous humor3. Pupil4. Lens5. Vitreous humor6. Retina, picked up by rods and cones 7. Carried to optic nerve8. Brain (occipital lobe)

PATHWAY OF LIGHT THROUGH THE EYE

• Image formed on the retina is a real image• Real images are:

• Reversed from left to right • Upside down• Smaller than the object

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VISION

• Emmetropia—eye focuses images correctly on the retina

• Myopia (nearsighted)-Distant objects appear blurry due to elongated eyeball

• Hyperopia (farsighted)-Near objects are blurry due to shortened eyeball• Age-related hyperopia is called presbyopia- stiffness of lens

• Astigmatism-Images are blurry• Results from light focusing as lines, not points, on the retina due

to unequal curvatures of the cornea or lens

• Convergence- medial movement of eyes when focusing on close objects.

• Night blindness- decreased function of rods.

Focalplane

(a) Emmetropic eye

Correction

None required

Concave lens

Convex lens(b) Myopic eye

(nearsighted)

(c) Hyperopic eye(farsighted)

EYE DISEASES

• Glaucoma- aqueous humor does not drain properly causing increased pressure.

• Macular degeneration- progressive loss of vision• Wet- leaking blood vessels• Dry- thinning of the retina

• Diabetic retinopathy- long term diabetes causes leaking blood vessels (healthy living can prevent type 2 diabetes)Currently the leading cause of blindness in American adults.

DO YOU UNDERSTAND?

1. Describe the path of light through your eye.2. Briefly describe each structure from question 3’s

answer.3. Compare myopia and hyperopia.

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ACTIVE CLOSURE

• Create a short study guide for your eye and stem quiz that is next class.

WARM-UP #3

• Name the purpose of the vitreous and aqueous humors.

SPECIAL SENSES- EARS

• OBJECTIVES:• Identify structures and functions of the special• senses.• Explain the processes of vision, hearing, balance,

taste, and smell.• Summarize disorders of the special senses.• Describe the changes that occur in the special

senses with aging.

THE EAR

• Houses two senses• Hearing • Equilibrium (balance)

• Receptors are mechanoreceptors• Different organs house receptors for each sense• The ear is divided into three areas

• External (outer) ear• Middle ear (tympanic cavity)• Inner ear (bony labyrinth)

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Figure 8.12

Auricle(pinna)

External (outer) ear Middle ear

Internal (inner) ear

Oval window

Vestibule

Round window

Hammer(malleus)

Anvil(incus)

Stirrup(stapes)

Auditory ossicles

Semicircularcanals

Pharyngotympanic(auditory) tube

Cochlea

External acousticmeatus(auditory canal)

Tympanicmembrane(eardrum)

Vestibulocochlearnerve

THE EXTERNAL (OUTER) EAR

• Directs sound toward the eardrum. • Two parts:

• Auricle (pinna)- visual part• External auditory canal-

• AKA: External acoustic meatus• Narrow chamber in the temporal bone• Lined with skin and ceruminous (wax) glands• Ends at the tympanic membrane, which vibrates when hit by

sound. AKA: eardrum

THE MIDDLE EAR (TYMPANIC CAVITY)

• Separated from external ear by the eardrum.• Air-filled and located within the temporal bone. • 2 openings: oval and round window• The internal auditory tube (Eustachian tube)-

connects the middle ear with the pharynx (throat).• Allows for equalizing pressure during yawning or swallowing• This tube is otherwise collapsed

• Three bones (ossicles) span the cavity• Malleus (hammer)• Incus (anvil)• Stapes (stirrup)

OSSICLES

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FUNCTION

• Vibrations from eardrum move to the malleus incus stapes inner ear.• The tympanic membrane and auditory ossicles

convert sound waves into mechanical movement within the middle ear and then transmit that motion to the “oval window”

• The oval window opens into the cochlea of the inner ear

• The vibrations of the stapes causes the fluid within the inner ear to move stimulating the receptors for hearing

EARACHES

• AKA otitis media• Inflammation of the middle ear• Eardrum bulges and becomes inflamed• Pus accumulates in the cavity• Common in children because their internal auditory

tubes run more horizontally• Tiny tubes are placed in the eardrum to aid drainage

(known as a myringotomy)

INNER EAR OR BONY LABYRINTH

• Includes sense organs for hearing and balance• Filled with fluid (perilymph)• Contains a maze of bony chambers (bony

labyrinth) within the temporal bone• Three sections:

• Cochlea (contains organ of Corti) – This is the organ for hearing. Hair receptors are here.

• Vestibule• Semicircular canals

Contain receptors for sense of balance (equilibrium)

INNER EAR

• The Semicircular Canals - three loops that lie at right angles to each other

• The Vestibule - the chamber between the cochlea and the semicircular canals• Both the semicircular canals and the vestibule are

involved with maintaining balance or equilibrium

• The Cochlea - shape resembles a snail shell• Contains the organs of hearing (Corti)• Receptor cells that move in response to fluid motion • Releases neurotransmitters that stimulate nerve impulses

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PATH OF SOUND

1. Ear canal2. Tympanic membrane3. Malleus 4. Incus5. Stapes 6. Oval Window7. Hair cells8. Vestibulocochlear nerve9. Brain

http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120108/bio_e.swf::Effect%20of%20Sound%20Waves%20on%20Cochlear%20Structures

DEAFNESS- HEARING LOSS

• Conduction• Vibrations are

inhibited anywhere along the route in the ear

• Can be caused by some kind of obstruction in the ear from wax buildup to a tumor.

• Sensorineural• Usually due to

problems with the nerve, inner ear, or brain.

• Most often caused by poor hair cell receptors.

• Can be congenital, but often caused by prolonged exposure to LOUD noises.

EQUILIBRIUM-RESPONDS TO VARIOUS MOVEMENTS OF

HEAD.• Static equilibrium

• concerned with changes in position of head when body is not moving

• Receptors found in vestibule

• Provides information on which way is up or down (important for swimming in dark depths)

• Dynamic equilibrium• concerned with

changes in position of head when body is moving

• Receptors found in semicircular canals

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REVIEW DO YOU UNDERSTAND?

1. What are the three main parts of the ear?2. Describe the path of sound from the environment

to your brain.3. Compare and contrast the two types of hearing

loss.4. Describe equilibrium.

ACTIVE CLOSURE

• Today's portable electronic devices make it easy to listen to music, podcasts, videos, and movies wherever you maybe. This generally includes attaching earphones or earbuds to the device so that you can listen without disturbing others. However, research has shown that using earphones or earbuds can be hazardous if they are not used properly. Conduct research to find out more about using earphones safely. What factors should be considered?

• CopyrightGoodheart-WillcoxCo.,Inc.

WARM-UP #4

C.

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UNIT 8- SPECIAL SENSES (SMELL AND TASTE)

• OBJECTIVES:• Identify structures and functions of the special• senses.• Explain the processes of vision, hearing, balance,

taste, and smell.• Summarize disorders of the special senses.

TASTE AND SMELL

• Contain chemoreceptors: receptors for taste and smell

• Respond to chemicals in solution• Receptors complement each other and

respond to same stimuli

OLFACTION—THE SENSE OF SMELL

• Olfactory receptors are in the roof of the nasal cavity• Olfactory hairs protrude from the tissue.• Chemicals must be dissolved in mucus for detection

• Impulses are transmitted via the olfactory nerve• Interpretation of smells is made in the cortex

• Must travel through the part of brain that holds memories and is responsible for emotions (limbic system).

• Differences between people are due to genetics. There are about 400 genes, with 900,000 variations, coding the olfactory receptors.

Figure 8.18

Olfactory bulb

Olfactory tract

Mucus layer(a)

(b)

Supporting cell

Olfactory receptorcell

Olfactory hairs(cilia)Route of inhaled air

containing odor molecules

Cribriform plateof ethmoid bone

Olfactory filamentsof the olfactorynerve

Olfactorymucosa

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DISORDERS OF THE NOSE

• Deviated septum-• Blocks air flow

• Perforated septum-• Hole in septum

THE SENSE OF TASTE

• Gustatory sense• Receptor organs= taste buds• Scattered throughout the

entire mouth• Most found on the sides of

papillae (peg-like projections on dorsal surface of tongue).• Filiform papillae—sharp with no

taste buds, all over tongue.• Fungiform papillae—rounded

with taste buds, tips and side of tongue.

• Circumvallate papillae—large papillae with taste buds, back of tongue.

GUSTATORY CELLS

• Cells that respond to specific chemicals dissolved in the saliva

• Located in the taste buds and are surrounded by support cells.

• Cells form gustatory hairs that protrude through openings called taste pores

• Hairs send impulses to gustatory cortex of brain when they are stimulated

TASTE SENSATIONS

• Taste buds can contain 50-100 gustatory cells that respond to various taste sensations. • Sweet receptors (sugars)

• Saccharine• Some amino acids

• Sour receptors• Acids

• Bitter receptors• Alkaloids (many are poisonous).

• Salty receptors• Metal ions

• Umami (savory)• glutamate

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SMELL AND TASTE

• Approximately 75%- 90% of what you taste is attributed to smell.

• This is also why temperature can affect taste. • This allows the average person to distinguish about

10000 different flavors.

• https://www.youtube.com/watch?v=mFm3yA1nslE

DO YOU UNDERSTAND?

1. Describe how you smell the scent of a rose.2. Why do you think when you breath deeper the

scent is stronger?3. What are taste buds?4. How is smell and taste linked?

ACTIVE CLOSURE

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WARM-UP #5 (MATCHING)

1.Smell2. Taste3.Vision4.Equilibrium5.Hearing

A.GustatoryB. MechanoreceptorsC.ChemoreceptorD.OlfactoryE. Rods and conesF. PhotoreceptorsG.VestibuleH. Semicircular canals