chapter 35 special senses 35-2 learning outcomes (cont.) 35.1 describe the anatomy of the nose and...

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35Special Senses

35-2


Learning Outcomes (cont.)

35.1 Describe the anatomy of the nose and the function of each part.

35.2 Describe the anatomy of the tongue and the function of each part.

35.3 Describe the anatomy of the eye and the function of each part, including the accessory structures and their functions.

35-3



35.4 Explain the visual pathway through the eye and to the brain for interpretation.

35.5 Describe the causes, signs and symptoms, and treatments of various disorders of the eyes.

35.6 Describe the anatomy of the ear and the function of each part, and the role of the ear in maintaining equilibrium.

35-4



35.7 Explain how sounds travel through the ear and are interpreted in the brain.

35.8 Describe the causes, signs and symptoms, and treatments of various disorders of the ears.

35-5


Introduction

• Special senses – receptors in the head– Nose – Tongue – Eyes – Ears

• Touch is a generalized sense

• Stimulus nervous system brain response

35-6


The Nose and the Sense of Smell

• Olfactory receptors– Chemoreceptors – respond to changes in

chemical concentrations

– Chemicals must be dissolved in mucus

– Located in the olfactory organ

35-7


The Nose and the Sense of Smell (cont.)

The information is sent along olfactory bulbs and tracts

Cerebrum – interprets information as a type of smell

Activation of smell receptors information sent to olfactory nerves

Sensory Adaption

35-8


Apply Your Knowledge

ANSWER: After a few minutes, smell receptors undergo sensory adaptation and no longer respond to the chemical, and the patient can no longer smell the odor.

You notice an odor coming from a patient when you enter the exam room. Why would the patient not be able to smell it?

Very Good!

35-9


The Tongue and the Sense of Taste

• Gustatory receptors – on the taste buds

• Taste buds – Papillae of the tongue– Roof of mouth– Walls of throat

Tongue

} fewer than on tongue

35-10


The Tongue and the Sense of Taste (cont.)

• Taste buds – Taste cells ~ chemoreceptors that react to

chemicals in food and drink must be dissolved in saliva to activate

– Supporting structures ~ fill in space

Tongue

35-11



• Taste sensations – Sweet – tip

– Sour – sides

– Salty – tip and sides

– Bitter – back

• Umami – 5th basic taste

– Glutamate

• Spicy foods– Activate pain

receptors

– Interpreted by brain as “spicy”

Tongue

35-13



Activation of taste cells

Cranial nerves

Gustatory cortex of cerebruminterprets information as

a particular taste

Taste sensation

35-14



What are the four primary taste sensations and where are their corresponding taste cells located?

ANSWER: The four primary taste sensations are:

Sweet – concentrated on the tip of the tongue

Sour – concentrated on the sides of the tongue

Salty – concentrated on the tip and sides of the tongue

Bitter – concentrated on the back of the tongue

35-15


The Eye and the Sense of Sight

• Vision system– Eyes

– Optic nerves

– Vision centers in the brain

– Accessory structures

• Eye – Processes light to

produce images

– Three layers

– Two chambers

– Specialized parts

35-16


The Eye and the Sense of Sight (cont.)

• Outer Layer– Sclera

• Tough outer layer

• Light cannot pass through the sclera

• Sense receptors

– Limbus ~ corneal-scleral junction

– Cornea • Transparent

• “Window” that allows light into eye

Eye

35-17



• Middle layer – choroid – Contains blood vessels

– Iris• Muscle tissue relaxes and contracts to alter the

size of the pupil

• Regulates the amount of light entering the eye

Eye

35-18



• Middle layer (cont.) – Ciliary body ~ wedge-shaped muscles

that controls the shape of the lens

– Lens • Changes shape to focus light on retina• Accommodation – the ability of the lens to change

shape

Eye

35-19



• Inner layer – retina– Optic disc – optic nerve enters retina

– Rods • Sensitive to light • Function in dim light – “night” and peripheral vision• Do not provide sharp image or detect color

Eye

35-20



• Inner layer (cont.)

– Cones

• Function in bright light

• Sensitive to color and provide sharp images

• Enable differentiation of tones and hues of color

35-21



• Anterior chamber of the eye– Front of lens– Filled with aqueous humor – nourishes and bathes

anterior eye

• Posterior chamber – Behind lens– Contains vitreous humor – maintains shape of eyeball

and keeps the retina flat

Eye

35-23


Visual Accessory Organs

• Eye orbits – form a protective shell around the eyes

• Eyebrows protect eyes

35-24


Visual Accessory Organs

• Eyelids – Skin, muscle, and connective tissue– Blinking

• Prevents surface from drying out• Keeps foreign material out of eye

35-25


Visual Accessory Organs (cont.)

• Conjunctivas – produce mucus to keep the surface of the eyeball moist

• Lacrimal apparatus– Lacrimal glands ~

produce tears

– Nasolacrimal ducts ~ drain tears into nose

35-26


Visual Accessory Organs (cont.)

• Extrinsic eye muscles– Six per eye – Move the eye

Levator palpebrae superioris (cut)

Optic Nerve

Inferior Rectus

Trochlea

Superior oblique

Superior rectus

Lateral rectus

Inferior oblique

35-27



Matching:___ Middle layer of eye A. Lacrimal glands___ Eye sockets B. Aqueous humor___ Controls shape of lens C. Retina___ Outer layer of eye D. Sclera___ Anterior chamber E. Vitreous humor___ Tears F. Ciliary body___ Ability of lens to G. Choroid

change shape H. Orbits___ Posterior chamber I. Accommodation___ Inner layer of eye

I

HF

E

D

C

BA

G

ANSWER:

35-28


Visual Pathways

• Eye works like a camera– Light enters the eye through the lens

– Refraction – bending of light to focus it on the retina

– Projected upside down on the retina

35-29


Opticchiasm

Visual Pathways

Opticnerve

Occipital lobe of

cerebrum

Retina convertslight to nerve

impulse

Image upside down on retina Image turned

right-side up

35-30



What is refraction and which part of the eye carries out refraction?

ANSWER: Refraction is the bending of light that enters the eye to focus it on the retina. The cornea performs this function.

Well done!Well

done!

35-31


The Aging Eye

• Tears altered

• Eyes dryer

• Lens more rigid

• Retinal changes

• Less adaptable to light

• Impaired night and peripheral vision

• Impaired depth perception

35-32


Common Diseases and Disorders

Disorder/Disease Description

Astigmatism Cornea or lens has abnormal shape; blurred images

Dry eye syndrome Results from a decreased production of the oil within the tears

Ectropin Eversion of lower eyelid

35-33


Common Diseases and Disorders


Entropion Inversion of lower eyelid

Nystagmus Rapid, involuntary eye movements

Retinal detachment

Layers of retina separate; medical emergency

35-34



What vision changes can occur in the elderly patient?

ANSWER: An elderly patient may have difficulty seeing because of drooping eyelids. Focusing may be more difficult because less light enters the eye. He may have difficulty distinguishing colors due to yellowing of the lens. Vision may be fuzzy because of changes in the retina. Night vision can become impaired. The patient may see floaters or “sparks.”

Nice job!

35-35


The Ear and Senses of Hearing and Equilibrium

• External ear– Auricle (pinna) - collects sound waves

– External auditory canal• Lined with hairs and glands that produce cerumen

• Guides sound wave to the tympanic membrane which separates external ear and middle ear

Ear

35-36


The Ear and Senses of Hearing and Equilibrium (cont.)

• Middle ear– Ear ossicles

• Malleus

• Incus

• Stapes

–Ossicles • Vibrate

• Hit the oval window

Ear

35-37



• Middle ear (cont.)

– Eustachian tube• Connects middle ear to throat• Equalizes pressure on eardrum

– Oval window – separates middle ear from inner ear

Ear

35-39



• Inner ear – labyrinth of communicating chambers– Semicircular canals ~ equilibrium

– Vestibule ~ equilibrium

– Cochlea• Hearing receptors • Organ of Corti – organ of hearing

Inner ear

35-41



Head movement

Activates equilibrium and

hearing receptors

Vestibular nerves transmit

information

Cerebrum interprets information and

advises the body to make adjustments

35-42



Matching:

___ Pinna A. Organ of Corti

___ Malleus, incus, and stapes B. Cerumen

___ Hearing receptors C. Ear ossicles

___ Inner ear D. Tympanic membrane

___ Organ of hearing E. Auricle

___ Earwax F. Cochlea

___ Eardrum G. Labyrinth

___ Detect balance of body H. Semicircular canalsH

G

F

D

C

B

A

E

ANSWER:

35-43


The Hearing Process

• External ear– Collect sound waves

– Channels waves to the tympanic membrane

– Tympanic membrane vibrates

• Middle ear – ossicles amplify vibrations

35-44


The Hearing Process (cont.)

• Inner ear– Amplified waves bend hairs lining cochlea

– Movement of hairs trigger nerve impulses

– Impulses are transmitted by auditory nerve to the brain for interpretation

35-45


The Hearing Process (cont.)

• Bone conduction– Alternate sound pathway to inner ear

– Bones of the scull conduct sound waves

• Identification of hearing problems– Normal bone conduction

– Problem likely in middle or external ear

35-46



How do we hear?ANSWER: Sound waves are collected by the external ear and are funneled down the ear canal to the tympanic membrane. The waves make the tympanic membrane vibrate. The ossicles amplify these vibrations which enter the inner ear and cause movements of the hairs that line the cochlea. These movements trigger nerve impulses which are sent to the brain via the auditory nerve. The brain perceives the impulses as sound.

Great Answer

!

35-47


The Aging Ear

• External ear – Larger– Cerumen drier– Canal narrows

• Middle ear– Eardrum shrinks– Joints between ossicles degenerates

• Inner ear – less sensitive to position changes

35-48


How to Recognize Hearing Problems in Infants

• Infants to 4 months– Startled by loud noises– Recognize mother’s voice

• 4 to 8 months– Regularly follow sounds– Babble at people

• 8 to 12 months– Respond to the sound of

their name– Respond to “no”

35-49


Common Diseases and Disorders of the Ear


Acoustic Neuroma

Benign tumor of the cranial nerve involved in hearing and balance; commonly causes gradual hearing loss in one ear

Cerumen impaction

Build up of wax within external auditory canal with some degree of hearing loss due to blocked sound waves

35-50


Common Diseases and Disorders of the Ear


Hearing loss Deafness; the loss of the ability to hear sounds at normal levels. Conductive – blockage of sound waves

Sensorineural – damage to auditory nerve

35-51


Common Diseases and Disorders of the Ear (cont.)


Otitis

Otitis externa

Otitis media

Otitis interna

Inflammation of the ear

Swimmers’ ear

Middle ear infection; common infection

Labyrinthitis; inner ear infection

Osteosclerosis Immobilization of the stapes; common cause of conductive hearing loss

Presbycusis Hearing loss due to aging process

35-52



True or False:

___ Otitis media is also called swimmers’ ear.

___ Presbycusis is hearing loss due to the aging process.

___ Otitis interna is an inflammation of the labyrinth.

___ Otosclerosis is the immobilization of the stapes.

Conductive hearing loss is caused by damage to the auditory nerve.

Labyrinthitis often causes nausea and vertigo.

T

T

T

F

ANSWER:

externa

Sensorineural

F

T

35-53


In Summary

35.1 Olfactory receptors – the sense receptors for the sense of smell – are found in the olfactory organ located in the upper part of the nasal cavity.

31.2 Gustatory receptors are found on the taste buds, which are located on the papillae (bumps) of the tongue.

35-54


In Summary35.3 The eye is composed of three layers. The sclera is the

outer protective layer and includes the cornea.

The middle vascular layer is the choroid consisting of the iris, pupil, ciliary body, and lens, and is the area of light regulation and focusing.

The innermost layer is the retina containing the rods and cones, the optic nerve, and the optic disk. This is where the nerve impulse is picked up and brought to the brain for interpretation.

The accessory organs are the orbits, eyelids, conjunctivas, lacrimal apparatus, and extrinsic eye muscles, all of which are protective for the eye.

35-55


In Summary (cont.)

35.4 The cornea, lens, and fluids focus light on the retina. The retina converts the image into nerve impulses that the optic nerve transmits to the brain for interpretation.

35.5 There are many common diseases and disorders of the eyes with varied signs, symptoms, and treatments. Some of these include astigmatism, dry eye syndrome, ectropion, entropion, nystagmus, and retinal detachment.

35-56


In Summary (cont.)

35.6 There are three parts to the ear. The external ear includes the auricle or pinna and the external auditory canal to the tympanic membrane.

The middle ear begins at the tympanic membrane and ends at the oval window and includes the ear ossicles.

The inner ear is composed of the labyrinth and contains the organ of Corti as well as perilymph and endolymph – the fluids of hearing.

The semicircular canals and vestibule in the inner ear function in the body’s equilibrium and balance, sending impulses to the vestibular nerves, which bring information to the cerebrum for interpretation.

35-57


In Summary (cont.)

35.7 The outer ear collects sound waves and channels them to the tympanic membrane, which vibrates. The vibrations are amplified by the ear ossicles and enter the inner ear and cochlea. The movements of the hairs in the cochlea trigger nerve impulses that the auditory nerve transmits to the brain.

35.8 There are many common diseases and disorders of the ears with varied signs, symptoms, and treatments. Some of these include acoustic neuroma, cerumen impaction, hearing loss, otitis, otitis externa, otitis media, otitis interna, otosclerosis, and presbycusis.

35-58


Every closed eye is not sleeping, and every open

eye is not seeing.

~ Bill Cosby

End of Chapter 35

chapter 35 special senses 35-2 learning outcomes (cont.) 35.1 describe the anatomy of the nose and...

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