Turn to Chapter 8: Special Senses

Complete the worksheet

“I See What Doesn’t Belong”

Ambiguous Illusions  This man looks like your

average Joe right?

But what else is he? Is this a rabbit or a duck?

Special Senses

Objectives

3.7 Analyze (explain) sensory perceptions.

3.8 Analyze (explain) diseases as related to eachsystem

Seeing Hearing Smelling

Special Senses

• Special senses allow body to react to the environment

• Body able to see, hear, taste, smell, and to

maintain balance

• Senses occur because the body has structures that receive sensation, nerves carry message to brain, and brain interprets and responds to message

The Eye and Vision

• Sense of sight• Light rays transmitted to the optic nerve• Optic nerve relays information to brain

for interpretation• Eye is well protected by:

– Bony socket– Eyelids and eyelashes– Lacrimal glands– tears empty into nasal cavity – Conjunctiva– thin membrane lines eyelids

Tunics of the Eyeball

• Sclera

• Choroid coat

• Retina

Sclera

1. Outer layer

2. White of the eye

3. Tough coating, helps maintain shape of eye

4. Muscles responsible for moving eye attached to sclera = extrinsic muscles

Choroid coat

1. Middle layer of eye, contains blood vessels to nourish eyes

2. Opening in front is pupil

3. Colored, muscular layer surrounding pupil

is iris

4. Intrinsic muscles – change size of iris to control amount of light entering through pupil

Retina

1. Innermost layer

2. Light rays focus image on retina

3. Image travels to the cerebral cortex via optic nerve

4. Rods –special cells sensitive to dim light

5. Cones – special cells sensitive to bright

light and color

6. Optic disc – on retina, known as blind spot, nerve fibers that form optic nerve

Other Special Structures

• Lens1. Crystalline structure located behind iris and pupil

2. Elastic, disc-shaped, biconvex

3. Situated between the anterior and posterior chambers

• Anterior Chamber- filled w/ Aqueous humor

• Posterior Chamber- filled w/ Vitreous humor

• Muscles

Internal Anatomy of Eye

Internal Anatomy of Eye

Diseases and AbnormalConditions

• Amblyopia – lazy eye

• Astigmatism

• Cataract

• Conjuctivitis – pink eye

• Glaucoma

Diseases and AbnormalConditions (continued)

• Hyperopia – farsightedness

• Myopia – nearsightedness

• Presbyopia

• Strabismus

In addition to examiningthe cornea, lens, and vitreous humor foropacities (cloudiness), the examiner can see the blood vessels at the back of the eye (fundus) and note degenerative changes in the retina.

Ophthalmoscope.

The Ear: Hearing and Balance

• Controls hearing and balance

• Sound waves transmitted to the auditory nerve

• Auditory nerve relays information to the brain for interpretation

• Consists of the outer ear, middle ear, and inner ear

Outer Ear

• Pinna or auricle

a. Visible ear

b. Collects sound waves

• External auditory canal- ear canal

• Tympanic membrane-– ear drum, separates outer and middle ear

Middle Ear

1. Cavity in temporal bone2. Connects with pharynx by Eustachian

tube - which equalizes pressure in the middle ear with outside atmosphere

3. Bones - transmit sound waves from ear drum to inner eara. Malleus (hammer)b. Incus (anvil)c. Stapes (stirrup)

Inner Ear1. Cochlea - spiral shaped organ of hearing, contains a

membranous tube,the cochlear duct – which is filled with fluid that vibrates when soundwaves are transmitted by the stapes

2. Organ of Corti – delicate hairlike cells that pick up vibrations of fluid andtransmit them as a sensory impulse along the auditory nerve to the brain

3. Semicircular canals – three structures in inner ear that contain liquid setin motion by head and body movements

4. Impulses sent to cerebellum to help maintain body

balance (equilibrium)

Internal Anatomy of Ear

Internal Anatomy of Ear

Diseases and Abnormal Conditions

• Hearing loss

• Meniere’s disease

• Otitis externa

• Otitis media

• Otosclerosis

The Chemical Senses: Taste and Smell

• Taste receptors located on the tongue

• Four main tastes– Sweet – Salty– Sour– Bitter

Sense of Smell

• Nose is the organ of smell

• Olfactory receptors in nasal cavity

• Impulses carried from the olfactory nerve to the brain for interpretation

• Humans can detect over 6,000 smells

• Sense of taste and smell related