Ch 12: Special Senses

Nose, Eyes, Ear, and Tongue

External Anatomy of the Eye

• Eyelids: Protection, Lubrication

• Eyelashes: Protection

• Glands: Meibomian and Ciliary

–Meibomian: Oil glands, modified sebaceous glands on eyelids

–Ciliary: Modified sweat glands.

Third eye-lidGathers dust and produces eye crispies.

In other animals It can cover the

Eye.

What is the Lacrimal apparatus and what does it do?

• Lacrimal apparatus. Fig 12.5– Lacrimal glands: release tears– Lacrimal ducts (eyelid) and canals (nose)– Nasolacrimal ducts: empties into the nose

• Lacrimal Secretion: Tears have antibodies and lysozyme. Cleans, moistens.

• Why is it called a healthy cry?

Lysozyme

What are the Muscles of the eyeand how do they move it?

• Lateral rectus: Moves eye laterally

• Medial rectus: Moves eye medially

• Superior rectus: Moves eye up

• Inferior rectus: Moves eye down

• S & I Obliques

• Fig 8.15, 197

• Fig 12.7, pg 296

Practice using The Eye Muscles

What are the internal structures of the eye? Pg. 295, Fig 12.6

• Sclera: white of the eye

• Cornea: Clear

• Iris: colorful part of the eye

• Pupil: Opening of the Iris

• Lens and ciliary body: Ciliary body holds the lens in place. The lens focuses light on the back of the eye.

What fills the inner eye? Pg 298

• Aqueous Humor: Circulates from the cornea to the Lens through the canal of Schlemm.

• Vitreous Humor: In the space behind the lens. Keeps the eyes shape, and keeps intraocular pressure stable.

• Floaters?

• Glaucoma?

What lines the back of the eye?

• Retina: photoreceptor layer– Rods: Black and white– Cones: Color

• Choroid coat: Dark, vascularized layer. Absorbs light. *Non-humans are different

• Sclera: Thick, white covering

How do you see? Pg. 299

• .

How we See Details of VisionAdam

Light travels through the…

Cornea to the Aqueous humor to the Pupil to the lens.

In the Lens light is bent so that it will hit the Retina of the eye.

To get to the Fovea Centrals light must continue to pass through Vitreous humor.

Light then hits the Retina where Rods and Cones interpret the image and sends it to the Optic nerve to the brain.

Where is your vision the best and the worst?

• Worst vision: The blind spot. To find your blind spot go to pg 297 in the book.– Blind spot is where the optic nerve takes the

image to your brain. There are no rods or cones here. Your brain just fills in the gaps.

• Best vision: Fovea Centralis. Lateral to the blind spot, only contains cones. This is the spot of greatest visual acuity.

Focalplane

Light

Lens

Emmetropia(normal)

Myopia(nearsightedness)

Hyperopia(farsightedness)

Presbyopia(aged)

Why do cones see better than rods?

• See Fig 12.8

• Many Rods, one nerve = blurred edges.

• One Cone, one nerve = crisp lines.– Which do you think causes Night Blindness?

• What type of cones do you have:– Blue cones: see blue light– Green cones: see green light– Red cones: see red and green light.

Component colors are detected by cone cells in the retina. All colors in the visible spectrum can be represented as a combination of red, green, and blue. In the retina, a full-color image is broken up into component colors by cone cells specialized to detect red light (long wavelength), green light (med. wavelength), blue light (short wavelength).

What is colorblindness?

• The lack of a type of cone, or all cones.

• Sex-linked gene.

• Men suffer from color blindness more often than females.

Vision of the Colorblind

Steps to

LASIK Surgery

How is Lasik’s performed?

Steps to

LASIK Surgery

Optic nerve

Optic tract

Lateral geniculate nucleus

Optic radiation

Optic chiasm

Primary visual cortex

Illusions

More Illusions

The EarPg. 302& 303

Functions: Hearing and Equilibrium…………….

External Ear

• Auricle• External Auditory Meatus-2.5 cm

long leads to Middle ear

How the Ear hears.

The Middle Ear

• Tympanic Cavity: air-filled space• Tympanic Membrane- ear drum• Pressure changes cause it to vibrate,

enhances the sound wave• Auditory Ossicles: smallest bones in

the body. Malleus, incus, and stapes.• The Stapes vibrate at the oval window

causing fluid in the inner ear to move, stimulating hearing receptors.

STAPES

INCUS

MALLEUS

Auditory tube mucous membranes connect directly with the middle ear linings. Thus, mucous membrane infections of the throat may spread through these tubes and cause a middle ear infection.

Question: Why is it important to keep a babies head up when bottle feeding?

How the Tubes work

Xylitol gum and chewing it could help prevent ear infections.

Inner Ear. Pg. 304Cochlea: hearing• Oval Window: the stapes vibrates

this in order for your nerves to fire and for you to hear sound.

Review of the Ear:In depth on Cochlea

And Hearing

Sound on Cochlea

Quick Review

Inner Ear: pg. 306 - 307

• Semicircular Canals: maintain equilibrium

The vestibular system

Hearing Illusions

The Nose. Fig 12.3

• Smells using Olfactory Receptors– Yellow-brown mass located at the top of each

nasal cavity– Size of a postage stamp.

Sex andSmell

Factoid:These swirl the

Air so that Dust and germs

Stick to the Mucus. How we smell

How do olfactory receptor cells smell?• Use Olfactory Hairs

– Must be covered in mucus– Chemicals dissolve in mucus– Trigger nerve

• Olfactory Nerve– Connects to the Olfactory Bulb in Brain.

Travels to temporal lobe for interpretation. – Tied to the limbic system (emotional system)

of the brain. Smells stimulate memories.

Interesting Nose facts

• Olfactory neurons that are over stimulated shut off. (Can’t smell X after a while.)

• Anosmias: loss of smell due to head injuries, nasal cavity inflammation (cold, allergy, smoking) or age.– Often caused by a zinc deficiency

• Olfactory auras: epileptics may have smell hallucinations before a seizure.

• Because dust in space does not settle Austronoauts sneeze about 100 times a day!

The Tongue.Fig. 12.4

.

Factoid: You can detect and distinguish

between 10,000 odors, but

only 5 tastes.

How Do You Taste?• Gustatory cells- respond to chemicals

that are dissolved in saliva

• Taste buds- receptor sites for tastes. Most are on the tongue. Some are on the roof of the mouth and cheeks

• Papillae- on the sides of this structure is where taste buds are found

How do youTaste?

Basic Taste Sensations

• Sweet- sugar, OH- groups

• Sour- acidic, H+

• Umami- meaty or savory

• Bitter- alkaloid bases, very few H+ bonds

• Salty- metal ionsThe science

Of Picky Eaters

What effects taste?

• Temperature

• Smell

• Texture

• Genetics