ch 12: special senses nose, eyes, ear, and tongue
TRANSCRIPT
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