Chapter 15 part 1) Special Senses Flashcards
1
Q
The Eye and Vision
A
- 70% of the body’s sensory receptors are in the eye
- nearly half of the cerebral cortex is involved in visual processs
- Small sphere; only about a 6th of eye shows
- rest is protected by fat and orbit bones
2
Q
Acessory Structure of the Eye
A
- Eyebrows
- Shade eyes, prevents perspiration (sweat) from entering eye
- Eyelids (Blink, Moisten eyeball, and protectins)
- Palpebral Fissue) slit of eye
- Corners) Medial and Lateral commusires
- Lacrimal Carnucle) Locaded at medial commisure, contains oil and sweat glands.
- Eyelashes)
- Have hair follicles that are innervated; initiate blink reflex
- Lubricating Glands
- Tarsal Glands) Modified sebacous glands that lubricates eye
- Ciliary glands) Between eyelash hair follicles, modified sweat glands
- Conjunctiva (mucous membrane that prevents eye from drying)
- Palpebral conjuntica) Lines underside of eyelids
- Bulbar Conjuntiva) covers white of eyes (not cornea)
- Conjuntival sac) lies between the two conjuntiva
- Lacrimal Apparatus (Lacrimal gland and duct)
- Lacrimal Secretion) made by lacrimal gland
- Tears drain into lacrimal sac and nasolacrimal duct.
3
Q
Entrinsic Eye Muscles
A
- Six Straplike muscles
- orginate from bony orbit and insert on eyeball
- Enable eye to follow object, mantain shape, and hold it in place
- Rectus Muscles (move eyeball in direction name signifies)
- Superior, inferior, lateral and medial
- Oblique Muscles (rotate eyeball)
- Superior and Inferior
4
Q
Conjuntivitis/ Pinkeye
A
- Conjuctivitus) Inflmation of the conjuntiva resulting in redness
- Pinkeye) Infection caused by bacteria or virus
- very contagiois
- Nasal cavity inflamation causes tears to be trapped in the eye
5
Q
Diplopia
A
- Also known as double vision
- occurs when movments of eye muscles are not perfectly cordinated.
- eyes cannot focus on same image
6
Q
A
7
Q
Strabismus
A
- Also known as cross-eye. Congenital weakess of external eye muscles
- One eye rotates medially or lateraly
- may alternate focus on objects
8
Q
Structure of the Eyeball
A
- Eye is made of three layers
- Fibrous
- Vascular
- Inner
- Internal cavity filled with humor
- Lens seprates internal cavity into anterior and posterior segments.
9
Q
Fibrous Layer
A
- Outermost layer of eye
- Made of Dense avascular connective tissue.
- Two regions.
- Sclara
- Posterior region
- Protects and shapes eyeball
- Anchors extrensic eye muscles
- Where the optic nerve exits the sclera is continuous with the dura mater of the brain.
- Cornea
- Anterior 1/6th of fibrous layer
- Forms a clear window that lets light enter as it bends
- Epithelium covers both surfaces.
- Outer) protects cornea
- Inner) Mantains clarity of cornea,.
10
Q
Vacsular Layer (Uvea)
A
- Middle Pigmented Layer of the Eye
- Three regions
- Choroid Region (membrane)
- Posterior part of Uvea
- Supplies blood to all layers of eye
- Brown pigment absorbs excess light
- Ciliary Body
- Anterior Part of Uvea (Chorid turns into Ciliaru body)
- Cilary muscles) smooth muscle that controls lens size
- Ciliary processes) secrete fluid for anterior segment of the eye
- Cilary Zonule) holds lens in position
- Iris (colored part of eye)
- Between conrnea and lens
- Pupil) Regulates ammount of light let into the eye
- Sphincter Pupillae) Constricts pupils (parasympathetic control)
- Dilator Pupillae) Dialates Pupils (Sympathetic Control)
11
Q
Inner Layer: The Retina
A
- The retina Contains millions of photoreceptor cells. It is a delicate two-layered membrane.
- Outer) Pigmented Layer
- Inner) Neural Layer
- Pigmented Layer of Retina)
- Single cell thick lining next to chorid
- Absorbs light and prevnets it from scatering, stores vitamin A
- Neural Layer of Retina
- Tranparent layer of the eye that runs anteriorly to margin of cilary body
- Composed of Photoreceptors, Bipolar Cells, and Ganglion Cells
- Bipolar Cells) internuerons
- Ganglion Cells) Axons exit eye as optic nerve
- Optic Disc) site where optic nerve leaves eye, called our blind spot.
12
Q
Photoreceptors
A
- Rods
- Dim light, prepherial vison receptors
- More numerous than cones
- do not provide color or sharp images
- Cones)
- Bright Light Receptor
- High-Resolution Images
- Macula Lutea (yellow spot)
- At posterior pole lateral to blind spot.
- Made of mostly cones
- Fovea Centralis
- Center of Macula Lutea
- Contains All cones
13
Q
Retinal detachment
A
- Pigmenteted and Nueral Layers of eye seperate.
- allows jellylike humor to seep betwen them
- can lead to blindness
- Treatment is to reattach retina with laser surgery.
14
Q
Posterior Segment of Internal Eye Chamber
A
- Contains a Vitrous Humor fluid
- transmits light
- supports posterior surface of lens
- holds layers of retina togehter
- Our Vitrous Humor forms in our embro and is not replaced our whole life
15
Q
Anterior Segment of Internal Chamber
A
- Iris Divides anterior segment into two chambers
- Anterior Chamber) between cornea and Iris
- Posteior Chamber) between iris and lens
- Entire Segment is filled with Aqueous Humor
- Contnusolly formed throuought ones life.
- Drains via Scleral Venous Sinus.
16
Q
Lens
A
- Biconvex, Transpararent and flexible structure that changes shape to focus light on the retina.
- Is also avascular
- Two Lens Regions
- Lens Epithelium) Anterior Region of Cubodial cells
- diffreientiate lens into fiber cells.
- Lens Fibers) Form Bulk of Lens
- Filled with transparent protein crystallin
- Fibers are continually added so lens becomes more dense and less elastic (less functional) with age.
- Cataract) Clouding of Lens.
17
Q
Visible Light
A
- Small portion of electromagnetic spectrum
- wavlength of 400-700nm
- Light) packets of photons that travel in waves
- Redlight) lowest frequency (long wavelength)
- Violent) Hightst Frequency (short wavelength)
- Color That eye precives is reflection of that wavlength
- Grass is green because it absorbs all colors except green
- White reflects all colors, and black absorbs all colors
18
Q
Refraction and Lenses
A
- Refraction) bending of light rays
- Lenses can refract light because they are curved on both sides
- Convex lenses bend light passing through them and focus them on focal point
- Image is upside-down and reversed (left is on right) after focusing
- brain takes information and corrects image
19
Q
Focusing Light on the Retina
A
- Light pathway in eye
- cornea > aqueous humor > lens> vitreous humor> entire neural layer of retina> and finally photoreceptors
- Light is refracted three times along the path of the eye
- When entering the cornea
- When entering the lens
- When leaving the lens
20
Q
Focusing for Distant Vision
A
- Eyes are best adapted for distant vision
- Far point of vision) Distance beyond which no change of lens shape is needed for focusing
- Distance is 20 feet for a normal eye
- at 20 feet the lens is perciscly focused on the retina
- Cilary Muscles Relaxed = Tension in Cilary Zonule = Streatched Lens
21
Q
Focusing for Close Vision
A
Requires three adjustments
- Accomodation of the lenses
- Changes lense shape to increase refraction
- Near Point of vision) Closest Point on which the eye can focus
- Presbyopia) loss of accomidation
- Constriction of Pupils
- Prevent divergent rays from entering the eyes
- managed by parasympathetic nervous system
- Convergence of the eyeball
- Medial roation of eyeballs toward object being viewd
22
Q
Problems with Refraction
A
- Myopia (nearsightedness)
- Eyeball is too long, so focal point is in front of retina
- Corrected with a concave lens
- Hyperopia (farsightedness)
- Eyeball is too short, so focal point is behind retina
- Corrected with a convex lens
- Astigmatism
- Unequal curvatures in different parts of cornea or lens
- Corrected with cylindrically ground lenses or laser procedures