Vision is the most dominant sense, about 70% of all sensory receptors in the body are in the eyes Accessory Structures of the eye : Eyelashes :

Transcription

1 Sight By Jess Kapp

2 Vision is the most dominant sense, about 70% of all sensory receptors in the body are in the eyes Accessory Structures of the eye : Eyelashes : Protect eye from debris and bacteria Eyebrows : Shade eyes from sunlight, protect from perspiration Eyelids : Anteriorly protect the eye, called mobile eyelids or palpebrae Separated by palpebral fissure or eyelid slit Contains the medial and lateral commissures(canthi), which are the corners of the eyes

3 Tarsal glands: produce an oily secretion that lubricates the eye Conjunctiva : Covers part of the exposed surface of the eyeball, fuses to the cornea via corneal epithelium Lacrimal apparatus and glands : Drain secretions into the nasal cavity and produce a saline solution to coat the eye Extrinsic eye muscles : There are 6 extrinsic (external) eye muscles which make it possible for the eye to follow an object

4

5 Internal structures of the eye Fibrous layer : outer layer, protective sclera (white connective tissue) and clear cornea Vascular layer:

6 Internal structures cont d Sensory layer : Contains the sensitive two layer retina, which extends only to the ciliary body Neural layer :

7 Internal structures cont d Optic disc : Photoreceptor cells are distributed throughout the entire retina besides where the optic nerve leave the eyeball, called the optic disc or blind spot

8 Physiology of sense - Light, the stimulus for sight, is refracted to the retina where photoreceptors called rods and cones pick up the message - In rods, the chemical rhodopsin breaks down to form scotopsin and retinal - Rhodopsin is regenerated in a slower chemical reaction - In cones, chemical reactions happen from different wavelengths of light. The types of cones are believed to be : - Red, blue, and green absorbing

9

10 - Impulses from the rods and cones are transmitted to bipolar cells, to amacrine cells, then to ganglion cells, which converge at the optic disc to become the optic nerve - Optic nerves from both sides converge at the optic chiasm, just in front of the pituitary gland

11 - At the optic chiasm medial fibers of the optic nerve cross to the other side - Visual areas are located in the occipital lobe and cerebral cortex of the brain

12 - Images appear on the retina upside down but the pathway vision takes through the brain rights the image, allowing us to see the way we do - Each eye transmits a slightly different image, but visual areas put them together to create binocular vision

13 - The main cranial nerve involved in sight is the optic nerve, which is the sensory nerve for vision and transmits signals to the brain - The other three cranial nerves involved are : oculomotor, trochlear, and the abducens

14 Homeostatic imbalance #1: Pink eye (conjunctivitus) - Pink eye is the inflammation of the conjunctiva, which is a thin clear membrane that line the eye and inside of the eyelid - Many things cause pink eye including: - Viruses, Bacteria, irritants and allergies - Spreads easily from person to person but is not serious if treated in a timely manner - If caused by bacteria, antibiotics will treat it, but if it is caused by a virus it must run its course

15

16 Homeostatic imbalance #2 : Cataracts - Cataracts are cloudy areas in the lens of the eye which cause changes in vision - Symptoms include blurred vision and sensitivity to glare - Can cause blindness - Treated with surgery

17

18 Activity!!! - Blind spot detection - You will be able to detect your blind spot which is the area where the optic disc allows the optic nerve to pass through, making a hole in the retina where information is not sent to the visual cortex of the brain

19 Work cited