Vision: Accessory structures of the Eye! (pg. 581)

1. Vision: Accessory structures of the Eye! (pg. 581) • Eyelids- shade and protect the eyes and provide lubrication • Eyelashes and Eyebrows- protection from perspiration, direct sun light and foreign objects (Yes, eyelashes secrete oil as well!) • Lacrimal apparatus- a group of structures that produce and drains lacrimal fluid- tears. Apparatus includes glands, ducts, canals, sacs. • Eye muscles- six total that move each eye.

2. Main structures of the EYE (pg. 582) • Eyeball- three layers: fibrous tunic, vascular tunic, retina • Sclera- the white of your eye- gives shape- connective tissue. “white of the eye” • Iris-colored part of the eye- smooth muscle fibers w/ melanocytes- regulates light • Pupil- hole in the eye- leads to the retina • Cornea-Transparent central anterior portion of the sclera through which light enters the eye.

3. Main structures, continued! • Retina- lines the posterior ¾ of the eyeball and is the beginning of the visual pathway- contains rods (gray scale) and cones (color). Has 3 sets of color receptors that are sensitive to blue, green and red visible light wavelengths. • Optic disc- place where the optic nerve leaves the eyeball and enters the brain! The “blind spot” of the eye.

4. Main structures, continued! • Lens- located behind the pupil and iris- helps focus images on the retina- dense tissue • Aqueous humor- nourishes lens and cornea • Vitreous body- gives retina an even surface for the reception of clear images. “gel-like”

6. Eye conditions • Conjunctivitis- inflammation of the conjunctiva, the membrane that lines the eyelids and covers exposed areas of the sclera. “pink-eye” • Glaucoma- damage to the optic nerve; excess of aqueous humor • Macular Degeneration- when tissue in the macula, the part of your retina that's responsible for central vision, deteriorates • Cataract- a clouding of the normally clear lens of your eye • Night Blindness- inability to see images in the dark; images are not portrayed on the retina; may be caused by lack of vitamin A • Color Blindness- an inability to distinguish between certain shades of color; pigments in the cones are missing.

7. Hearing: Structures of the Ear (pg. 596) • External Ear- auricle or pinna, external auditory canal and tympanic membrane or ear drum- collects sound waves • Middle Ear- ossicles (malleus, incus, stapes) and auditory tube (regulates pressure)- conveys sound waves to the oval window • Inner Ear- semicircular canal, cochlea, vestibular membrane- houses receptors for hearing and equilibrium

8. Anatomy of the Ear

9. Balance- equilibrium! • Two types: Static (body at rest) and Dynamic (body in response to a sudden movement). • The receptor organs for equilibrium are called the vestibular apparatus, which consist of the saccule, utricle and semicircular ducts. • In the walls of the saccule and the utricle is a region called the macula, that contain hair cells that detect motion. • As hair cells depolarize and repolarize, messages are sent from the vestibulocochlear nerve to the brain.

11. Fetal Development • Eye formation- 22 days after fertilization • Ear formation- 22 days after fertilization • Taste- 14 weeks after fertilization* • Smell- 15 weeks after fertilization* • Last two only* http://www.birthpsychology.com/lifebefore/fetalsense.html

12. The sense of smell goes straight to the brain! From the nasal cavity, to the receptors, to the olfactory nerve, to the bulbs, to the limbic system and finally to the cerebral cortex. Olfaction- Sense of Smell

13. Process of Smell… • Smells are sensed by olfactory sensory neurons in the olfactory epithelium. • Molecules pass through the nasal passages, mix with the lining of the cavity and are detected by receptors on the dendrites of the olfactory sensory neurons. • Olfactory receptors are in the roof of the nasal cavity • Neurons with long cilia • Chemicals must be dissolved in mucus for detection • Impulses are transmitted via the olfactory nerve. • Interpretation of smells is made in the cortex.

14. Smell- Olfaction… • Contained in the olfaction epithelium, which is in the superior part of the nasal cavity. • Smell plays a major role in flavor perception. • Smell is the sense of odor- the detection of chemicals dissolved in air. • Mammals generally have about 1000 genes for odor receptors. • Of these genes, only a portion code for functional odor receptors.

15. Smell, continued… • Odor information is easily stored in long term memory and has strong connections to emotional memory. • This is possible due to the olfactory system’s close ties to areas of the brain that have long been known to be involved in emotion and place memory.

17. Gustation- taste • Refers to the ability to detect flavor • Stimulated by chemical receptors • The sense of taste partners with olfaction in the brain’s perception of flavor • Flavor is based on chemical composition of the item tasted

18. Taste- continued… • Taste is a sensory function of the central nervous system. • Receptor cells are found on the tongue and in the back of the throat. • Three cranial nerves carry impulses from the taste buds to the brain: • Facial nerve • Glossopharyngeal nerve • Vagus nerve

19. You have five primary taste buds: Sour Sweet Bitter Salty Umami Found in the papillae- rough, raised part of your tongue. Gustation- Sense of Taste

20. Sweet receptors Sugars Saccharine Some amino acids Sour receptors Acids Bitter receptors Alkaloids Salty receptors Metal ions Classification of Taste

21. Connection…. • An adult has over 10,000 taste buds, which are located primarily on the tongue (papillae). • The human tongue can only distinguish among 7-8 distinct types of taste, while the nose can distinguish among hundreds of substances, even in minute quantities. • Smell amplifies the sense of taste!