1. Anatomy and Physiology 2

2. The Special Senses Smell Taste Sight Hearing These allow us to experience and interpret the world around us

3. Anatomy of the Eye A sphere that is about 1in in diameter Only about 1/6 of the eye is seen and rest is protected The eye is protected by bone, eyelids and eyelashes

4. Anatomy of the Eye There are several glands and ducts around the eye Tarsal glands: lubricate the eye Lacrimal gland: produce tears Nasolacrimal duct: empties tears into the nasal cavity

5. Anatomy of the Eye Eye muscles Lateral rectus: moves laterally Medial rectus: moves medially Superior rectus: elevates Inferior rectus: depresses Inferior oblique: elevates and turns laterally Superior oblique : depresses and turns laterally

6. Anatomy of the Eye Structures: Sclera: the “white of the eye: Cornea: where light enters Lens: focuses the light that enters through the cornea Iris: the pigmented part of the eye Pupil: controls the amount of light that enters the eye Retina: responds to the light

7. Anatomy of the Eye Structure: Retina continued: Contains rods and cones which are called photoreceptors Cones allow us to see colors Rods allow us to see in dim light and use our peripheral vision Optic nerve: transfers information to the optic cortex of the brain

8. How we see When light passes through cornea and lens the light is bent or refracted as they move through the aqueous humor The image is then projected on the retina upside down That information is then carried to the optic nerve and process by the brain

9. Eye Problems Myopic eye (nearsighted): distant objects appear blurry, results of an eyeball that is too long Hyperopic eye (farsighted): close objects appear blurry, results from a too short eye Astigmatism: the cornea has an unusual curve to it Conjunctivitis: bacteria or viral infection of the conjunctive (membrane that covers the eye)

10. Anatomy of the Ear Outer ear: Pinna or auricle what is typically called the ear External acoustic meatus: a narrow chamber carved into the temporal bone Lined with ceruminous glands that produce earwax or cerumen

11. Anatomy of the Ear Middle Ear Ear drum: vibrates in response to sound waves Ossicles: the three smallest bones in the body Incus (anvil), malleus (hammer) and stapes (stirrup) Vibrations trigger the coordinated movements of these bones

12. Anatomy of the Ear Inner Ear Bony labyrinth Cochlea Vestibule Semicircular canals Vestibular apparatus (responsible for equilibrium)

13. Equilibrium Static equilibrium Static = at rest Provides information on which way is up or down Helps maintain posture and balance when standing upright Dynamic equilibrium Provides information for angular movements (e.g. twirling, spinning. Etc.)

14. How We Hear The auricle works to capture as much sound waves as possible The waves travel through the ear until they reach the cochlear duct Hair follicles move in response to the vibrations Once the follicles are triggered they send the impulse to the cochlear nerve

15. Hearing and Equilibrium Deficits Deafness is defined as hearing loss of any degree Conduction deafness = problems in the ear Sensorineural deafness = problems in the cochlear nerve or brain Vertigo is the sense of falling or spinning Usually result in nausea and difficulty in maintaining balance

16. Chemical Senses: Smell The nose contains thousands of olfactory receptors that can respond to thousands of different smells The olfactory receptors lead to the olfactory nerve, which leads to the olfactory cortex in the brain (here the smells are “identified”)

17. Chemical Senses: Smell The olfactory cortex of the brain is tied to the emotional part of the brain, thus many smells with trigger memories and emotions The receptors are quickly triggered, but also quickly adapt to smells

18. Chemical Senses: Taste Taste buds are the receptors for taste The tongue contains about 10,000 taste buds The small peg like projections on the tongue are called papillae The papillae contain tiny hairs that are linked to 3 nerves that carry the information to the brain

19. Chemical Senses: Taste 5 basic taste sensations: Sweet = responds to sugars, saccharine and certain amino acids Sour: responds to acids Bitter: responds to alkaloids Salty: responds to metal ions Umami: recently discovered to respond to food additives

20. Chemical Senses: Taste Historically, each taste on the tongue had “it’s own part”, but only slight differences have been found between the parts Typically, cravings are linked to deficits in the body, but like smell the taste part of the brain is close to the emotionally part of the brain

21. Developmental Aspects All special senses are functional at birth; however, vision is the only one not fully functional Newborns see only in gray tones and cannot see much further that a foot in front of them It takes until about 5 years of age to have fully functioning vision The lens will continue to grow throughout life causing “old vision” Hearing is very important to language development Smell and taste also developmentally important