Special Senses

1. Special Senses

2. General Senses • Widely distributed throughout the body • Examples • Touch • Pain • Proprioception (provides information about the position of the body)

3. Special Senses • Produced by highly localized sensory organs • Examples • Smell • Taste • Sight • Hearing Model of the human nose

4. The Inner Ear

5. Structures of the outer and middle ear • Outer ear • Pinna- collects and focuses sound waves • External auditory canal- passage way that leads to the ear drum • Ear drum- also called tympanic membrane. It vibrates with sound waves. • Middle ear • hammer, anvil, and stirrup- bones that transmit vibrations • Oval and round windows- two openings that connect the middle ear to inner ear • Auditory tube- angles air pressure to be equalized

6. How We Hear • Sound waves are collected by the auricle and conducted through external auditory meatus toward the tympanic membrane which causes vibrations • The vibrations of the stirrup produce waves in the perilymph of the cochlea. This makes the perilymph move and this pushes against the membrane of the round window • This causes the vestibular membrane to vibrate. It creates waves in the indolymph and the basilar membrane • Cochlear nerves (located in the cochlar ganglion), send axons to the cochlar nueculas in the brain stream • Neurons project to other areas of the brain stream to inferior collicuculus thalamus auditory cortex of the cererum.

7. Olfactory - nose

8. Smell- Olfactory • Molecules in the air enter the nasal cavity and dissolve in the mucus lining of the uppermost shelf of the nose (chemoreceptors – cilia) • The olfactory neurons of the molecules contact the olfactory receptors who send impulses to the axons. • The olfactory bulbs send this to the brain which interprets each scent.

9. Taste - tongue *

10. Taste • Saliva breaks down the food into fluid. The chemicals in the fluid attach to the taste cells. • Nerve fibers send impulses to the facial nerves, which send impulses to taste cortex of parietal lobe for interpretation.

11. Structures of the eye pictures

12. Accessory structures of the eye • Eyebrows-protect eyes by preventing perspiration from running down the forehead. • Eyelids- protect the eyes from foreign objects • Conjunctiva- covers inner surface of the eyelids • Lacrimal Apparatus- produces tears • Extrinsic Eye Muscles- help movement of the eye

13. Eye structures • Sclera – outermost, white, hard, layer • Cornea – transparent part of sclera, light in • Choroid – 2nd layer, black, absorbs light • Retina – innermost layer, bipolar cells: rods- night vision and cones- color vision • Ciliary body – holds the lens in place • Iris – colored part of eye, regulates light • Fovea Centralis – area producing sharpest vision

14. Chambers of the eye • Anterior compartment- between the lens and cornea, divided into anterior chamber and posterior chamber • Filled with aqueous humor • Helps maintain pressure in the eye • Bends light • Provides nutrients to inner eye • Circulates around the cornea • Posterior compartment • Filled with a transparent jellylike substance called the vitreous humor • Holds the retina in place • Has many similar functions to the aqueous humor • Unlike aqueous humor, it does not circulate

15. Path of sight input • The rods / cones synapse • bipolar sensory cells • to the optic nerve • reaches the thalamus of brain • Visual cortex of occipital lobe of cerebrum

16. Eye Disorders • Conjunctivitis- also called pink eye, an infection of the conjunctiva • Chalazion- a small lump in the eyelid caused by obstruction of an oil producing gland • Cataract- clouding of the natural lens • Glaucoma- malformation or malfunction of the eye’s drainage structures • Myopia- nearsightedness • Presbyopia- an eye in which the natural lens can no longer accommodate • Stye- same as chalazion