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Special Senses General Senses • Widely distributed throughout the body – Examples • Touch • Pain • Proprioception (provides information about the position of the body) Special Senses • Produced by highly localized sensory organs – Examples – – – – Smell Taste Sight Hearing Model of the human nose The Inner Ear 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 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. Olfactory - nose • 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. Taste - tongue * 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. Structures of the eye pictures 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 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: rodsnight 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 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 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 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
