5 Structures of the outer and middle ear Outer earPinna- collects and focuses sound wavesExternal auditory canal- passage way that leads to the ear drumEar drum- also called tympanic membrane. It vibrates with sound waves.Middle earhammer, anvil, and stirrup- bones that transmit vibrationsOval and round windows- two openings that connect the middle ear to inner earAuditory tube- angles air pressure to be equalized
6 How We HearSound waves are collected by the auricle and conducted through external auditory meatus toward the tympanic membrane which causes vibrationsThe 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 windowThis causes the vestibular membrane to vibrate. It creates waves in the indolymph and the basilar membraneCochlear nerves (located in the cochlar ganglion), send axons to the cochlar nueculas in the brain streamNeurons project to other areas of the brain stream to inferior collicuculus thalamus auditory cortex of the cererum.rt
8 Smell- OlfactoryMolecules 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.
10 TasteSaliva 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.
12 Accessory structures of the eye Eyebrows-protect eyes by preventing perspiration from running down the forehead.Eyelids- protect the eyes from foreign objectsConjunctiva- covers inner surface of the eyelidsLacrimal Apparatus- produces tearsExtrinsic Eye Muscles- help movement of the eye
13 Eye structures Sclera – outermost, white, hard, layer Cornea – transparent part of sclera, light inChoroid – 2nd layer, black, absorbs lightRetina – innermost layer, bipolar cells: rods- night vision and cones- color visionCiliary body – holds the lens in placeIris – colored part of eye, regulates lightFovea Centralis – area producing sharpest vision
14 Chambers of the eyeAnterior compartment- between the lens and cornea, divided into anterior chamber and posterior chamberFilled with aqueous humorHelps maintain pressure in the eyeBends lightProvides nutrients to inner eyeCirculates around the corneaPosterior compartmentFilled with a transparent jellylike substance called the vitreous humorHolds the retina in placeHas many similar functions to the aqueous humorUnlike aqueous humor, it does not circulate
15 Path of sight input The rods / cones synapse bipolar sensory cells to the optic nervereaches the thalamus of brainVisual cortex of occipital lobe of cerebrum
16 Eye DisordersConjunctivitis- also called pink eye, an infection of the conjunctivaChalazion- a small lump in the eyelid caused by obstruction of an oil producing glandCataract- clouding of the natural lensGlaucoma- malformation or malfunction of the eye’s drainage structuresMyopia- nearsightednessPresbyopia- an eye in which the natural lens can no longer accommodateStye- same as chalazion