Nervous+System+Project-+kat

=__**Mechanoreceptors**__= Mechanoreceptor is a sensory receptor that responds to mechanical stimuli such as tensions or pressure. =__**My Focus: HEARING**__= The ear has three parts:
 * Mechanoreceptors respond to touch, pressure, sound, muscular contraction, and equilibrium.
 * [[image:touching.jpg width="220" height="351"]][[image:hearing-device.jpg width="227" height="354"]][[image:balance2.gif width="264" height="352"]]
 * 1) The **outer part**: the pinna (external flap) and the auditory canal direct sound waves to the middle of the ear. (**filled with air**)
 * 2) The **middle part**: the tympanic membrane (ear drum) and the ossicles (malleus, incus, and stapes) amplify sound waves. (**filled with air**)
 * 3) The **inner part**: the semicircular canals detect rotational equilibrium; the utricle and saccule detect gravitational equilibrium; and the cochlea houses the spiral organ, which contains mechanoreceptors for hearing. (**filled with fluid**)
 * 4) [[image:ears.gif width="342" height="314"]]

Auditory Pathway to Brain

 * The sound pathway begins with the auditory canal located in the outer ear region. After going through the auditory canal, hearing requires other parts of the ear, the cochlear nerve, and the brain.
 * **Through the Auditory Canal and Middle Ear**
 * Process of hearing begins with sound waves traveling through Auditory Canal.
 * Just like ripples on a pond, __sound waves travel by the successive vibrations of molecules__.
 * When large amount of sound waves strike the tympanic membrane (ear drum) it vibrates ever so slightly.
 * The malleus then takes the pressure from the inner surface of the ear drum and passes it, by the incus, to the stapes in a way that the pressure is multiplied about 20 times.
 * The stapes strikes the membrane of the oval window, causing it to vibrate, which moves the pressure to the fluid in the cochlea.
 * **From the Cochlea to the Auditory Cortex**
 * The cochlea has three canals.
 * 1) **The Spiral Organ**--> sense organ for hearing
 * 2) [[image:spiral_organ.jpg]]
 * 3) **Tectorial Membrane**--> tiny hair cells in the spiral organ
 * 4) **Cochlear Nerve (auditory nerve)**--> carry nerve impulses from the spiral organ to the brain


 * When the stapes strike the membrane of the oval window, pressure waves move from the vestibular canal to the tympanic canal across the basilar membrane.
 * The basilar membrane moves up and down, and the stereocillia of the hair cells embedded in the tectorial membrane bend.
 * The nerve impulses begin the cochlea nerve and travel all the way to the brain.
 * __When reaching the auditory cortex in the temporal lobe they are interpreted as a sound!__
 * **Pitch and Volume [[image:sound.GIF width="228" height="196"]]**
 * Each part of the spiral organ is sensitive to different frequencies, or pitch.
 * Near the tip, spiral organ responds to low pitches and near the base (beginning), it responds to higher pitches.
 * Volume is a function of the amplitude of sound waves.
 * Loud noises cause the fluid in the vestibular canal to exert more pressure and the basilar membrane to vibrate at a greater extent.
 * The result--> **volume**
 * The brain interprets the tone of sound based on the distribution of the hair cells stimulated.

__**Sources:**__
 * http://medical-dictionary.thefreedictionary.com/mechanoreceptor (**information**)
 * Human Bio Book (**information**)
 * http://www.wise4living.com/hfhear/images/hearing-device.jpg (**picture**)
 * http://www.tulanelink.com/tulanelink/balance2.gif (**picture**)
 * http://eppsnet.com/images/touching-palms.jpg (**picture**)
 * http://www.nlm.nih.gov/medlineplus/ency/images/ency/fullsize/1092.jpg (**picture**)
 * http://www.medicalook.com/systems_images/Cochlea.jpg (**picture)**
 * http://www.eslkidstuff.com/images/ears.gif (**picture**)
 * http://aacintervention.com/sound.GIF (**picture**)