Anatomy Study Guide Chpt. 8 by Jenna Kozlowski

Terms in this set (60)

• Within the cochlear duct, the endolymph-containing membranous labryinth of the cochlea is the spiral organ of Cortical which contains the hearing receptors or hair cells.
• The chambers (scalae) above and below the cochlear duct contain perilymph. Sound waves then reach the cochlea through vibrations of the eardrum, ossicles,a nd oval window set the cochlear fluids into motion. As the sound of waves are transmitted by the ossicles front he eardrum to the oval window, their force (amplitude) is increased by the lever activity of he ossicles. In this way, nearly the total force exerted on the much larger eardrum reaches the tiny oval window, which in turn sets the fluids of the inner ear into motion, and these pressure waves set up vibrations in the basilar membrane.
• The receptor cells positioned on the basilar membrane in the spinal organ of cortical, are stimulated when their "hairs" are bent or tweaked by the movement of the fuel-like tectorial membrane that lies over them.
• The length of the fibers spanning the basilar membrane "tunes" specific regions to vibrate at specific frequencies. In general, high pitched sounds disturb the shorter, stiffer fibers of the basilar membrane and stimulate receptor cells close to the oval window, whereas low-pitched sounds affect longer, more floppy fibers and activate specific hair cells further along the cochlea
• Once stimulated, the hair cells transmit impulses along the cochlear nerve (a division of cranial nerve AVIII—the vestibulocochlear nerve) to the auditory cortex in the temporal lobe, where interpretation of the sound, or hearing occurs.
• Sound usually reaches the two ears at different times; functionally, this helps us to determine where sounds are coming from in our enviornment
• When the same sounds, or tones, keep reaching the ears, the auditory receptors tend to adapt, or stop responding, to those sounds, and we are no longer aware of them
• However, hearing is the last sense to leave our awareness when we fall asleep or receive anesthesia (or die) and is the first to return as we awaken.
• The thousands of olfacotry receptors, receptors for the sense of smell, occupy a postage stamp-sized area in the roof of each nasal cavity.
• Air entering the nasal cavity make a hairpin turn to enter the respiratory passageway below, so sniffing, which causes more air to flow superiorly across the olfactory receptors, intensifies the sense of smell.
• The olfactory receptor cells are neurons equipped with olfactory hairs, long cilia that protrude fronm the nasal epithelium and are continuously bathed by a layer of mucus secreted by underlying glands.
• When the olfactory receptors located on the cilia are stimulated by chemicals dissolved in the mucus, they transmit impulses along the olfactory filaments, which are bundled axons of olfactory neurons that collectively make up the olfactory nerve (cranial nerve I).
• The olfactory nerve conducts the impulses to the olfactory cortex of the brain. There the odor is interpreted, and an "odor snapshot" is made.
• The olfactory pathways are closely tied into the limbic system (emotional-visceral part of the brain). Thus, olfactory impressions are long-lasting and very much a part of our memories and emotions.
• Our reactions to odors are rarely neutral. We eith like or dislike certain odors and we change, avoid, or add odors according to our preferences.
• The olfactory receptors are exquisitely sensitive—just few molecules can activate them. Like the auditory receptors, the olfactory neurons tend to adapt rather quickly when they are exposed to an unchanging stimulus, in this case, an odor