stimulating sympathetic NS which increase heart rate & vasoconstriction 44.3 Hearing, Vibration, Detection of Body Position Fishes’ lateral line system provides “distant touch,” enabling them to sense objects that reflect pressure waves & vibrations Hair cells have hairlike cilia that project into a gelatinous cupula; the smaller hairs are stereocilia (made of actin) & the single big hair is the kinocilium o When stereocilia move in the same direction of the kinocilium, it depolarizes the neuron; opposite direction has inhibitory effect Fish hearing o Otoliths: rocks of calcium carbonate found in the membranous labyrinth , a system of fluid-filled chambers; when otoliths vibrate against hair cells, action potentials are produced Vertebrate hearing o Vibrations channeled through the ear canal to the eardrum (tympanic membrane), part of outer ear o Vibrations of the tympanic membrane move small bones in the middle ear (stapes aka stirrup, malleus aka hammer, and incus aka anvil) o Movement of these bones against the oval window (inner membrane) create pressure waves in the fluid in the canals of the cochlea (snail) which cause cilia to bend, producing signals o KNOW HOW TO LABEL THE EAR (FIGURE 44.6) o The middle ear is connected to the throat through the Eustachian tube (auditory tube) that equalizes the pressure between the middle ear and the external environment Transduction occurs in the cochlea: pressure waves go through the cochlea to the round window which causes the cochlear duct to vibrate o Basilar membrane: bottom of the cochlear duct, contains sensory hair cells with stereocilia that project into the overhanging tectorial membrane ; this whole system of hair cells & membranes is called the organ of Corti which resides in the cochlea o Frequency localization in the cochlea o Basilar membrane consists of elastic fibers varying in length and flexibility embedded in the gelatinous material o At the base (near oval window), the fibers are short & stiff, respond to high pitch o At the end (apex) of the cochlea, the fibers are 5x longer & 100x more flexible, respond to low pitch 1. Sound enters cochlea through oval window 2. Sound wave imparts the most energy to the part of the basilar membrane that matches the frequency (pitch) of the sound
TA: Victor Vinh ([email protected]) 3. Hair cell depolarization at the area w/ most energy is greatest & afferent neurons stimulated the most there 4. Brain interprets as pitch Range of hearing o Children: 20-20,000 Hz which decays w/ age o Dogs: up to 40,000 Hz o Efferent axons in hair cells can increase ability to concentrate on specific signals, ex. A voice in the crowd Echolocation: emit sounds & determine the time it takes for the sounds to return; sonar & radar do the same Detection of body position o Statocyst: ciliated hair cells in gelatinous membrane containing carbonate crystals; used for orientation in invertebrates o Vertebrates: utricle & saccule o Contain stereocilia and kincilium o Hair cells embedded in gelatin (otolith membrane) containing calcium carbonate crystals (otoliths) o
You've reached the end of your free preview.
Want to read all 3 pages?
- Summer '09