1 Biology 2204: Human Physiology for Nursing Lab Exam 2 STUDY GUIDE 2019 LAB 5: PHYSIOLOGY OF THE EAR The ordered sequence of events involved in the mechanism of hearing. 1. Sound waves pass through the external auditory canal. 2. Hit the tympanic membrane - causing the membrane to vibrate with the same frequency and amplitude as the waves. 3. Malleus (lateral ossicle/hammer), is in contact with the tympanic membrane, it also begins vibrate 4. Vibrating malleus makes the incus (middle ossicles/anvil) vibrate, which in turn makes the stapes (medial ossicles/stirrup) vibrate. 5. Medial side of the stapes vibrates the oval window (membrane covering the opening into the cochlea). The perilymph fluid on the opposite side of the oval window forms pressure waves within the scala vestibuli of the cochlea. *** Basically, vibration of the tympanic membrane leads to vibration of the three ossicles, which in turn leads to creation of pressure waves in perilymph in the cochlea. Therefore, the ossicles have formed a lever system that transmit the vibrations from the outer to the inner ear. 6. Inaudible sounds cause pressure waves in the perilymph that move along the scala vestibuli through the helicotrema and along the scala tympani. The Organ of Corti is not activated. Audible sounds cause movement of the perilymph within the scala vestibuli, which causes movement of the vestibular membrane (separating the scala vestibuli from the cochlear duct). Vestibule membrane movement causes endolymph movement in the cochlear duct, which propagates down the basilar membrane. 7. Movement of the basilar membrane causes movement of the hair cells of the organ of Corti. 8. These hair cells generate electrical potential, and stimulate the sensory nerves of the cochlear division of the vestibulucochlear nerve (located at the base of the hair cells)
9. Pressure wave force is dissipated into the tympanic cavities through the movement of the round window. Identify the structures involved in the mechanism of hearing; know the role of each structure. External auditory canal Tympanic membrane Malleus Incus Stapes Oval window Cochlea Perilymph Scala vestibuli Helicotrema Scala tympani Organ of corti Vestibular membrane Cochlear duct Endolymph Basilar membrane Tectorial membrane Stereocilia Cochlear division Vestibulocochlear nerve Primary auditory complex Temporal lobe Round window
Hearing, or audition, is the transduction of sound waves into a neural signal that is made possible by the structures of the ear. The large, fleshy structure on the lateral aspect of the head is known as the auricle. Some sources will also refer to this structure as the pinna, though that term is more appropriate for a structure that can be moved, such as the external ear of a cat.
- Summer '20
- oval window, scala tympani, scala vestibuli