2 Physiology of hearingOuter ear (auricle): collects, directs sound into the external auditory canal.Ear wax and hairs keep foreign objects out.2. Eardrum (tympanic membrane) vibrates when sound reaches it
4 Middle ear Small, air-filled cavity 3. Malleus, incus, & stapes transmit vibrations to the oval windowEustachian tube connects to the throat – helps equalize pressure
5 Inner ear: Cochlea 4. Cochlea Fluid-filled organ Pressure waves in the fluid cause hair cells to vibrate5. Round window bulges outward6. Bending hairs release impulses to the VIII nerve to auditory center in brain.
6 Inner ear: semicircular canals Canals and vestibule are the organs of equilibrium and balance.Cristae: hair cells in s.c. canals detect position of the head and linear acceleration
7 3 canals lie at right angles Rotation of the head/body bends hairs, which send an electrical signal to the brain.
8 Equilibrium pathways Impulses reach the medulla or cerebellum. Messages are sent to regions that control eye, head, and neck movementsCerebellum adjusts signals from the motor cortex to maintain equilibrium.