MGSLG. (2020). Module 4 Unit 2
Hearing and balance functions in the human ear
Functioning
of the human ear - path of sound:
Sound
waves move from the vibrating source (for example, a person talking or a car
driving past) in horizontal waves. Humans hear sounds with a vibration
frequency of between 16 and 20 000 Hz.
|
Part of ear |
Function during hearing process |
|
Pinna |
Traps the sound waves and directs them into the auditory canal |
|
Tympanic membrane (ear drum) |
Vibrates to the frequency of the sound waves and transmits the vibration to the ossicles in the middle ear |
|
Ossicles |
|
|
Oval window |
Vibrates and causes pressure wave movements in the liquid of the perilymph in the inner ear to the endolymph inside the cochlea |
|
Cochlea |
These vibrations cause the sensory cells in the Organ of Corti (the mechanoreceptors) to brush or bend against the membranes converting the stimulus into an impulse |
|
Auditory nerve |
Transmits the impulse to the cerebrum where the sensation of sound is perceived and interpreted |
|
Round window |
Excess vibrations are passed out through the round window, to prevent pressure and echoes |
The pathway of sound through the ear:
Balance
and equilibrium:
The human
ear is responsible for maintaining balance.
- The semi-circular canals each have a swelling called the ampulla. The ampulla contains fine sensory hair cells called crista. When there is a change in speed or direction, the cristae are stimulated and a nerve impulse is discharged. This impulse is transmitted along the auditory nerve to the cerebellum where it is interpreted. The cerebellum will send impulses to the muscles, to restore balance
- The sacculus and utriculus contain sensory hair cells called maculae. When the head position changes, the pull of gravity stimulates the maculae, which convert the stimulus into an impulse, transmitted along the auditory nerve to the cerebellum where it is interpreted. The cerebellum will send impulses to the muscles, to restore balance.
