The Ear Parts, Functions and Hearing Process. MMHS Advanced Biomedical Science. Hearing Attributes. The senses of equilibrium and hearing are provided by the inner ear , a receptor complex located in the temporal bone of the skull.
Advanced Biomedical Science
The Ear provides input for 2 senses:
1. Equilibrium- which informs us of the position of the body in space by monitoring gravity, linear acceleration, and rotation.
2. Hearing- which enables us to detect and interpret sound waves.
The ear is divided into three anatomical regions:
External ear- is the visible portion of the ear.
Fnxn: collects and directs sound waves to the eardrum.
Parts of the External Ear:
Middle ear- is a chamber located in a thickened portion of the temporal bone,
Fnxn: collects and amplifies sound waves and
transmit them to a portion of the inner ear.
Parts of the Middle Ear:
Auditory ossicles- the bones of the middle ear.
Inner ear- concerned with hearing and equilibrium. Receives input from the middle ear.
Fnxn: contains the sensory organs responsible for equilibrium sensations.
Membranous labyrinth- contains the receptors
Bony labyrinth- is a shell of dense bone that surrounds and protects the membranous labyrinth.
Parts of the Inner Ear:
2. Semicircular canals- stimulated by rotation of the head or dynamic equilibrium.
3. Cochlea- provides the sensation of hearing.
Hair cells- line the inner ear, communicates with a sensory neuron by continually releasing small quantities of neurotransmitter.
Dynamic equilibrium- refers to when the head and body are moved suddenly.
Static equilibrium- maintains our posture and stability when the body is motionless.
1. Sound waves arrive at the tympanic membrane or eardrum
2. The vibration of the tympanum causes movement of the auditory ossicles.
3. The movement of the stapes at the oval window establishes pressure waves in the perilymphof the vestibular duct.
4. The pressure waves distort the basilar membrane on their way to the round window of the tympanic duct.
5. The vibration of the basilar membrane causes the vibration
of hair cells against the tectorial membrane.
6. Information about the region and intensity of stimulation is relayed to the CNS over the cochlear branch of the cranial nerve VIII.