Hearing. By: Jimmy, Dana, and Karissa

Transcription

1 Hearing By: Jimmy, Dana, and Karissa

2 Anatomy - The ear is divided up into three parts - Sound enters in through the outer ear and passes into the middle where the vibrations are received and sent to the inner ear

3 Outer ear - Consists of external pinna (auricle) and the auditory canal - Collect sound waves and channel them to the Tympanic membrane (eardrum) - Tympanic membrane absorbs the vibrations and transfers them to the middle ear bones

4 Middle ear Consists of 3 small bones (ossicles) - Malleus (hammer) - Incus (anvil) -Stapes (stirrup) - The vibrations are transmitted from the tympanic membrane to these bones to the oval window - Membrane beneath the stapes - Middle ear also opens up to the eustachian tube - Connects the middle ear to the pharynx and equalizes pressure between the middle ear and the atmosphere

5 Inner ear - Consists of fluid filled chambers including the semicircular canals which function in equilibrium - Cochlea - a bony chamber involved in hearing - Looks like a snail - 2 large canals - upper vestibular canal and lower tympanic canal - Contains the organ of corti

6 Organ of Corti - Contains mechanoreceptors of the ear - Hair cells with hairs projecting into the cochlear duct - The floor of the cochlear duct, the basilar membrane, will vibrate due to sound waves - Results in the bending of the hairs and depolarization of the hair cells in the tectorial membrane - Tectorial membrane- hangs over the Organ of Corti

7 Hair cells - Each hair cell has a bundle of rod-shaped hairs containing a core of actin filaments - When the basilar membrane vibrates from sound waves the hairs are lowered or raised and bend in the tectorial membrane and surrounding fluid - When the hairs are bent it activates the mechanoreceptors and the membrane potential of the hair cell is changed

8 Equilibrium from the ear - Semicircular canals provide information about orientation to the brain to help maintain balance - The utricle and saccule allow us to perceive position with respect to gravity or linear movement - Each has hair cells that project into gel-like material that contains otoliths or small calcium carbonate particles ( ear stones ) - For example when you tilt your head the otoliths press on the hairs and this results in a change to the output of sensory neurons - Signals to your brain that your head is at an angle - Also involved in acceleration

9 Physiology Hearing process 6 basic steps Sound waves enter the external acoustic canal and travel toward the tympanic membrane. The tympanic membrane provides a surface for the collection of sound and it vibrates in resonance, as do the malleus and through their articulations, the incus and stapes. The sound is amplified. Movement of stapes at the oval window establishes pressure waves in the perilymph of the vestibular duct. Stapes have a In-Out movement, when stapes move inward, the round window bulges outward, into the middle ear cavity. This vibrates the frequency of the sound arriving at the tympanic membrane, it creates pressure waves within the perilymph.

10 Physiology The pressure waves travel through the perilymph of the vestibular and tympanic ducts to reach the round window.with this the waves distort the basilar membrane. Information about frequency is translated into information about position along the basilar membrane. Vibration of the Basilar Membrane causes vibration of hair cells against tectorial membrane. Which leads to the displacement of the stereocilia, which in turn opens ion channels in the hair cell membranes. The resulting inrush of ions depolarizes the hair cells, leading to the release of neurotransmitters and thus to the stimulation of sensory neurons. Information about the region and intensity of stimulation is relayed on the CNS over the cochlear branch of the vestibulocochlear nerve(viii). The information is carried by the cochlear branch of cranial nerve VIII to the cochlear nuclei of the medulla oblongata for subsequent distribution to other centers in the brain.

11

12 Homeostatic Imbalances Auditory Processing Disorder Conductive Hearing Loss Sensorineural Hearing Loss Mixed Hearing Loss

13 Conductive Hearing Loss Outer or Middle Ear Earwax, infections, punctured eardrum, fluids, or otosclerosis Surgery, Hearing aids, and bone anchored hearing devices

14 Sensorineural Hearing Loss Cochlea or Auditory nerve malfunction Permanent Genetic, old age, disease, loud noises, or accidents Hearing aids and implants

15 Video

16 Work Cited Fundamentals of Anatomy and Physiology Seventh Edition, Frederic H. Martini Campbell Biology Ninth Edition, Reece, Urry, Cain, Wasserman, Minorsky, Jackson,