special sense 2

Audition
process in which audible variations in air pressure (compressions) result in molecules to be displaced forward leaving a corresponding area of lower pressure.
Sound waves have 2 features:

Amplitude or intensity: peak to trough; perceived as differences in loudness

b. Frequency or pitch: number of compressions per second, its unit is hertz (1 cycle/second)
PHYSIOLOGICAL ANATOMY OF HEARING SYSTEM:
Hearing System divided into 4 parts (by function):
?Outer Ear
?Middle Ear
?Inner Ear
?Central Auditory Nervous System
External ear • It`s formed by:
-the auricle (or pinna), a funnel shaped outer ear made of skin and cartilage.
-the external auditory meatus, 2.5 cm tube.
-Functions:
-1- Collection of sound stimuli.
-2- Amplify sound pressure at the tympanic membrane.
- 3- Sound localization.
-4- Protective function: Wax, Keep air moist & warm.
Middle ear
? is air-filled cavity, contains:
1-the tympanic membrane
2-the auditory ossicles (malleus, incus, and stapes).
The stapes inserts into the oval window (membrane between the middle ear and the inner ear)
3- Two muscles;
-Tensor tympani muscle ,stiffens tympanic membrane
–Stapedius muscle, reduces extra-movement of stapes at oval window .
…. Contracts in response to loud sounds; (the Acoustic Reflex)