Sound Detection and Auditory Pathways

Flashcards based on lecture notes about sound detection and auditory pathways.

Sound

A pressure disturbance (alternating areas of high and low pressure) produced by a vibrating object and propagated by molecules of the medium (air).

Compression

Area of high pressure due to compression of molecules together when air molecules are displaced by object movement.

Rarefaction

Area of low pressure due to presence of fewer air molecules when an object returns to its original position.

Frequency

Number of waves that pass a given point in a given time; perceived as pitch.

Amplitude

Height of wave crests; perceived as loudness.

Hearing

Reception of an air sound wave that is converted to a fluid wave that ultimately stimulates mechanosensitive cochlear hair cells that send impulses to the brain for interpretation.

Tympanic Membrane

Vibrates due to sound waves.

Auditory Ossicles

Vibrate and amplify pressure.

Helicotrema

Structure through which sounds with frequencies below hearing travel.

Hair cells

Move with the basilar membrane when it vibrates.

Stereocilia

Microvilli that make up the 'hairs' on hair cells.

Tip links

Fibers connecting stereocilia to mechanically gated ion channels.

Resonance

Movement of different areas of basilar membrane in response to a particular frequency.

Outer hair cells

Convey messages from the brain to the ear; change stiffness of basilar membrane.

Functions of outer hair cells

Fine tuning responsiveness of inner hair cells. Protect inner hair cells from loud noises.

Perception of pitch

Sound waves of different frequencies activate hair cells in different positions along the length of the basilar membrane; impulses from specific hair cells are interpreted as specific pitches.

Detection of loudness

Larger movements of the tympanic membrane/auditory ossicles/oval window and pressure waves of greater amplitude in the fluids of the cochlea which lead to larger graded potentials.

Localization of sound

Depends on relative intensity and relative timing of sound waves reaching both ears.