Unit 2: Nervous System

Hearing Notes

(1) Ear Design

• Ear is like a well designed funnel.

• Sound waves spiral down into auditory canal.

• Sound Waves smack against ear drum (tympanic membrane).

(2) Vibrations

• Sound Waves Tympanic Membrane– Eardrum literally like the leather on a drum

• T-Membrane Hammer Anvil Stirrup– Hammer, Anvil and Stirrup are very small bones

in inner ear

• Stirrup Oval Window Inner Ear Fluid

(3) Cochlea

• Cochlea = Snail like structure in inner Ear.

• Contains Organ of Corti:– Contains hearing receptors / hair cells– Hair cells stimulated by movement of Inner Ear Fluid

• Basilar Membrane– Type of membrane on specific receptors– Responds to changes in pitch

• Fluid Receptors Cochlear Nerve Brain

(4) Equilibrium & Balance

• Your ears keep track of your body’s position.

• Equilibrium receptors lie within the inner ear of your ears (Vestibular Apparati).

• 2 Types of Equilibrium:– Static– Dynamic

(5) Static Equilibrium

• Head Balance

• Static Receptors = Maculae:– On top of maculae lies the otolithic membrane

(gel-like)– Head Moves Otoliths Moves!– Movement of Otolithic Receptor Impulse to

Vestibular Nerve & Brain

• Tells your brain when your head is not upright.

(6) Dynamic Equilibrium

• Rotation & Angles of Head

• Semicircular Canals of Cochlea:– Contain receptors = Crista Ampullari– Crista Ampullari contain receptor hairs,

endolymph fluid and a capula cap– Body Movement endolymph movement

Push on Capula Cap Receptor Hairs Vestibular Nerve & Brain

http://www.youtube.com/watch?v=vTiGskc1o48

(7) Motion Sickness

• Inefficient dynamic equilibrium…– Semicircular Canals either too sensitive or too

slow at sending messages

• Too many visual messages

• Too many inner ear messages

• Visual conflicts with Inner Ear

• Unique to each individual

(8) Deafness

• Deaf = Any hearing loss

• Types:– Conduction– Sensorineural

(9) Conduction Deafness

• Something Blocks Tympanic Membrane

• Sound Waves cannot reach Ear Drum + Inner Ear

• Causes:– Ear Wax– Ruptured Ear Drum– Injured Hammer, Anvil and/or Stirrup

• Usually Temporary, Solved by Surgery

(10) Sensorineural Deafness

• Damage to actual parts of ears:– Receptor Cells– Cochlea– Vestibular Nerve

• Can be hereditary, damage from disease/virus, damage from loud noises

• Often permanent