The Ear, Hearing and Balance Upper Sixth Biology

Aims By the end of the lesson you should understand The anatomy of the ear How the ear facilitates hearing How the ear facilitates balance

utriculus sacculus

Hearing Vibrations are transmitted in the air into the middle ear, along the bones (amplification) Fluid filled cochlea, makes hairs vibrate Hair cells have a resting potential Vibration ->release of neurotransmitter Depolarisation of endings of the nerve cells of the cochlea nerve -> Brain

Hearing - Pitch How high or how low High pitched sounds are detected by area closest to the middle ear Low pitched sounds Furthest away Also use differences in frequency to discriminate Ability is lost with age 20Hz to Hz -> 8000Hz

Hearing- Loudness Based on the amplitude of the wave Louder= Bigger amplitude Bigger amplitude= more action potentials= louder sound Some hair cells only respond if the sound is very loud Direction…two ears comparing timing and loudness of stimuli

Ear and Balance Receptor cells in the semi circular canals the utriculus and the succulus Macula, otoliths and hair cells Otoliths sensitive to gravity…opens Na channels

Ear and Balance Changes in position of the head will change the direction the hairs, change the pattern of firing Utriculus- hair cells lie in horizontal plane- sense when we are upright Sacculus vertical –sense when we are lying down

Balance –The semi circular canals Filled with viscous fluid Swelling at the end called the ampulla Hairs embedded in the Cupula Movement, lag, moves the cupula, bends the hairs, depolarisation Information sent from all 3 SSC in vestibular nerve