2a) Hair cells transduce sound waves into action potentials via mechanoreception

Question

2a) Hair cells transduce sound waves into action potentials via mechanoreception. They communicate intensity of sound (loudness) because they fire more action potentials when the stimulus is louder; however, they are not able to transduce information regarding the location of the sound in the environment. How is location of sound determined in the brain?

b) Describe the receptive field for a hair cell (hint, what makes a given hair cell fire an action potential?). What is the main characteristic of the basilar membrane that determines the specific receptive field for an individual hair cell?  

Explanation / Answer

Hi,

The sound localization is a combined work of shape of the ear and calculation of time and angle of sound wave. The sound localization is possible because we use plenty of multiple monaural and binaural cues.
The horizontal dimension ( judging whether the sound originated from right or left of the brain): If a sound reaches the right ear earlier than the left ear, then the sound is originated from right hemifield.
The vertical dimension is localized by detecting the changes in the sound spectrum generated by the pinna. The smaller the pinae, higher is the frequency.

The resting membrane potential of hair cellis about -50mV. When a sound wave hits the ear, it moves the basilar membraneup or down. The stereocilia of the hair cell bend and this opens up the K channels. THe hair depolarizes and hyperolarizes. THis releases the neurotransmitters. THe probability of action potentialis increased by glutamate vascles in the postsynaptic spiral ganglion cell. The number fof action potential fired per cycle is > increase in the amplitude of the stmulus.

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