3) What is the path of a sound wave moving through the ear until the hair cells

Question

3) What is the path of a sound wave moving through the ear until the hair cells on the basilar membrane vibrate? What structures transmit the sound waves? What is the purpose of each of these structures?

4) a) What is the path of the spinal reflex through the spinal cord? Through which spinal root does the axon of the afferent neuron travel?
b) Where is the cell body of the afferent neuron?
c) Where would the afferent neuron form a synapse with the cell body or dendrites of a cell interneuron?
d) Where is the cell body of the efferent neuron?
e) Through which spinal root does the axon of the efferent neuron travel?

Explanation / Answer

Ans3. The path of sound wave waving through the ear until the hair cells on the basilar membrane vibrate as the sound waves enter the ear then it travels through the outer ear also having external auditory canal where it strike with ear drum and results in vibration. The central part of the eardrum is connected to a small bone of a middle ear called as malleus and when malleus vibrates then sound waves transmit s to another two bones known as incus and stapes. As the stapes vibrate then it moves the structure oval window in and out. After that this action is passed on to the cochlea; it is filled with fluid and looking as snail like structure having a receptor organ of hearing i.e organ of corti. The organ of corti consists of hair cells present on basilar membrane which translate fluid vibration of sound from its surrounding ducts into electrical impulses that are carried to brain by sensory nerve.

The bones present in middle ear malleus, incus and stapes and organ of corti present in cochlea transmits the sound waves. These 3 bones malleus, incus and stapes work as a piston and couple the vibration of tympanic membrane to the oval window.

The organ of corti is sound receptor organ of hearing present in cochlea and its function is to transduce auditory signals and minimise the hair cell extraction of sound energy.

Ans4.a) The path of spinal reflex through the spinal cord as a reflex arc is a neural pathway that control a reflex .

In this case most of the sensory neurons do not directly pass through the brain but synapse in the spinal cord. This allows the faster reflex action by somatic motor nerve and without the delay of routing signal through the brain. The brain will receive a sensory input while the reflex is being carried out and analysis of signal takes place after the reflex action. There are of 2 types autonomic and somatic reflex arc.

During somatic reflex nerve signal travel along the pathway as somatic receptor travels along skin, muscles and tendons.

Afferent nerve fiber carry signals from somatic receptor to the posterior horn of spinal cord.

Integrating center is the point at which neuron consists of gray matter of spinal cord.

Efferent nerve fiber that carry motor nerve signal from anterior horn to muscles.

Effector muscle innervated by efferent nerve fiber carries out the response.

The axon of afferent neuron travel from ganglion to ganglion and lead back to spinal cord.

Ans4.b)The cell body of the afferent neuron are located in ganglia of peripheral nervous system.

Ans4.c) The afferent neuron form a synapse with the cell body or dendrites of a cell interneuron as majority of these having a unipolar axon so they don't form any synapse having a single axon so leave the cell body and sent towards the sensory organ.

Ans4.d) Efferent neuron is located in peripheral nervous system but their cell body originates in central nervous system.

Ans 4.e) The axon of the efferent neuron travel as it carry motor nerve signal from anterior horn to muscles.

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