Problem 141 - Objective Biology for NEET

Question

Assertion: After hearing a sound, the nerve impulse passes from neurons to the brain. Reason: The neurons which pass nerve impulses from the body organ to the brain is called afferent neuron.

Step-by-Step Solution

Answer

Both the assertion and reason are correct, and the reason is a valid explanation of the assertion. The process after hearing a sound involves nerve impulse transmission from neurons (specifically afferent neurons) to the brain.

Step 1: Analyze the assertion

The assertion states that after hearing a sound, the nerve impulse passes from neurons to the brain. This is a correct statement as, in response to sound, nerve impulses are generated in the inner ear and then transmitted to the brain through neurons.

Step 2: Analyze the reason

The reason given is the neurons which pass nerve impulses from the body organ to the brain are called afferent neurons. This is also correct as afferent neurons, also known as sensory neurons, carry signals from the periphery of the body to the brain.

Step 3: Validate Assertion and Reason Link

Now, it's necessary to validate if the reason justifies the assertion. The assertion is a general statement about nerve impulse transmission, and the reason is a specification about the name of the type of neuron. The reason correctly justifies the assertion as it does provide the accurate type of neuron responsible for transmitting signals to the brain in response to a sound stimulus.

Key Concepts

Nerve Impulse Transmission

Nerve impulse transmission is a fascinating and crucial process that enables our bodies to respond to a variety of stimuli every day. It involves the movement of electrical signals between neurons, which are specialized cells designed for this remarkable task. When a nerve impulse is generated, it travels along the length of a neuron in a wave-like manner. These electrical signals, also known as action potentials, occur due to the movement of ions, primarily sodium (Na\(^+\)) and potassium (K\(^+\)), across the neuron's cell membrane.

The transmission begins at the neuron's dendrites, which receive a signal from a neighboring cell or sensory organ. This signal triggers a change in electrical charge, leading to the opening of ion channels and initiating the action potential. The impulse travels along the axon, which is often insulated by a myelin sheath that speeds up the transmission process. Finally, when the impulse reaches the axon terminal, it causes the release of neurotransmitters into the synaptic cleft, allowing the signal to be passed to the next neuron or a target cell, such as a muscle or gland. This process is essential for effective communication within the nervous system.

Sensory Neurons

Sensory neurons, also known as afferent neurons, are a vital component of the nervous system. These specialized cells are responsible for converting external stimuli into nerve impulses that can be comprehended by the brain. Each sensory neuron is equipped to detect specific types of stimuli, such as light, sound, touch, or chemical signals.

When a sensory neuron encounters a stimulus, it responds by generating an electrical signal. This signal travels along the neuron's axon toward the central nervous system, often culminating at the brain, where it is interpreted and processed. This processing enables the brain to formulate an appropriate response to the sensation, whether it be moving away from a hot surface or comprehending a musical note.

Sensory neurons play a crucial role in maintaining the body's homeostasis by providing the brain with constant feedback about the environment. They have distinct structures depending on their function, but are collectively key players in experiencing and reacting to the physical world.

Sound Stimulus Response

The response to a sound stimulus involves a series of complex and coordinated processes that begin at the ear and end in the brain. When a sound wave reaches the ear, it first encounters the outer ear and is funneled through the ear canal to the eardrum, causing it to vibrate. These vibrations are then transmitted to the tiny bones in the middle ear known as the ossicles, which amplify the sound and pass it on to the cochlea in the inner ear.

Inside the cochlea, which is filled with fluid, the sound vibrations create waves that move through the fluid, bending tiny hair cells within the cochlea. These hair cells convert the mechanical vibrations into electrical signals. These signals then travel on afferent pathways via the auditory nerve to the brain's auditory cortex. This area of the brain processes and interprets the sound, allowing us to understand and react to auditory stimuli.

Such mechanisms enable us to detect diverse sound characteristics like pitch, volume, and direction, which are vital for communication, music perception, and even alerting us to danger.