Nervous System in Animals – Long Answer Questions (CBSE Class 10)

Medium (Application & Explanation)

Q1. Explain the structure and function of the central and peripheral nervous systems in animals.

Answer:
The nervous system in animals is divided into the Central Nervous System (CNS) and the Peripheral Nervous System (PNS). The CNS includes the brain and spinal cord, which act as control centers. The brain analyzes signals, controls memory, emotions, and decision making. The spinal cord carries messages to and from the brain and the rest of the body. The PNS consists of nerves that branch out from the CNS and reach all parts of the body. The PNS also has the somatic system for voluntary movements (like moving your hand) and the autonomic system for involuntary activities (like heartbeat and digestion). Together, they help animals respond to their environment and maintain body functions.

Q2. Describe the structure of a neuron with the help of a labeled diagram. Explain why myelin sheath is important.

Answer:
A neuron has three main parts:

The cell body (soma) contains the nucleus and controls cell activities.
Dendrites are short branches that receive signals from other cells.
The axon is a long, thin fiber that carries impulses away from the cell body.
At the end, the axon has axon terminals to communicate with other neurons or muscles.

The myelin sheath is a fatty layer wrapped around some axons. It acts as an insulator, allowing electrical signals to travel much faster along the axon. This helps quick responses, which is vital for animal survival.
[Include a clear labeled drawing of neuron showing cell body, dendrites, axon, myelin sheath, axon terminals]

Q3. Explain the steps involved in the transmission of a nerve impulse along a neuron.

Answer:
Transmission of a nerve impulse happens in a series of steps:

At rest, a neuron has a resting potential (inside negative).
When a stimulus arrives, sodium ions enter the neuron, reversing the charge at that spot (action potential).
This change in charge travels down the axon like a wave.
The myelin sheath (if present) speeds up this movement, as impulses "jump" between gaps called nodes of Ranvier.
The impulse finally reaches the axon terminals, ready to pass to the next cell.
This process allows quick and organized responses across the animal’s body.

Q4. Differentiate between sensory, motor, and interneurons using examples from animals.

Answer:
Sensory neurons carry messages from sense organs to the CNS. For example, when a fish senses cold water, the sensory neurons carry this message to its brain.
Motor neurons carry commands from the CNS to muscles or glands. For example, in a dog, motor neurons tell the leg muscles to jump.
Interneurons connect sensory and motor neurons, only found in the CNS. They decide how to respond. For example, in a reflex, interneurons in the spinal cord quickly connect sensory input to the right motor output, such as withdrawing a hand from a prick.

Q5. Give an example of a reflex action in animals and explain how the nervous system carries it out.

Answer:
An example is the withdrawal reflex when a person touches something sharp.

Sensory neurons in the skin detect pain and send signals to the spinal cord.
An interneuron in the spinal cord processes this information.
The interneuron passes the message to a motor neuron.
The motor neuron sends a signal to the muscles of the arm to pull away.
This quick reaction happens without the brain’s involvement at first, making reflex actions fast and automatic. This helps animals respond instantly to danger.

High Complexity (Analysis & Scenario-Based)

Q6. Imagine a situation where the myelin sheath of neurons is damaged in an animal. Predict and explain the consequences on nerve impulse transmission.

Answer:
If the myelin sheath is damaged, the neuron’s axon loses its insulation. Normally, myelin speeds up the transmission of impulses. Without it, impulses travel much slower or may not travel at all. This can lead to weaker or delayed responses. For example, in animals, muscle movements may become slower or uncoordinated. In severe cases, the animal might lose balance, not react to danger quickly, or show poor muscle control. Diseases like multiple sclerosis in humans show similar symptoms because of myelin damage.

Q7. Analyse how the nervous system coordinates both voluntary and involuntary actions in animals, providing suitable examples.

Answer:
The nervous system manages voluntary actions through the somatic system. For instance, when a cat chooses to chase a ball, its brain plans and sends signals to muscles via motor neurons.
Involuntary actions are controlled by the autonomic system (a part of PNS). For example, the heart beating faster when a rabbit gets scared is involuntary—controlled without conscious thought. In both cases, the CNS (brain and spinal cord) processes information, and the PNS carries out the necessary action. This dual control ensures survival, allowing animals to make conscious choices and keep essential processes running automatically.

Q8. Evaluate the adaptive significance of reflex actions in animals with at least two different examples.

Answer:
Reflex actions allow animals to respond instantly to danger without waiting for the brain to process information. For example, a frog’s leg withdraws automatically when touched by something hot, protecting it from injury. In earthworms, touching the front end causes quick contraction so it moves away from the stimulus. These rapid actions increase the animal’s chance of survival by minimizing the damage from threats in their environment, such as predators or harmful substances.

Q9. Suppose the synapse between two neurons does not function properly. How would it affect the nervous system’s ability to coordinate responses in animals? Give reasons.

Answer:
The synapse is the gap between neurons where neurotransmitters pass signals chemically. If the synapse fails, neurotransmitters cannot be released or received properly. As a result, the signal will not pass to the next neuron or muscle. This means the chain of communication breaks down. In animals, this may cause muscles not to move when they get a signal, delayed reflexes, or no sense responses (like not feeling pain or touch). Overall, poor synaptic function leads to slow or failed reactions, affecting the animal’s survival.

Q10. Consider an aquatic animal like a fish, which must constantly respond to the movement of water. Analyse how its nervous system enables it to survive in such an environment.

Answer:
A fish’s nervous system is adapted for quick sensing and response. Sensory neurons detect changes in water pressure, movement, and vibrations using structures called lateral lines along their bodies. This information is sent to the brain for processing. The brain then rapidly sends messages via motor neurons to muscles for fast swimming or turning away from predators. By quickly interpreting and reacting to the environment, the fish avoids danger and catches food efficiently. This rapid coordination through the nervous system is crucial for surviving in ever-changing aquatic surroundings.