Question 1

Question 3Describe the human central nervous system along with its parts and functions.

Accepted Answer

The central nervous system consists of the brain and the spinal cord. It is the control centre for all body functions. It is the site for all information processing in the body. It is responsible for processing every sensation and thought a human being experiences. It has two parts — Brain and Spinal Cord.Brain — The Brain is the main control centre of the nervous system situated in the cranium of the skull. It controls our thinking, feelings, movement and senses. It has three parts — Cerebrum, Cerebellum and Medulla oblongata.Cerebrum — The cerebrum is the uppermost, largest and the most prominent part of the brain. It is responsible for the sensation of pain, temperature, touch, sight, sound, taste and smell. It also controls mental activities such as memory, intelligence, thinking and reasoning.Cerebellum — The cerebellum is a small, egg-shaped lobe located at the base under the cerebrum. It helps in the muscle coordination and balance of the body.Medulla oblongata — The Medulla oblongata is the lowermost part of the brain located at the base of the skull. It controls breathing, heartbeat, coughing, sneezing and other involuntary functions.Spinal cord — The spinal cord is the continuation of the medulla oblongata of the brain. It is like a cord that emerges from a hole at the base of the skull and runs through the vertebral column. The spinal cord conducts reflexes below the neck. It conducts sensory impulses from the skin and muscles to the brain. It conducts motor responses from the brain to the muscles of the trunk and limbs.

Question 2

Question 4What is reflex action? Explain the reflex arc with the help of an example.

Accepted Answer

An automatic, spontaneous and mechanical response to a stimulus controlled by the spinal cord without the involvement of the brain is called a reflex action.The path that an impulse takes in a reflex action is called a reflex arc. The reflex arc involves three neurons — sensory neurons, association neurons and motor neurons.If we touch a hot object, a stimulus triggers an impulse in a receptor on the skin.The impulse then travels from the receptor through a sensory neuron to the spinal cord.In the spinal cord, it passes through an association neuron to a motor neuron and finally reaches the muscles.The muscles of the effector organ contract moving it away from the hot object.Below flow chart shows a simple reflex action of immediate withdrawal of hand on touching a hot object:

Question 3

Question 6Write the function of the cerebrospinal fluid.

Accepted Answer

The functions of the cerebrospinal fluid are:It nourishes the brain.It protects the brain from shocks by absorbing them.

Question 4

Question 8Give two examples of reflex actions.

Accepted Answer

Two examples of reflex actions are:Blinking of eyes when a foreign particle enters the eye.Immediate withdrawal of hand if you unknowingly touch a hot object.

Question 5

Question 1sensory nerves and mixed nerves.

Accepted Answer

Sl.No.Sensory NervesMixed Nerves1.Sensory nerves are the nerves that carry messages from the sense organs to either the spinal cord or the brain.Mixed nerves perform the function of both sensory nerves and motor nerves. They transmit messages from the central nervous system to the muscles of the body.2.They contain only sensory fibres.They contain sensory fibres as well as motor fibres.3.For example, the optic nerve that sends messages from the eye to the brain is a sensory nerve.For example, the nerve that transmits messages to the tongue is a mixed nerve.

Question 6

Question 5brain and spinal cord

Accepted Answer

Sl.No.BrainSpinal Cord1.The brain is the main control centre of the nervous system.The spinal cord is the continuation of the medulla oblongata of the brain.2.It is situated in the cranium of the skull.It runs through the vertebral column.3.It controls your thinking, feeling, movement and senses.It conducts reflexes below the neck.

Question 7

Question 2The diagram shows a reflex arc. Study it and answer the following questions.Name the parts numbered a to d.Using the letters of alphabet shown in the diagram, indicate the direction in which the impulse enters and leaves part c. X to Y or Y to X?What is reflex action?With the help of a flow chart, show a simple reflex action.

Accepted Answer

The parts numbered a to d are:a → sensory neuronsb → motor neuronsc → association neuronsd → cell body of motor neuronsThe impulse enters through X and leaves through Y.An automatic, spontaneous and mechanical response to a stimulus; controlled by the spinal cord without the involvement of the brain is called a reflex action.Below flow chart shows a simple reflex action of immediate withdrawal of hand on touching a hot object:

Question 8

Question 7Breathing and heartbeat are controlled by thecerebellumcerebrummedullanerve cells

Accepted Answer

medullaReason — The medulla oblongata controls involuntary actions of the body like breathing, heartbeat, coughing, sneezing, etc.

Question 9

Question 9Reflex actions are the actions controlled bybrainspinal cordboth brain and spinal cordneither brain nor spinal cord

Accepted Answer

spinal cordReason — Reflex actions are the actions controlled by spinal cord.

Question 10

Question 10The peripheral nervous system transmits messages to and from the sense organs and is responsible forinvoluntary actionsreflex actionsautonomic actionsvoluntary actions

Accepted Answer

voluntary actionsReason — Peripheral nervous system is responsible for voluntary actions such as cycling, swimming, etc.

Nervous System in Humans

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