Rani did not wear a helmet. Some people wear a helmet but don't fasten the strap. When they fall down from the bike, the helmet falls off and they are injured. Thus a helmet worn properly can save lives.

(i) All the information from the environment ate detected by the receptors located in our sense organs such as the eyes, the nose, the skin etc.
(ii) Information from the receptors is transmitted as electrical impulse and is received by the dendritic tips of the neuron.
(iii) This impulse travels from the dendrite to the cell body and then along the axon to its terminal end
(iv) On reaching the axonal end, it causes the nerve endings to release a chemical (neurotransmitter) which diffuses across a synapse and starts a similar electrical impulse in the dendrites of the next neuron, then to their cell body to be carried along the axon.
(v) In this way, the electrical signal reaches the brain or spinal cord. The response from brain (or spinal cord) is similarly passed on to the effector organs such as the muscle or gland cell, that undergoes the desired response.
(vi) The flow of nerve impulses from axonal end of one neuron to dendrite of another neuron through a synapse is called synaptic transmission.
(vii) Neurotransmitters are the chemicals which allow the transmission of nerve impulse.
(viii) The important neurotransmitter released by neurons is called Acetylcholine.

(i) If someone pricks our hand with a needle, a reflex action occurs in one body that makes our hand to withdraw immediately without our consciousness
(ii) The stimulus is the pain which is sensed by receptors in our hand. This stimulus in turn triggers an impulse in sensory neuron.
(iii) The sensory neuron. transmits or conveys the message to the spinal cord.
(iv) Spinal cord interprets the stimulus and the impulse is passed on to the relay neuron which in turn transmits it to a motor neuron.
(v) Motor neurons carry command from spinal cord to our arm.
(vi) Muscle in our arm contracts and we withdraw our hand immediately from the pan.
(vii) In this example, muscle is an effector organ which has responded to the pain.

A human brain is formed of three main parts:
(a) forebrain
(b) midbrain and
(c) hindbrain.
(1) Forebrain:
A. Cerebrum(cortex)
B. Diencephalon
i) Thalamus ii) Hypothalamus
(2) Midbrain
(3) Hindbrain:
A. Cerebellum
B. Pons
C. Medulla Oblongata

Peripheral nervous system is formed by the nerves arising from the brain and the spinal cord. The nerves arising from the brain are called cranial nerves. Nerves arising from spinal cord are called spinal nerves. In man, there are 12 pairs of cranial nerves and 31 pairs of spinal nerves.

Outer Duramater, Middle Arachnoid and Inner Piamater.

A neuron typically consists of three basic parts: cyton, dendrites and axon.

Neuroglia: Neuroglia are also called as glial cells. They are the non-exciting, supporting cell of the nervous system. They do not initiate or conduct nerve impulse.

(i) Spinal cord.
(ii) Central canal.
31 pairs of nerves are produced from spinal cord.