i) Human nervous system is differentiated into central nervous system (CNS), peripheral nervous system (PNS) and autonomic nervous system (ANS).
ii) The CNS acts as centre for information processing and control. It consists of the brain and the spinal cord. The PNS is made up of the nerves which connect the brain and spinal cord to all parts of the body. The ANS is formed of sympathetic and parasympathetic nerves.

Sympathetic nerrous and para sympathetic nerrous system are the two components of autonomic nervous system.

Electroencephalogram (EEG) is an instrument which records the electrical impulses of brain. An EEG can detect abnormalities in the brain waves and help in diagnoses of seizures, epilepsy, brain tumors, head injuries, etc.

Frontal lobe, parietal lobe, temporal lobe and occipital lobe.

Neurotransmitters are the chemicals which allow the transmission of nerve impulse from the axon terminal of one neuron to the dendron of another neuron or to an effector organ. eg. Acetylholine.

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

Conditional reflexes are the result of practice and learning. Playing harmonium by striking a particular key on seeing a music note is an example of conditioned reflex which requires conscious training effort.

Hind brain is formed of three parts (1) cerebellum, (2) pons and (3) medulla oblongata.

Sudden quick action in response to something occurring in environment is known as reflex action.
(i) Reflex action is a rapid, automatic response to a stimulus, which is not under the voluntary control of the brain, i.e. it is an involuntary action.
(ii) It is a simple form of behaviour in which the same stimulus produces the same response every time, e.g.
(i) if we unknowingly touch a hot plate, we immediately move our hand away from it.
(ii) moving our foot away on stepping something sharp.

When we are pricked by a cactus, the sensory neurons are activated immediately. They take the message to the brain or spinal cord. The message given by the brain or spinal cord is brought back by the Motor neuron. The motor neuron carries the message to the hand muscles. We immediately pull our hand away from the cactus.