:- Question 1 :- Main Organs of Nervous system :- We can divide the whole nervous system in Two Parts 1⟩ Central Nervous System ( C.N.S ) 2⟩ Peripheral Nervous System ( P.N.S ) Now we can Further divide them into :- CNS :- (i) Brain → It is the swollen END of CNS made up of billions of nervous tissues. It controls the main FEATURES of the BODY such thinking , Controlling actions...etc. (ii) Spinal Cord → It is long structure extending below the brain . It is also made up of many nervous tissues . It perform reflex action and also work as a signal transporter from sensory organs to brain . PNS :- (i) Sensory Organs → These organs are responsible for the sensing the stimulus from the surroundings.(ii) Nerves → They transfer the stimulus from sensory organs to CNSOr there are Four main Organs (i) Brain (ii) Spinal Cord(iii) Sensory Organs(iv) NervesQuestion 2 :- Spinal Cord is protected by the Spine or a structure with vertebrae . Vertebrae is bony structure separated by DISKS which act as the shock absorber. Question 3 :- Fusion of egg with a sperm is called FERTILIZATION . It further results into the formation of zygote. Now by further division of zygote the formation of Embryo takes place.