ICSE Class 10 Answered

1. The nerve impulse flows in only one direction, i.e., from the dendrites, then to the cell body and finally along the axonal length. It then crosses the synapse and again reaches the dendrites of the next neuron and the process of conduction of nerve impulse continues. This happens because of the alternate polarisation and depolarisation of the nerve fibre generated by the sodium ions which allows the impulse to travel in only one direction.

2. The autonomic nervous system controls the involuntary actions of the internal organs. Involuntary actions like blood pressure, vomiting and salivation are controlled by medulla of hindbrain which is a part of the central nervous system. Also, the activity of the motor neurons of the autonomic nervous system called autonomic ganglia is modulated by preganglionic neurons located in the central nervous system.