What is meant by stimulus and reaction?
Stimulus is the change in the environment or environmental factors to to which the organism can respond or react. Theresponse shown by organisms towards or awaya stimulus is called reaction.
Adrenal gland is called emergency gland. Why?
We all know, adrenal gland secretes adrenalin hormone at the time of emergency which prepares the body to face an emergency situation. So, it is called emergency gland.