Question

How do animals respond to stimuli?

Answer 1

All complex animals have a complete system to respond to stimuli. The master of that system is brain of the animals, which direct the body to act accordingly by sending electrical and chemical signals ( hormonal ).
Response is any reaction the living organisms make to anything happening internally as well as externally. Here in humans we have neurons that work on a charge relay system to send and receive signals to and from brain for external stimulations and hormones generally maintain the internal stimulations. Not that I mean is only hormones control internal and neurons see external but it can be vice versa , what I mean is in general terms like usually that happens but for you know the neurons are responsible for muscular activity and hormones tell us if we are hungry and help in maintenance of body. so the nervous + hormonal systems in animal body makes them to respond accordingly to the stimuli.