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.
What is ganglia? Where are they located?
The groups of small nerves tissues that is located near the spinal cord made up of grey matter is ganglia.
It is located near the spinal cord. They establish connection between the spinal cord and the brain.