External stimulus and internal stimulus

Stimuli from the external environment include light, sound smell, taste, surrounding temperature, pressure and touch.

Stimuli from the internal environment include changes in blood osmotic pressure, changes in body temperature and changes in blood sugar level.

Special sensory cells to detect stimuli

When a receptor detects a stimulus it is converted to a nerve impulse that is sent to the brain through nerve cells or neurons.

Also known as nerve cells that process and transfer information to the brain.

The integration centre translates nerve impulses and coordinates an appropriate response.

Refers to the way organisms react after detecting a stimulus.