| A | B |
| Stimuli | A change in the environment |
| Sensitivity | The ability to respond appropriately to a stimulus |
| Tropism | A response to a directional stimuli in a plant |
| Kinesis | A behavioural response involving random movement |
| Taxis | A behavioural response involving directional movement |
| Reflex arc | The nerve pathway which transmits information rapidly from a receptor to an effector |
| Heart rate | is determined by pacemaker cells in the SAN |
| Baroreceptors | Sense changes in pressure and are found in the carotid sinus and walls of the heart |
| Pacinian corpuscle | Mechanoreceptor sensitive to changes in pressure and touch |
| Visual acuity | The ability to discriminate fine details |
| Rods | Contain rhodopsin |
| Cones | enable us to see colour and detail and contain iodopsin |