2.1 Responding to Change

An animal’s response to a stimulus is coordinated by their central nervous system (CNS).

Receptors are groups of specialised cells that can detect changes in the environment called stimuli.

Receptors located in sense organs ---- Stimuli

·         ·         Eyes (sight) --- Light

·         ·         Ears (sound) --- Sound

·         ·         Mouth (taste) --- Chemicals

·         ·         Skin (touch) --- Preasure/Temperature

·         ·         Nose (smell) --- Chemicals

The CNS consists of the brain and spinal cord. When a receptor is stimulated it sends a signal along the nerve cells, also called neurones, to the brain. The brain then coordinates the response.

 Sensory Neurons carry impulses from receptors to CNS. Motor Neuron carry impluses from CNS to effector organs(muscles/glands). The muscles respond by contracting. Glands respond by secreating (releasing) chemicals.