Have you seen this clip of the 'sneezing panda'? It is very famous.
AND it is a great example of a reflex action. So, todays GCSE science tutor booster is on the nervous system and reflex arc.
The NERVOUS SYSTEM allows the body to communicate with its surroundings and the different parts of the body. It sends messages along the various neurones in the form of very quick electrical impulses.
RECEPTORS pick up these messages from the surroundings. The receptors are really your senses. For example, your skin has millions of touch receptors. These enable your body to ‘feel’ or sense changes in its surroundings and respond accordingly. These changes are called a STIMULUS or STIMULI (plural).
For example, if you touch something hot, the stimulus is heat, the receptor is touch and the sense organ is the skin.
Once the receptor has detected a stimulus there is an immediate energy change to electrical energy so that the nervous system can bring about a response. For example, in the ‘touching something hot’ scenario the heat energy is transferred into electrical energy. This electrical energy then travels along a SENSORY NEURONE to the CNS to bring about a response.
Sensory neurones connect the receptors to the brain. Once the CNS has processed the information it then selects an appropriate response. This information is sent along a MOTOR NEURONE to an EFFECTOR (usually a muscle) to bring about that response.
In summary:
The 'touching a hot object' example is really an example of a reflex action. A REFLEX ACTION is an automatic response to a stimulus. This means it does not require the CNS to process the information. The result is the brain being bypassed and the impulse being taken through the spinal cord by a relay neurone. This process speeds up the response so that the action taken is much quicker. This pathway is called a REFLEX ARC.
In summary:
Reflex actions allow the body to respond automatically to stimuli preventing injury.