THE REFLEX ARC

Your nervous system rescues you from imminent harm using hard-wired reflex actions

1 DETECTION When your cells are at risk, such as when you accidentally touch a hot stove, receptors in your skin initiate a nerve impulse. 2 SENSOR NEURON

The nerve impulse travels from the dendrites of the sensory neuron towards the spinal cord.

3 INTERNEURON

Located in the spinal cord, the interneuron acts as a relay between the sensor and motor neurons, passing the impulse onto the latter.

4 MOTOR NEURON

The nerve impulse travels away from the spinal cord and towards the target muscle receptors via the motor neuron.

5 MOTOR FUNCTION

The signal forces muscles to contract, pulling your hand away from the heat source automatically without any conscious thought needed.

6 CLOSE NEIGHBOURS

The nerve impulse reaches connected neurons by ‘jumping’ across the synapse, a small gap that lies between them.

7 ONE-WAY TRAFFIC

The nerve impulse travels in one direction, starting at the sensory neuron and terminating at the end of the motor neuron.

8 POLYSYNAPTIC REFLEX

Reflexes can trigger either simple or complex responses. Polysynaptic reflexes can send signals to many muscles, allowing us to simultaneously contract them during a reflex.