Describe what happens when you step on a pin (this is about the nervous system)

The pin is the stimulus and your skin is the receptor. Your skin sends an electric impulse which travels in a sensory neuron. The electrical impulse travels over synapses by going through a chemical reaction. It travels to your central nervous system. as a motor neuron, it then is an effector which your body shows the response to. The response is you quickly lifting your foot up.