18. Long answer question III

 

The reflex arc describes the path taken by the electrical impulsenerve impulse  as it travels from the neuron to the effectoraffector organ, which generates and shows the response.

 

The stimulus is prick (touch) pain, which is perceived by touch or pain receptors photo and chemoreceptors in the skin of our hand when the hand is pierced by a needle. This input in the tum causes a sensory neuron motor neuron  to release an impulse. The message is transmitted or conveyed to the brainspinal cord  by the motor neuronsensory neuron. The stimulation is interpreted by the spinal cord, and the impulse is sent to the sensory neuronrelay neuron, which in turn sends the signal to the motor neuronrelay neuron. The spinal cord skin send signal to our arm via motor neurons. Our arm muscle contracts, and we quickly pull our hand away from the needle prick. The effectoraffector organ that has responded to the puncture is muscle.