As this question is a 2 mark question, the examiner is looking for two AO1 (description) points. A motor neuron transmits electrical signals from the brain (or spinal chord) to an effector muscle. (1 mark)This causes the muscle to either contract and produce movement or relax. (1 mark) It is important to keep responses to AO1 questions short and simple, therefore the examiner finds it easy to pick out the marks.