Describe how an impulse passes from the relay neurone to the motor neurone.(3)..............................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................(ii) Explain the function of a reflex arc.

(i) The process of an impulse passing from the relay neuron to the motor neuron involves the following steps:

1. The relay neuron receives the impulse from the sensory neuron. This happens at a synapse, where the electrical signal of the impulse triggers the release of neurotransmitters.

2. These neurotransmitters cross the synaptic gap and bind to receptors on the motor neuron. This process converts the chemical signal back into an electrical one.

3. The electrical impulse then travels down the motor neuron to the muscle or gland that it is connected to, triggering a response.

(ii) The function of a reflex arc is to provide a rapid, automatic response to a stimulus. This is crucial for protecting the body from harm. For example, if you touch something hot, the reflex arc causes your hand to pull away before the information even reaches your brain. This is because the sensory neuron directly communicates with the motor neuron via the relay neuron in the spinal cord, bypassing the brain and thus speeding up the response time.