Final answer:
A reflex action involves three neurons: sensory, interneuron, and motor neurons. They work together to quickly and unconsciously respond to a stimulus. In the example of Ariana holding a hot mug, her sensory neuron detects the heat, which triggers a series of events leading to the withdrawal of her hand.
Step-by-step explanation:
A reflex action involves the coordinated activity of three neurons: sensory neurons, interneurons, and motor neurons. In the example of Ariana holding a hot mug, when the heat stimulus is detected by the sensory neuron in her hand, it sends a nerve impulse to the spinal cord. In the spinal cord, the sensory neuron communicates with an interneuron, which relays the message to the motor neuron. The motor neuron then carries the impulse to the muscles in Ariana's arm, causing her to je-rk her arm back and remove her hand from the hot mug.