For the reticular activating system (RAS) to work correctly, what three substances are needed?

The reticular activating system (RAS) plays a crucial role in regulating wakefulness and alertness, and its proper functioning relies on a few essential substances. Oxygen is vital for perfusing brain tissue, as it is necessary for aerobic metabolism, which produces the energy required for brain function. Glucose is the primary energy source for the brain; without it, neurons cannot perform essential functions such as communication and maintenance of homeostasis. Lastly, water is essential for maintaining hydration within brain cells and ensuring optimal communication and biochemical processes.

The other choices present alternatives that do not align with the physiological needs of the RAS. For instance, the mention of insulin instead of glucose overlooks the fact that the brain directly utilizes glucose as its primary fuel source. Similarly, while sodium plays important roles in various cellular functions, it does not substitute for the critical energy needs met by glucose. Hence, the combination of oxygen, glucose, and water reflects the correct requirements for the RAS to function properly.