The health of a neuron depends on

• A. Glucose
• B. Myelin integrity
• C. Frequency of firing
• D. Oxygen

Answer: (A)

Neuronal health hinges on having enough energy to power the ion pumps that maintain resting membrane potential and support signaling. The Na+/K+ ATPase, for example, uses ATP to keep the gradients that neurons rely on for action potentials and neurotransmission. If energy runs short, these pumps fail, the membrane potential collapses, and neuron function deteriorates quickly.

Glucose is the brain’s primary fuel under normal conditions. It feeds ATP production through glycolysis and subsequent oxidative phosphorylation, supplying the energy neurons need to fire and recover from activity. Neurons depend on a steady glucose supply because they have high energy demands and relatively limited energy reserves. While oxygen is also essential—it lets mitochondria generate ATP efficiently—it's not enough on its own. Without glucose, ATP production slows dramatically even if oxygen is plentiful, and neuronal function collapses. Conversely, with glucose but insufficient oxygen, ATP yield drops, but the available glucose still supports some energy production that can delay damage—yet optimal neuronal health requires both substrates, with glucose supplying the baseline energy needed for survival and function.

So, the best answer centers on glucose because it provides the fundamental fuel for maintaining neuronal energy and viability.