Final answer:
Voltage-gated sodium channels opening at a lower voltage would increase neuronal excitability because the channels would open more readily, leading to more frequent sodium influx and action potentials with smaller stimuli.
Step-by-step explanation:
The voltage-gated sodium channels are critical in the generation and propagation of action potentials in neurons. If these channels were to open at a lower voltage than normal, it would lead to increased neuronal excitability. This is because the channels would open more readily in response to smaller depolarizations, allowing influx of sodium ions (Na+) into the neuron more frequently. This can create a positive feedback loop where sodium entry depolarizes the neuron, leading to the opening of more sodium channels and further depolarization.
Neuronal excitability refers to the ease with which a neuron can fire an action potential. Depolarization of the neuron to its threshold potential causes voltage-gated Na+ channels to open and the neuron to reach its action potential. During the repolarization phase, voltage-gated potassium channels open to allow potassium ions (K+) out, bringing the membrane potential back down. Neuronal excitability would be affected if the threshold for activating sodium channels were lowered, as neurons would be more likely to reach action potential with smaller stimuli, affecting the overall neural activity.