What does convergence allow at the secondary sensory neuron?

• A. To inhibit secondary neuron firing
• B. For simultaneous subthreshold stimuli to sum and at the secondary sensory neuron to initiate an AP
• C. To decrease conduction velocity
• D. To block pain signals completely

Answer: (B)

Convergence lets many inputs feed into a single second-order sensory neuron, allowing their effects to combine at that neuron. When several subthreshold signals arrive together (temporal or spatial summation), their postsynaptic potentials add up. If the combined input crosses the threshold, an action potential is generated and the signal is transmitted onward. This is why simultaneous subthreshold stimuli can sum to trigger firing at the secondary sensory neuron.

Convergence isn’t about inhibiting firing, reducing conduction velocity, or completely blocking pain on its own. Inhibition can modulate activity, conduction velocity is set by fiber properties, and blocking pain entirely would require other mechanisms beyond simple convergence.