Final answer:
A high intensity stimulus leads to more synaptic vesicles undergoing exocytosis compared to a low intensity stimulus due to a greater influx of calcium ions when Ca²⁺ channels are opened by the action potential.
Option 1 is the correct answer.
Step-by-step explanation:
Comparing the low intensity stimulus to the high intensity stimulus, the high intensity stimulus causes more synaptic vesicles to undergo exocytosis. When an action potential reaches the axon terminals, it depolarizes the membrane and causes voltage-gated Ca²⁺ channels to open. The influx of Ca²⁺ facilitates the fusion of neurotransmitter-containing synaptic vesicles with the presynaptic membrane, allowing the release of neurotransmitters into the synaptic cleft through the process of exocytosis. A higher intensity stimulus will result in a greater influx of calcium ions, which in turn results in a larger number of vesicles releasing their neurotransmitter content into the synaptic cleft.
In synaptic transmission, high intensity stimuli prompt more synaptic vesicles to undergo exocytosis than low intensity stimuli. When an action potential reaches axon terminals, it opens voltage-gated Ca²⁺ channels, leading to an influx of calcium ions. This influx facilitates the fusion of neurotransmitter-filled vesicles with the presynaptic membrane, enabling the release of neurotransmitters into the synaptic cleft through exocytosis. A higher intensity stimulus increases the influx of calcium ions, resulting in a greater number of vesicles releasing neurotransmitters, amplifying synaptic transmission efficacy.