What mechanism is responsible for increasing the rate of heart conduction?

The sympathetic nervous system plays a crucial role in increasing the rate of heart conduction through its activation. When the sympathetic nervous system is stimulated, it releases neurotransmitters like norepinephrine, which bind to β-adrenergic receptors in the heart. This leads to an increase in the heart rate and the force of each contraction by enhancing the conduction velocity through the atrioventricular (AV) node and the Purkinje fibers. As a result, the electrical impulses that initiate heartbeats travel more rapidly, contributing to an overall increase in cardiac output, especially during times of stress or physical activity.

In contrast, options that focus on the parasympathetic nervous system activate a slowing effect on heart rate, while the release of endorphins typically relates more to pain relief and mood enhancement rather than direct effects on heart conduction. Decreased oxygen levels can also stimulate different cardiovascular responses, but they do not directly enhance the heart's conduction rate.