It initiates electrical signals about 70-80 times per minute. Once initiated the electrical signal spreads over both atria, slows briefly at the AV node, and then spreads rapidly over the ventricles. Control of heartrate, strength of contraction -The nervous system can only adjust the rate and strength of the heartbeat. H. Blood pressure in the vascular system 1. Blood pressure drops along the way from the heart to the veins, due to energy loss from the increase of resistance.
Arteries have higher pressure than capillaries, and capillaries have higher pressure than veins.
This equation can be applied to individual vessels, or to whole sections of circulatory system. The greater the cross-sectional area, the lower the resistance. Arterial blood pressure - Arteries are elastic and muscular. The pressure in the arteries fluctuates with each beat, but the average pressure does not drop much because the diameter of arteries is so large they offer little resistance to flow. They present a substantial increase in resistance to flow, and there is thus a large drop in pressure from the upstream to the downstream ends of arterioles.