Question

Question 3 Pulse wave velocity is used to measure the speed of blood as it moves through the arterial system. (i) What evidence is there that blood moves through the arterial system in the form of a wave? (10 marks] How does the pressure and flow rate change as the blood moves though the system? In you answer, describe how reflections of the initial pulse wave affect the following wave travelling behind it. (10 marks)

Answer 1

The arteries carry the blood away from the heart at higher physiologic pressure. In arteries, the blood pressure is more because due to the pumping action of the heart, pressure waves are formed in the arteries. The mechanical interaction between the arterial wall and the blood is responsible for the release of the pressure wave from the heart to the entire body. Thus the arterial blood flow is that it is pulsatile in nature. The heart ejects blood and again and fills in cycles called systole and diastole. The blood is pumped out from the heart during systole and then the heart rests during diastole.

Answer 2

Blood pressure and flowrate are unsteady throughout the body. Blood is pushed throughout the body with pressure due to the pumping action of the heart. With each pumping cycle, blood is pushed away from the heart, along the main artery, the aorta, and further in the arteries, arterioles and finally to the capillaries, the flow of blood drastically lowers down. The flow rate of blood in the aorta is 30 cm/sec, while in the capillaries, it shows down to 0.026 cm/sec. The blood travels very slowly in the capillaries because it has to reach each cell for gas and nutrient exchange.

Wave reflection from the periphery augments the aortic systolic pressure. A wave traveling from the left ventricle comes at the small vessels and reflects back to the aorta. Thus, the pressure in the aorta is the addition of the pressures of the incident and reflected wave