Systolic-Diastolic Pressure, Pulse Pressure, Mean Arterial Pressure & Transmission of Pressure Pulse

Summary

This video from nonstopneuron.com explains arterial pressure pulsations, distinguishing them from blood flow. It details how pressure waves travel through the arterial tree, affecting systolic and diastolic pressures to create pulse pressure. The video also explores mean arterial pressure, the velocity and damping of pulses in vessels, and how these factors relate to the heart's function and the body's circulatory system.

Takeaways

• 😀 Pressure pulses are distinct from blood flow; they are waves of pressure that travel through the blood.
• 🔍 The pressure wave's origin is the heart during systole, which pushes existing blood forward and creates a pressure rise in the aorta.
• 🌊 Pressure waves spread throughout the arterial tree like a wave, causing fluctuations in blood pressure.
• 📈 Systolic pressure is the highest pressure during a pulse, while diastolic pressure is the lowest, with the difference being the pulse pressure.
• 💡 Pulse pressure is influenced by stroke volume and arterial distensibility, with greater stroke volume and less distensibility leading to higher pulse pressure.
• 📊 Mean arterial pressure is calculated by considering the time spent at different pressure levels, not simply averaging systolic and diastolic pressures.
• 🏃‍♂️ During exercise, the mean arterial pressure tends to rise as diastolic time shortens, moving the average closer to systolic pressure.
• 🚀 The velocity of pressure waves increases as they travel from the aorta to smaller, stiffer arteries.
• 🌀 Damping of the pressure pulses occurs due to vessel distensibility and resistance, causing the pulses to weaken as they reach the capillaries.
• 🎯 The transmission of pressure pulses results in vessel wall distension, which is what is felt as radial pulses at the wrist.

Q & A

What is the main difference between blood flow and pressure pulses?

Blood flow refers to the actual movement of blood, while pressure pulses are the waves of pressure that travel through the blood, similar to how sound waves move through air without displacing the air molecules significantly.

How does the pressure pulse travel along the arterial tree?

The pressure pulse is generated by the heart during systole and initially causes a rise in pressure in the aorta. This pressure then spreads throughout the arterial tree like a wave, much faster than the blood itself.

What are systolic and diastolic pressures, and how is pulse pressure calculated?

Systolic pressure is the upper pressure during a pulse, while diastolic pressure is the lower pressure. Pulse pressure is the difference between systolic and diastolic pressures, calculated as systolic pressure minus diastolic pressure.

What factors influence pulse pressure?

Pulse pressure depends on two factors: stroke volume, which is the amount of blood pushed into the arteries with each heartbeat, and the distensibility of the arteries, which affects how much the arteries expand and contract with each pulse.

Why is the mean arterial pressure not simply the average of systolic and diastolic pressures?

Mean arterial pressure is not just the average of systolic and diastolic pressures because it must take into account the time spent at each pressure level. Since arteries spend more time at diastolic pressure, the mean is closer to the diastolic level.

How does the velocity of pressure pulses change as they travel from the aorta to smaller arteries?

The velocity of pressure pulses increases as they travel from the aorta to smaller arteries. This is because smaller arteries are stiffer, and less energy is lost in distension, allowing the wave to travel faster.

What causes the damping or fading out of pulsations as they travel through the arterial tree?

Pulsations fade out due to the distensibility of the vessels and the resistance encountered as blood moves forward. Energy is lost in causing vessel distension, and resistance opposes blood flow, both contributing to the weakening of the pressure wave.

What is the relationship between the stiffness of blood vessels and the velocity of pressure pulses?

In stiffer vessels, less energy is lost in distension, which results in an increase in the velocity of pressure pulses. Conversely, in more compliant vessels, more energy is lost, slowing down the wave.

How does the mean arterial pressure change during exercise?

During exercise, the duration of diastole becomes relatively shorter, which causes the mean arterial pressure to move towards systolic pressure.

Why can we feel the distension of vessel walls at the wrist when examining radial pulses?

We can feel the distension of vessel walls at the wrist because the traveling pressure pulses cause the vessel walls to expand and contract, which can be detected through the skin as the radial pulse.