Lecture 5 – Blood Flow

1) What are total blood flow and local blood flow?

Total blood flow is the amount of blood through the whole cardiovascular system per unit time. Local blood flow is the amount of blood into a tissue per unit time, also called perfusion.

2) What two things affect total blood flow and how is it calculated?

Total blood flow is affected by the blood pressure gradient and peripheral resistance. It is calculated as Blood Flow = Pressure Gradient / Resistance.

3) What is a blood pressure gradient and what has the greatest effect on it?

A blood pressure gradient is the change in pressure from one end of a vessel to the other. The greatest factor that affects it is cardiac output.

4) If cardiac output increased, what would happen to the pressure gradient and total blood flow? What if cardiac output decreased?

If cardiac output increases, the pressure gradient and total blood flow increase. If cardiac output decreases, the pressure gradient and total blood flow decrease.

5) If the blood vessels are stimulated to vasodilate, how would this affect total blood flow? What if the blood vessels are stimulated to vasoconstrict?

When blood vessels vasodilate, resistance decreases and total blood flow increases. When blood vessels vasoconstrict, resistance increases and total blood flow decreases.

6) What are the two reasons during exercise, there is less blood in the vein reservoirs? How does this affect total blood flow?

There is less blood in veins because of skeletal muscle pumps and sympathetic constriction of veins. This makes more blood circulate, which increases total blood flow.

7) Between capillaries and arteries, which has the greatest total cross-sectional area?

Capillaries have the greatest total cross-sectional area.

8) As blood travels from arteries to capillaries, what happens to the speed of blood flow?

As blood moves from arteries to capillaries, the speed decreases.

9) Is there enough blood in the body to fill all capillaries at one time?

No, there is not enough blood to fill all capillaries at once.

10) What four things affect local blood flow?

Local blood flow is affected by degree of vascularization, myogenic response, local regulatory factors, and total blood flow.

11) What is angiogenesis and why does it happen? How does it affect local blood flow?

Angiogenesis is the formation of new blood vessels. It happens with aerobic training, weight gain, or blocked vessels. It increases local blood flow by adding more vessels.

12) What is regression and why does it happen? How does it affect local blood flow?

Regression is the loss of blood vessels. It happens when tissues are less active, like with sedentary lifestyle or weight loss. It reduces local blood flow.

13) What does the myogenic response of the arterioles help to ensure?

The myogenic response ensures a constant local blood flow even when systemic blood pressure changes.

14) If systemic blood pressure increases, how would the arterioles respond to maintain local blood flow? What if systemic blood pressure decreases?

If pressure increases, arterioles vasoconstrict. If pressure decreases, arterioles vasodilate.

15) If a tissue isn’t receiving adequate blood flow (its perfusion is too low), what would happen to the oxygen/nutrient levels? What would happen to the level of waste products within the tissue?

Oxygen and nutrients decrease. Waste products increase (CO₂, lactate, H⁺, K⁺).

16) How do increasing concentrations of waste products within a tissue affect local blood flow?

Waste products cause precapillary sphincters to relax, which increases local blood flow.

17) When tissues must autoregulate their blood flow due to not having an adequate perfusion for too long, a greater volume of blood flows into the capillary than normal. What do we call this?

This is called reactive hyperemia.

18) Why is the pressure in the fetal heart greater on the right side in comparison to after birth where its greater on the left side?

Fetal lungs are not functional, so blood does not go to lungs. This keeps pressure higher on the right side of the heart.

19) When blood enters the right atrium of the fetal heart it can move to the left atrium through a hole in the interatrial septum called the ….

It moves through the foramen ovale.

20) Blood that enters the right ventricle is pumped into the pulmonary trunk but then is moved to the aorta through a shunt called the ….

It moves through the ductus arteriosus.

21) With the lungs of a fetus being nonfunctional, where does the fetal blood get rid of carbon dioxide and replenish oxygen levels?

It happens at the placenta.

22) When a baby is born, what causes the pressure on the right side of the heart to decrease?

At birth the lungs open and pulmonary vessels dilate, lowering right side pressure.