LECTURE 3 - 1ST SEMESTER

Question 1

What makes a force pump different from a lift pump?

Answer 1

• ## The force pump does not rely on atmospheric pressure directly and can be used to circulate liquids in a sealed closed liquid circuit

Question 2

Why is the heart considered to be a pump?

Answer 2

It increases pressure in a fluid to enable the fluid to move in a desired manner

Question 3

How does the heart act as a forced pump?

Answer 3

• The heart receives blood from the venous system and raises the pressure to push it out into the arterial system
• Action of ventricles force pump blood out, which causes pressure through contractions.

Question 4

Explain how blood is pumped out of the right/Left ventricle?

Answer 4

1. Right or Left ventricle expands, causing the atrioventricular value to open to let venous blood flow into the ventricle.
   - Semilunar value remains closed to prevent backflow of pumped blood.
   - Once the ventricle contracts the valves reverse and blood is pumped through the pulmonary artery

• If the Left side, blood returns to the lungs undergoing the same process.
• Ventricles expand and contract pumping oxygenated blood out through the aorta.

Question 5

What are the common faults with valves?

Answer 5

• Valves having holes or not closing completely.

Question 6

What are the consequences of atrioventricular valves not closing?

Answer 6

• On contraction of the right ventricle, blood is pumped back into the venous system
• Central venous system will results in periodic high pressure in the veins through venous pressure movements.

Question 7

What are the consequences of the semilunar valve not closing properly?

Answer 7

Blood flows backward in the arterial system during the expansion of the ventricle.

Question 8

What causes pressure variations in the circulatory system?

Answer 8

As fluids flow through the system and back to the pump, pressure drops back to the original pressure if the flow has reached a stable uniform rate.

Question 9

How does pressure behave throughout the circulation system?

Answer 9

• Left ventricle is the main pump providing pressure for systemic circulation throughout the body.
• Base pressure at which fluid enters the pump
• There is peak pressure when fluid leaves the pump
• Pressure is highest when it leaves the left ventricle and lowest as it enters the right attrium

Question 10

What does Poseuille’s law state about the circulation system pressure?

Answer 10

• Pressure drops that occur in any segment of the circulatory system depend on the flow rate and resistance of the segment.

Question 11

Why is the pressure drop across arterioles greater than that across capillaries?

Answer 11

• Due to Poiseuille’s law, pressure drop equals the flow rate x the resistance.
• And, resistance is proportional to the tube length/radius^4
• So since there are many times more capillaries than arterioles, the flow rate in each capillary is much smaller.

Question 12

How does the heart react to cells not receiving adequate demands?

Answer 12

• Cells generate ‘feedback’ to the heart and circulatory system.
• Causing an increase in supply and an increase in the flow rate of blood.

Question 13

How does the heart increase the flow rate of blood in times of high demand by cells/tissue?

Answer 13

• Through Poiseuille’s law the rate of flow is determined by the pressure drop, radius, length, and viscosity of the liquid.
• Therefore the circulatory system uses blood pressure and internal radii of blood vessels to control the rate of flow.
• Arterioles then act as resistance vessels of the circulatory system to control blood flow due to being surrounded by muscles.
• Surrounding muscles cause a change in vessel diameter.
• These changes control the local blood flow of tissues.