Unit 1 Section 5: The heart basics

Question 1

atria ventricular valves (AV)

Answer 1

link the atria to the ventricles

Question 2

semi-lunar valves (SL)

Answer 2

link the ventricles to the pulmonary artery(right) & the aorta(Left)

Question 3

tendons

Answer 3

valves are prevented from being inverted because of tendons.

Question 4

valves and pressure

Answer 4

Higher pressure behind a valve it’s forced open

Higher pressure in front of the valve it’s forced shut.

Question 5

thickness of chamber walls

Answer 5

the left ventricle has a thicker muscle than the rest of the heart because it needs to contract more powerfully to pump blood around the whole body.

• The right side only needs to force blood to the lungs
• The atria just have to pump blood into the ventricles

Question 6

(NOT IMPORTANT BUT JUST IN CASE) heart chamber wall measurements

Answer 6

atrium - 2mm
right ventricle - 4-5mm
left ventricle - 8-15mm

Question 7

hydrostatic pressure

Answer 7

blood leaving heart in arteries is under high pressure from ventricle contraction

Question 8

The cardiac cycle

Answer 8

an ongoing sequence of contraction and relaxation of the atria and ventricles that keeps blood continuously circulating around the body.

Question 9

The cardiac cycle - 1.DIASTOLE

Answer 9

• blood enters the atria of the heart through the pulmonary vein and the vena cava.
• Pressure in atria rises forcing open the Atrioventricular valves allowing blood to move into the ventricles
• all cardiac muscles are relaxed at this point.
• this causes the pressure in the ventricles to reduce to lower than that of the aorta and pulmonary artery so the semi-lunar valves close maintaining a one way flow.

Question 10

The cardiac cycle - 2.ATRIAL SYSTOLE

Answer 10

• atria muscle contracts forcing the remaining blood into the ventricles
• during this the ventricle walls remain relaxed (ventricular diastole)

Question 11

The cardiac cycle - 3.VENTRICULAR SYSTOLE

Answer 11

• after a short delay the ventricles contract, increasing their blood pressure, forcing shut the AV valves preventing back-flow
• This causes the pressure to rise further forcing open the semi-lunar valves allowing blood into the pulmonary artery and aorta.

Question 12

The cardiac cycle - 3.VENTRICULAR SYSTOLE

Answer 12

• after a short delay the ventricles contract, increasing their blood pressure, forcing shut the AV valves preventing back-flow
• This causes the pressure to rise further forcing open the semi-lunar valves allowing blood into the pulmonary artery and aorta.

Question 13

Pocket (SL) valves in veins

Answer 13

ensure that when the vein is squeezed blood flows back to the heart rather than away from it.