Circulation & Cardiac Cycle

Question 1

Describe the general pattern of blood circulation in a mammal:

Answer 1

1. Closed double circulatory system - blood passes through heart twice for every circuit around body:
2. Deoxygenated blood in right side of heart pumped to lungs; oxygenated returns to left side
3. Oxygenated blood in left side of heart pumped to rest of body; deoxygenated returns to right

Question 2

Suggest the importance of a double circulatory system :

Answer 2

1. Prevents mixing of oxygenated / deoxygenated blood. So blood pumped to body is fully saturated with o2 for aerobic respiration
2. Blood can be pumped to body at a higher pressure (after being lower from lungs) Substances taken to / removed from body cells quicker / more efficiently

Question 3

Name the blood vessels entering and leaving the heart and lungs

Answer 3

1. Vena cava – transports deoxygenated blood from respiring body tissues →heart
2. Pulmonary artery – transports deoxygenated blood from heart → lungs
3. Pulmonary vein – transports oxygenated blood from lungs → heart
4. Aorta – transports oxygenated blood from heart → respiring body tissues

Question 4

Name the blood vessels entering and leaving the kidneys:

Answer 4

1. Renal arteries – oxygenated blood → kidneys
2. Renal veins – deoxygenated blood to vena cava from kidneys

Question 5

Name the the blood vessels that carry oxygenated blood to the heart muscle

Answer 5

Coronary arteries - located on surface of the heart, branching from aorta

Question 6

Suggest why the wall of the left ventricle is thicker than that of the right:

Answer 6

1. Thicker muscle to contract with greater force
2. To generate higher pressure to pump blood around entire body

Question 7

Atrial systole:

Answer 7

1. Atria contract, so their volume decreases, pressure increases
2. Atrioventricular valves open when pressure in atria
   exceeds pressure in ventricles. Semilunar valves remain shut as pressure in arteries exceeds pressure in ventricles
   3.So blood pushed into
   ventricles.Ventricles contract So their volume decreases, pressure increases.
3. Atrioventricular valves shut

Question 8

Ventricular Systole:

Answer 8

1. When pressure in ventricles exceeds pressure in atria
2. Atriventricular valves shut when pressure in ventricles exceeds pressure in atria.
3. Semilunar valves open when pressure in ventricles exceeds pressure in arteries.
4. So blood pushed out of heart through arteries

Question 9

Diastole

Answer 9

1. Atria & ventricles relax. So their volume increases, pressure decreases
2. Semilunar valves shut when pressure in arteries exceeds pressure in ventricles
3. Atrioventricular valves open when pressure in atria
   exceeds pressure in ventricles
4. So blood fills atria via veins & flows passively to ventricles

Question 10

Semilunar valves closed (graphs):

Answer 10

1. Pressure in [named] artery higher than in ventricle
2. To prevent backflow of blood from artery to ventricles

Question 11

Semilunar valves open: graphs

Answer 11

1. When pressure in ventricle is higher than in [named] artery
2. So blood flows from ventricle to artery

Question 12

Atriventricular valves closed graphs:

Answer 12

1. Pressure in ventricle higher than atrium
2. To prevent backflow of blood from ventricles to atrium

Question 13

Atrioventricular valves open graphs

Answer 13

1. When pressure in atrium is higher than in ventricle
2. So blood flows from atrium to ventricle

Question 14

How can heart rate be calculated from cardiac cycle data?

Answer 14

Heart rate (beats per minute) = 60 (seconds) / length of one cardiac cycle (seconds)

Question 15

Describe the equation for cardiac output

Answer 15

Cardiac output (volume of blood pumped out of heart per min) = stroke volume (volume of blood pumped in each heart beat) x heart rate (number of beats per