The cardiac cycle

Question 1

What is the cardiac cycle?

Answer 1

the sequence of events taking place during one complete heart beat

Question 2

What are the 3 steps in the cardiac cycle?

Answer 2

diastole, atrial systole, ventricular systole

Question 3

What happens during diastole?

Answer 3

-atrial and ventricular muscles relax
-volume in the atria is high, so the pressure is low
-so blood enters the atria from veins with higher pressure, and the semi lunar valves then shut
-as blood enters, pressure increases in the atria which causes blood to start to move into the ventricles as they have lower pressure
-atrioventricular valves open

Question 4

What happens during atrial systole?

Answer 4

-atrial muscles CONTRACT, which decreases the volume of the atria, hence increases pressure in the atria
-ventricle muscles RELAXED, so lower volume and lower pressure
-blood is pushed from the atria to the ventricle
-atrioventricular valves are open, semi-lunar valves are shut

Question 5

What happens during ventricular systole?

Answer 5

-atrial muscles RELAXED
ventricle muscles CONTRACT, decreasing the volume and so increasing the pressure of the ventricles
-arteries have a lower pressure so blood is pushed out of the heart and into the arteries
-semi-lunar valves are open, and atrioventricular valves are forced shut to prevent backflow

Question 6

When is the only time AV valves are shut?

Answer 6

ventricular systole

Question 7

How can having a large amount of muscle reduce blood flow to a particular part of the body?

Answer 7

larger amount of muscle means it has a smaller lumen when it contracts, which restricts the volume of blood flowing

Question 8

What is the advantage of having a double circulatory system?

Answer 8

higher blood pressure is maintained throughout the body

Question 9

What causes atrial pressure to increase during diastole?

Answer 9

due to the atrium filling with blood

Question 10

Why is there a slight jump in atria pressure at the end of diastole?

Answer 10

semi-lunar valves have shut, so there is less volume in the aorta, so slightly higher pressure

Question 11

What is cardiac output and how do you calculate it?

Answer 11

the volume of blood pumped by the heart in one minute

stroke volume x heart rate

Question 12

What is stroke volume?

Answer 12

the volume of blood pumped by the heart per beat, usually around 80cm^3 in adults

Question 13

How is stroke volume controlled?

Answer 13

via blood pressure

Question 14

What is heart rate?

Answer 14

number of beats per minute

Question 15

Why is there an increase in cardiac output during exercise?

Answer 15

-to supply oxygen AND GLUCOSE to muscles/respiring cells faster
-to remove carbon dioxide AND LACTATE from the muscles/respiring cells faster
-to remove heat away from muscles faster

Question 16

How do athletes increase their cardiac output?

Answer 16

-their heart muscle is stronger/thicker, and the volume of each chamber can be increased
-this enable them to increase their stroke volume as thicker muscles can contract with greater force to expel more blood
-athletes pump more blood out in each heartbeat, so can expel the same volume of blood in fewer beats

Question 17

What is CHD?

Answer 17

coronary heart disease- any disease that interferes with the coronary arteries

Question 18

What do the coronary arteries do and why is it dangerous if they get blocked?

Answer 18

supply the heart muscle with the glucose and oxygen needed for respiration, if they become blocked/narrowed, the supply of glucose and oxygen will be reduced, potentially leading to the death of the cells- leading to a myocardial infarction

Question 19

What is CVD, and how do most diseases start?

Answer 19

cardiovascular diseases that concern the heart and blood vessels- most CVD starts with atheroma (the formation of fatty deposits in the walls of arteries

Question 20

What cause atheromas?

Answer 20

salt, saturated fats, smoking, stress, high blood pressure

Question 21

What is angina?

Answer 21

chest pain caused by reduced blood flow to the heart muscles

Question 22

What is thrombosis?

Answer 22

the formation of a blood clot

Question 23

What can thrombosis cause in the:
heart
brain
lungs

Answer 23

heart- myocardial infarction
brain- stroke
lungs- pulmonary embolism

Question 24

What are the risk factors for CHD?

Answer 24

-eating a diet with high levels of saturated fats and salt
-older age
-males more likely over females
-high levels of LDL cholesterol in blood
-smoker
-high blood pressure