The cardiac cycle Flashcards
What is the cardiac cycle?
the sequence of events taking place during one complete heart beat
What are the 3 steps in the cardiac cycle?
diastole, atrial systole, ventricular systole
What happens during diastole?
-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
What happens during atrial systole?
-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
What happens during ventricular systole?
-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
When is the only time AV valves are shut?
ventricular systole
How can having a large amount of muscle reduce blood flow to a particular part of the body?
larger amount of muscle means it has a smaller lumen when it contracts, which restricts the volume of blood flowing
What is the advantage of having a double circulatory system?
higher blood pressure is maintained throughout the body
What causes atrial pressure to increase during diastole?
due to the atrium filling with blood
Why is there a slight jump in atria pressure at the end of diastole?
semi-lunar valves have shut, so there is less volume in the aorta, so slightly higher pressure
What is cardiac output and how do you calculate it?
the volume of blood pumped by the heart in one minute
stroke volume x heart rate
What is stroke volume?
the volume of blood pumped by the heart per beat, usually around 80cm^3 in adults
How is stroke volume controlled?
via blood pressure
What is heart rate?
number of beats per minute
Why is there an increase in cardiac output during exercise?
-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
How do athletes increase their cardiac output?
-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
What is CHD?
coronary heart disease- any disease that interferes with the coronary arteries
What do the coronary arteries do and why is it dangerous if they get blocked?
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
What is CVD, and how do most diseases start?
cardiovascular diseases that concern the heart and blood vessels- most CVD starts with atheroma (the formation of fatty deposits in the walls of arteries
What cause atheromas?
salt, saturated fats, smoking, stress, high blood pressure
What is angina?
chest pain caused by reduced blood flow to the heart muscles
What is thrombosis?
the formation of a blood clot
What can thrombosis cause in the:
heart
brain
lungs
heart- myocardial infarction
brain- stroke
lungs- pulmonary embolism
What are the risk factors for CHD?
-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
