The Heart and Circulatory System Flashcards
What must the cells of the body do in order to sustain exercise? And how is this process achieved?
They must require a continuous supply of nutrients and their waste products must be removed. This process is achieved by the circulatory system.
What is the heart?
A muscular pump.
What is the job of the heart?
To push blood into the tissues.
What is the size of the heart?
About the size of a man’s clenched fist.
Where is the heart located?
Behind and to the left of the sternum.
What does the heart consist of?
Four chambers: two upper, smaller chambers called atria (left and right atrium) and two lower, larger chambers called ventricles.
What is the predominant tissue of the heart?
Cardiac muscle, which is referred to as the myocardium (‘myo’ refers to muscle and ‘cardiac’ refers to the heart)
What is the right hand side of the heart responsible for?
Receiving blood from the upper and lower body via the veins.
How does blood enter the right atrium?
Through either the inferior or superior vena cava.
What happens to blood when it enters the right atrium?
Is it saturated with CO2 and is referred to as deoxygenated blood. It is ejected to the lungs (pulmonary circulation) by the right ventricle via the pulmonary artery.
What happens in the pulmonary capillaries?
CO2 diffuses into the lungs to be expired while O2 enters the blood. This oxygenated blood enters the left atrium of the heart via the pulmonary vein. The left ventricle then ejects the blood and O2, via the aorta, to the tissues of the body (systemic circulation).
What colour is deoxygenated blood?
Dark red.
What colour is oxygenated blood?
Bright red.
Which way do arteries carry blood?
Away from the heart.
Which way do veins carry blood?
To the heart.
What does the heart have to do to function effectively as a pump?
It needs to direct blood through the atria, ventricles and then the arteries of the body.
What does the heart prevent?
Unwanted back-flow of blood into the chambers using a number of valves.
When do the hearts valves open and close?
When in response to changes in pressure as the heart contracts and relaxes.
What does the structure of the valves mean?
That they only allow blood to flow in one direction by shutting once blood has been pushed through the,. This is fundamental to effective circulation.
What does back-flow through the heart compromise and affect?
The efficiency of each heartbeat, which is likely to affect exercise performance and health.
What are the main valves of the heart?
The atrioventricular (AV) valves and the semilunar (SL) valves.
Where are the AV valves located?
Between the atria and the ventricles.
What do the AV valves do?
They prevent the back-flow of blood from the ventricles to into the atria.
What happens when the ventricles contract?
Pressure rises and forces the AV valves to snap shut, allowing blood to be directed through the arteries leaving the heart (pulmonary artery and aorta).
Where are the SL valves located?
At the base of the arteries leaving the heart (aorta and pulmonary artery).
What happens after each contraction of the SL valves?
There is a relative drop in pressure within the ventricles as they relax. At this point, the blood within the pulmonary artery and aorta could potentially flow back into the ventricles.
How is blood, within the pulmonary artery and aorta, that flows back into the ventricles prevented?
Both sets of arteries have SL valves positioned at the point where they emerge from the ventricles, the SL valves snap shut so blood cannot re-enter.
What causes the distinct ‘Lub-dub’ noises associated with the heartbeat?
The sequential shutting of the valves during the cardiac cycle.
What happens when the AV valves snap shut?
They are anchored in place by tendon-like chords (chordae tendineae) which prevent the valve flaps from being pushed too far into the atria.
What stimulates the heart to contract?
A complex series of integrated systems.
What initiates the cardiac muscle contraction?
The heart’s pacemaker - the sinoatrial (SA) node.
Where is the SA node located?
In the wall of the right atrium.
What is the myocardium (heart muscle) simulated to do?
Contract about 72 times per minute by the SA node as part of the autonomic nervous system.
What is coronary circulation?
The circulation of blood to the heart.
What does the heart require?
A constant supply of oxygen and nutrients; these are carried in the blood.
How does the heart achieve a continuous supply of blood?
The heart has its own network of blood vessels. Blood is delivered to the tissues of the heart via two coronary arteries. These arteries branch out from the base of the aorta and and subdivide into a crown-like network of blood vessels across the heart wall. Blood is then circulated through both the superficial and deep tissues of the heart via this network of blood vessels before being drained away through coronary veins.
What is the aorta?
The major vessel for removing blood from the left ventricle.
What does the right coronary artery do?
Primarily supplies blood to the myocardium of the right ventricle.
What does the left coronary artery do?
Divides into two branches, suppling blood to the left ventricle and the posterior of the heart.
What are most regions of the heart served by?
More than one branch of coronary arteries.
What happens if the blood flow through one vessel becomes reduced (e.g. through heart disease)?
Blood supply to the tissues can be maintained through other vessels.
What are the coronary arteries most renowned for?
Their association with heart disease. The flow of blood through these arteries is critical to the health of the heart.
What can most heart problems be attributed to?
Poor coronary circulation as a result of blood clots, fatty plaques building up in the coronary arteries or spasms in the smooth muscle of their walls.
What can blood clots, fatty plaques and spasms do?
They will reduce the amount of blood flowing through the coronary arteries and therefore decrease the volume of oxygen and nutrients reaching the heart muscle; ultimately this may cause the heart to fail.
What is ischaemia?
Reduction in blood flow.
What is the myocardium?
The heart muscle.
What is myocardial ischaemia?
A reduction in blood flow to the heart through coronary circulation.
What can myocardial ischaemia cause?
A myocardial infarction (heart attack).