The Cardiac cycle Flashcards
In summary, what is the cardiac cycle?
A series of events required to generate one single heartbeat
What is responsible for the cardiac cycle?
The cardiac conduction system (The electrical pathways through the heart)
What must happen in order for blood to move successfully through the heart?
Coordination must occur between the valves opening and closing and the contraction of the chambers of the heart
What is the cause of valves opening and closing?
Contractions
What state is the heart in at the start of the cardiac cycle?
All the chambers are relaxed and all valves are closed
Contraction, also known as…
Systole
Relaxation, also known as…
Diastole
When blood fills the atria what does the change in pressure do?
Pushes the AV valve open
Where is the right atria filled from?
The superior and inferior vena cava
Where is the left atria filled from?
The pulmonary veins
In order for an atrial chamber to be filled, what must be true?
The chambers must be relaxed
Why does blood flow into the ventricles?
To equalise the pressure between the atrium and ventricle
When does blood stop flowing from the atrium into the ventricle?
When around 70% of the blood volume from the atria is in the ventricles
What causes the remaining 30% of blood to flow from the atria into the ventricles?
The atria begin to contract
Once all blood is in the ventricles, the atria relax
What happens when the ventricles contract?
The AV nodes close
What does this drop in pressure in the atria cause?
A vacuum that pulls the flaps of the AV valves closed
What effect do papillary muscles have on the AV valves?
When the papillary muscles within the walls contract, they pull on the chordae tendineae to ensure that the valves stay closed
Therefore preventing back flow
As ventricular systole increases due to increase pressure inside the ventricles, what happens?
Semi-lunar valves are pushed open, allowing blood to flow through the aorta and pulmonary arteries
What happens when the ventricles relax?
Pressure within the ventricles decreases
Semi-lunar valves are pulled shut
Movement of blood through the heart is a result of?
Changes in pressure apposed to contractions
What must always be balanced for the cardiac cycle to work correctly?
The output of the atria and the ventricles
What is a normal heart rate, i.e number of cardiac cycles per minute in the average adult?
60 to 100
To summarise, the cardiac cycle consists of…
Atrial systole
Ventricular systole
Complete cardiac diastole
Cardiac diastole occurs when…
All chambers are relaxed and blood flows into the heart
Atrial systole / ventricular diastole occurs when…
The atria contracts pushing the blood into the ventricles
Atrial diastole / ventricular systole occurs when…
After the atria relax, the ventricles contract, pushing blood out of the heart
Describe the positioning of the inferior and superior vena cava?
Off centre, right side of the heart and body
Describe the positioning of the aorta?
Left ventricle of the heart, extends upwards into the heart
Describe the positioning of the carotid arteries?
Located on each side of the neck (supplies brain, face etc…)
Describe the positioning of the pulmonary arteries?
Divides the heart into two branches towards the lungs
Describe the positioning of the pulmonary veins?
Two located at each lung that drain into the left atrium
Describe the positioning of the femoral artery?
Thigh, supplies blood to the lower limbs
Describe the positioning of the renal arteries/veins?
The left interior side of the abdominal aorta, supplies the kidneys
Describe the positioning of the coronary arteries?
Above the aortic valve, subdivide and cover the surface of the heart
Describe the positioning of the circle of willis?
Joining area of several arteries at the inferior side of the brain.
Branch into smaller arteries that supply blood to over 80% of the cerebrum.
