The Cardiac Cycle Flashcards
what is the cardiac cycle?
series of events that occur when the heart beats, circulates blood through pulmonary & systemic circuits that make up double circulatory system.
why is the double circulatory system more efficient?
keeps the oxygenated & deoxygenated blood separate.
where does the pulmonary circuit carry the blood?
to the lungs to be oxygenated & back to the heart.
what happens in the lungs?
CO2 is removed from the blood & O2 taken up by haemoglobin in RBC
where does the systemic circuit carry the blood?
around the body to deliver O2 & returns deoxygenated blood to the heart
what is the cardiac cycle broken down into?
the sequence of mechanical & electrical events that are repeated every heartbeat. 2 phases - diastole, systole.
whats diastole?
relaxation phase, during this stage blood pressure is at lowest.
whats systole?
contraction phase, this is when the blood pressure rises.
how do we monitor the frequency of the cardiac cycle?
heart rate - number of beats per minute.
how does the cardiac cycle start in the left side of the heart? CC in LSoH
blood drains into the left atrium from the lungs along the pulmonary vein.
what happens after the blood enters the left atrium? CC in LSoH
raise of BP in left atrium forces the left bicuspid valve open.
what happens when the left bicuspid valve is forced open? CC in LSoH
contraction of the left atrial muscle forces more blood through the valve.
what happens after the left atrial muscle is done contracting? CC in LSoH
the left ventricular muscles start to contract.
what happens after left ventricular systole is done?
forces the left bicuspid valve to close & opens the aortic valve causing blood to leave left ventricle via aorta.
whats cardiac diastole?
when heart refills with blood
whats ventricular diastole?
when the ventricles are refilling & relaxed
what does the heart need to beat?
electrical signals to trigger the muscles to contract & relax.
what are the components of the specific pathway for the heartbeat?
sinoatrial node, atrioventricular node, bundle of his, purkinje fibres.
describe the sinoatrial node.
known as natural pacemaker - causes impulse to travel through the atria causing them to contract & forces blood into ventricles. It also sets hearts rhythm & rate.
describe the atrioventricular node.
detects impulse travelling through the atria & redirects it to bundle of his - causes a delay , slowing the spread of electrical impulse across the heart & allowing atria to contract before ventricles.
describe the bundle of his (atrioventricular bundle)
group of fibres in the septum which the impulse travels through to base of ventricles
describe the purkinje fibres.
act as neurons & are found in the walls of the ventricles. the impulse from bundle of his reach here which cause ventricles to contract.
what are baroreceptors?
the detect changes in pressure of blood filling the atria, they send signals to the CNS which triggers vasodilation which reduces pressure in the blood.
