Cardiac Cycle Flashcards
What are the 3 stages of the cardiac cycle?
Atrial systole (contraction of atria)
Ventricular systole (contraction of ventricles)
Diastole (relaxation of heart)
What happens during atrial systole/ ventricular diastole?
Muscles of Atria contract, pushing blood into the ventricles
This causes atrial:
Volume to decrease
Pressure to increase
What happens during ventricular systole/ atrial diastole?
The atria relaxes. Once it’s relaxed the ventricles contract pushing blood out of the heart
This causes ventricular:
Volume to decrease
Pressure to increase
What happens during (cardiac) diastole?
All chambers are relaxed and blood flows into the heart
What does diastole mean?
Relax
What does systole mean?
Contract
What happens to volume and pressure during systole?
Volume decreases whilst pressure increases as heart chambers contract
What happens to volume and pressure during diastole?
Volume increases whilst pressure decreases as the hearts chambers relax
What valves open during diastole?
The atrioventricular valves open
as pressure in atria > pressure in ventricles
What valves close during diastole?
Semi lunar valves close
As pressure in ventricles < pressure in arteries
What happens during diastole?
Blood passively trickles from the atria to ventricles
Causes pressure to:
Decrease in the atria
Slightly increase in ventricles
what muscle is known as the pacemaker and controls the cardiac cycle?
The myogenic muscle
What are myocytes?
Polarised muscle cells found in the heart
What do myocytes do?
They can reverse their charges (depolarise) causing the heart to contract
What is the SAN?
Its found in the upper wall of the right atrium and sets the base heart rate
What does the SAN do?
The SAN initiates a wave of depolarisation causing the atria walls to contract almost simultaneously
What does the AVN do?
The AVN after a short delay, depolarises after the SAN and causes the ventricles to contract once all the blood has left the atria
What type of blood do the arteries transport?
Arteries carry oxygenated blood with the exception of the pulmonary artery
What type of blood do veins carry?
Veins transport deoxygenated blood with the exception of the pulmonary vein
What is the endothelium?
It is the inner lining of all blood vessels. It is made of a single layer of cells.
they are smooth to reduce friction with the flowing blood
what are elastic fibres?
they are made out of the protein elastin and provide flexibility allowing the blood vessel to stretch and recoil.
This evens out surges of blood from the pumping heart, enabling a continuous flow
What is the smooth muscle?
It provides strength to withstand high blood pressure. its main role is to contract and relax, altering the flow of blood to particular tissues.
