the cardiac cycle Flashcards
phases of the cardiac cycle
- diastole (both)
- atrial systole
- ventricular systole
what 3 phases are the ventricles filled in
diastole
atrial systole
ventricular diastole
what is systole
contraction
what is diastole
relaxation
what causes the movement of blood from one region to another
pressure difference
high pressure area to a low pressure area
what prevents the backflow of blood around the heart
and give their name
AV valves
semilunar valves
what are cardiac cells and what does this mean
myogenic
these generate their own contraction and dont require a neural input to initiate a contraction
what is the cardiac cycle controlled by
electrical impulses
first stage of cardiac cycle
what happens during diastole
- both atria and ventricles are relaxed and under low pressure
- blood flows in through the atria to the ventricles from the pulmonary veins and vena cava
- blood flows into ventricles
- ventricles fill until theyre the same pressure as the veins
- at the end of diastole, atrial systole occurs
what happens during atrial systole
- the atrial muscle contracts and pushes a tiny bit more blood into the ventricles (started by the SA node)
- this causes the pressure in the ventricles to become greater than the atria
- the difference in pressure causes the blood to attempt to flow back into the atria
- this closes the AV valves
what happens in ventricular systole
at the beginning- both valves are closed
- the ventricle muscles contract
- the pressure difference in the ventricles compared to the pulmonary artery and aorta is steep
- the contraction causes blood to surge through the ventricle opening the semilunar valves and travel into the great arteries
at the end- contraction relaxes and ventricles relax
what happens in late ventricular systole early secondary diastole
now that the ventricles have relaxes their pressure decreases
- the pressure in the arteies is greater
- the blood attempts to travel back into ventricles
- this only closes the semilunar valves
- blood is then pumped through the arteries
what causes the av valves to open again
when the pressure in the ventricles decrease after systole
what is the atrial systole initiated by
a wave of excitation
from the SA node
where is the SA node located
in specialised cardiac tissue in the right atrium
where does the SA node send electrical impluses
and what does this cause
- to the whole atrial area
- causing a coordinated contraction of both atria at the same time
what is the benefit of the electric impulse only traveling to the atrial area
- causes a small time delay between atrial systole and ventricular systole
- makes sure the ventricles are fully filled before they contract
what causes ventricular contraction
an electric impulse generated from the atrioventricular node after the SA node impulse has caused a contraction
how does the ventricles contract (process)
- AVN picks up the SAN impulse and generates its own
- the impulse is sent through specialised fibres within the septum called as plural bundle of His
- the impulse travels through each purkunje fibre around the whole ventricle
- once the impulse reaches the apex of the heart, the ventricular cardiac muscle contracts from the bottom upwards
what is the benefit of the ventricle contracting from the bottom upwards
this navigates the flow of the blood to the aorta or pulmonary artery
