Cardiac Cycle Flashcards
(29 cards)
What is the cardiac cycle
The sequence of events that take place during one heartbeat
What are the 3 phases of the cardiac cycle (in order)
atrial systole, ventricular systole, diastole
what happens during atrial systole
The atria contract and increase
blood pressure in atria. The
semi lunar valves in the vena
cava close whilst the cuspid
valves open. Blood flows into
the ventricles.
How long does atrial systole last
about 0.1 s.
What happens during ventricular systole
The ventricles contract and
increase blood pressure in
ventricles. The cuspid valves close
and the pulmonary and aortic
valves open. Blood flows from the
ventricles into the pulmonary artery
and aorta.
how long does ventricular systole last for
about 0.3 s
What occurs during diastole
The heart muscle relaxes and
so ventricular pressure drops.
As a result, pulmonary and
aortic valves close (preventing
backflow of blood). Blood
returning to the atria is able to
flow into the ventricles.
How long does diastole last for
about 0.4 s.
Where is blood pressure greater - the artery or ventricle
In the artery
what are valve tendons like during atrial systole
slack
what are valve tendons like during ventricular systole
taut.
Papillary muscles contract to
prevent the valve from
inverting
What makes the ‘lub’ in the ‘lub dub’ sound in the heart
the atrioventricular valves closing when ventricle contracts
What makes the ‘dub’ in the ‘lub dub’ sound in the heart
the semilunar valve closing as the ventricle relaxes.
what is cardiac output
The amount of blood pumped around the body
What does cardiac output depend on
Stroke volume, heart rate
What is stroke volume
the volume of blood pumped by the left ventricle in each heart beat (a typical value for an adult at rest is 75 ml).
What is heart rate
the number of times the heart beats per minute (a typical value for an adult at rest is 70 bpm).
What is the equation for cardiac output
cardiac output = stroke volume x heart rate
what is a typical resting cardiac output
4 - 6 litres per minute, can rise to 40 litres per minute in highly trained endurance athletes
In what direction does blood always move
from a region of high to low pressure.
What keeps blood flowing in one direction
The pressure from the heart muscle
What are valves used to manage
Situations when pressure differences could result in blood flowing in the opposite direction. (Close when pressure in front is greater)
Where are the atrioventricular valves positioned
Between atrium and ventricle
what is the function of atrioventricular valves
Close when ventricle pressure is greater than that of atrium. Ensures blood flows into arteries when ventricle contracts
