The structure and function of the heart Flashcards
What is the cardiac output
the volume of blood pumped through each ventricle per minute
What is the stroke volume
the volume of blood pumped out by one ventricle with each heartbeat
What is diastole
relaxation of the heart
What is systole
contraction of the heart
Describe diastole
during diastole the atria and ventricles are relaxed
as the blood returns to the atria via the vena cava and pulmonary vein the volume of blood in the atria increases
once the pressure in the atria exceeds the pressure in the ventricles the AV valves open and blood flows into the ventricles
the semi lunar valves are closed
Describe atrial systole
both atria contract simultaneously
any blood remaining in the atria is transferred into the ventricles through the open AV valves
the ventricles are still relaxed and fill up with blood
the semi lunar valves are closed
Describe ventricular systole
both ventricles contract
the AV valves close
the pressure on the blood in the ventricles builds and is soon greater than the pressure in the arteries and the semi lunar valves are pushed open
blood is pumped out of the heart into the pulmonary artery and aorta through the semi lunar valves
What is the sino atrial node also known as
natural pacemaker of the heart
What does the SAN contain
auto rhythmic cells which sets the rate at which the heart contracts
Where is the SAN located
the wall of the right atrium
What is the timing of cardiac muscle cell contraction controlled by
impulses from the SAN
When do contractions in the heart begin
when electrical impulses are sent from the SAN
Where is the atrio ventricular node located
centre of the heart
Describe the path of the electrical impulse as it generates a heart beat
an impulse originates from the SAN
the impulse travels across the walls of the atria making them contract simultaneously and reaches the AV node
the AV node sends impulses down fibres in the central wall of the heart and then up through the walls of the ventricles causing the ventricles to contract
this is followed by diasotle
What is the p wave
the wave of electrical impulses spreading over the atria from the SAN causing atrial systole
What is QRS
the electrical impuslses through the ventricles
What is T
the electrical recovery of the ventricles at the end of ventricular systole
What is T to P
diastole
What does antagonistic action mean
have the opposite effect on the same structure
What does the medulla control
the cardiac cycle
What does the sympathetic nerve do
releases noradrenaline causing an increase in heart rate
What does the parasympathetic nerve do
releases acetylcholine causing a decrease in heart rate
What is the blood pressure during ventricular systole
at its maximum
What is the blood pressure during ventricular diastole
drops to a minimum
What is the typical blood pressure for a young adult
120/80
What is blood pressure measured using
sphygmomanometer
Describe the effects of the autonomic nervous system on the SAN
parasympathetic nerve decreases heart rate sympathetic nerve increases heart rate
