2.6 Flashcards
what is the heart
a muscle that pumps blood around the body via the blood vessels
what are the 4 chambers of the heart
the left & right atrium
the left & right ventricle
what are the steps of blood flow through the heart
- deoxygenated blood enters the right atrium through the vena cava, the right atrium contracts and is forced into the right ventricle
- at the same time oxygenated blood enters the left atrium through the pulmonary vein, the left atrium contracts and blood is forced into the left ventricle
- the right ventricle contracts and deoxygenated blood is pumped through the pulmonary artery where it travels to the lungs to get oxygen
- the left ventricle contracts and oxygenated blood is pumped through the aorta to the rest of the body
what are the walls of the heart made of
cardiac muscle
why is the muscular wall of the left ventricle thicker than the right
because it has to pump blood all around the body whereas the right only has to pump blood to the lungs
where are valves found in the heart
between the artiums and the ventricles and between the ventricles and pulmonary artery
why are valves present in the heart
to prevent the back flow of blood and ensure that blood travels in one direction
what is the cardiac output
the volume of blood pumped through each ventricle per minute
what is the formula to calculate CO
CO=heart rate x stroke volume
what is stroke volume
the volume of blood (litres) pumped out by the left ventricle during one contraction
what is the cardiac cycle
the pattern of contractions (systole) and relaxation (diastole) in one complete heartbeat
how long does the average cardiac cycle last
0.8 seconds based on a heart beat of 75bpm
what happens during atrial and ventricular diastole
- blood returns to the atria through the vena cava and pulmonary veins
- increased volume of blood in atria causes valves to open
- higher pressure in the arteries closed the SL valves
what happens during atrial systole
the atria contract together pushing remaining blood into the ventricles through the open AV valves
what happens during ventricular systole
- the ventricles contract causing AV valves
- the SL valves open and blood is pumped out of the heart and into the aorta and pulmonary artery
what causes the heart sounds heard with a stethoscope
the opening and closing of the AV and SL valves
where does the heartbeat originate
in the heart itself
what regulates the heart rate
nervous and hormonal control
where is the SAN located
in the wall of the right atrium
what does the SAN do
set the rate at which the heart contracts
what controls the timing of cardiac muscle cell contraction
impulses from the SAN spreading through the atria causing atrial systole
where is the AVN located
in the centre of the heart
what do impulses from the AVN do
they travel down fibres in the central wall of the heart and then up through the wall of the ventricles causing ventricular systole
what does an electrocardiogram detect
currents generated by impulses in the heartb
