Studied by 2 people
which side of heart is deoxygenated blood
right side, pulmonary artery pump blood to lungs
which side of heart is oxygenated blood
left side, aorta pump blood to body
role of coronary arteries
supply cardiac muscle with oxygenated blood needed to keep contracting and relaxing
how blood passes through right side of heart
deoxygenated blood enter right atrium from superior and inferior vena cava (relatively low pressure)
slight pressure build up in atrium until atrio-ventricular valve/tricuspid valve opens to let blood into right ventricle, right atrium contract to force blood into right ventricle
right ventricle start to contract, tricuspid valve close, prevent backflow into atrium, tendinous cords make sure valves are not turned inside out by pressures
blood pumped through semilunar valves into pulmonary artery
how blood passes through left side of heart
oxygenated blood enters left atrium form pulmonary vein
biscuspid valve prevents backflow of blood into left atrium
same as right side
blood pumped through semilunar valves into aorta
why is the wall of muscle thicker on the left side
left side needs to produce sufficient force to pump blood to all extremities of body
diastole
heart relaxes, atria then ventricles fill with blood
volume m and pressure in heart build as heart fill, pressure in arteries at min
systole
atrial systole: atria contract
ventricular systole: ventricles contract
pressure increases and blood forced out,
volume and pressure in heart are low, blood pressure in arteries at max
diagram for pressure changes in heart during cardiac systems
heart sounds and ecg diagram of cardiac cycle
what does myogenic mean
own intrinsic rhythm at around 60 bpm, prevent body wasting resources maintaining basic heart rate
how is rhythm of heart maintained
wave of electrical excitation begin in sino-atrial node (SAN), cause atria to contract, initiate heartbeat, layer of non-conducting tissue prevent first excitation passing directly into ventricles
electrical activity form SAN picked up by atria-ventricular node (AVN), imposes slight delay before stimulating bundle of His (conducting tissue made up of Purkyne fibres), penetrate through septum
bundle of His splits into two branches and conducts excitation to apex of heart
purkyne fibres spread out through walls of ventricles on both sides, triggers contraction of ventricles starting at apex
why is there a delay in the wave of excitation
to allow all blood to flow into ventricles before ventricular systole
what does electrocardiogram measure
tiny electrical differences in skin which result from electrical activity of heart
how to get an ECG
electrodes stuck to clean skin to get good contact, signal from each of electrodes fed into machine, produce ECG
why do people have ECGs
to help diagnose heart problems
what is a normal heart rate
beats evenly spaced 60-100min^-1
tachycardia
heartbeat >100min^-1
normal after excerise, frightened etc
if abnormal may be caused by problems in electrical control of heart, may need to be treated by medication or surgery
bradycardia
heart rate <60min^-1
normal for fit athletes
severs bradycardia can be serious and maybe need artificial pacemaker to keep heart beating steadily
ectopic heartbeat
extra heartbeat out of normal rhythm
usually normal but can be linked to serious conditions when very frequent
atrial fibrillation
example of arrhythmia
rapid electrical impulses in atria fibrillate but to 400 times a minute
don’t contract properly and only some of impulses are passes on to the ventricles, heart does not pump blood very effectively
how to work cardiac output
stroke volume/ heart rate
what are the units for cardiac output
cm³ min^-1
Note 
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