8.5 the heart Flashcards
how does deoxygenated blood travel through the heart
it comes from the body and and if it comes from the upper body it enters the right atrium through the superior vena cava and if it comes from the lower upper body it enters through the inferior vena cava. at first the pressure is low but as blood flows in the pressure builds up and the tricuspid valve opens and blood flows through into the right ventricle so it is in both the right atrium and right ventricle and then the right atrium contracts and forces all the blood into the right ventricle and then the tricuspid valves shut to prevent the backflow of blood, the right ventricle then contracts fully and forces the deoxy blood through the semi-lunar valves into the pulmonary artery which transports the deoxy blood to the capilary beds of the lungs
how does oxygenated blood travel through the heart
it comes from the lungs and enters the heart through the pulmonary veins to the left atrium at first the pressure is low but as blood flows in the pressure builds up and the bicuspid valve opens and blood flows through into the left ventricle so it is in both the left atrium and left ventricle and then the left atrium contracts and forces all the blood into the left ventricle and then the bicuspid valves shut to prevent the backflow of blood, the left ventricle then contracts fully and forces the oxy blood through the semi-lunar valves into the aorta which transports the oxy blood to the rest of the body
what do the coronary arterys do
it supplys the cardiac muscle with the oxygenated blood it needs to keep contacting and relaxing
what prevents the heart from over filling with blood
the heart is surrounded by inelastic pericardial membranes to prevent the heart from over-distending with blood
what is the heart made of and what does this mean
its made of cardiac muscle which means it doesnt get fatigued and need to rest
which side of the heart does deoxygenated blood pass through
the right side
which side of the heart does oxygenated blood pass through
the left side
what do the tendinous cords do
make sure that the valves arent turned inside out by pressures exerted when the ventricles contracts
which side of the hearts muscular wall is thicker
the left side
why is the muscular wall on the left side of the heart thicker than the right
because the lungs are relatively close to the heart and are much smaller than the rest of the body so the right side of heart has to pump the blood a relatively short distance and only has to overcome the resistance of the pulmonary circulation, the left side has to produce sufficient force to overcome the resistance of the aorta and the arterial systems of the whole body and move the blood under pressure to the whole body
what does the septum do
it separates the left and right sides of the heart so the oxygenated and deoxygenated blood never mixes
whats the cardiac cycle
it describes the events in a single heart beat
how long does the cardiac cycle last (a single heartbeat)
0.8 seconds approx
what happens in diastole
the heart relaxes, the atria and then the ventricles fill with blood, the volume and pressure of the blood in the heart build as the heart fills, but the pressure in the arteries in kept at a minimum
what happens is systole
the atria contract closely followed by the ventricles the pressure inside the heart increases dramatically and blood is forced outside the right side of the heart to the lungs and forced out of the left side of the heart to the main body circulation, the volume and pressure of blood in the heart are low at the end of systole and the blood pressure in the arteries is at a maximum
whats the sounds of the heart beat made by
blood pressure closing the heart valves
what causes the first sound of the heartbeat
it comes as blood is forced against the atrio-ventricular valves (tricuspid and bicuspid) as the ventricles contracts
what causes the second sound of the heartbeat
it comes as the backflow of blood closed the semi-lunar valves in the aorta and pulmonary artery as the ventricles relax
the heart is myogenic what does this mean
it can generate/maintain its heartbeat by itself
what is the benefit of the heart being myogenic
it prevents the body wasting resources maintain the basic heartbeat
what is the basic rhythm of the heart maintained by
a wave of electrical excitation rather like a nerve impulse
whats tachycardia and if its severe how can it be treated
when the heart beat is very rapid over 100bpm eg during exercise or when frightened
if abnormal can be cause by electrical control in the heart treated by med/surgery
whats bradycardia and if its severe how can it be treated
when the heart beat is very slow below 60bpm when people are fit
if severe may need an artificial pacemaker to keep the heartbeating steadily
whats ectopic heatbeat
extra heart beats that are out of rhythm its an extra heart beat followed by a longer than normal pause most people has one a day but many more can be severe and can be linked to a serious condition
whats artial fibrillation and what causes it
this is an example of arrythmia an abnormal rhythm of the heart
rapid electrical impulses are generated in the atria they contract very fast up to 400x a minute however they dont contract properly and only some impulses are passed onto the ventricle which contracts much less often as a result the heart doesnt pump blood very effectively
what does an electrocardiogram (ECG) measure
the spread of electrical excitation throughout the heart as it contracts
its doesnt directly measure the electrical activity of the heart it measures tiny electrical differences on the skin which result from electrical activity of the heart
where does the wave of electrical excitation begin
in the pacemaker area, the sino-arterial node (SAN)
what does the sino-arterial node do
it causes the atria to contract and in so initiates a heatbeat, a layer of non-conducting tissues prevent the excitation passing directly to the ventricles
what picks up the electrical activity from the
the atrio-ventricular node (AVN)
what do the atrio-ventricular nodes do
they impose a slight delay before stimulating the bundle of His
what are His and where do they penetrate
they are a bundle of conducting tissue made up of purkyne fibres, which penetrate through the septum between the ventricles
what does the bundle of His do
they split into two branches and conduct the wave of excitation to the apex (bottom) of the heart
why does the AVN need to delay the wave of excitation
to make sure the atria have finished contracting before the ventricles begin to contract
how is the contraction of the ventricles triggered using purkyne fibres
at the apex of the heart the purkyne fibres spread out through the walls of the ventricles the spread of excitation triggers the contraction of the ventricles, contraction starts at the apex to allow more efficient emptying of the ventricles
