the cardiovascular system (part 2 of 3)
degree of valve damage
seriousness of a heart murmur depends on what?
1. atria contracts, blood pushed from A-V valve to ventricles 2. A-V valve closes 3. chordae tendinae prevents A-V valve from opening back into atria 4. pulmonary and aortic valves open, blood flows out, ventricles begin to relax 5. A-V valves open, ventricles begin to fill again
cardiac cycle
relaxation
function of diastole
contraction
function of systole
the closing of the valves
heart sounds are due to the vibrations in the heart tissues associated with what?
contraction
high pressure corresponds to contraction or relaxation?
40-60
how many beats per minute in the A-V node?
70-80
how many beats per minute in the S-A node?
lubb
sound that occurs during ventricular contraction, when A-V valves are closing
dupp
sound that occurs during ventricular relaxation, when the pulmonary and aortic valves are closing
myocardium
specialized cardiac fibers in the CCS distribute impulses through which heart layer?
atrial syncytium
impulses pass along fibers of the conduction system from the S-A node into the ____ ____
relaxation
low pressure corresponds to contraction or relaxation?
the A-V valve closes
what happens when ventricular pressure exceeds atria pressure?
"lubb-dupp"
what is the sound of the heart?
rhythmic, one impulse after the other
S-A node activity
S-A node
pacemaker of the heart
S-A node
a mass of specialized cardiac tissue that sits beneath the epicardium
Purkinje fibers
the bundle branches give rise to the _____ _____ about halfway down the septum
valves going from atrium to ventricle (atrioventricular)
what are A-V valves?
pressure rising and falling within the heart chamber
what causes valves to open and close during a cardiac cycle?
eroded edges of the valve cusps
what does inflammation of the endocardium cause?
the left and right bundle branches
what does the A-V bundle divide into?
the events of the cardiac cycle
what does the cardiac conduction system coordinate?
cusps may not close completely, allowing some blood to leak back into atria
what happens if valve cusps erode?
they pass through a large group of fibers that make up the A-V bundle
what happens once cardiac impulses reach the distal side of the A-V node?
it's pushed through the A-V valve into the ventricles
what happens to blood when atria contracts?
appropriate valves open, blood flows out, ventricles begin to relax
what happens when ventricular pressure exceeds pressure in pulmonary trunk and aorta?
A-V valves open, ventricles begin to fill again
what happens when ventricular pressure is less than the atrial pressure?
papillary muscle
what muscle pulls on the chordae tendinae to prevent the A-V valve from opening back into the atria?
relaxes
when the atria contracts, the ventricle _____
ventricles, stimulate contraction
where do the Purkinje fibers lead into and what do they do?
in the septum
where do the bundle branches lie?
A-V node
where does the atrial syncytium lead?
septum below atria
where is the A-V node located?
right atrium, below superior vena cava
where is the S-A node located?
tricuspid, mitral
which valves are A-V valves?