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Know the basic anatomy of heart and blood flow through the heart and body.
- body
- vena cava
- right atrium
- tricuspid valve
- right ventricle
- pulmonary valve
- pulmonary arteries
- lungs
- pulmonary veins
- left atrium
- mitral valve
- left ventricle
- aortic valve
- aorta
- body
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What is "depolarization"?
electrical activity that results in contraction of an individual cardiac cell. Na+ is put outside the cell (by the Na-K pump) while it is not contracting. then Na+ channels open, Na+ rushes into the cell - this is depolarization - which causes the cell to contract.
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What is "automaticity"?
the ability that each cardiac cell has to spontaneously depolarize - to "fire off" on its own, at its own rate. normal cardiac cells outside of the sinoatrial node have a spontaneous depolarizing rate slower than the cardiac cells in the sinoatrial node, therefore the SA node sets the heart rate
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What is a "resting" cardiac cell?
a cardiac muscle cell that is not depolarizing, or contracting. it is "polarized" - Na+ segregated to the outside of the cell membrane K+ to the inside.
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Is a "resting" cardiac muscle cell contracting or not contracting?
not contracting
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Is a resting cardiac cell using energy? For what?
yes - for the sodium-potassium pump (Na-K-ATPase pump). pumps Na+ out and K+ in to maintain polarization. and for other cell functions. "resting" only means that it is not contracting at that time.
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Does a resting cardiac cell pump Na+ inside or outside of its cell membrane? How about K+?
Na+ out, K+ in
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Is a resting cardiac cell polarized or depolarized?
polarized
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Is a polarized cell contracting or not contracting?
not contracting
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What and where are Na+ and K+ "channels"?
"gates" through the cell membrane. specialized protein molecules in the cell membrane that can "open" to let these ions in, or "close" to keep them out
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When the Na+ channels in a cardiac cell are not "officially open" (resting state), can Na+ "leak" into the cell?
yes
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If enough Na+ leaks through the Na+ channels into a cardiac cell, can it cause the Na+ concentration inside the cell to get high enough (reach the threshold) to cause the Na+ channels to open (causing depolarization)?
yes
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Under what 2 conditions can Na+ channels in an individual cardiac cell open, causing the cell to depolarize and contract?
adjacent cells depolarize - a wave of depolarization spreads from cell to cell. enough Na+ "leaks" into the cell and builds up to a high enough concentration - the "threshold" concentration.
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What is a "refractory" period of a cardiac cell?
time immediately after depolarization, when a cardiac cell cannot contract again - Na+ and K+ are on the "wrong" side of the cardiac cell membrane. cell cannot contract again until the Na-K pump has repolarized the cell.
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Do calcium levels in cardiac cells affect their ability to contract? Are Ca++ channels also present in cardiac cell membranes?
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In a normal heart, do all of the cardiac cells contract at random or do they contract in a coordinated fashion in order to pump blood?
coordinated
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An electrical impulse, or wave of depolarization, spreads through the heart to cause coordinated contraction. Where does this electrical impulse originate?
sino-atrial node - pacemaker of heart
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What is another name for the sino-atrial node?
pacemaker
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Do the atria and ventricles contract at the same time?
no
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Can an electrical impulse pass directly from the atria to the ventricles at just any old site?
no
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Where does an impulse pass from the atria to the ventricles?
at the atrio-ventricular node
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Why does the atrio-ventricular node delay the impulse as it passes from the atria to the ventricles?
so the atria can pump the ventricles full of blood before the ventricles contract
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What specialized group of cardiac muscle cells conduct the wave of depolarization from the atrio-ventricular node to the apex of the heart?
bundle branches, bundle of His
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What specialized group of cardica muscle cells come off of the bundle branches to further spread the wave of depolarization throughout the ventricles?
Purkinje fibers
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Why is it nice to have the ventricles contract from the apex toward the base in an organizsed fashion?
to force the blood out of the ventricles and into the pulmonary artery and aorta
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On the EKG, what does the P wave represent?
atrial depolarization
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What does the P-R interval represent?
the delay at the atrio-ventricular node
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What does the QRS complex represent?
ventricular depolarization
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What does the T wave represent?
ventricular depolarization
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When compensating for increased exercise or stress, does the heart rate generally increase or decrease?
increase
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When compensating for increased exercise or stress, does the size of the heart generally increase or decrease?
increase
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What are the 3 main categories of heart problems?
- valvular disease
- myocardial disease
- arrhythmias
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List 3 of the features of congestive heart failure.
- heart is not beating effectively
- blood volume increases as the body retains fluid to compensate for low blood pressure
- fluid starts to accumulate in the lungs, abdomen, etc.
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In general, would it be better to give drugs that cause vasoconstriction or drugs that cause vasodilation to a patient in congestive heart failure?
drugs that cause vasodilation
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What is a cardiac arrhythmia? Is it good or bad? Why?
- abnormal pattern of electrical activity in the heart
- bad
- the heart is not pumping as effectively
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What is an "ectopic focus"?
a cardiac muscle cell or group of cardiac muscle cells, not in the sino-atrial node, that depolarize out of sequence of faster than the sino-atrial node, causing an arrhythmia
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Can an ectopic focus cause a cardiac arrhythmia?
yes
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Why is a cardiac arrhythmia a problem?
the abnormal beat is not contracting the heart in the most effective way - less blood is being pumped by the abnormal beats
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What causes ectopic foci?
areas of damaged cardiac muscle cells - have "leaky" cell membranes. damaged by anoxia, trauma, drugs, toxins, electrolyte imbalances, increased levels of or sensitivity to epinephrine, etc.
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How can you tell on the EKG if an ectopic focus originates in the atria?
there will be an abnormal P wave.
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How can you tell on the EKG is an ectopic focus originates in the ventricles?
there will be an abnormal QRS complex
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Where does a supraventricular tachycardia originate?
"above the ventricles" - in the atria
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Will the QRS complex associated with a supraventricular tachycardia be normal or abnormal?
normal. the abnormal wave of depolarization originating in the atria still hits the atrioventricular node and travels down the bundle branches and the Purkinje fibers in the normal way
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What is heart flutter or fibrillation?
- rapid
- irregular
- uncoordinated contractions
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Which is more dangerous - atrial fibrillation or ventricular fibrillation? Why?
ventricular fibrillation is most dangerous. with atrial fibrillation, the heart still has normal ventricular contractions and is pumping blood. with ventricular fibrillation, no blood is being pumped.
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What is PVC (or VPC)? Is it good or bad?
premature ventricular contraction - single large bizarre QRS wave coming too early in the cycle. bad. ineffective heart beat, not the normal volume of blood being pumped for the beat. PVC's can indicate a problem. heart problems, anesthesia too deep, hypoxia, drugs, cardiac stimulation, etc.
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