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59 Cards in this Set
- Front
- Back
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Where is the heart located?
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Inferior to the mediastinum
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Where is the base of the heart? Apex?
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Base- at the top
Apex- at the bottom |
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Where are the great vessels enclosed?
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Within the pericardium
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How is the heart developed embryologically?
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From a pair of blood vessels.
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How many layers does the heart have? What are they?
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3- endocardium, myocardium, epicardium
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What is the endocardium?
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The inner most layer of the heart. It has a smooth endothelial like lining. It is continuous with the vessels of the heart.
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What is the myocardium?
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It is the muscle of the heart. Closely related to skeletal muscle- thicker the muscle the more force it can produce.
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How much thicker is the left ventricle than the right on average?
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4-5 times thicker.
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What is the epicardium?
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It is the outerlayer of the heart. Physically attached to the pericardium. Sometimes referred to as the parietal pericardium.
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What is contained within the wall of the heart that allows for attachment of cardiac muscles and valves?
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Collagen fibers.
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Why are there NO VALVES between the inferior and superior vena cava?
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Because flow is directly related to pressure.
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What needs to happen to ensure that there is venous return?
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There must be a higher pressure in the veins than in the atria.
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What is the origin of a healthy heart beat?
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SA node
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What special structure of cardiac muscle allows for the rapid spread of the electrical impulse leading to a heart beat?
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Gap junctions- interconnect the heart muscle cells to rapidly spread the message.
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What is the location of the AV node?
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Right atrium
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What is AV nodal delay?
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The AV node holds the impulse sent from the SA node momentarily to avoid overstimulation of the muscles.
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What is the order of electrical impulse through the heart?
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SA -> AV -> Right/Left Bundle branches -> Bundle of His -> Purkinje fibers
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What are the only vessels within the vasculature that conduct gas exchange?
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CAPILLARIES
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What is the largest artery?
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Aorta
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Describe the distribution of elasticity of arteries
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The closer to the heart the artery is, the more elasitic it is.
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What are the two major vessels which supply the myocardium with blood?
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Right and left coronary arteries
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What are the only blood vessels which arise from the ascending aorta?
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Right and left coronary arteries- from behind the cusps of the semi lunar valves
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What are the major differences between cardiac muscle and skeletal muscle?
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Cardiac muscle pulls the Ca needed from the ECF. The cardiac muscle also contains intercalated discs.
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What is the electrical reisistance within a gap junction?
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1/400 of the reisistance that exsists where there is no gap junction.
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How does stroke volume vary?
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With the amount of force that is able to be produced by the heart muscle.
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Compare the length of the sarcomere of cardiac muscle with that of skeletal muscle?
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Skeletal- long. Cardiac - short.
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What is the EDV?
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End diastolic volume- volume of the ventricle before it contracts.
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What is a unique feature of the SA node?
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It is autorhythmic and its cells are ineffective at keeping Na ions out.
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What is an absolute refractory period?
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Will not respond to another stimulus once it has already been stimulated. Absolute refractory period for cardiac muscle is equal to that of the duction of action- so that tetanus will not occur.
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What is a relative refractory period?
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Tissue will respond to another stimulus if the stimulus is of great enough force. Hasppens when the membrane potential is below zero and returning to -80 mV.
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What is the order of events in the cardiac cycle?
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Electrical -> mechanical -> acoustic.
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What is the definition of diastole?
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The dilation or dilation period of the heart- especially within the ventricles.
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What is the definition of systole?
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The contraction or contraction period within the heart- especially within the ventricles.
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When are the atria in systole? Ventricles? What is unique about this process?
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Atria in systole when ventricles are in diastole. Ventricles in diastole when atria are in systole. The upper and lower chambers cannot be in systole at the same time, but can be in diastole at the same time.
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What is ESV?
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End systolic volume- the amount of blood left in the ventricles after systole.
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What is the ejection fraction?
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The stroke volume expressed as a percentage. SV/EDV = EF (normally 66%)
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What is the P wave representative of?
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Represents atrial depolarization (atrial diastole, results in atrial systole)
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What is the QRS complex a representation of?
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Ventricular DEPOLARIZATION. Occurs because of atrial systole and results in ventricular diastole
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What is the T wave representative of ?
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Ventricular REPOLARIZATION. Results in ventricular diastole.
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What is the ST segment?
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Ventricular systole.
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What is the PQ segment?
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atrial systole.
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What is the TP segment?
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Atrial diastole.
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What are the 5 things that can be determined from EKGs?
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1. Heart rate
2. Heart rhythm 3. Axis of the heart 4. Hypertrophy 5. MI |
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What causes the acoustics of the heart?
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Closing of the valves
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What causes the first heart sound?
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Closing of the AV valves. Ventricles contract
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Waht causes the second heart sound?
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Closing of the semi lunar vavles. Ventricles relax.
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What is a stenosis?
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The heart valve does not open properly
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What is a regurgitation?
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The heart valve does not close properly
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What is cardiac output?
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The volume of the blood ejected by the heart every minute.
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How is cardiac output calculated?
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Q = SV x HR
Q= mL/min SV = mL/beat HR = beats/min |
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What is the average heart rate?
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72 bmp
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What is the average stroke volume?
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80 mL/beat
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What is the average cardiac output?
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5000 mL/min
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What effects do epinepherine and norepinepherine have on the heart?
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Increase the rate of the SA node (positive chronotropic agent). Increase the rate of diastolic repolarization, conduction rate through the AV node, force of atrial and ventricular contraction. Positive inotropic agents- increase EDV
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What effects does ACh have on the heart?
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Hyperpolarizes the cells of the SA node bringing them further away from threshold which decreases: rate of diastolic repolarization, force of atrial contraction (negative chronotropic agent). NO significant effects on the ventricles.
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What is EDV?
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End diastolic volume or the volume within the ventricles before it contracts. Considered to be the pre-load.
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What is the after load?
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The pressure in the aorta that is holding the valve closed. Works against ejection.
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Within the venous system, where is pressure always the lowest?
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Within the atria (0.5 mmHg).
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What actions facilitate venous return?
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Movement of skeletal muscles and movement of the diaphragm.
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