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Where is the heart located?
Middle of the thoracic cavity, attached to the thorax via great vessels
- Apex - Just above diaphragm left of midline
- Base - ~ 2nd rib
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Heart tissue layers
Endocardium - Inner most layer
Myocardium - Thick middle layer
Pericardium - protective sac surrounding the heart.
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Pericardium Layers
Visceral Pericardium(Epicardium) - Inner layer in contact with heart muscle.
Parietal pericardium - Outer fibrous layer.
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Which heart layer is responsible for contraction and pumping?
Myocardium
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Atria vs. Ventricles
- Atria: receive blood from the body
- Ventricles: pump blood to lungs and body
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Where do the Tricuspid and Mitral (Bicuspid) valves lie?
- Tricuspid: between R atrium and R ventricle
- Mitral: between L atrium and L ventricle
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Where do the Semilunar Pulmonary and Aortic valves lie?
- Pulmonary: from the R ventricle to the pulmonary artery
- Aortic: from the L ventricle to the Aorta
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Describe Blood flow through the heart.
Superior/Inferior vena cava(deoxygenated blood) ---> R atrium ---> Tricuspid valve ---> R ventricle ---> Pulmonary Valve ---> Pulmonary artery ---> Lungs ---> Pulmonary Vein(oxygenated blood) ---> L atrium ---> Mitral Valve ---> L Ventricle ---> Aortic Valve ---> Aorta ---> Body
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What supplies the heart with oxygen?
Coronary Arteries
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Coronary Circulation LCA. It's branches and what does it supply?
Supply the left ventricle, interventricular septum, parts of the right ventricle and the hears conduction system.
Anterior descending artery
Circumflex artery
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Coronary Circulation RCA. It's branches and what does it supply?
Supplies portion of the right atrium/ventricle and part of the conduction system.
- Posterior descending artery
- Marginal artery
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Cardiac Output Formula is...
CO= SV (stroke volume) x HR (heart rate)
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Define Cardiac Output. What's the normal adult CO?
- CO: amount of blood ejected (pumped) by the ventricles in 1 minute
- Normal adult CO= 5LPM
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Neurotransmitter of the Sympathetic Nervous system and its action.
- Norepinephrine
- Increases HR and Cardiac contractile force
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Neurotransmitter of the Parasympathetic Nervous System and its actions.
- Acetylcholine
- Slows both the HR and atrioventricular conduction.
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Define - Chronotropy, Inotropy, Dromotropy
Chronotropy - Refers to HR
Inotropy - Strength of cardiac muscular contraction.
Dromotropy - The rate of nervous impulse conduction.
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List where Alpha1/Beta1,2 receptors are located and their actions.
Alpha 1 - Located in the peripheral blood vessels. Responsible for vasoconstriction.
Beta 1 - Primarily in the heart. Increase HR and Contractility.
Beta 2- Lungs and Peripheral blood vessels. Brochodilation and peripheral vasodilation.
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Define Exitability
Cells can respond to an electrical stimulus
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Define Conductivity
Cells can propagate the electrical impulse from one cell to another
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Define Automaticity
Ability to spontaneously initiate an electrical impulse
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Define Contractility
The ability to contract
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Conductive system's intrinsic rate of self-excitation?
- SA Node = 60-100 BPM
- AV Node = 40-60 BPM
- Purkinje system = 15-40 BPM
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Major ions in cardiac function
Potassium (K) - Influences repolorization.
Sodium (Na) - Major role in depolarizing the myocardium
Calcium (Ca) - Takes part in myocardial depolarization and contraction
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Describe the Polarized state of a cell. What does it appears as on an EKG?
- Resting state with no electrical activity. The inside of the cell is negative, outside is positive with uneven distribution of ions across the cell membrane.
- EKG Baseline
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Describe the Depolarized cell state.
Inside of cell is positive, outside of cell is negative.
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Absolute Refractory Period
From the onset of QRS to approximately the peak of T wave. Cells are depolarized and cannot be stimulated.
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Relative Refractory Period
- "Vulnerable Period" because cells are repolarizing and can be stimulated (if stimulus is strong enough) thus possibly resulting in ventricular chaos.
- Downslope of T wave.
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EKG provides information about...
conduction disturbances, electrical effects of meds and electrolytes, and ischemic damage and injury.
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When depolarization moves toward a positive or toward a negative the waveform deflection appears as...
- Toward positive electrode= upward
- Toward negative electrode= inverted (downward)
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When electrical activity is not detected on an EKG, what appears?
A straight line is recorded, called the "baseline" or "isoelectric" line
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In the bipolar leads, which is always positive? negative?
- Positive = L leg electrode
- Negative = R arm electrode
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Lead axis I is?
RA (-) ----> LA (+)
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Lead axis II is?
RA (-) -----> LL (+)
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Lead axis III is?
LA (-) ----> LL (+)
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EKG paper: Small squares?
Small square: 1mm x 1mm, 0.04 sec
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EKG paper: Large squares?
Large square: 5mm x 5mm, 0.2 sec
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P wave represents...
atrial depolarization and spread of impulse across the L & R atria
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PR Segment
End of P wave, beginning of QRS complex. Usually represented by an isoelectric line
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PR Interval. What is the normal range?
- From the beginning of the P wave to the beginning of QRS Complex. Reflects the impulse travel time from the SA node through the AV node, Bundle of His, R & L bundles, and into the Purkinje fibers.
- Normal range= 0.12- 0.20
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Q Wave...
a negative deflection following the P wave. Always appears as a negative waveform.
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R Wave...
First positive deflection following the P Wave or Q wave (if present). Always appears as a positive waveform.
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S Wave...
Negative waveform that follows the R wave.
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R & S waves represent?
R & S waves represent the depolarization of the L & R ventricles.
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QRS Complex. Normal range?
- Represents the depolarization of the ventricles and HR.
- Normal range= 0.04- 0.12
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ST segment
End of the S wave, beginning of the T wave
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ST elevation/ depression occurs on EKG if...
above or below by 1mm of the PR segment
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ST depression can indicate? ST elevation?
- Depression: myocardial ischemia, digoxin, or low K
- Elevation: myocardial injury, infarction, or pericarditis, or cardiac tamponade.
3 I's of MI (ischemia, injury, infarction)
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T Wave
represents ventricular repolarization
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QT Interval. Normal range?
- From beginning of Q to the end of the T wave. Represents total ventricular activity.
- Normal range= 0.33-0.42
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Describe cardiac conduction system from start to finish.
SA ---> Internodal Pathways ---> AV Junction ---> AV Node ---> Bundle of His ---> L/R Bundle Branch --- (R Bundle) ---> apex of the R ventricle ---> Perkinje system --- (L Bundle) ---> Anterior/Posterior fascicles ---> Perkinje System
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