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66 Cards in this Set
- Front
- Back
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S.A. node heart rate
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72-75 bpm
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A.V. node heart rate
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50-60 bpm
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Beats per minute when ventricles are causing the contractions
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30-40 bpm
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Factors that increase heart rate
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Excitement
anger painful stimuli hypoxia (not enough oxygen) exercise epinephrine norepinephrine thyroid hormones fever breathing in |
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Factors that decrease heart rate
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breathing out
grief |
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Normal heart rate
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60-100 bpm
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Bradycardia
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less than 60 bpm
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Tachycardia
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greater than 100 bpm
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Inotropic
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(+) or (-) strength or force of contraction
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Factors that have a positive inotropic effect
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Frank Starling's law of the heart
Catecholamines Xanthines Digitalis |
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Frank Starling's law of the heart
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the greater the filling during diastole, the greater the force of contraction during systole
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Catecholamines
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Epinephrine and norepinephrine
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Xanthines
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Caffeine and theophylline
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Digitalis
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Drug used for cardiac failure derived from foxglove plant
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Chronotropic (+) or (-)
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The rate of contraction
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Dromotropic (+) or (-)
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The rate of conduction of impulse
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How do nerves affect cardiac pumping (2 ways)
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1. Changing the heart rate - chronotropic
2. Changing the strength of contraction - inotropic |
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Sympathetic control of heart
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1. Increases rate and force of contraction
2. Maximum sympathetic stimulation = 250 bmp 3. Norepinephrine - increases the permeability of cardiac cells to Na+ and Ca++ |
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Parasympathetic control of heart
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1. Decreases the rate and force of contraction
2. Maximum parasympathetic stimulation = 20-30 bpm 3. SA node - right vagus, AV node - left vagus 4. Acetylcholine - increases the permeability of membrane to K+ |
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Stroke volume
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The amount of blood pumped out of each ventricle per beat
average = 60-80 mL |
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Cardiac Output (CO)
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Volume pumped by each ventricle per minute
Stroke volume x heart rate |
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Average person CO
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72 bpm x 80 ml/beat = 5.76 L/minute
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Factors that cause an increased CO
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Anxiety
Eating Exercise Increased body temperature Pregnancy |
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Fick Method (measuring CO)
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CO = (oxygen consumption ml/min)/(arterial O2-venous O2)
End up with L/minute |
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Heart impulse pathway
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Impulse starts in SA node
Spreads over atrial muscle fibers -> atrial contractions Travels through AV bundle and purkinje fibers Produces coordinated ventricular contractions |
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Things that can alter heart rate
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Sympathetic impulses
Parasympathetic impulses Hormones Body temperature Exercise Drugs Emotions Stimulus from various exteroceptors |
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What can cause abnormal cardiac rhythms?
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Abnormal rhythms in SA node
Ectopic pacemaker Blockage of impulses throughout the conduction system |
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Ectopic pacemaker
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Shift of pacemaker activity from SA node to other portions of the conduction system or other parts of the heart
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EKG
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Recording of the electrical activity associated w/ muscle contraction
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P-wave
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First wave
Depolarization of atria |
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QRS complex
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Second wave
Depolarization of ventricles |
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T-wave
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Repolarization of ventricles
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Einthoven's triangle
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EKG: Electrodes are attached to left shoulder, right shoulder, and left leg
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Atria
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Upper heart chambers
Also called auricles |
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Ventricles
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Lower chambers of heart
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Direction of blood flow through heart:
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Right atrium
Tricuspid valve Right ventricle pulmonary valve pulmonary arteries lungs pulmonary vein left atrium mitral valve left ventricle aortic valve aorta body vena cava right atrium |
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Three layers of heart wall
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Endocardium - thin layer of endothelium
Myocardium - muscle layer Epicardium - thin external layer |
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Sinoatrial node
(SA node) (natural pacemaker) |
Located in posterior wall of atrium, near vena cava
Rhythmical impulses originate in the SA node |
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Four unique characteristics of SA node
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1) First half of the pacemaker potential is result of funny (If) channels
2) Second half of pacemaker potential is the opening of T-type Ca+ channels (decrease funny channels) 3) Once threshold is reached, there's a decrease in T-Ca+ channels and opening of L-Ca+ channels (long lasting Ca+ channels) 4) Falling phase is a result of the opening of K+ channels |
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Funny (If) channels
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Permit...
Inward Na+ movement Closure of outward K+ channels |
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Atrioventricular node (AV node)
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Located within the lower right interatrial septum.
Impulse is delayed in the AV node for about a tenth of a second to allow the atria to contract before ventricular contraction |
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Atrioventriuclar bundle
(AV bundle or bundle of HIS) |
Originates in the AV node, dividing into two bundle branches which extend down the tow sides of the interventricular system and branch out to purkinje fibers
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Is control of the conduction in the heart an extrinsic or intrinsic system?
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Intrinsic
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Systole
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Phase of contraction in cardiac cycle
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Diastole
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Phase of reaction in cardiac cycle
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Auscultatory method
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Clinical method of measuring blood pressure, based on the correlation of blood pressure and atrial sounds
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Sounds of Korotkoff
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the sounds of turbulent blood as heard in a stethoscope during auscultatory method
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What does the first blood pressure sound represent?
The second? |
First = systolic
Second = diastolic |
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Pulse pressure
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difference between systolic and diastolic pressures
Generally about 40-50 mmHg Represents pressure difference that drives blood along arteries to the capillaries |
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What are the 12 different leads?
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3 standard limb leads
3 augmented limb leads 6 chest leads |
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What information do the first two chest leads give? (V1 and V2)
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Info about what's happening in the left ventricle
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What information do the third and fourth chest leads give? (V3 and V4)
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Info about the septum (muscle between ventricles)
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What information do the last two chest leads give? (V5 and V6)
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Info about what's happening in the right ventricle
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Cardiac arrhythmia
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Deviations from normal heart rate or from normal electrical activity of the conduction system
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What can cause cardiac arrhythmia?
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Abnormal rhythmicity of the SA node
Shift of pacemaking function from the Ectopic or abnormal pacemaker Abnormal pathway or blockage of impulses in the conduction system |
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Causes of ectopic or abnormal pacemakers:
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Localized areas of ischemia (lack of blood flow)
Areas of heart damage Dilation of the heart Toxic irritants (nicotine, caffeine, alcohol) Lack of sleep Anxiety Extremes in body temperature Changes in body pH |
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What are the "big three" toxins that affect the heart?
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Nicotine
Caffeine Alcohol |
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Atrial premature beat
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P-wave comes early
Can be normal-looking or introverted |
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AV nodal premature beat
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Originates from an ectopic discharge of the AV node, then proceeds down the Bundle of His
Normal QRS complex, just early Generally not preceded by a p-wave |
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Premature ventricular depolarization (PVD or PVC)
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Originates from an ectopic pacemaker
Characteristics: no p-wave, wide QRS complex, high voltage, T-wave is usually inverted May become coupled with one or more normal beat |
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What does a wide QRS wave indicate?
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Conduction through the muscle cells
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Bigeminy (relating to PVD's)
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One normal end and one PVD
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Trigeminy (relating to PVD's)
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Two normal ends and one PVD
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SA block
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Pacemaker temporarily stops for at least one complete cycle, then resumes pacing
p-waves before and after block are identical n_N_n___n_N_n______________n_N_n___n_N_n |
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Atrial flutter
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Originates in an atrial ectopic pacemaker
P-waves are very rapid and coordinated, look similar to each other 2:1, 3:1, 4:1 Treatment = digitalis __n_N_n___n_N_nnnn_N_nnnn_N_n___ |
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Atrial fibrillation
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Caused by many ectopic pacemakers in the atria
Uncoordinated or irregular P-waves Decrease in cardiac output QRS-T usually looks normal |
