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32 Cards in this Set
- Front
- Back
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How many Americans have CVD?
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57 million
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How many Americans have HTN?
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50 million
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How many Americans have CHD?
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14 million
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How many Americans have strokes?
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4 million
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What percentage of deaths are CVD related?
How about those under 65? |
42% CVD related
16% <65y/o |
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Heart Muscle
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- Is stimulated by nerves and is self-excitable (automaticity)
- Contracts as a unit - Has a long (250 ms) absolute refractory period |
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Extrinsic Innervation of the Heart
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- stimulated by the sympathetic cardioacceleratory center
- inhibited by the parasympathetic cardioinhibitory center |
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Sinoatrial (SA) node
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generates impulses about 75 times/minute
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Atrioventricular (AV) node
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delays the impulse approximately 0.1 second
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Atrioventricular Bundle
(bundle of His) |
- Passes impulses from atria to ventricles
- splits into two pathways in the interventricular septum (bundle branches) |
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Bundle branches
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carry the impulse toward the apex of the heart
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Purkinje fibers
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carry the impulse to the heart apex and ventricular walls
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Systole
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contraction of heart muscle
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Diastole
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relaxation of heart muscle
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Ventricular filling
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- mid-to-late diastole
- Heart blood pressure is low as blood enters atria and flows into ventricles - AV valves are open, then atrial systole occurs |
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Ventricular systole
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- Atria relax
- Rising ventricular pressure results in closing of AV valves - Isovolumetric contraction phase - Ventricular ejection phase opens semilunar valves |
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Cardiac Output (CO)
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- is the amount of blood pumped by each ventricle in one minute (ml/min)
= HR (beats/min) x SV (ml/beat) |
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Stroke Volume (SV)
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- is the amount of blood pumped out by a ventricle with each beat
= end diastolic volume (EDV) minus end systolic volume (ESV) |
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Cardiac reserve
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is the difference between resting and maximal CO
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EDV
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end diastolic volume
- amount of blood collected in a ventricle during diastole |
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ESV
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end systolic volume
- amount of blood remaining in a ventricle after contraction |
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Preload
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amount ventricles are stretched by contained blood
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Contractility
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- cardiac cell contractile force due to factors other than EDV
- the increase in contractile strength, independent of stretch and EDV |
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Afterload
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back pressure exerted by blood in the large arteries leaving the heart
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Frank-Starling Law of the Heart
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- Preload, or degree of stretch, of cardiac muscle cells before they contract is the critical factor controlling stroke volume
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What causes an increase in Stroke Volume?
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Slow heartbeat and exercise increase venous return to the heart
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What causes a decrease in Stroke Volume?
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Blood loss and extremely rapid heartbeat
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Increase in contractility comes from
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- Increased sympathetic stimuli
- Certain hormones - Ca2+ and some drugs |
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Agents/factors that decrease contractility include
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- Acidosis
- Increased extracellular K+ - Calcium channel blockers |
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Regulation of Heart Rate
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Increase heart rate= Positive chronotropic factors
Decrease heart rate= Negative chronotropic factors |
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Sympathetic nervous system and heart rate
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- stimulation is activated by stress, anxiety, excitement, or exercise
- stimulation releases norepinephrine and initiates a cyclic AMP second-messenger system |
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Parasympathetic nervous system and heart rate
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- stimulation is mediated by acetylcholine and opposes the SNS
- stimulation is mediated by acetylcholine and opposes the SNS |
