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40 Cards in this Set
- Front
- Back
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Cardiac Output= |
Heart Rate X Stroke Volume |
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Cardiac Output: |
4-7 l/min per minute |
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Stroke Volume: |
The amount of blood pumped out by the heart PER BEAT (ml per beat) |
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Stroke volume is determined by: |
-Preload -Afterload -Contractility |
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"Ejection Fraction" |
-Measurement of stroke volume as a percentage -Normal= 60-70% |
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Control of Heart Rate: |
-Autonomic nervous system -Stretch Receptors -Peripheral chemoreceptors -Central Chemoreceptors(resp center) |
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Autonomic nervous system: |
-Beta 1 receptors -Beta 2 receptors -Alpha receptors |
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Beta 1 receptors: |
-Located in the heart, when stimulated they cause increased heart rate, increased contractility, and increased excitability. |
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Beta 2 receptors: |
-Located in peripheral vascular and bronchial smooth muscle; when stimulated cause vasodilation and bronchodilation. |
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Alpha receptors: |
- peripheral vascular smooth muscle: vasoconstriction when stimulated |
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Stretch receptors: |
- receptors in the vena cava and RA: sensitive to stretch or pressure changes. -Ex: hypovolemia, decreased pressure, increased HR |
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Peripheral chemoreceptors: |
-Receptors in aortic arch and carotid arteries; changes in O2 are a stimulus for increasing or decreasing the heart rate. -Decreased oxygen level, increased heart rate |
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Central Chemoreceptors: |
-Located in the Respiratory Center -Extremely sensitive to CO2 changes -hypercapnia increases HR |
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When CO2 increases.... |
-Heart rate increases to get better gas exchange |
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Other heart rate controls: |
-Physical activity -Emotion -Body Temperature -All affect metabolic demand |
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Preload: |
-The amount of VOLUME in the ventricles prior to contraction; the amount of STRETCH on the ventricles prior to contraction -END-DIASTOLIC VOLUME |
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Factors affecting preload: |
-Blood volume -Vascular resistance -Patient position -Atrial Contraction |
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Loss of volume= |
less preload |
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Vasodilation= |
less preload |
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Vasoconstriciton= |
more preload |
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Patient position= |
Gravity decreases preload |
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Atrail contraction= |
-loss of atrial "kick" decreases preload by a small amount |
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Starling Law of The Heart: |
-"The greater the fiber length (stretch), the greater the force of contraction", and therefore the greater the stroke volume. |
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Afterload: |
-The amount of RESISTANCE that the heart must pump against -Reflected in the amount of vasoconstriction or vasodilation in the arterial system. |
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Anything that narrows the blood vessels is going to increase... |
Afterload -Ex: plague and stenosis |
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High after load= |
Alot of O2 being used |
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Factors affecting afterload: |
-Diastolic pressure - Systemic vascular resistance -Valve Function |
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Diastolic pressure affect on afterload: |
-The higher the pressure, the higher the afterload and more work for the heart |
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Systemic vascular resistance affect on afterload: |
-The greater the constriction of the arteries, the higher the afterload. |
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Valve function affect on afterload: |
-malfunctioning or narrowed valves increase the work it takes for the heart to propel blood; therefore increased afterload |
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Direct way to measure afterload: |
-Diastolic pressure |
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Heart patients NEED: |
LOW afterload |
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Isovolumetric contraction: |
-90% of oxygen consumed by the heart occurs during the exertion it takes for the heart to overcome afterload, in order to pump blood |
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Diastolic blood pressure reflects: |
a patient's afterload |
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Contractility: |
-The intrinisic ability of the muscle fibers in the myocardium to stretch; this is a built in mechanism. |
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Contractility changes on a BEAT by BEAT basis, depending on: |
-volume - Loss of muscle (infarction) - Electrolytes (esp calcium) -Drugs( stimulate/inhibit) -Hypoxia |
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INCREASED volume, INCREASE stretch, = |
INCREASED force of contraction |
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Hypoxia DEPRESSES= |
Contractility |
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Increase in heart rate means less filling time, which means a decrease in... |
Stroke Volume |
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Effects of Aging on Cardiovascular system: |
-Decrease in elasticity in walls of blood vessels -Calcification/stiffening of valves -BP elevation -Orthostatic hypotension -HR does not respond as well to exercise and stress -Increase in dysrhythmias -Advancement of CAD -Heart Failure #1 reason for hospitilization |
