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Ch 17 Heart Function

Function of the Heart

QuestionAnswer
Contraction of the myocardium Systole
Relaxation of the myocardium after diastole Diastole
Cardiac cycle represent the: Events that occur in the heart during one heartbeat (0.8 sec for a heart rate of 70 bpm)
Atrial systole def. Atria contract pumping blood into ventricles
Ventricular systole def. Ventricles contract pumping blood into pulmonary trunk and aorta
Diastole def. Heart relaxes allowing blood to fill chambers
The ANS can affect heart activity in several ways 1.) Alter the rate at which the cardiac impulse is fired
The ANS can affect heart activity in several ways 2.) Change the speed at which it travels through the heart
The ANS can affect heart activity in several ways 3.) Increase the force of myocardial contraction
Sympathetic stimulation of the heart results in increased: SA node activity -> increased HR, transmission of impulse through His system, force of myocardial contraction
Potential clinical results of excessive sympathetic stimulation of heart Racing heart due to "fight or flight" response, circulatory shock; heart hailure, Tachydysrhythmias
Function of sympathomimetic drugs: Mimic effects of SNS
Function of sympatholytic drugs: Inhibit effects of SNS
What happens to SA node activity as a result of parasympathetic stimulation of the heart? Decreased SA node activity -> Decreased HR, which has an inhibiting effecton SA node to achieve 'normal' heart rate Decreased transmission of impulse to AV node
Another name for parasympathetic stimulation of the heart Vagal stimulation
Results of vagal heart stimulation Bradycardia, Bradydysrhythmia
Bradycardia def. Caused by excessive vagal discharge to the point where the heart beats below 60 bpm
Bradydysrhythmia def. Abnormal heart rhythm with a rate of less than 60 bpm
Function of vagomimetic drugs Mimic effects of PSNS
Function of vagolytic drugs Inhibit effects of PSNS
Def. of cardiac output The amount of blood pumped by each ventricle in 1 minute (usually about 5L per minute)
Cardiac Output = Heart Rate x Stroke Volume
Heart rate def. Number of times heart beats in one minute
Stroke volume def. Amount of blood pumped by ventricle in each heart beat
Normal heart rate 60-100 bpm
Average heart rate 72 bpm
Average resting stroke volume 60-80 mL per beat
Ventricles normally only pump approximately ____________ of blood 67%
Starling's Law of the Heart The greater the stretch of the myocardial fibers the greater the force of contraction (i.e. the more blood in the ventricle the more forceful the contraction, the greater the stroke volume)
Positive Inotropic Effect def. Stimulation of heart by sympathetic NS
End Diastolic Volume (EDV) def. Amount of blood in ventricle at the end of resting phase (AKA Preload)
Ejection Fraction def. The % of blood pumped from ventricle following contraction (typically 67%)
Afterload def. Resistance to blood flow from the ventricles (ex. semilunar valve stenosis, hypertension)
Inotropic Effect def. A change in myocardial contraction not related to stretch of myocardium
Positive Inotropic Effect def. Increases the force of myocardial contraction
Negative Inotropic Effect def. Decreases the force of myocardial contraction
Chronotropic Effect def. A change in HR (Pos or Neg Chronotropic Effect)
Dromotropic Effect def. Change in speed of the transmission of the cardiac impulse (positive and negative dromotropic effect)
Left heart failure happens when the left: Ventricle fails to pump blood into aorta. Usually due to MI or chronic hypertension
Backward left heart failure blood backs up where? Pulmonary circulation
Pulmonary Edema happens as a result of Backward left heart failure. Fluid builds up in the lungs
Symptoms of Pulmonary Edema Dyspnea, cyanosis, cough, orthopnea, tachycardia
Treatment for Pulmonary Edema Nitroglycerin, oxygen, morphine, upright posture, diuretic
Forward left heart failure - what happens? Systemic circulation does not effectively receive oxygenated blood and increased sympathetic stimulation
In right heart failure, the right: Ventricle fails to pump blood into pulmonary arteries
Right heart failure is usually due to: Left-sided heart failure or chronic lung disease
During right heart heart failure especially chronic lung disease what happens to blood flow? Blood backs up into venous system. Results in jugular vein distension, hepatomegaly, splenomegaly, digestive symptoms. Pitting edema.
Created by: CBaney