Flashcards in Cardiac Physiology Deck (29):
What effect do the following have on calcium?
Volatile anesthetics = decrease
Nitrous oxide = decrease
Local anesthetics = decrease
Acidosis = decrease
Digitalis = increase
Primary regulation of heart rate and blood pressure are controlled where?
Parasympathetic fibers primarily innervate what?
Atria and conducting tissues
Where do the cardiac Excelerator fibers originate?
Thoracic spinal cord T1 to T4
Merrill receptors in the lungs have what effect on the heart rate during inspiration?
Increase the heart rate
What are baroreceptors And where they located?
Pressure receptors in the wall of the carotid sinuses and aorta detect changes in atrial pressure in the circulation
What is usually the most important determinant of myocardial bloodflow?
Myocardial oxygen demand
The myocardium usually extracts what percentage of the oxygen in arterial blood compared with what percentage in most other tissues?
25% other tissues
At what stage is the heart perfused?
An increase in heart rate will do what to the time in diastole?
It will diminish it
How is coronary perfusion pressure measured?
CPP = Arterial diastolic pressure - LVEDP
What factor has the largest effect on oxygen supply in the CaO2 equation?
What effect will aortic stenosis and regurgitation have on myocardial oxygen supply and why?
Both will decrease supply by worsening blood flow into the coronary arteries
Ventricular ____ function involves ventricular ejection whereas _____ function is related to ventricular filling
What is a normal cardiac index and how is it calculated?
Normal C.I. = 2.5 - 4.2 L/min/m2
C.I. = CO/BSA
What is a normal mixed venous O2 saturation?
65 to 73%
Wedge pressure is equivalent to ?
Cardiac output is generally directly proportional to what?
Stroke volume is regulated primarily by what three factors?
What is preload and what is it equivalent to?
Pressure generated in the left ventricle at the end of diastole
What is afterload and what is equivalent to?
Resistance or impedance to ejection of blood from the ventricle
Atrial arrhythmias can reduce ventricular filling due to a loss of the atrial kick. why?
15 to 20% of the volume in the right ventricle comes from the atrial kick
What is a normal CVP?
What effect do respiration and cardiac output have on CVP?
Respiration = increases CVP
Cardiac output = decreases CVP
What normally has the most important effect on contractility?
Sympathetic nervous system activity
What are some causes of myocardial contractility depression?
Depletion of catecholamine
Loss of functioning muscle mass
Stenosis of an AV valve reduces stroke volume by what mechanism?
By decreasing ventricular preload
Stenosis of a semilunar valve reduces stroke volume by what mechanism?
By increasing ventricular afterload