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General organization of heart
located in mediastinum, enclosed in pericardium, functions as a double pump
What are the three circulatory divisions?
systemic, pulmonary, and coronary
What is systemic circulation?
oxygenated blood from the left ventricle to body, returns deoxygenated blood to the right atrium
What is pulmonary circulation?
deoxygenated blood from the right ventricle to lungs, return oxygenated blood to the left atrium
what is coronary crcualtion?
supplies blood to the heart itself
How does blood move through the heart?
systemic circulation (venous blood) → superior vena cava / inferior vena cava → right atrium → right ventricle → pulmonary arteries (L/R) → pulmonary circulation → pulmonary veins (4) → left atrium → left ventricle → aorta → systemic circulation (arterial blood)
What are the four parts of heart wall?
pericardium, epicardium, myocardium, and endocardium
What is the pericardium?
fibrous and serous layers of heart
What is the epicardium?
outer visceral layer of heart
What is the myocardium?
contractile muscle tissue of heart
What is the endocardium?
inner layer of heart, contains connective and elastic fibers
What is the difference between cardiac and skeletal muscles?
cardiac muscles: single nucleus, intercalated discs, gap junctions, and syncytium
skeletal muscles: multinucleated, and no gap junctions
What is the resting membrane potential of cardiac muscles?
-85 to -95 mV for cardiac cells
-90 to -100 mV for conductive fibers
What are the five action potential phases?
1. depolarization (Na+ influx)
2. early repolarization (Na+ channels inactive)
3. plateau (Ca2+ influx)
4. repolarization (K+ efflux)
5. ion distribution restored (Na+/K+ pump)
What is excitation-contraction coupling?
1. action potential triggers Ca2+ influx
2. Ca2+ binds to troponin and removes tropomyosin inhibition
3. cross-bridge formation leads to contraction
What are the 5 steps of the cardiac cycle?
1. Atrial contraction and ventricular filling
2. Isovolumetric contraction
3. Ventricular ejection
4. Isovolumetric relaxation
5. Atrial relaxation and passive ventricular filling
How long is systole and what cardiac cycle steps does it include?
250 to 300 ms, steps 1-3
How long is diastole and what cardiac cycle steps does it include?
500 to 550 ms, steps 4-5
What are the four heart sounds?
S1 "Lub", S2 "Dub", S3, and Murmurs
What causes S1 "Lub"?
AV valves closing (beginning of systole)
What causes S2 "Dub"?
closure of aortic and pulmonary valves (end of systole, begin of diastole)
What is S3?
an occasional weak sound
What are heart murmurs?
abnormal heart sounds due to valve issues
What are the effects of the sympathetic nervous system?
increased heart rate and contractility
What are the effects of the parasympathetic nervous system?
decreased heart rate
What are the basics of electrocardiogram (ECG)?
P wave, QRS complex, and T wave
What is P wave?
atrial depolarization
What is QRS complex?
ventricular depolarization
What is T wave?
ventricular repolarization
What is arterial supply?
The left and right coronary arteries originate from the aorta at the sinuses of Valsalva
What is venous return?
the flow of blood back to the heart
What is myocardial oxygen consumption?
high oxygen demand, most flow occurs during diastole
What causes myocardial ischemia?
atherosclerosis and thrombosis
What are the effects of myocardial ischemia?
reduced circulation, contractility, stroke volume and cardiac output
What are metabolic markers of myocardial ischemia?
decreased oxygen, ATP, Na+/K+ ATPase
increased hydrogen, lactate and intracellular Ca2+
What are the two types of humoral regulation
vasoconstrictors and vasodilators
What are types of vasoconstrictors?
epinephrine, norepinephrine, angiotensin, endothelin and vasopressin
What are types of vasodilators?
epinephrine, bradykinin, serotonin, histamine, prostaglandins, and nitric oxide
What is nervous regulation?
Direct: sympathetic and vagal effects
Indirect: myocardial contractility
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