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"Q: What connects pulmonary arteries to pulmonary veins?"

"A: The pulmonary capillaries."

"Q: What gas exchange occurs in pulmonary capillaries?"

"A: They pick up oxygen (O₂) from the alveoli and release carbon dioxide (CO₂) into the lungs."

"Q: Which valves open and close together?"

"A: The atrioventricular (AV) valves close together

"Q: What happens to oxygen as blood circulates through the body?"

"A: Cells absorb oxygen for ATP (energy) production and send CO₂ back to the heart to be exhaled."

"Q: What is the muscular layer of the heart called

and what does it need to contract?"

"Q: How does the myocardium receive oxygen and nutrients?"

"A: From the right and left coronary arteries

"Q: How does deoxygenated blood from the myocardium return to the heart?"

"A: It drains into the coronary veins

"Q: What happens to the deoxygenated blood after entering the right atrium?"

"A: It is sent to the lungs to become oxygenated again."

"Q: How are cardiac muscle cells connected to one another?"

"A: They are joined by intercalated discs

"Q: Do the atrial and ventricular cells beat at the same rhythm?"

"A: No — the atria beat slightly faster than the ventricles."

"Q: What is the intrinsic (nodal) conduction system?"

"A: A collection of specialized cardiac tissue that initiates and conducts electrical impulses through the heart

"Q: What is the role of the sympathetic and parasympathetic nervous systems in heart rate control?"

"A: Sympathetic nervous system increases heart rate; Parasympathetic nervous system decreases heart rate."

"Q: In what direction does the heart depolarize?"

"A: It depolarizes in one direction only — beginning at the SA node and spreading downward through the atria and ventricles."

"Q: What is the SA node

and what is its function?"

"Q: What happens when the impulse reaches the AV node?"

"A: The impulse pauses briefly at the AV node to allow the atria to finish contracting before the ventricles are stimulated."

"Q: After the AV node

what is the correct conduction pathway?"

"Q: Where do the right and left bundle branches go?"

"A: Right bundle branch: Up the lateral walls of the right ventricle; Left bundle branch: Up the lateral walls of the left ventricle"

"Q: What are Purkinje fibers

and what do they do?"

"Q: What motion does the heart make during contraction?"

"A: The heart contracts in a wringing or twisting motion

"Q: What is the correct order of the conduction system?"

"A: SA node → AV node → AV bundle (Bundle of His) → Right & Left bundle branches → Purkinje fibers"

"Q: How do the atria and ventricles contract in relation to one another?"

"A: The right and left atria contract together

"Q: What is systole?"

"A: Systole is the phase of contraction or squeezing — associated with blood ejection and sympathetic activity (SNS)."

"Q: What is diastole?"

"A: Diastole is the phase of relaxation

"Q: What makes up one complete heartbeat?"

"A: One heartbeat = Systole + Diastole of both atria and ventricles."

"Q: What causes blood to move forward through the heart?"

"A: Pressure changes — as blood fills a chamber

"Q: Where does blood come from on each side of the heart?"

"A: Right side: From the body (via the vena cava); Left side: From the lungs (via pulmonary veins)"

"Q: What happens when the atria are in systole?"

"A: The atria contract

"Q: What happens when the atria are in diastole?"

"A: They are relaxed and filling with blood from their respective veins."

"Q: Describe the sequence of atrial and ventricular activity during the cardiac cycle?"

"A: 1. Atria fill with blood (diastole)\n2. Atria contract (systole) → push blood into ventricles\n3. Atria relax again\n4. Ventricles fill

"Q: What prevents blood from flowing backward into the atria when ventricles contract?"

"A: The AV valves (bicuspid and tricuspid) close tightly during ventricular systole."

"Q: What happens to blood during ventricular systole?"

"A: Right ventricle: Pumps blood to lungs via pulmonary arteries; Left ventricle: Pumps blood to the body via the aorta"

"Q: What happens during ventricular diastole?"

"A: The ventricles relax

"Q: What causes the “lub” sound of the heartbeat?"

"A: The closing of the AV valves (tricuspid and bicuspid) during ventricular systole."

"Q: What causes the “dub” sound of the heartbeat?"

"A: The closing of the semilunar valves (aortic and pulmonary) during ventricular diastole."

"Q: What causes an abnormal “swishing” heart sound?"

"A: When valves do not close tightly