Q: Which equation correctly calculates ejection fraction (EF) given stroke volume (SV) and end-diastolic volume (EDV)?

$$EF = \frac{SV}{EDV} \times 100$$

Question 1

Which structural feature of cardiac muscle cells allows them to function as a coordinated unit, and what is its primary physiological role?

Accepted Answer

Gap junctions; they allow rapid electrical communication for functional syncytium

Question 2

Which of the following best describes the difference in the source of Ca$$^{2+}$$ for contraction between cardiac and skeletal muscle?

Accepted Answer

Cardiac muscle uses both sarcoplasmic reticulum and extracellular Ca$$^{2+}$$, while skeletal muscle uses only sarcoplasmic reticulum

Question 3

A patient’s ECG shows absent P waves and a heart rate of 45 bpm. Which arrhythmia is most likely present, and what is the underlying cause?

Accepted Answer

Junctional rhythm; SA node dysfunction and AV node pacing

Question 4

During the plateau phase of a ventricular contractile cell action potential, which ion is primarily responsible for maintaining depolarization?

Accepted Answer

Ca$$^{2+}$$ influx

Question 5

Calculate the stroke volume (SV) if the end-diastolic volume (EDV) is 120 ml and the end-systolic volume (ESV) is 50 ml. Use the formula $$SV = EDV - ESV.$$

Accepted Answer

$$SV = 120 - 50 = 70 ml$$

Question 6

Which of the following is the correct sequence for the electrical conduction system of the heart?

Accepted Answer

SA node → AV node → AV bundle → bundle branches → Purkinje fibers

Question 7

Which equation correctly relates cardiac output (CO), stroke volume (SV), and heart rate (HR)?

Accepted Answer

$$CO = SV 	imes HR$$

Question 8

A patient has a systolic blood pressure of 120 mmHg and a diastolic blood pressure of 80 mmHg. What is the mean arterial pressure (MAP)? Use the formula $$MAP = 	ext{Diastolic} + (	ext{Systolic} - 	ext{Diastolic})/3.$$

Accepted Answer

$$MAP = 80 + (120 - 80)/3 = 80 + 13.33 = 93.33$$ mmHg

Question 9

Which factor has the greatest impact on total peripheral resistance (TPR) according to Poiseuille’s law?

Accepted Answer

Vessel diameter

Question 10

Which of the following best explains the Frank-Starling law of the heart?

Accepted Answer

Increased preload (EDV) increases stroke volume due to greater stretch of cardiac muscle fibers

Question 11

Which of the following is a positive inotropic agent that increases contractility of the heart?

Accepted Answer

Norepinephrine

Question 12

During exercise, which physiological change occurs to ensure increased blood flow to skeletal muscles?

Accepted Answer

Vasodilation of arterioles due to decreased pH and increased CO$$_2$$

Question 13

Which blood vessel type is most responsible for regulating blood flow to tissues and systemic arterial blood pressure?

Accepted Answer

Arterioles

Question 14

Which of the following best describes the pathophysiology of ventricular fibrillation?

Accepted Answer

Disorganized electrical activity and random action potentials in the ventricles

Question 15

Which equation correctly calculates ejection fraction (EF) given stroke volume (SV) and end-diastolic volume (EDV)?

Accepted Answer

$$EF = \frac{SV}{EDV} 	imes 100$$

Question 16

Which division of the autonomic nervous system is dominant in controlling heart rate at rest?

Accepted Answer

Parasympathetic division

Question 17

Which of the following best describes the relationship between blood flow (F), pressure gradient ($$\Delta P$$), and resistance (R)?

Accepted Answer

$$F = \frac{\Delta P}{R}$$

Question 18

Which blood vessels experience pulsatile flow, and why?

Accepted Answer

Arteries; because they receive blood directly from the heart during systole and diastole

Question 19

Which local factor is most likely to cause vasodilation in skeletal muscle during intense exercise?

Accepted Answer

Decreased pH (increased H$$^+)$$

Cardiovascular Physiology: Cardiac Muscle, Conduction, and Blood Flow

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