Q: A patient has an end-diastolic volume (EDV) of 140 mL and an end-systolic volume (ESV) of 60 mL. What is the stroke volume (SV)?

$$SV = EDV - ESV = 140\ \text{mL} - 60\ \text{mL} = 80\ \text{mL}$$

Q: A patient’s heart rate is 75 beats per minute and their stroke volume is 70 mL. What is their cardiac output?

$$CO = 75 \times 70 = 5,250\ \text{mL/min}$$

Question 1

Which of the following best describes the difference in fatigue resistance between skeletal, cardiac, and smooth muscle?

Accepted Answer

Skeletal muscle fatigues quickly, cardiac muscle is highly fatigue-resistant, and smooth muscle is also highly fatigue-resistant.

Question 2

During skeletal muscle contraction, which of the following events occurs at the sarcomere level?

Accepted Answer

The Z lines move closer together as actin filaments slide past myosin filaments.

Question 3

Which of the following best explains why smooth muscle can maintain contraction for long periods with minimal energy expenditure?

Accepted Answer

Smooth muscle uses the latch-bridge mechanism, allowing myosin heads to remain attached to actin for extended periods without using ATP.

Question 4

Which of the following is true regarding the action potential in cardiac muscle compared to skeletal muscle?

Accepted Answer

Cardiac muscle action potentials have a prolonged plateau phase due to slow $$Ca^{2+}$$ influx, while skeletal muscle action potentials are much shorter.

Question 5

A patient has an end-diastolic volume (EDV) of 140 mL and an end-systolic volume (ESV) of 60 mL. What is the stroke volume (SV)?

Accepted Answer

$$SV = EDV - ESV = 140\ 	ext{mL} - 60\ 	ext{mL} = 80\ 	ext{mL}$$

Question 6

Which of the following best describes the role of preload in cardiac physiology?

Accepted Answer

Preload is the degree of stretch of cardiac muscle fibers at the end of diastole, directly influencing stroke volume according to the Frank-Starling law.

Question 7

Which of the following best explains the difference in the source of calcium for contraction in skeletal versus cardiac muscle?

Accepted Answer

Skeletal muscle relies almost entirely on calcium from the sarcoplasmic reticulum, while cardiac muscle uses both sarcoplasmic reticulum and extracellular calcium.

Question 8

During an ECG, which wave corresponds to ventricular depolarization?

Accepted Answer

QRS complex

Question 9

Which of the following equations correctly represents cardiac output (CO)?

Accepted Answer

$$CO = HR 	imes SV$$

Question 10

A patient’s heart rate is 75 beats per minute and their stroke volume is 70 mL. What is their cardiac output?

Accepted Answer

$$CO = 75 	imes 70 = 5,250\ 	ext{mL/min}$$

Question 11

Which of the following best describes the relationship between blood flow, pressure, and resistance in the cardiovascular system?

Accepted Answer

$$Flow = \dfrac{\Delta P}{R}$$, where $$\Delta P is $$the pressure difference and $$R is $$resistance.

Question 12

Which of the following is a key anatomical difference between skeletal and smooth muscle?

Accepted Answer

Skeletal muscle fibers are striated and multinucleated, while smooth muscle fibers are non-striated and have a single nucleus.

Question 13

Which of the following best explains why the refractory period in cardiac muscle is longer than in skeletal muscle?

Accepted Answer

The prolonged refractory period in cardiac muscle prevents tetanus, ensuring rhythmic contractions.

Question 14

Which of the following best describes the sequence of events in the skeletal muscle contraction cycle?

Accepted Answer

Calcium binds to troponin, tropomyosin shifts, myosin binds to actin, power stroke occurs, ATP binds to myosin, myosin detaches.

Question 15

A patient with high blood pressure is found to have increased peripheral resistance. According to the relationship $$Flow = \dfrac{\Delta P}{R}$$, what will happen to blood flow if resistance increases and pressure remains constant?

Accepted Answer

Blood flow will decrease.

Question 16

Which of the following is true regarding the regulation of blood vessel diameter and its effect on resistance?

Accepted Answer

A small decrease in vessel radius greatly increases resistance, as resistance is inversely proportional to the fourth power of the radius ($$R \propto \dfrac{1}{r^4$}).$$

Question 17

Which of the following best describes the function of the T-tubules in skeletal muscle fibers?

Accepted Answer

They transmit action potentials deep into the muscle fiber, triggering calcium release from the sarcoplasmic reticulum.

Question 18

Which of the following is a unique feature of cardiac muscle cells compared to skeletal muscle cells?

Accepted Answer

Cardiac muscle cells are connected by intercalated discs, allowing synchronized contraction.

Question 19

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

Accepted Answer

Increased venous return stretches cardiac muscle fibers, leading to a stronger contraction and increased stroke volume.

Question 20

Which of the following best describes the main difference in the mechanism of contraction between smooth and skeletal muscle?

Accepted Answer

Smooth muscle contraction is regulated by phosphorylation of myosin light chains, while skeletal muscle contraction is regulated by troponin binding to calcium.

Muscle Physiology and Cardiovascular System: Comparative Study Notes

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