Question 1

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

Accepted Answer

Skeletal muscle contracts rapidly and fatigues quickly; cardiac muscle contracts at an intermediate speed and is resistant to fatigue; smooth muscle contracts slowly and is highly resistant to fatigue.

Question 2

During the contraction cycle of skeletal muscle, which event occurs immediately after the power stroke?

Accepted Answer

ATP binds to myosin, causing it to detach from actin.

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 additional ATP.

Question 4

Which of the following statements about the action potential in cardiac muscle compared to skeletal muscle is correct?

Accepted Answer

Cardiac muscle action potentials have a prolonged plateau phase due to sustained calcium influx, while skeletal muscle action potentials are much shorter.

Question 5

A patient’s ECG shows an abnormally prolonged QRS complex. What does this most likely indicate?

Accepted Answer

Delayed ventricular depolarization, possibly due to a bundle branch block.

Question 6

Which of the following best describes what happens to the sarcomere during skeletal muscle contraction?

Accepted Answer

The Z lines move closer together as the actin and myosin filaments slide past each other.

Question 7

Which formula correctly represents cardiac output ($$CO) $$and its relationship to heart rate ($$HR) $$and stroke volume ($$SV$$)?

Accepted Answer

$$CO = HR 	imes SV$$

Question 8

If a patient has an end-diastolic volume ($$EDV) of 140 mL $$and an end-systolic volume ($$ESV) of 60 mL$$, what is their stroke volume ($$SV$$)?

Accepted Answer

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

Question 9

Which of the following best describes the effect of increased preload on stroke volume, according to the Frank-Starling law?

Accepted Answer

Increased preload stretches the ventricular muscle fibers, resulting in a greater force of contraction and increased stroke volume.

Question 10

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

Accepted Answer

Skeletal muscle fibers are multinucleated and striated, while smooth muscle fibers are uninucleated and lack striations.

Question 11

A patient’s blood pressure is measured as 120/80 mmHg. Which vessel type is primarily responsible for regulating systemic vascular resistance and thus blood pressure?

Accepted Answer

Arterioles

Question 12

Which of the following best explains why cardiac muscle cannot undergo tetanus (sustained contraction)?

Accepted Answer

The prolonged refractory period in cardiac muscle prevents summation of action potentials.

Question 13

During the skeletal muscle contraction cycle, what is the role of calcium ions ($$Ca^{2+}$$)?

Accepted Answer

$$Ca^{2+}$$ binds to troponin, causing a conformational change that moves tropomyosin and exposes myosin-binding sites on actin.

Question 14

Which of the following best describes the relationship between blood flow ($$Q$$), pressure difference ($$\Delta P$$), and resistance ($$R) in $$the cardiovascular system?

Accepted Answer

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

Question 15

A 60-year-old patient has a heart rate of 75 beats per minute and a stroke volume of 70 mL. What is their cardiac output ($$CO$$)?

Accepted Answer

$$CO = HR 	imes SV = 75 	imes 70 = 5250\ \mathrm{mL/min}$$

Question 16

Which of the following is true regarding the regulation of blood flow through capillaries?

Accepted Answer

Precapillary sphincters regulate blood flow into capillary beds in response to local metabolic needs.

Question 17

Which of the following best describes the sequence of events in a normal ECG?

Accepted Answer

P wave (atrial depolarization), QRS complex (ventricular depolarization), T wave (ventricular repolarization)

Question 18

Which of the following is a unique feature of smooth muscle contraction compared to skeletal muscle contraction?

Accepted Answer

Smooth muscle contraction is initiated by phosphorylation of myosin light chains via myosin light chain kinase (MLCK).

Question 19

A patient is experiencing increased afterload due to hypertension. How will this affect their end-systolic volume ($$ESV) $$and stroke volume ($$SV$$), assuming all other factors remain constant?

Accepted Answer

Increased afterload will increase $$ESV$$ and decrease $$SV.$$

Chapter 12,13,14,15 Check your Understanding

Guida di studio - Domande di pratica

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