Q: Which equation best represents the action of the Na+/K+ pump in muscle fibers?

$$3\ \mathrm{Na}^+_{\text{in}} + 2\ \mathrm{K}^+_{\text{out}} + \mathrm{ATP} \rightarrow 3\ \mathrm{Na}^+_{\text{out}} + 2\ \mathrm{K}^+_{\text{in}} + \mathrm{ADP} + \mathrm{P}_i$$

Question 1

Which of the following is NOT a function of muscle tissue?

Accepted Answer

Production of hormones

Question 2

Which property of muscle tissue allows it to return to its original length after being stretched?

Accepted Answer

Elasticity

Question 3

What is the main function of the sarcoplasmic reticulum in skeletal muscle fibers?

Accepted Answer

Storing and releasing calcium ions

Question 4

Which protein is responsible for linking actin in the outermost myofilaments to the endomysium, and is defective in Duchenne muscular dystrophy?

Accepted Answer

Dystrophin

Question 5

During the resting membrane potential, which ion is found in higher concentration inside the muscle cell compared to outside?

Accepted Answer

K+

Question 6

Which equation best represents the action of the Na+/K+ pump in muscle fibers?

Accepted Answer

$$3\ \mathrm{Na}^+_{	ext{in}} + 2\ \mathrm{K}^+_{	ext{out}} + \mathrm{ATP} ightarrow 3\ \mathrm{Na}^+_{	ext{out}} + 2\ \mathrm{K}^+_{	ext{in}} + \mathrm{ADP} + \mathrm{P}_i$$

Question 7

Which of the following best describes the sequence of events during an action potential in a muscle fiber?

Accepted Answer

Depolarization by Na+ influx, then repolarization by K+ efflux

Question 8

A patient is exposed to curare, which blocks acetylcholine receptors at the neuromuscular junction. What is the most likely result?

Accepted Answer

Flaccid paralysis

Question 9

Which of the following is true regarding the sliding filament mechanism of muscle contraction?

Accepted Answer

Thin filaments slide past thick filaments, shortening the sarcomere

Question 10

Which phase of a muscle twitch corresponds to the time when calcium ions are actively pumped back into the sarcoplasmic reticulum?

Accepted Answer

Relaxation period

Question 11

Which type of muscle contraction occurs when the muscle length does not change, but tension increases?

Accepted Answer

Isometric

Question 12

Which of the following best explains why rigor mortis occurs after death?

Accepted Answer

ATP is no longer available to detach myosin heads from actin

Question 13

Which energy pathway provides the fastest source of ATP for muscle contraction?

Accepted Answer

Immediate cytosolic reactions (creatine phosphate)

Question 14

A muscle fiber is stimulated repeatedly before it can fully relax. What is the result?

Accepted Answer

Wave summation

Question 15

Which of the following is a regulatory protein found in thin filaments that binds calcium ions during muscle contraction?

Accepted Answer

Troponin

Question 16

Which of the following best describes the role of calmodulin in smooth muscle contraction?

Accepted Answer

It binds calcium ions and activates myosin light chain kinase

Question 17

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

Accepted Answer

Presence of intercalated discs

Question 18

Which of the following best describes the length-tension relationship in skeletal muscle?

Accepted Answer

Maximum tension is generated at about 100–120% of the sarcomere's natural length

Question 19

Which of the following is true regarding motor units?

Accepted Answer

As greater force is required, more motor units are recruited

Muscular System: Histology and Physiology Study Guide

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