Question 1

Which of the following best describes the role of the sarcoplasmic reticulum (SR) in skeletal muscle contraction?

Accepted Answer

It stores and releases calcium ions ($$\mathrm{Ca$$^{2+}$$}) $$necessary for muscle contraction.

Question 2

A patient presents with muscle stiffness several hours after death. Which of the following best explains this phenomenon (rigor mortis)?

Accepted Answer

ATP is no longer produced, preventing detachment of myosin heads from actin.

Question 3

Which connective tissue sheath surrounds individual muscle fibers?

Accepted Answer

Endomysium

Question 4

During the sliding filament model of contraction, what happens to the I band and H zone?

Accepted Answer

Both the I band and H zone shorten.

Question 5

Which of the following is the correct sequence of events for muscle contraction, starting with nerve stimulation?

Accepted Answer

Nerve stimulation → Action potential in sarcolemma → Propagation of action potential → Increase in intracellular $$\mathrm{Ca$$^{2+}$$}$$

Question 6

Which protein directly blocks the myosin-binding sites on actin in a relaxed muscle fiber?

Accepted Answer

Tropomyosin

Question 7

A drug that inhibits acetylcholinesterase would have what effect on muscle contraction?

Accepted Answer

It would prolong muscle contraction by preventing breakdown of acetylcholine.

Question 8

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

Accepted Answer

They conduct action potentials deep into the muscle fiber.

Question 9

Which of the following is true regarding the molecular composition of thick filaments?

Accepted Answer

They are composed primarily of myosin molecules with heads that form cross bridges during contraction.

Question 10

A mutation that prevents voltage-gated Na$$^+$$ channels from opening in the sarcolemma would result in which of the following?

Accepted Answer

Failure to generate an action potential and thus no muscle contraction.

Question 11

Which of the following best explains why skeletal muscle fibers are multinucleated?

Accepted Answer

They are formed by the fusion of multiple myoblasts during development.

Question 12

Which of the following is a function of the elastic filament protein titin in the sarcomere?

Accepted Answer

It helps the sarcomere return to its resting length after contraction.

Question 13

Which event directly triggers the exposure of myosin-binding sites on actin?

Accepted Answer

Calcium ions bind to troponin, causing a conformational change.

Question 14

Which of the following best describes the difference between direct and indirect muscle attachments?

Accepted Answer

Direct attachments involve the epimysium fusing to the periosteum, while indirect attachments use tendons or aponeuroses.

Question 15

Which of the following is NOT a characteristic shared by all muscle tissue?

Accepted Answer

Ability to secrete hormones.

Question 16

A patient is exposed to a toxin that blocks the Na$$^+/K$^+$$ pump in skeletal muscle fibers. What is the most likely consequence?

Accepted Answer

The muscle fiber will not be able to restore ionic conditions after an action potential.

Question 17

Which of the following best describes the role of acetylcholine (ACh) at the neuromuscular junction?

Accepted Answer

It binds to receptors on the sarcolemma, initiating an action potential in the muscle fiber.

Question 18

Which of the following is the smallest contractile unit of a skeletal muscle fiber?

Accepted Answer

Sarcomere

Question 19

Which of the following best explains why smooth muscle can contract without nervous system stimulation?

Accepted Answer

Smooth muscle cells have intrinsic pacemaker activity.

Question 20

Which of the following is a real-life example of skeletal muscle function?

Accepted Answer

Walking up stairs to reach a classroom.

Muscles and Muscle Tissue: Structure and Function

Study Guide - Practice Questions