Question 1

Which of the following statements best describes the role of the sarcoplasmic reticulum in skeletal muscle contraction?

Accepted Answer

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

Question 2

During the crossbridge cycle, what is the immediate effect of ATP binding to the myosin head?

Accepted Answer

It causes the myosin head to detach from actin.

Question 3

Which protein is responsible for covering the myosin-binding sites on actin in a relaxed muscle fiber?

Accepted Answer

Tropomyosin

Question 4

A patient presents with muscle stiffness after death (rigor mortis). What is the primary cause of this phenomenon?

Accepted Answer

Depletion of ATP preventing myosin detachment from actin

Question 5

Which of the following correctly matches the muscle type with its control mechanism?

Accepted Answer

Smooth muscle: involuntary control via autonomic neurons and endocrine modulation

Question 6

What is the function of titin in the sarcomere?

Accepted Answer

It provides elasticity and stabilizes the position of contractile elements.

Question 7

Which of the following best describes the sliding filament theory of muscle contraction?

Accepted Answer

Actin and myosin filaments slide past each other, shortening the sarcomere.

Question 8

In a multi-step scenario, if a muscle fiber is stimulated and calcium is released from the sarcoplasmic reticulum, but ATP is not available, what will happen to the crossbridge cycle?

Accepted Answer

The myosin head will remain bound to actin, resulting in a rigor state.

Question 9

Which structure allows action potentials to penetrate deep into the muscle fiber, ensuring coordinated contraction?

Accepted Answer

Transverse tubules (T-tubules)

Question 10

A muscle group that moves bones in opposite directions is called:

Accepted Answer

Antagonistic muscles

Question 11

Which of the following is the correct sequence of events in excitation-contraction coupling?

Accepted Answer

Action potential in sarcolemma → release of calcium from sarcoplasmic reticulum → crossbridge formation

Question 12

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

Accepted Answer

They are formed by the fusion of multiple precursor cells during development.

Question 13

Which band of the sarcomere contains only thin filaments?

Accepted Answer

I band

Question 14

What is the role of troponin C in muscle contraction?

Accepted Answer

It binds $$\mathrm{Ca$$^{2+}$$} to $$initiate the removal of tropomyosin from actin's binding sites.

Question 15

Which of the following is a correct description of the origin and insertion of a skeletal muscle?

Accepted Answer

Origin: closest to the trunk or stationary bone; Insertion: more distal or mobile attachment

Question 16

Which of the following is true regarding the function of satellite cells in skeletal muscle?

Accepted Answer

They differentiate into muscle fibers for growth or repair.

Question 17

If a person is unable to produce enough ATP, which step in the crossbridge cycle will be directly affected?

Accepted Answer

Myosin will not be able to detach from actin after the power stroke.

Question 18

Which accessory protein aligns actin filaments within the sarcomere?

Accepted Answer

Nebulin

Question 19

Which of the following is a function of smooth muscle?

Accepted Answer

Influence movement of material into, out of, and within the body

Question 20

Which event directly triggers the power stroke in the crossbridge cycle?

Accepted Answer

Release of $$\mathrm{P_i}$$ from the myosin head

Muscle Structure and Function: An Overview (Chapter 12 Study Notes)

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