NCLEX : Musculoskeletal System and Anatomy

Study concepts, example questions & explanations for NCLEX

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Example Questions

Example Question #51 : Musculoskeletal System And Anatomy

The length of long bones is increased via the hypertrophy and eventual apoptosis of chondrocytes which leave cavities that are then colonized by osteoprogenitor cells. This process is referred to as __________.

Possible Answers:

endochondral mineralization

osteoblast mineralization

apoptotic ossification

endochondral ossification

Correct answer:

endochondral ossification

Explanation:

Long bones are lengthened during childhood and adolescence via a process referred to as endochondral ossification. In this process, chondrocytes of the growth plate hypertrophy and eventual die, leaving cavities that are then colonized by osteoprogenitor cells. These osteoprogenitor cells then differentiate into osteoblasts, which mineralize the newly forming bone. None of the other answers are actual processes in bone formation or physiology.

Example Question #51 : Musculoskeletal System And Anatomy

Which of the following is not a common site of hematopoietic bone marrow in an adult?

Possible Answers:

Pelvis

Tibia and fibula

Skull

Sternum

Correct answer:

Tibia and fibula

Explanation:

In adults, hematopoietic bone marrow is generally confined to the flat bones, including the sternum, the skull, the ribs, and the pelvis. Hematopoietic bone marrow also exists in the proximal end of the femur in most adults, but is not generally found in the tibia or fibula. 

Example Question #52 : Musculoskeletal System And Anatomy

Muscle is attached to the periosteum of bone via which of the following?

Possible Answers:

Tendons

Sutures

Ligaments

Articular cartilage

Correct answer:

Tendons

Explanation:

Muscle attaches to bone via tendons, fibrous extensions of the sheath of the muscle body that are primarily composed of tightly packed collagen fibers. In comparison, ligaments attach bones to other bones without involvement with a muscle, such as the ligaments between the metacarpals of the wrist. Sutures are fibrous joints of the cranium, and hyaline cartilage is at the point of articulation of many bones but it is neither incorporated into muscle structure, nor does it attach to the bone with which it articulates. Rather, articular cartilage primarily serves to allow bones to glide more easily over each other during movement.

Example Question #1 : Muscle Physiology

The individual unit of muscle contraction in a muscle fibril is referred to as the __________.

Possible Answers:

sliding filament

sarcomere

sarcoplasmic reticulum

sarcolemma

Correct answer:

sarcomere

Explanation:

The individual contractile unit of a muscle fibril is referred to as the sarcomere. These units are made of actin and myosin filaments and joined by Z-lines. The sliding filament theory refers to the idea that muscle contraction is the result of myosin strands within the fibril pulling themselves along actin strands similar to pulling on a rope, which shortens the whole sarcomere. The sarcolemma is the specialized cell membrane around the muscle fibril, and the sarcoplasmic reticulum is the smooth endoplasmic reticulum found within the muscle cell.

Example Question #1 : Muscle Physiology

Which of the following is the correct order of structures in a skeletal muscle, from largest to smallest?

Possible Answers:

Fiber - fascicle - fibril

Fascicle - fibril - fiber

Fiber - fibril - fascicle

Fascicle - fiber - fibril

Fibril - fascicle - fiber

Correct answer:

Fascicle - fiber - fibril

Explanation:

The largest unit of muscle tissue is the fascicle. Each fascicle is made up of a bundle of muscle fibers, and every muscle fiber is made up of many fibrils (called myofibrils).  

Example Question #1 : Muscle Physiology

The muscle body is encased in which of the following?

Possible Answers:

The endomysium

The perimysium

The epimysium

None of these

Correct answer:

The epimysium

Explanation:

The muscle body is encased in a fibrous elastic sheath called the epimysium (epi meaning on or above and mys meaning muscle). It is composed of dense irregular connective tissue and is continuous with tendon fibers. The perimysium surrounds muscle fascicles, while the endomysium surrounds muscle fibers.

Example Question #1 : Muscle Physiology

Which of the following correctly describes an isometric muscle contraction?

Possible Answers:

The amount of muscle tension increases without any change in the length of the muscle or the angle of the joint

This form of contraction can either be eccentric or concentric

There is a rapid burst of mechanical energy for a short powerful movement

The length of the muscle shortens and the angle of the joint changes during the contraction

Correct answer:

The amount of muscle tension increases without any change in the length of the muscle or the angle of the joint

Explanation:

Isometric muscle contraction are those in which the tension in the muscle increases, but the muscle does not change length, nor does the angle of the joint change. An example would be attempting to push or lift an object that is too heavy to move. This is in contrast to isotonic contraction, in which muscle tension remains constant, but the muscle length and joint angle both change.

Example Question #2 : Muscle Physiology

During contraction, the A band of the sarcomere does which of the following?

Possible Answers:

It lengthens

It does not change

It shortens

It thickens

Correct answer:

It does not change

Explanation:

The A band in the sarcomere is created by the bipolar myosin filaments, joined at the M band. During contraction, the heads of the myosin filaments bind with the actin filament and pull it toward the M band at the center of the sarcomere. The myosin filaments do not themselves change length, and because of that the width of the A band does not change during contraction.

Example Question #1 : Muscle Physiology

In the sliding filament theory of muscle contraction, all but which of the following are functions of ATP?

Possible Answers:

ATP does all of these things during muscle contraction

It moves the myosin head into a high energy "cocked" position

It allows the myosin head to detach from the actin filament

It moves tropomyosin off of actin binding sites

Correct answer:

It moves tropomyosin off of actin binding sites

Explanation:

According to the sliding filament theory of muscle contraction, ATP binds to the myosin head and is hydrolyzed to ADP and inorganic phosphate. The energy released during this change draws the myosin head back into a high energy state, from which it is able to bind with actin and execute its "power stroke," leading to muscle contraction. ADP and inorganic phosphate then are released from the myosin head and replaced by a new molecule of ATP, which allows the myosin head to detach from the actin binding site.  

Example Question #1 : Muscle Physiology

All of the following features are unique to cardiac muscle cells except:

Possible Answers:

They are linked together via intercalated discs

They form branching chains

There are gap junctions between cells

They are non-striated

Correct answer:

They are non-striated

Explanation:

Cardiac muscle cells are striated, branching cells that are linked by structures called intercalated discs. These discs are composed of gap junctions, which allow the free passage of electrical signaling between heart cells, and very strong attachment points called desmosomes.

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