Histology Testbank: Muscle 3a

Instructions: For each histology question, pick the one best answer. This histology test bank is also useful for the histology questions on the USMLE (USMLE step 1).

1.
What is the plasma membrane of a muscle cell called?
a. Endomysium
b. Sarcolemma
c. Sarcoplasm
d. Perimysium
e. Epimysium

Answer: b

The outer connective tissue covering of a muscle is the epimysium. Within the muscle, there are subdivisions called fascicles. The perimysium surrounds these muscle fascicles. The endomysium is the covering around an individual muscle fiber. The sarcolemma is the plasma membrane of a muscle cell. The sarcoplasm is the cytoplasm of a muscle cell.

2. What are the thin filaments?
a. Myocardium
b. Myofibrils
c. Myofilaments
d. Muscle fibers
e. Myosin

Answer: c

Myofilaments are the contractile protein within a muscle cell. The myofilaments are actin and myosin. The thin filaments are actin and the thick filaments are myosin. The muscle cell is a muscle fiber. The term "muscle cell" and "muscle fiber" are synonymous. A myofibril is a longitudinal bundle of myofilaments within a muscle cell. Myocardium is the muscular layer of the heart. Thus, the myocardium is composed of cardiac muscle.

3.
Which of the following is composed of skeletal muscle?
a. Tongue
b. Blood vessel
c. Walls of the visceral organs
d. Lower esophagus
e. Heart

Answer: a

There are two chief categories of muscle: striated and non striated muscle (smooth muscle).

Striated muscle can be sub-categorized into cardiac muscle and skeletal muscle. The tongue, biceps muscle, and upper esophagus are made of striated muscle. The heart is composed of cardiac muscle.

Non striated muscle is also called smooth muscle. Smooth muscle is involuntary muscle. It is found in viscera and blood vessels.

4.
What type of muscle is composed of spindle shaped cells?
a. Skeletal muscle
b. Cardiac muscle
c. Smooth muscle
d. Both "a" and "b"
e. "a" "b" and "c"

Answer: c

Smooth muscle is composed of spindle shaped cells.

5.
What type of muscle is always multinucleated?
a. Skeletal muscle
b. Cardiac muscle
c. Smooth muscle
d. Both "a" and "b"
e. "a" "b" and "c"

Answer: a

Skeletal muscle is multinucleated. The nuclei are seen on the periphery. Occasionally, cardiac muscle is bi-nucleated.

6.
Which fiber type is smaller in diameter?
a. Red fibers
b. White fibers
c. Intermediate fibers
d. All of the above
e. None of the above

Answer: a

Skeletal muscle fibers can be classified as red fibers, white fibers or intermediate fibers. Red fibers are smaller in diameter; white fibers are larger in diameter. Red fibers have more mitochondria than white fibers. Red fibers make up slow-twitch muscle; white fibers make up fast-twitch muscle. Red fibers are more resistant to fatigue than are white fibers. Red fibers have more myoglobin (oxygen binding pigment) than white fibers. White fibers store glycogen and use anaerobic metabolism.

Red fiber and slow twitch muscle is for endurance.

White fiber and fast twitch muscle is for a burst of power.

7.
Which fiber type fatigues more readily?
a. Red fibers
b. White fibers
c. Intermediate fibers
d. All of the above
e. None of the above

Answer: b

Skeletal muscle fibers can be classified as red fibers, white fibers or intermediate fibers. Red fibers are smaller in diameter; white fibers are larger in diameter. Red fibers have more mitochondria than white fibers. Red fibers make up slow-twitch muscle; white fibers make up fast-twitch muscle. Red fibers are more resistant to fatigue than are white fibers. Red fibers have more myoglobin (oxygen binding pigment) than white fibers. White fibers store glycogen and use anaerobic metabolism.

Red fiber and slow twitch muscle is for endurance.

White fiber and fast twitch muscle is for a burst of power.

8.
What type of muscle probably predominates in Charles Atlas, the worlds most famous power weight lifter?
a. Red fibers
b. White fibers
c. Intermediate fibers
d. All of the above
e. None of the above

Answer: b

Skeletal muscle fibers can be classified as red fibers, white fibers or intermediate fibers. Red fibers are smaller in diameter; white fibers are larger in diameter. Red fibers have more mitochondria than white fibers. Red fibers make up slow-twitch muscle; white fibers make up fast-twitch muscle. Red fibers are more resistant to fatigue than are white fibers. Red fibers have more myoglobin (oxygen binding pigment) than white fibers. White fibers store glycogen and use anaerobic metabolism.

Red fiber and slow twitch muscle is for endurance.

White fiber and fast twitch muscle is for a burst of power.

9.
What is line that bisects the light band in muscle?
a. A band
b. I band
c. Z line
d. H band
e. M line

Answer: c

The A band is the darker staining band. The I band is the light band. The I band is made of thin filaments. The Z line runs through the I band. The H band bisects the A band. The M line runs through the H band.

A sarcomere is the segment that runs from Z line to Z line.

10.
What is the name of the tissue which surrounds muscle fascicles?
a. Perimysium
b. Periosteum
c. Perichondrium
d. Perineurium
e. Endosteum

Answer: a

The perimysium is the connective tissue sheath which surrounds muscle fascicles.

The periosteum is the connective tissue covering of a bone.

The perichondrium is the connective tissue which surrounds cartilage.

The perineurium is the covering of nerve fascicles.

The endosteum is the lining of the inner bone (the side which abuts the
medullary cavity).

Note from Sarah Bellham: The prefix "peri" means around, such as in the word
"perimeter". The prefix "endo" means within or inner, such as in "endosteum",
"endocrine", "endoscope".