Question 1

Which layer forms the fascicles in skeletal muscle?
A) Tendon sheath
B) Endomysium
C) Epimysium
D) Perimysium

Accepted Answer

The perimysium is the layer of connective tissue that surrounds and separates muscle fascicles within a skeletal muscle.

Question 2

Skeletal muscle is controlled directly by the central nervous system via a system of motor and sensory nerve fibers. Which of the following terms is not used to describe skeletal muscle?
A) Voluntary
B) Striated
C) Extrafusal
D) Fibrotic

Accepted Answer

Skeletal muscle is described as voluntary (meaning it can be consciously controlled), striated (due to the arrangement of actin and myosin fibers), and extrafusal (meaning it is the primary contractile unit of skeletal muscle). Fibrotic is not used to describe skeletal muscle, as this term typically refers to the formation of fibrous tissue in response to injury or inflammation.

Question 3

An isolated muscle is believed to be a type 2 fiber. Which of the following should be observed upon stimulation?
A) Slow contraction speed
B) Fatigued easily
C) Profuse capillary supply
D) Oxidative metabolism

Accepted Answer

Type 2 fibers are categorized as fast-twitch fibers which contract quickly and fatigue faster than type 1 fibers.

Question 4

Which structure is the contractile subunit of the myofibril?
A) Sarcoplasmic reticulum
B) Actin
C) Motor endplate
D) Sarcomere

Accepted Answer

The sarcomere is the contractile subunit of the myofibril, consisting of overlapping thick and thin filaments made up of myosin and actin, respectively. The sarcoplasmic reticulum is the organelle responsible for storing and releasing calcium ions during muscle contraction, while the motor endplate is the specialized region of the neuromuscular junction where the nerve fiber and muscle fiber meet.

Question 5

During which stage of muscle contraction does actin bind to myosin?
A) Coupling
B) Relaxation
C) Discharging
D) Excitation

Accepted Answer

The answer of During which stage of muscle contraction does...

Question 6

_____ ions directly control the contraction of muscles.
A) Sodium
B) Potassium
C) Calcium
D) Magnesium

Accepted Answer

Calcium ions directly control the contraction of muscles by binding to the protein complexes actin and myosin, which initiates the sliding of filaments and contraction of the muscle fibers. Sodium and potassium ions are important for generating the action potential necessary for muscle contraction, but do not directly control the contraction process. Magnesium ions play a role in muscle relaxation, but are not directly involved in muscle contraction.

Question 7

The main energy source or fuel for skeletal muscle contraction is:
A) calcium.
B) lactic acid.
C) ATP.
D) actin.

Accepted Answer

ATP (adenosine triphosphate) is the main energy source or fuel for skeletal muscle contraction. When muscles contract, ATP is broken down into ADP (adenosine diphosphate) and inorganic phosphate, releasing energy that is used for muscle contraction. Calcium plays an important role in muscle contraction by binding to troponin, which initiates a series of events that leads to the sliding of actin and myosin filaments. Lactic acid is a byproduct of anaerobic metabolism and can contribute to muscle fatigue but is not the main energy source for muscle contraction. Actin is a protein involved in the sliding of filaments during muscle contraction but is not an energy source.

Question 8

An isolated muscle is believed to be a type 1 fiber. Which of the following should be observed upon stimulation?
A) Slow contraction speed
B) Large fiber diameter
C) Rapid firing frequency
D) Glycolysis metabolism

Accepted Answer

Type 1 fibers are known for their slow contraction speed, as they rely on oxidative metabolism and have a high density of mitochondria. Additionally, they have a small fiber diameter, are able to sustain contractions for longer periods of time, and have a low firing frequency. Glycolysis metabolism is more characteristic of type 2 fibers.

Question 9

The epimysium, perimysium, and endomysium are made of:
A) bone.
B) epithelium.
C) fascia.
D) cartilage.

Accepted Answer

The epimysium, perimysium, and endomysium are all connective tissue layers that make up the structure of skeletal muscles. They are composed of fascia, a type of connective tissue that supports and separates muscles and other organs in the body. Bone, epithelium, and cartilage are not components of these layers.

Question 10

The lowest ratio of motor units per unit of muscle would be seen in which of the following muscle groups?
A) Lower leg muscles
B) Back muscles
C) Upper arm muscles
D) Finger muscles

Accepted Answer

Finger muscles have a higher ratio of motor units per unit of muscle compared to other muscle groups due to their fine motor control requirements.

Question 11

When a muscle acts as the prime mover, it is called the:
A) flexor.
B) recruiter.
C) antagonist.
D) agonist.

Accepted Answer

When a muscle acts as the prime mover, it is called the agonist. The agonist is responsible for producing a particular movement.

Question 12

Which molecule prevents a muscle contraction from occurring when the muscle is at rest?
A) Calcium
B) Troponin-tropomyosin
C) Actin
D) Myosin

Accepted Answer

Troponin-tropomyosin complex prevents the interaction between actin and myosin, preventing muscle contraction at rest. Calcium ions are needed for muscle contraction to occur, and actin and myosin are the proteins involved in muscle contraction.

Question 13

Which of the following structures is the contractile unit of a muscle cell?
A) Motor unit
B) Basement membrane
C) Myofibril
D) Ribosome

Accepted Answer

The myofibril is the contractile unit of a muscle cell. It is composed of repeating units called sarcomeres, which are responsible for muscle contraction. The other choices, motor unit, basement membrane, and ribosome, do not directly contribute to muscle contraction.

Question 14

Which of the following describes a functional muscle contraction in which the muscle contracts but the limb does not move?
A) Isotonic contraction
B) Isometric contraction
C) Eccentric contraction
D) Concentric contraction

Accepted Answer

An isometric contraction is a functional muscle contraction in which the muscle contracts, but the length of the muscle does not change, and therefore the limb does not move. In contrast, an isotonic contraction involves a change in muscle length and movement of the limb, while eccentric and concentric contractions involve muscle lengthening and shortening, respectively, during movement.

Quiz 36: Structure and Function of the Musculoskeletal System

Which layer forms the fascicles in skeletal muscle?

Skeletal muscle is controlled directly by the central nervous system via a system of motor and sensory nerve fibers. Which of the following terms is not used to describe skeletal muscle?

An isolated muscle is believed to be a type 2 fiber. Which of the following should be observed upon stimulation?

Which structure is the contractile subunit of the myofibril?

During which stage of muscle contraction does actin bind to myosin?

_____ ions directly control the contraction of muscles.

The main energy source or fuel for skeletal muscle contraction is:

An isolated muscle is believed to be a type 1 fiber. Which of the following should be observed upon stimulation?

The epimysium, perimysium, and endomysium are made of:

The lowest ratio of motor units per unit of muscle would be seen in which of the following muscle groups?

When a muscle acts as the prime mover, it is called the:

Which molecule prevents a muscle contraction from occurring when the muscle is at rest?

Which of the following structures is the contractile unit of a muscle cell?

Which of the following describes a functional muscle contraction in which the muscle contracts but the limb does not move?