Structure of a Skeletal Muscle

Fill in the blank: The outer covering of the muscle is known as the _______.

• The outer covering of the muscle is known as the epimysium.

• The outer covering of the muscle is known as the perimysium.

• The outer covering of the muscle is known as the endomysium.

• The outer covering of the muscle is known as the sarcolemma.

Answer explanation

The outer covering of the muscle is known as the epimysium. It encases the entire muscle, while the perimysium surrounds bundles of muscle fibers, and the endomysium covers individual fibers.

Fill in the blank: The _______ is the basic unit of a muscle fiber.

• The sarcomere is the basic unit of a muscle fiber.

• The mitochondrion is the basic unit of a muscle fiber.

• The nucleus is the basic unit of a muscle fiber.

• The ribosome is the basic unit of a muscle fiber.

Answer explanation

The sarcomere is the fundamental unit of a muscle fiber, responsible for muscle contraction. Other options like mitochondrion, nucleus, and ribosome serve different functions within the cell but are not the basic unit of muscle fibers.

What is the outermost layer of a skeletal muscle called?

• Epimysium

• Perimysium

• Endomysium

• Sarcolemma

Answer explanation

The outermost layer of a skeletal muscle is called the epimysium. It surrounds the entire muscle, providing protection and support, while the perimysium and endomysium are layers that surround fascicles and individual muscle fibers, respectively.

What is the name of the connective tissue that surrounds each muscle fiber?

• Endomysium

• Perimysium

• Epimysium

• Fascia

Answer explanation

The connective tissue that surrounds each muscle fiber is called the endomysium. It provides support and protection to individual muscle fibers, distinguishing it from the perimysium, which surrounds bundles of fibers, and the epimysium, which encases the entire muscle.

What is the name of the bundle of muscle fibers?

• Fascicle

• Myofibril

• Sarcomere

• Tendon

Answer explanation

The correct answer is 'Fascicle', which refers to a bundle of muscle fibers. Myofibrils are smaller structures within muscle fibers, sarcomeres are the contractile units of myofibrils, and tendons connect muscles to bones.

Which part of the skeletal muscle is responsible for contraction?

• The part of the skeletal muscle responsible for contraction is the sarcomere.

• The part of the skeletal muscle responsible for contraction is the myofibril.

• The part of the skeletal muscle responsible for contraction is the endomysium.

• The part of the skeletal muscle responsible for contraction is the perimysium.

Answer explanation

The sarcomere is the fundamental unit of muscle contraction in skeletal muscle, containing the actin and myosin filaments that slide past each other to produce contraction.

In the diagram, what does the 'A band' represent?

• The 'A band' represents the region in a sarcomere where thick filaments (myosin) are present, and it appears dark under a microscope.

• The 'A band' represents the region in a sarcomere where only thin filaments (actin) are present, and it appears light under a microscope.

• The 'A band' represents the region in a sarcomere where no filaments are present, and it appears clear under a microscope.

• The 'A band' represents the region in a sarcomere where both thick and thin filaments overlap, and it appears light under a microscope.

Answer explanation

The 'A band' is the dark region in a sarcomere where thick filaments (myosin) are present. It does not represent only thin filaments or a clear area, making the first choice the correct one.

In the fully contracted state, what happens to the H Zone?

• The H Zone disappears

• The H Zone widens

• The H Zone remains the same

• The H Zone narrows

Answer explanation

In the fully contracted state, the H Zone, which is the region of the sarcomere where only thick filaments are present, disappears as the actin filaments overlap completely with the myosin filaments.

Fill in the blank: Force development by a muscle is dependent upon the velocity of muscle ________.

• contraction

• relaxation

• extension

• flexion

Answer explanation

Force development by a muscle is primarily influenced by the velocity of muscle contraction. Faster contractions typically generate less force due to the reduced time for cross-bridge formation, making 'contraction' the correct choice.

Fill in the blank: Force development by a muscle is dependent upon the length of muscle ________.

• tension

• fiber

• contraction

• strength

Answer explanation

Force development by a muscle is influenced by the length of muscle tension, which refers to the optimal overlap of actin and myosin filaments during contraction. This relationship is crucial for effective force generation.