Structure & Function of Muscle

Which of the following correctly lists the three layers of connective tissue found in a muscle, from outermost to innermost?

• Endomysium, Perimysium, Epimysium

• Perimysium, Endomysium, Epimysium

• Epimysium, Perimysium, Endomysium

• Epimysium, Endomysium, Perimysium

What constitutes a motor unit?

• A single muscle fiber and its associated blood vessels.

• A motor neuron and all the muscle fibers it innervates.

• All the muscle cells within a fasciculus.

• The epimysium, perimysium, and endomysium.

What is the primary function of T-tubules and the sarcoplasmic reticulum in muscle cells?

• To produce ATP for muscle contraction.

• To store and release sodium ions for nerve impulses.

• To rapidly spread action potentials and release calcium ions for contraction.

• To synthesize new actin and myosin filaments.

Where does sarcomere run from?

• M-Line to Myosin

• Z-Line to Myosin

• Myosin to M-Line

• Z-Line to Z-Line

Which region of a sarcomere contains only actin filaments and appears lighter in color?

• The A-band

• The H-zone

• The M-line

• The I-band

How do calcium ions facilitate muscle contraction at the molecular level?

• They directly bind to myosin heads, initiating the power stroke.

• They provide the necessary ATP for the cross-bridge cycle.

• They cause the troponin-tropomyosin complex to shift, exposing actin binding sites for myosin.

• They strengthen the Z-lines, preventing sarcomere overstretching.

According to the sliding filament theory, what happens to the sarcomere and muscle fiber when actin filaments slide inward on myosin filaments?

• The muscle fiber lengthens, and the sarcomere expands.

• The sarcomere shortens, and the muscle fiber shortens.

• The Z-lines move further apart, increasing muscle length.

• The muscle enters a state of relaxation.

Why does a stretched muscle have low force potential?

• Due to increased overlap between myosin and actin filaments.

• Due to elongated I-bands and H-zone, reducing crossbridge-actin alignment.

• Due to an abundance of ATP, preventing crossbridge formation.

• Due to high calcium concentration, inhibiting muscle contraction.

What causes low force potential in a completely contracted muscle?

• Optimal alignment of actin and myosin filaments.

• Increased space for myosin heads to bind.

• Reduced crossbridge-actin alignment due to myosin running into Z-lines.

• Excessive ATP leading to muscle fatigue.

What is the primary factor that determines the force production of a muscle?

• The speed of muscle contraction.

• The number of motor units recruited.

• The number of crossbridges formed between actin and myosin.

• The type of muscle fibers present.