Skeletal Muscle Physiology Practice Questions
20 free Skeletal Muscle Physiology practice questions for the Physiology. Tap an option to answer — you get instant feedback, the correct answer, and a detailed explanation for every question.
Which ion is essential for initiating skeletal muscle contraction?
- A Sodium
- B Potassium
- C Calcium
- D Chloride
Correct answer: Calcium
Calcium binds to troponin, causing a conformational change that exposes myosin-binding sites on actin. This initiates cross-bridge formation and muscle contraction.
The functional unit of skeletal muscle is the:
- A Myofibril
- B Sarcomere
- C Muscle fiber
- D Actin filament
Correct answer: Sarcomere
The sarcomere is the basic contractile unit of skeletal muscle. It extends from one Z-line to the next and contains organized actin and myosin filaments.
Which protein blocks the myosin-binding sites on actin in resting muscle?
- A Troponin
- B Tropomyosin
- C Myosin head
- D Actin filament
Correct answer: Tropomyosin
Tropomyosin covers the binding sites on actin, preventing cross-bridge formation. When calcium binds to troponin, tropomyosin moves away.
What is the primary role of ATP in muscle contraction?
- A Bind to actin
- B Release calcium
- C Detach myosin from actin
- D Activate sodium channels
Correct answer: Detach myosin from actin
ATP binds to myosin heads, causing them to detach from actin. It is also required for re-cocking the myosin head for the next contraction cycle.
Which structure stores calcium ions in skeletal muscle?
- A T-tubules
- B Sarcoplasmic reticulum
- C Mitochondria
- D Rough endoplasmic reticulum
Correct answer: Sarcoplasmic reticulum
The sarcoplasmic reticulum stores calcium and releases it during muscle activation. This calcium triggers contraction.
The T-tubules function to:
- A Store energy reserves for later muscle contraction
- B Transmit action potentials into muscle fibers
- C Synthesize new muscle proteins
- D Store glycogen for anaerobic metabolism
Correct answer: Transmit action potentials into muscle fibers
T-tubules carry electrical signals deep into muscle fibers, ensuring synchronized contraction.
Which band of the sarcomere shortens during contraction?
- A A band
- B H zone
- C Z line
- D I band
Correct answer: I band
The I band shortens as actin filaments slide over myosin. The A band remains constant in length.
Which event directly triggers the release of calcium from the sarcoplasmic reticulum?
- A ATP binding to myosin heads
- B Myosin binding to actin filaments
- C Potassium influx into the cell
- D Action potential in T-tubules
Correct answer: Action potential in T-tubules
An action potential traveling along T-tubules activates calcium release channels in the sarcoplasmic reticulum.
Which condition occurs when ATP is absent in muscle fibers?
- A Relaxation
- B Muscle fatigue
- C Rigor mortis
- D Hyperpolarization
Correct answer: Rigor mortis
Without ATP, myosin heads cannot detach from actin, leading to sustained contraction known as rigor mortis.
Which type of muscle fiber is most resistant to fatigue?
- A Fast glycolytic
- B Fast oxidative
- C Slow oxidative
- D Intermediate fibers
Correct answer: Slow oxidative
Slow oxidative fibers have high mitochondrial content and rely on aerobic metabolism, making them highly fatigue-resistant.
Which neurotransmitter is released at the neuromuscular junction?
- A Dopamine
- B Serotonin
- C Norepinephrine
- D Acetylcholine
Correct answer: Acetylcholine
Acetylcholine is released from motor neurons and binds to receptors on muscle fibers to initiate contraction.
Which receptor is activated by acetylcholine at the neuromuscular junction?
- A Muscarinic receptor
- B Adrenergic receptor
- C GABA receptor
- D Nicotinic receptor
Correct answer: Nicotinic receptor
Nicotinic receptors on muscle cells respond to acetylcholine, leading to depolarization and muscle contraction.
What is the sliding filament theory?
- A Actin and myosin slide past each other
- B Filaments break during contraction
- C Filaments shrink in length
- D Myosin disappears from the sarcomere entirely
Correct answer: Actin and myosin slide past each other
According to the sliding filament theory, actin filaments slide over myosin filaments, shortening the sarcomere.
Which phase of muscle contraction involves myosin binding to actin?
- A Cross-bridge formation
- B Relaxation phase of the cycle
- C Recovery phase
- D Calcium release
Correct answer: Cross-bridge formation
Cross-bridge formation occurs when myosin heads attach to actin, initiating contraction.
Which molecule binds to troponin to initiate contraction?
- A Calcium
- B ATP
- C Sodium
- D Potassium
Correct answer: Calcium
Calcium binds to troponin, causing a shift in tropomyosin and exposing binding sites for myosin.
What is muscle fatigue primarily caused by?
- A Accumulation of metabolic byproducts
- B Insufficient oxygen delivery to the working muscle
- C Excess ATP
- D Decreased calcium levels
Correct answer: Accumulation of metabolic byproducts
Muscle fatigue results from accumulation of lactic acid, inorganic phosphate, and depletion of energy reserves.
Which type of contraction occurs when muscle length remains constant?
- A Isometric contraction
- B Isotonic contraction
- C Concentric contraction
- D Eccentric contraction
Correct answer: Isometric contraction
In isometric contraction, muscle tension increases without a change in length.
Which type of contraction involves muscle shortening?
- A Isometric
- B Eccentric
- C Plyometric
- D Concentric
Correct answer: Concentric
Concentric contraction occurs when muscle shortens while generating force.
Which ion movement is responsible for depolarization of skeletal muscle?
- A Potassium efflux from the cell
- B Calcium influx through voltage-gated channels
- C Chloride influx into the cytoplasm
- D Sodium ion influx across the membrane
Correct answer: Sodium ion influx across the membrane
Sodium influx through voltage-gated channels causes depolarization of the muscle membrane.
Which structure connects muscle fibers to bone?
- A Tendon
- B Ligament
- C Cartilage
- D Fascia
Correct answer: Tendon
Tendons connect skeletal muscles to bones, allowing force generated by muscles to produce movement.