Muscular System Practice Questions
20 free Muscular System practice questions for the General Science. Tap an option to answer â you get instant feedback, the correct answer, and a detailed explanation for every question.
Which type of muscle tissue is characterized by being multinucleated, striated, and under voluntary control?
- A Smooth muscle
- B Cardiac muscle
- C Skeletal muscle
- D Myoepithelial tissue
Correct answer: Skeletal muscle
Skeletal muscle is attached to bones and allows for conscious movement. Its fibers are long, cylindrical, and contain multiple nuclei and visible striations caused by the arrangement of sarcomeres.
The functional unit of a skeletal muscle fiber, located between two Z-discs, is called a:
- A Sarcolemma
- B Sarcomere
- C Sarcoplasmic reticulum
- D H zone
Correct answer: Sarcomere
The sarcomere is the smallest contractile unit of a muscle fiber. It consists of highly organized thick (myosin) and thin (actin) filaments that slide past each other during contraction.
During muscle contraction, which ion is released from the sarcoplasmic reticulum to bind with troponin?
- A Sodium (Na+)
- B Potassium (K+)
- C Calcium (Ca2+)
- D Magnesium (Mg2+)
Correct answer: Calcium (Ca2+)
Calcium ions are essential for contraction; they bind to troponin, which causes a conformational change in tropomyosin. This shift exposes the myosin-binding sites on the actin filaments.
Which of the following describes the 'Sliding Filament Theory' of muscle contraction?
- A Actin filaments physically shorten as the muscle contracts.
- B Myosin filaments coil up and shorten during contraction.
- C Thin and thick filaments slide past each other without changing length.
- D The Z-discs are pushed further apart while the sarcomere lengthens overall.
Correct answer: Thin and thick filaments slide past each other without changing length.
The sliding filament theory states that muscle contraction occurs as actin filaments are pulled toward the center of the sarcomere by myosin cross-bridges. The filaments themselves do not change length; rather, the degree of overlap between them increases.
The connective tissue sheath that surrounds an individual muscle fiber is the:
- A Epimysium
- B Perimysium
- C Endomysium
- D Deep fascia
Correct answer: Endomysium
The endomysium is a fine layer of areolar connective tissue that encases each muscle cell. The perimysium surrounds bundles of fibers called fascicles, and the epimysium covers the entire muscle.
Which muscle is primarily responsible for the abduction of the arm at the shoulder joint?
- A Pectoralis major
- B Teres major
- C Deltoid
- D Trapezius
Correct answer: Deltoid
The deltoid is a large, triangular muscle covering the shoulder. Its middle fibers are the prime movers for abducting the arm (moving it away from the midline) to a horizontal position.
What is the role of Acetylcholine (ACh) at the neuromuscular junction?
- A It provides the chemical energy needed for the power stroke of the myosin heads.
- B It acts as a neurotransmitter to trigger an action potential in the muscle fiber.
- C It breaks down ATP into ADP and inorganic phosphate to release energy.
- D It transports calcium ions back into the sarcoplasmic reticulum after contraction.
Correct answer: It acts as a neurotransmitter to trigger an action potential in the muscle fiber.
Acetylcholine is released from the motor neuron and binds to receptors on the sarcolemma. This binding opens ion channels, leading to a localized depolarization that initiates a muscle action potential.
Which of the following is a characteristic of 'Slow-Twitch' (Type I) muscle fibers?
- A They fatigue very quickly during sustained activity.
- B They contain very little myoglobin and rely on anaerobic glycolysis.
- C They are highly resistant to fatigue and rich in mitochondria.
- D They are primarily used for short, explosive bursts of movement.
Correct answer: They are highly resistant to fatigue and rich in mitochondria.
Slow-twitch fibers are specialized for endurance activities like maintaining posture or long-distance running. They rely on aerobic metabolism, possess many capillaries, and appear red due to high myoglobin content.
In the context of muscle terminology, the 'insertion' of a muscle refers to:
- A The attachment to the more stationary bone.
- B The attachment to the movable bone.
- C The fleshy middle of the muscle.
- D The point where the nerve enters the muscle.
Correct answer: The attachment to the movable bone.
The origin is the attachment site that remains relatively fixed during contraction, while the insertion is the attachment to the bone that is pulled toward the origin. For example, the biceps brachii originates on the scapula and inserts on the radius.
A muscle that opposes or reverses a particular movement is known as a(n):
- A Prime mover
- B Antagonist
- C Synergist
- D Fixator
Correct answer: Antagonist
While the agonist (prime mover) is responsible for a specific action, the antagonist provides resistance or reverses that movement. In elbow flexion, the biceps is the agonist and the triceps is the antagonist.
Which of the following molecules acts as a high-energy reserve to quickly regenerate ATP in muscle cells?
- A Glucose
- B Lactic acid
- C Creatine phosphate
- D Adenosine diphosphate
Correct answer: Creatine phosphate
Creatine phosphate stores a high-energy phosphate bond that can be transferred to ADP to form ATP. This system provides energy for the first 10-15 seconds of intense muscle activity.
Cardiac muscle cells are connected by specialized structures that allow for rapid electrical communication. These are called:
- A Tight junctions
- B Intercalated discs
- C Neuromuscular junctions
- D Synapses
Correct answer: Intercalated discs
Intercalated discs contain gap junctions and desmosomes. The gap junctions allow action potentials to spread quickly from cell to cell, ensuring the heart chambers contract in a coordinated, unified manner.
The 'All-or-None Law' as applied to muscle physiology states that:
- A A whole muscle contracts to its full strength or not at all.
- B An individual muscle fiber contracts completely once threshold is reached.
- C All muscles in a group must contract at the same time.
- D Energy consumption stays the same regardless of how much weight is being lifted.
Correct answer: An individual muscle fiber contracts completely once threshold is reached.
The All-or-None Law applies to single muscle fibers (and motor units), not the entire muscle. If a stimulus is strong enough to reach threshold, the fiber will trigger a maximal contraction; if not, no contraction occurs.
Hypertrophy in skeletal muscle is primarily the result of:
- A An increase in the total number of muscle cells, or fibers.
- B An increase in the size of existing muscle fibers through more myofibrils.
- C The gradual conversion of skeletal muscle tissue into cardiac muscle.
- D A decrease in the amount of connective tissue surrounding each individual muscle fiber.
Correct answer: An increase in the size of existing muscle fibers through more myofibrils.
Muscular hypertrophy occurs when repetitive high-intensity exercise stimulates the production of more myofibrils and sarcoplasm within existing cells. Humans generally do not grow new muscle fibers (hyperplasia) after birth.
Which muscle is commonly referred to as the 'calf muscle'?
- A Tibialis anterior
- B Gastrocnemius
- C Sartorius
- D Gracilis
Correct answer: Gastrocnemius
The gastrocnemius is the large, superficial muscle on the posterior of the lower leg. It works with the deeper soleus muscle to perform plantar flexion of the foot.
During a 'Power Stroke,' the myosin head releases which of the following to pull the actin filament?
- A Calcium ions and tropomyosin
- B ATP and a hydrogen ion
- C ADP and inorganic phosphate
- D Acetylcholine and creatine phosphate
Correct answer: ADP and inorganic phosphate
After the myosin head binds to actin, the release of ADP and Pi triggers the power stroke, where the head pivots and pulls the thin filament. A new ATP molecule must then bind to the myosin head to cause it to detach.
Muscle fatigue is often associated with the accumulation of which byproduct of anaerobic respiration?
- A Carbon dioxide
- B Uric acid
- C Lactic acid
- D Glucose
Correct answer: Lactic acid
When oxygen delivery cannot keep up with energy demand, cells switch to lactic acid fermentation. The buildup of lactate and associated hydrogen ions can lower pH, contributing to the sensation of muscle fatigue and soreness.
Which muscle group is located on the anterior thigh and is responsible for extending the knee?
- A Hamstrings
- B Quadriceps
- C Gluteus maximus
- D Adductors
Correct answer: Quadriceps
The quadriceps femoris consists of four muscles: the rectus femoris, vastus lateralis, vastus medialis, and vastus intermedius. Together, they are the powerful extensors of the knee joint.
A sustained, involuntary muscle contraction is known as:
- A Twitch
- B Summation
- C Tetanus
- D Atrophy
Correct answer: Tetanus
Tetanus occurs when the frequency of motor neuron stimulation is so high that the muscle has no time to relax between stimuli, resulting in a smooth, continuous, maximal contraction.
Which protein masks the active sites on actin in a relaxed muscle, preventing myosin from binding?
- A Titin
- B Tropomyosin
- C Dystrophin
- D Alpha-actinin
Correct answer: Tropomyosin
Tropomyosin is a regulatory protein that winds around the actin helix. In the absence of calcium, it physically blocks the myosin-binding sites, keeping the muscle in a relaxed state.