MUSCULAR

Question 1

A 35-year-old male comes to the clinic complaining of muscle weakness. Upon examination, his skeletal muscles show signs of atrophy, but no signs of trauma or disease were noted.

Question: What cellular structure is most likely responsible for the patient’s muscle regeneration if an injury occurs?

A) Satellite cells
B) Myofibrils
C) Sarcolemma
D) Sarcoplasmic reticulum

Answer 1

A) Satellite cells
Rationale: Satellite cells are reserve progenitor cells adjacent to skeletal muscle fibers that play a key role in muscle regeneration after injury.

Question 2

A patient with a history of heart disease suffers a myocardial infarction. Over time, his heart function deteriorates.

Question: Why does cardiac muscle have limited ability to regenerate after injury such as a heart attack?

A) It lacks mesenchymal satellite cells
B) It has too many mitochondria to regenerate effectively
C) Its myofibrils regenerate too quickly, leading to scarring
D) The sarcomeres in cardiac muscle are resistant to regeneration

Answer 2

A) It lacks mesenchymal satellite cells
Rationale: Cardiac muscle cells do not have satellite cells and thus cannot regenerate effectively. Instead, myocardial infarctions lead to scar formation by fibroblasts.

Question 3

A 22-year-old athlete is involved in intense resistance training. He notices significant muscle growth after several months of exercise.

Question: What is the most likely mechanism responsible for the increase in his muscle mass?

A) Increased mitosis of skeletal muscle fibers
B) Activation and fusion of satellite cells with existing fibers
C) Formation of new sarcolemma layers
D) Replacement of muscle fibers with connective tissue

Answer 3

B) Activation and fusion of satellite cells with existing fibers
Rationale: Satellite cells are activated in response to exercise, fusing with existing muscle fibers to contribute to muscle hypertrophy.

Question 4

A patient undergoes surgery for a traumatic injury in the lower leg. Despite proper care, the patient’s skeletal muscle in the area does not regenerate fully, leading to scar tissue formation.

Question: What likely limited the patient’s skeletal muscle regeneration?

A) The formation of excess connective tissue
B) Insufficient activation of the sarcoplasmic reticulum
C) The inability of actin and myosin filaments to bind
D) Increased collagen deposition by smooth muscle cells

Answer 4

A) The formation of excess connective tissue
Rationale: In cases of major traumatic injuries, skeletal muscle regeneration can be limited by scarring and the growth of excessive connective tissue.

Question 5

A 45-year-old woman develops weakness and tremors. She is diagnosed with a disorder affecting her neuromuscular junctions.

Question: What is the role of the neuromuscular junction (NMJ) in muscle contraction?

A) It stores calcium for muscle contraction
B) It transmits electrical impulses from nerves to muscles
C) It provides structural support for muscle fibers
D) It binds actin and myosin filaments for contraction

Answer 5

B) It transmits electrical impulses from nerves to muscles
Rationale: The NMJ is responsible for transmitting nerve signals to muscle fibers, triggering muscle contraction.

Question 6

A 55-year-old male presents with difficulty walking and generalized muscle stiffness. Upon examination, it is found that his skeletal muscle fibers are not relaxing properly after contraction.

Question: Which of the following proteins is most likely involved in the regulation of calcium release and muscle contraction?

A) Troponin
B) Myosin
C) Actin
D) Titin

Answer 6

A) Troponin
Rationale: Troponin binds calcium during muscle contraction, allowing for interaction between actin and myosin. Dysfunction in this process can lead to improper relaxation of muscles.

Question 7

A patient has sustained a crushing injury to his leg, affecting the blood supply to the muscles. After surgical intervention, his smooth muscle tissue is able to regenerate.

Question: Why is smooth muscle more capable of regeneration than skeletal or cardiac muscle?

A) It contains regenerative satellite cells
B) Smooth muscle cells can undergo mitosis
C) Its fibers are resistant to injury
D) It has increased collagen deposition

Answer 7

B) Smooth muscle cells can undergo mitosis
Rationale: Smooth muscle cells have the ability to undergo mitosis, allowing them to regenerate more actively compared to skeletal and cardiac muscle cells.

Question 8

A 29-year-old runner complains of muscle fatigue and weakness during long-distance runs. Her muscles are slow to recover after exercise.

Question: Which muscle fiber type is most likely responsible for endurance and long periods of contraction without fatigue?

A) Fast glycolytic fibers
B) Slow oxidative fibers
C) Fast oxidative-glycolytic fibers
D) Type IIB fibers

Answer 8

B) Slow oxidative fibers
Rationale: Slow oxidative fibers are adapted for long-duration, low-intensity activities such as endurance running, and are resistant to fatigue due to their high mitochondria content and oxidative metabolism.

Question 9

A patient is experiencing severe muscle cramps. The cramping is linked to improper depolarization of the muscle membrane.

Question: Which structure is responsible for transmitting the depolarization signal deep into the muscle fiber?

A) Sarcoplasmic reticulum
B) T-tubules
C) Neuromuscular junction
D) Endomysium

Answer 9

B) T-tubules
Rationale: T-tubules transmit the depolarization signal deep into the muscle fiber, ensuring that calcium is released uniformly for muscle contraction

Question 10

A 42-year-old woman presents with progressive muscle weakness. Lab results show a deficiency in ATP production in her muscle cells.

Question: What organelle is primarily responsible for ATP production in muscle cells?

A) Sarcoplasmic reticulum
B) Mitochondria
C) Myofibrils
D) Z-discs

Answer 10

B) Mitochondria
Rationale: Mitochondria are responsible for producing ATP, which is crucial for sustained muscle contraction and function

Question 11

A patient presents with a muscle injury where only partial regeneration occurs, resulting in significant scarring. The affected muscle shows reduced function.

Question: What factor most limits full regeneration of skeletal muscle after injury?

A) Lack of myosin production
B) Formation of excess connective tissue
C) Rapid breakdown of actin filaments
D) Reduced calcium availability

Answer 11

B) Formation of excess connective tissue
Rationale: In major injuries, the formation of scar tissue and connective tissue can impede the full regeneration of skeletal muscle.

Question 12

A 60-year-old man presents with difficulty breathing. Examination reveals impaired function of the intercostal muscles, which are essential for respiration.

Question: What type of muscle tissue makes up the intercostal muscles involved in breathing?

A) Smooth muscle
B) Cardiac muscle
C) Skeletal muscle
D) Elastic muscle

Answer 12

C) Skeletal muscle
Rationale: The intercostal muscles are skeletal muscles responsible for the expansion and contraction of the chest during breathing.

Question 13

A patient is diagnosed with a condition that affects the protein responsible for linking thick filaments to the Z-disc in skeletal muscle.

Question: Which protein is primarily responsible for this function?

A) Tropomyosin
B) Troponin
C) Titin
D) Nebulin

Answer 13

A patient is diagnosed with a condition that affects the protein responsible for linking thick filaments to the Z-disc in skeletal muscle.

Question: Which protein is primarily responsible for this function?

A) Tropomyosin
B) Troponin
C) Titin
D) Nebulin

Question 14

A young athlete suffers a muscle tear while playing sports. Despite therapy, the injured muscle does not regain full strength.

Question: What structure is most likely involved in transmitting the mechanical forces generated by the contracting muscle fibers?

A) Myofibrils
B) Connective tissue layers
C) Sarcoplasmic reticulum
D) T-tubules

Answer 14

B) Connective tissue layers
Rationale: Connective tissue layers such as the epimysium, perimysium, and endomysium transmit the mechanical forces generated by muscle contraction.

Question 15

A 30-year-old patient with a neuromuscular disease presents with muscle weakness due to insufficient calcium release during muscle contraction.

Question: Which structure stores calcium for release during muscle contraction?

A) T-tubules
B) Sarcoplasmic reticulum
C) Actin filaments
D) Z-discs

Answer 15

B) Sarcoplasmic reticulum
Rationale: The sarcoplasmic reticulum stores calcium and releases it upon stimulation, triggering muscle contraction.

Question 16

A patient is experiencing muscle weakness and cramping after exercising. A muscle biopsy reveals abnormal sarcoplasmic reticulum function.

Question: What is the primary role of the sarcoplasmic reticulum in muscle cells?

A) Transport oxygen to the mitochondria
B) Store and release calcium ions during muscle contraction
C) Synthesize proteins needed for contraction
D) Generate ATP for muscle contraction

Answer 16

B) Store and release calcium ions during muscle contraction
Rationale: The sarcoplasmic reticulum stores calcium and releases it in response to muscle depolarization, which is essential for muscle contraction.

Question 17

A young patient presents with involuntary muscle contractions and difficulty relaxing his muscles. Tests reveal a mutation affecting the protein responsible for sliding actin and myosin filaments during contraction.

Question: Which protein is directly involved in the sliding filament model of muscle contraction?

A) Myosin
B) Troponin
C) Actin
D) Tropomyosin

Answer 17

A) Myosin
Rationale: Myosin heads bind to actin filaments and, using ATP, slide the filaments past each other to cause muscle contraction.

Question 18

A patient complains of muscle pain and weakness after prolonged use of certain muscles. A deficiency in ATP production is suspected.

Question: What is the source of ATP for sustained muscle contraction in slow oxidative fibers?

A) Glycolysis
B) Oxidative phosphorylation
C) Creatine phosphate
D) Anaerobic respiration

Answer 18

B) Oxidative phosphorylation
Rationale: Slow oxidative fibers rely on oxidative phosphorylation in mitochondria to produce ATP for sustained muscle contraction.

Question 19

A 65-year-old patient suffers from heart failure. His cardiac muscle is unable to contract efficiently, leading to reduced cardiac output.

Question: Which of the following is a key difference between skeletal and cardiac muscle?

A) Cardiac muscle lacks sarcomeres
B) Cardiac muscle cells are multinucleated
C) Cardiac muscle cells are branched and connected by intercalated discs
D) Cardiac muscle contracts only with voluntary control

Answer 19

C) Cardiac muscle cells are branched and connected by intercalated discs
Rationale: Cardiac muscle cells are interconnected by intercalated discs, allowing for coordinated contraction.

Question 20

A patient is diagnosed with a genetic disorder that affects the development of the connective tissue around muscle fibers.

Question: Which connective tissue layer directly surrounds individual muscle fibers?

A) Epimysium
B) Perimysium
C) Endomysium
D) Myofibril sheath

Answer 20

C) Endomysium
Rationale: The endomysium is the thin connective tissue layer that surrounds each individual muscle fiber.

Question 21

A patient presents with difficulty in coordinating movements. The doctor suspects a problem with proprioception.

Question: Which structure in skeletal muscle is responsible for providing proprioceptive feedback to the nervous system?

A) Sarcomere
B) Muscle spindle
C) Sarcoplasmic reticulum
D) Neuromuscular junction

Answer 21

B) Muscle spindle
Rationale: Muscle spindles detect changes in muscle length and provide proprioceptive feedback to help regulate movement and posture.

Question 22

A 50-year-old patient is suffering from muscle wasting and weakness due to prolonged immobilization.

Question: What happens to skeletal muscle fibers during atrophy?

A) The number of muscle fibers increases
B) The size of individual muscle fibers decreases
C) The production of new muscle fibers increases
D) The number of mitochondria in muscle fibers increases

Answer 22

B) The size of individual muscle fibers decreases
Rationale: During atrophy, the muscle fibers shrink in size, leading to muscle weakness and wasting.

Question 23

A patient is suffering from a neuromuscular disease that affects the release of acetylcholine at the neuromuscular junction.

Question: What role does acetylcholine play at the neuromuscular junction?

A) It depolarizes the sarcoplasmic reticulum
B) It triggers the release of calcium from muscle fibers
C) It binds to receptors on the muscle membrane to initiate muscle contraction
D) It breaks down actin filaments in the muscle

Answer 23

C) It binds to receptors on the muscle membrane to initiate muscle contraction
Rationale: Acetylcholine is released from motor neurons and binds to receptors on the muscle membrane, initiating depolarization and muscle contraction.

Question 24

A 45-year-old woman complains of muscle cramps. Lab results suggest abnormal ATP utilization in her muscles.

Question: What happens during muscle contraction when ATP is hydrolyzed?

A) Actin binds to tropomyosin
B) Myosin heads pivot and pull actin filaments
C) Calcium is released from the sarcoplasmic reticulum
D) The muscle returns to its relaxed state

Answer 24

B) Myosin heads pivot and pull actin filaments
Rationale: ATP hydrolysis provides energy for myosin heads to pivot and pull actin filaments during contraction.

Question 25

A patient with a congenital disorder affecting muscle elasticity is diagnosed with a titin deficiency.

Question: What is the function of titin in muscle fibers?

A) It binds calcium to initiate contraction
B) It anchors thin filaments to the Z-disc
C) It provides structural support and elasticity to the sarcomere
D) It regulates the release of acetylcholine

Answer 25

C) It provides structural support and elasticity to the sarcomere
Rationale: Titin is a large protein that helps maintain the structural integrity of the sarcomere and provides elasticity during muscle contraction and relaxation.