Question 1

A 7-year-old boy presents with progressive muscle weakness and is later diagnosed with Duchenne Muscular Dystrophy (DMD). Which of the following best explains the underlying pathophysiology of this disease?

Accepted Answer

Defective gene for dystrophin leading to sarcolemma breakdown and muscle fiber death

Question 2

Which of the following is a characteristic histological finding in muscle tissue affected by Duchenne Muscular Dystrophy (DMD)?

Accepted Answer

Replacement of muscle fibers by fatty and fibrous connective tissue

Question 3

A patient develops muscle weakness and is found to have an autoimmune disease that destroys acetylcholine receptors at the motor end plate. Which of the following symptoms is most likely to occur?

Accepted Answer

Partial or full paralysis due to impaired action potential transmission

Question 4

Which of the following best describes the process of fibrosis in skeletal muscle following injury?

Accepted Answer

Replacement of lost tissue with dense irregular connective tissue produced by fibroblasts

Question 5

A patient presents with a muscle that feels hard and shortened, causing painful joint contractures. Which of the following best describes this condition?

Accepted Answer

Hypertonia

Question 6

Which of the following is a likely cause of a muscle spasm?

Accepted Answer

Dehydration or electrolyte imbalance

Question 7

Botulism poisoning leads to muscle paralysis by which of the following mechanisms?

Accepted Answer

Blocking acetylcholine at the neuromuscular junction, preventing muscle contraction

Question 8

A patient with a history of prolonged immobilization presents with decreased muscle diameter and reduced strength. Which of the following best explains the physiological changes in their muscle tissue?

Accepted Answer

Decrease in myofibrils and oxidative enzymes, leading to atrophy

Question 9

Which of the following best describes hypertrophy in skeletal muscle?

Accepted Answer

Increase in both the number of myofibrils and the diameter of muscle fibers

Question 10

A patient complains of persistent, localized muscle pain after repetitive exercise. Palpation reveals a tender, firm area in the muscle. What is the most likely diagnosis?

Accepted Answer

Muscle knot (myofascial trigger point)

Question 11

Which of the following is the most appropriate initial treatment for muscle knots (myofascial trigger points)?

Accepted Answer

Relaxation of muscle fibers through massage therapy and stretching

Question 12

A patient presents with muscle pain, swelling, and weakness. Laboratory tests reveal an inflammatory process in the muscle. Which of the following is the most likely diagnosis?

Accepted Answer

Myositis

Question 13

Which of the following best differentiates fibrosis from normal muscle regeneration after injury?

Accepted Answer

Fibrosis involves the replacement of lost muscle tissue with dense irregular connective tissue (scar tissue)

Question 14

A 25-year-old athlete increases his muscle mass after months of resistance training. Which of the following best explains the cellular changes in his skeletal muscle?

Accepted Answer

Increase in both the number of myofibrils and the diameter of muscle fibers

Question 15

A patient with botulism is at risk of death primarily due to which of the following complications?

Accepted Answer

Respiratory failure due to paralysis of respiratory muscles

Question 16

Which of the following best describes the difference between hypotonia and hypertonia?

Accepted Answer

Hypotonia is abnormally low muscle tone, while hypertonia is abnormally high muscle tone

Question 17

A patient presents with muscle pain after an unknown cause. Which term best describes this symptom?

Accepted Answer

Myalgia

Question 18

A 30-year-old woman develops muscle weakness, swelling, and pain after starting a new medication. Laboratory tests confirm muscle inflammation. Which of the following is the most likely diagnosis?

Accepted Answer

Myositis due to drug side effect

Question 19

A patient presents with a 'pulled muscle' after intense physical activity. Which of the following best describes the underlying pathology?

Accepted Answer

Excessive stretching and possible tearing of muscle fascicles

Question 20

Which of the following equations best represents the relationship between muscle fiber diameter ($$d$$), number of myofibrils ($$n$$), and muscle strength ($$S) in $$hypertrophy, assuming strength is proportional to cross-sectional area and number of myofibrils?

Accepted Answer

$$S = k 	imes n 	imes d^2$

Myopathology: Disorders of Muscular Tissue

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