Muscles utilized for controlling the flow of all substances within lumen are grouped as

Correct Answer: D

Rationale: Muscles controlling substance flow within lumens like blood vessels, digestive tract, or airways are smooth muscles. These involuntary muscles, found in organ walls, contract or relax to regulate movement, such as peristalsis in the gut or vasoconstriction in arteries, without conscious control. The hormonal system involves chemical signaling, not muscle action. The skeletal system includes voluntary muscles for locomotion, not lumen regulation. Cardiac muscles power the heart, a specific function unrelated to general lumen control. Smooth muscles' unique ability to modulate flow across diverse tubular structures makes them the best fit, as their autonomic regulation and adaptability distinguish them from striated muscles in managing internal transport.

Correct Answer: B

Rationale: Recruitment increases contraction strength by activating more motor units neurons and their muscle fibers as effort rises. This graded response builds force, like lifting heavier weights, without changing individual fiber contraction strength. Atrophy is muscle wasting from disuse, opposite to recruitment's effect. All-or-none applies to single fiber response, not the cumulative effect of recruitment. Fatigue follows prolonged effort, not recruitment itself. Stronger contractions via recruitment reflect motor unit summation, distinguishing it from wasting, binary responses, or exhaustion, key to muscle power modulation.

Correct Answer: B

Rationale: Masseter and temporalis are primary mastication muscles, closing the jaw for chewing. Masseter elevates the mandible, temporalis assists and retracts. Buccinator aids chewing indirectly via cheeks, not jaw movement. Orbicularis oris moves lips, unrelated. Zygomaticus smiles, not chews. These two excel in jaw power, distinct from accessory, lip, or facial roles, essential for biting and grinding.

Correct Answer: A

Rationale: The rotator cuff comprises infraspinatus, supraspinatus, teres minor, and subscapularis, stabilizing the shoulder joint and enabling rotation. 'Intraspinatus' is a typo correct is infraspinatus. Teres major and deltoid assist shoulder movement but aren't cuff muscles. These four anchor the humerus, distinct from larger or adjacent muscles, vital for shoulder integrity and motion.

Correct Answer: C

Rationale: Fibromyalgia features chronic muscle pain, tenderness, stiffness, and elevated substance P, a pain neurotransmitter, with no clear cause. Cancer may cause pain but isn't muscle-specific or tied to substance P. Diabetes affects nerves, not primarily muscles. Tetanus causes spasms from infection, not chronic ache. Fibromyalgia's diffuse, persistent symptoms set it apart, a musculoskeletal disorder.