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The blood-brain barrier is primarily composed of:
 A) Astrocytes
 B) Ependymal cells
 C) Microglia
 D) Endothelial cells
 Answer: D) Endothelial cells
 Rationale: The blood-brain barrier is formed by endothelial cells
that tightly regulate the passage of substances from the bloodstream
into the brain.
Which structure is responsible for the production of cerebrospinal
fluid?
 A) Arachnoid villi
 B) Choroid plexus
 C) Dura mater
 D) Pia mater
 Answer: B) Choroid plexus
 Rationale: The choroid plexus produces cerebrospinal fluid, which
cushions the brain and spinal cord.
During muscle contraction, what role does calcium ion (Ca2+) play?
 A) It breaks down ATP to release energy.
 B) It binds to troponin, changing its shape and removing the
blocking action of tropomyosin.
 C) It forms cross-bridges with myosin heads.
 D) It depolarizes muscle fibers to initiate contraction.
 Answer: B) It binds to troponin, changing its shape and removing
the blocking action of tropomyosin.
 Rationale: Calcium ions bind to troponin during muscle
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