The majority of nociceptors are free nerve endings. Which statement is true?

The majority of nociceptors are free nerve endings. Which statement is true?

• A. Most are free nerve endings
• B. Most are specialized nerve endings
• C. Most are located in brain
• D. Most are myelinated large fibers

Answer: (A)

Nociception in the periphery relies on free nerve endings—the bare terminals of small sensory neurons that extend into tissues and respond to damaging thermal, chemical, or mechanical stimuli. These free endings are typically carried by small-diameter fibers, including thinly myelinated A-delta fibers and unmyelinated C fibers, which explains the characteristic pain sensations (fast, sharp pain with A-delta; slower, dull pain with C fibers). Because of this basic arrangement, the majority of nociceptors are free nerve endings rather than specialized end organs, and they are distributed throughout peripheral tissues such as skin, mucosa, joints, and viscera, not in the brain itself. The brain lacks pain receptors, so nociception does not arise from brain parenchyma. In short, the true statement is that most nociceptors are free nerve endings; they are not large, myelinated fibers, and they are not located in the brain in the sense of sensing pain there.

Nociception in the periphery relies on free nerve endings—the bare terminals of small sensory neurons that extend into tissues and respond to damaging thermal, chemical, or mechanical stimuli. These free endings are typically carried by small-diameter fibers, including thinly myelinated A-delta fibers and unmyelinated C fibers, which explains the characteristic pain sensations (fast, sharp pain with A-delta; slower, dull pain with C fibers). Because of this basic arrangement, the majority of nociceptors are free nerve endings rather than specialized end organs, and they are distributed throughout peripheral tissues such as skin, mucosa, joints, and viscera, not in the brain itself. The brain lacks pain receptors, so nociception does not arise from brain parenchyma. In short, the true statement is that most nociceptors are free nerve endings; they are not large, myelinated fibers, and they are not located in the brain in the sense of sensing pain there.