[Campbell Biology P.929] The 'Visual Skills' section asks to explain why a particular nerve ... | Practice Question

The 'Visual Skills' section asks to explain why a particular nerve impulse signal has only one physical pathway but a particular hormone molecule can have multiple physical pathways. Which of the following statements best explains this difference?

  • A: Nerve impulses travel along dedicated, anatomically fixed neuronal pathways, whereas hormones are released into the circulatory system and can travel through any blood vessel to reach cells with appropriate receptors throughout the body.
  • B: Nerve impulses are electrical signals that diffuse rapidly through tissues, whereas hormones are chemical signals that only travel short distances.
  • C: The nervous system is adapted for gradual, widespread changes, whereas the endocrine system is suited for immediate, rapid responses.
  • D: Hormones are rapidly broken down after reaching their target cells, thus limiting their pathway, while nerve impulses persist longer to ensure widespread effects.

Explanation

Nerve impulses are transmitted along specific, anatomically defined neural networks axons , meaning a signal typically follows one 'wire' or pathway. Hormones, however, are released into the bloodstream and are thus distributed throughout the entire circulatory system. Any cell in the body that has the appropriate receptor for a given hormone, regardless of its location, can potentially be a target, giving the hormone's signal multiple 'physical pathways' to reach various responsive cells.