Which type of chemical messengers primarily act locally, affecting nearby cells rather than distant targets?

• A. Neurotransmitters
• B. Endocrine hormones
• C. Autocrine signals
• D. Paracrine signals

Answer: (D)

Verified step by step guidance

1. Understand the definitions of the different types of chemical messengers mentioned in the problem: neurotransmitters, endocrine hormones, autocrine signals, and paracrine signals.
2. Recall that neurotransmitters are chemical messengers that transmit signals across a synapse from one neuron to another or to a target cell, typically over very short distances.
3. Recognize that endocrine hormones are released into the bloodstream and travel long distances to reach their target cells, making them unsuitable for local signaling.
4. Understand that autocrine signals are chemical messengers that act on the same cell that secreted them, rather than affecting nearby cells.
5. Identify that paracrine signals are chemical messengers that act locally, affecting nearby cells in the immediate vicinity of the secreting cell, which matches the description in the problem.