An autocrine effect occurs when a cell secretes a signal that:

An autocrine effect occurs when a cell secretes a signal that:

• A. Acts on the same cell that secreted it
• B. Acts on nearby cells
• C. Circulates in blood to distant sites
• D. Is blocked by antibodies

Answer: (A)

Autocrine signaling is when a cell releases a signaling molecule and the same cell (or cells of the same type) has receptors for that molecule and responds to it. This self-targeting allows the cell to regulate its own activity, such as promoting growth or survival in response to the signal it produced. Therefore, the signal acts on the cell that secreted it. By contrast, signaling to nearby cells is paracrine, signaling through the bloodstream to distant sites is endocrine, and being blocked by antibodies describes an intervention rather than the mode of action itself.

Autocrine signaling is when a cell releases a signaling molecule and the same cell (or cells of the same type) has receptors for that molecule and responds to it. This self-targeting allows the cell to regulate its own activity, such as promoting growth or survival in response to the signal it produced. Therefore, the signal acts on the cell that secreted it. By contrast, signaling to nearby cells is paracrine, signaling through the bloodstream to distant sites is endocrine, and being blocked by antibodies describes an intervention rather than the mode of action itself.