Questions: Which describes neuroendocrine cells? They respond only to chemical signals. They stimulate endocrine organs. They release their secretions into the bloodstream. They are found in the gut only.

The answer is the third one: They release their secretions into the bloodstream.

Explanation for each option:

1. They respond only to chemical signals.

   • Incorrect. Neuroendocrine cells can respond to various types of signals, including neural and chemical signals.

2. They stimulate endocrine organs.

   • Incorrect. While neuroendocrine cells can influence endocrine organs, their primary function is not to stimulate them directly but to release hormones into the bloodstream.

3. They release their secretions into the bloodstream.

   • Correct. Neuroendocrine cells are specialized cells that release hormones into the bloodstream in response to neural signals, thus integrating the nervous and endocrine systems.

4. They are found in the gut only.

   • Incorrect. Neuroendocrine cells are found in various parts of the body, including the gut, but they are not limited to the gut.

In summary, neuroendocrine cells are characterized by their ability to release hormones into the bloodstream, which is why the third option is the correct description.