Neuropeptide Y (NPY) relaxes which type of muscle?

Neuropeptide Y (NPY) is primarily known for its role in the nervous system and in various physiological processes, including the modulation of vascular tone and the regulation of energy balance. When it comes to muscle relaxation, NPY specifically interacts with smooth muscle tissues. This interaction leads to vasodilation, which is the relaxation of the smooth muscle within blood vessels, allowing for increased blood flow.

Smooth muscle is involuntary and is found in structures like blood vessels, the gastrointestinal tract, and various other organ systems, distinguishing it from skeletal muscle, which is under voluntary control, and cardiac muscle, which is specialized for heart contractions.

The other types of muscle mentioned—skeletal muscle, cardiac muscle, and striated muscle (which is another term for skeletal muscle)—do not have the same response to NPY. Skeletal muscle typically contracts in response to neural stimulation and is not influenced by neuropeptides in the same way, while cardiac muscle contractions are closely regulated by different mechanisms such as the autonomic nervous system and hormonal influences. Thus, NPY's specific action on smooth muscle makes it the correct choice in this context.