Which of the following structures is responsible for respiratory control?

A. The peripheral nervous system is responsible for transmitting signals between the central nervous system and the rest of the body, but it does not directly govern the increase in peristalsis.

B. The central nervous system (CNS) processes information and coordinates responses but does not directly control the movement of the digestive system. The autonomic nervous system, which includes the parasympathetic and sympathetic divisions, controls peristalsis.

C. The parasympathetic nervous system is responsible for "rest-and-digest" activities. It stimulates peristalsis to promote digestion and the movement of food through the gastrointestinal tract, leading to an increase in peristalsis.

D. The sympathetic nervous system is involved in the "fight-or-flight" response, which inhibits digestive processes, including peristalsis, as the body prioritizes other functions.

A. T-helper cells (CD4+ cells) play a crucial role in initiating and coordinating the immune response. They stimulate the activation of B-cells to produce antibodies and help activate cytotoxic T-cells to target infected cells.

B. The first line of defense against infection is provided by physical barriers like the skin, mucous membranes, and innate immune responses, not by T-helper cells.

C. While T-helper cells can activate macrophages indirectly by releasing cytokines, their primary role is in helping to activate other immune cells like B-cells and cytotoxic T-cells, rather than directly activating macrophages.

D. T-helper cells are not directly involved in minimizing cell damage caused by T-cells. That role is more closely related to regulatory T-cells (Tregs) that help maintain immune tolerance and prevent excessive immune responses.