The document discusses physiology and the different levels of structure in the human body from cells to organ systems. It provides details on important organelles in cells and describes the 11 major organ systems in the human body, including their main structures and functions. Homeostasis is defined as the body's ability to maintain stable internal conditions through various feedback mechanisms.

4. A Prototypical Cell

30. Increased BP Sensed by pressure receptors in aortic arch and carotid sinus Input sent via afferent pathway to medulla oblongata Current BP compared with set point and error signal generated Output sent along efferent pathway to heart and blood vessels Heart rate & force of contraction decrease Blood vessel diameter increases BP DECREASES

36. What this means is that the homeostatic variables are NOT kept rigidly fixed upon a single value. They are kept within a certain range, and when they exit that range – that’s when negative feedback loops turn on to bring them back.

38. Positive Feedback in Blood Clotting

39. Dangerous Positive Feedback Rise in body temperature Increase in body metabolism Increase in body heat production

40. What stops a positive feedback loop?