Living Systems Capstone

A student wrote this essay about homeostasis in the human body

"The human body maintains homeostasis, stable internal conditions, through the work of several organ systems. When body temperature rises, the brain sends signals to the skin to produce sweat. As sweat evaporates, it absorbs heat and cools the body. [Sentence A] This is called a positive feedback loop, because the body is responding to a change by correcting it back toward normal."

"Blood glucose is also controlled by homeostasis. [Sentence B] After eating, the liver releases insulin into the bloodstream. Insulin signals cells to take up glucose, lowering blood glucose back to normal levels. This shows how the digestive and endocrine systems work together."

"The excretory system removes waste from the body. [Sentence C] The kidneys filter nitrogen-containing wastes such as urea from the blood and expel them in urine. The lungs also act as excretory organs, they remove oxygen from the blood, which would otherwise build up to toxic levels."

"Gas exchange in the lungs occurs across the alveoli. [Sentence D] Oxygen diffuses from the alveoli into the blood because there is a higher concentration of oxygen in the blood than in the alveoli. Carbon dioxide diffuses in the opposite direction."

"Finally, the interdependence of body systems means that a disruption in one system always causes total system failure. [Sentence E] For example, if the circulatory system slows, every other system immediately stops working completely."