All living organisms from one-celled to complex animals have a primary life function - to survive. How do cells, tissues, organs and body organ systems contribute to homeostasis (a balanced, internal environment for organism survival)?
All the elements of a functioning organ system, including cells, organs and tissues, work together to contribute to homeostasis. One way this is accomplished is through positive feedback and rapid change. This is the process in which the body senses a change and activates mechanisms that increase that change. Unfortunately, instead of aiding homeostasis it can produce the opposite effect and become life-threatening. An example of beneficial positive feedback is seen in childbirth, where stretching of the uterus triggers the secretion of a hormone, oxytocin, which stimulates uterine contractions and speeds up labor (biologyreference.com). The hormone oxytocin is mainly produced in the hypothalamus. It is released into the blood via the pituitary gland, or to other parts of the brain. It binds to oxytocin receptors to influence behavior and physiology. Here we see that the hormone is produced by an organ (hypothalamus), transported by specialized fluid connective tissue (blood), and arrives in another organ(pituitary gland) where it is received by the cells therein. All of this can take place within one organ system, or throughout the entire body.
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