|MadSci Network: Cell Biology|
First of all we need to define the "Fight-or-Flight Response". Definition: the reaction that occurs in the body when faced by a sudden, unexpected threat or source of stress. The name of this reaction comes from the fact that an animal experiencing this reaction almost immediately decides to fight or to run. In this reaction there is a sudden release of the hormones epinephrine and norepinephrine, which increase blood flow to the muscles, increase arterial blood pressure, improve muscle strength and mental ability, as well as increase blood glucose concentration. Through these actions the body prepares for a confrontation or a fast escape. -As single celled organisms do not possess any form of endocrine systems from which hormones such as epinephrine or norepinephrine are produced. These hormones also affect the ciculatory system and the nervous system, which single celled organisms do not possess. -Many single celled organisms such as viruses and bacteria do not possess the able to fight or run. In the case of viruses, which are simply a protein coat encapsulating a strain of RNA or DNA, the organism is incapable of nearly any action at all. Bacteria can response to various environmental conditions, but this is more a form of adaptation then an instinctive or hormonal response. -Protozoa do possess the able to "run away" from a potential danger. But whether or not the organism can recognize it is in danger or remains oblivious to it is a different matter. But this response is not influenced by a "fear" reaction but simply a matter of moving towards a more favorably surrounding. So while some single celled organisms may respond to environmental conditions, this response is quite different from the "fight-or-flight" system that multicellular animals. http://stress.about.com/cs/cortisol/g/def_fightflight.htm
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