Editing Suprachiasmatic nucleus (section)

===The SCN of endotherms and ectotherms===

In general, external temperature does not influence endothermic animal circadian rhythm because of the ability of these animals to keep their internal body temperature constant through homeostatic thermoregulation; however, peripheral oscillators (see [[Circadian rhythm]]) in mammals are sensitive to temperature pulses and will experience resetting of the circadian clock phase and associated genetic expression, suggesting how peripheral circadian oscillators may be separate entities from one another despite having a master oscillator within the SCN.<ref name="taka" /> Furthermore, when individual neurons of the SCN from a mouse were treated with heat pulses, a similar resetting of oscillators was observed, but when an intact SCN was treated with the same heat pulse treatment the SCN was resistant to temperature change by exhibiting an unaltered circadian oscillating phase.<ref name="taka"/> In ectothermic animals, particularly the [[ruin lizard]], ''Podarcis siculus'', temperature has been shown to affect the circadian oscillators within the SCN.<ref name="mag">{{cite journal | vauthors = Magnone MC, Jacobmeier B, Bertolucci C, Foà A, Albrecht U | title = Circadian expression of the clock gene Per2 is altered in the ruin lizard (Podarcis sicula) when temperature changes | journal = Brain Research. Molecular Brain Research | volume = 133 | issue = 2 | pages = 281–5 | date = February 2005 | pmid = 15710245 | doi = 10.1016/j.molbrainres.2004.10.014 | hdl = 11392/1198011 | url = http://doc.rero.ch/record/4325/files/1_albrecht_cec.pdf }}</ref> This reflects a potential evolutionary relationship among endothermic and ectothermic vertebrates as ectotherms rely on environmental temperature to affect their circadian rhythms and behavior while endotherms have an evolved SCN that is resistant to external temperature fluctuations and uses photoreception as a means for entraining the circadian oscillators within their SCN.<ref name="taka" /> In addition, the differences of the SCN between endothermic and ectothermic vertebrates suggest that the neuronal organization of the temperature-resistant SCN in endotherms is responsible for driving thermoregulatory behaviors in those animals differently from those of ectotherms, since they rely on external temperature for engaging in certain behaviors.