Epithelial review
https://www.wisc-online.com/learn/natural-science/life-science/ap14404/nervous-and-epithelial-tissue
Three muscle types
https://www.youtube.com/watch?v=raGl8bLkaAw&feature=related
negative feedback
https://www.youtube.com/watch?v=_QbD92p_EVs&feature=youtu.be
thermoregulation in animals
https://www.youtube.com/watch?v=NJEBfl_LKno&feature=youtu.be