regulation of digestive tract - controlled by nervous/endocrine systems 

• nervous system stimulates salivary/gastric secretions in response to food
• food in stomach >> gastrin secreted >> pepsinogen, HCl secreted (cycle controlled by negative feedback)
• chymes goes into duodenum >> inhibits stomach contractions >> no additional chyme enters small intestine
• enterogastrones - duodenal hormones in blood that controls stomach, gastric inhibition
• liver regulatory functions - can modify absorbed substances from digestive tract before they get to other part of body
  • removes toxins, poisons from body
  • produces most of proteins in blood plasma
  • edema - when concentration of plasma proteins drops too low
• regulation of blood glucose concentration - neurons get energy from glucose in blood plasma
  • insulin - stimulates conversion of glucose to glycogen
  • blood glucose level decrease >> liver secretes glycogen, gets broken down by glucagon through glycogenolysis to make glucose
  • gluconeogenesis - makes glucose from other molecules

energy expenditure - eat food >> provides energy source, raw materials 

• basal metabolic rate (BMR) - minimum rate of energy use
• obesity - having so much fat that it’s unhealthy
• regulation of food intake - adipose tissue secretes satiety factor to decrease appetite
  • obesity due to lack of sensitivity to protein created by satiety factor?
• anorexia nervosa - people starve themselves
• bulimia - people gorge themselves, then vomit everything
• essential nutrients - cannot be made by animal, but necessary for health
  • vitamins - organic substances needed in humans (humans can not longer made vitamin C)
  • not enough vitamin C >> scurvy
  • 9 essential amino acids for humans
  • essential minerals - calcium, phosphorus, inorganic substances