22.8.1 enteric nervous system

types of enteric neurons

• sensory neurons

• motor neurons

• interneurons (connectors betw. sensory and motor)

sensory neurons

• receptors are situated all throughout GI tract

  • stimulated receptors will send signal to sensory neuron

motor neurons

cause muscle contractions

basal electrical rhythm

• induced by the enteric nervous system

• brought to by action potentials by other triggers

functions

• regulates local reflexes

  • relays signals from the CNS for protection

3 phases of digestive system

• cephalic phase

• gastric phase

• intestinal phase

cephalic phase

STIMULATES STOMACH ACID SECRETION:

• sight and thought of food

• taste and smell of food

INHIBITS STOMACH ACID SECRETION:

• loss of appetite; depression (ex. bad smell can cause loss of appetite)

gastric phase

• when food enters the stomach
  STIMULATES STOMACH ACID:

  • stomach distension (volume of stomach inc. due to eating)

  • peptides, caffeine, rising pH in stomach (can also be caused by cephalic phase
    

INHIBITS STOMACH ACID:

• emotional upset (can cause you not to digest food as well)

• excessive stomach acid → gastrin release (slows down prod. of acid so food can go down)

intestinal phase

• shouldn’t have much activity in the stomach

STOMACH ACID STIM:

• peptides and amino acids in duodenum → gastrin release

INHIBIT ACID STIM:

• distension, fats, high osmolarity, and irritants in duodenum

endocrine regulation

• digestive system produces wide range of hormones

• act within and outside of digestive system

  • regulate muscle contraction and glandular secretions

physical regulation

• digestive system is influenced by presence of food inside tract

• distension induces smooth muscle contraction

• presence of specific food components and osmolarity also affect contraction and secretion