L22 - GI motility

passage of a food bolus from ORAL CAVITY to STOMACH

it protects airway and prevents entry of air into stomach

• coordinated activity of muscles in the oral cavity, pharynx, larynx and oesophagus • partly voluntary control • partly reflexive/ involuntary

Oral: voluntary Pharyngeal: reflex Oesophageal: reflex

• stimulated when food bolus stimulates PRESSURE RECEPTORS in back of throat and pharynx • signals to the swallowing centre in brain telling you to swallow • this triggers N.I’s • innervates (stimulates) skeletal muscle in pharynx and upper oesophagus • involuntary contraction in pharyngeal muscles pushes material into the oesophagus • epiglottis prevents passage of food into lungs Swallowing occurs in around 20 seconds.

• mixing and churning to dissolve food for absorption • gastric emptying into SI • drug stability

minimises the amount of time drug is present in small intestine so drugs cannot be as efficiently absorbed

type of food, e.g. high carb content passes through fastest, high fat content = slowest.

• mixed by segmentation (circular one) • movement through SI by peristalsis (wave like) • coordinated by enteric NS

• Auerbach’s (myenteric) plexus- muscle- neurones for movement • Meissner’s (submucosal) plexus: in submucosal layer - neurons which detect chemical changes

solely exists in gut, works independently from other NS.

• sensory neurons detect food presence and STRETCH • motor neurons trigger MUSCLE CONTRACTIONS/ RELAXATIONS • influenced by NT’s and autonomic input • ensures the smooth movement through GI • contraction behind food bolus: release of ACh • relaxation in front of food bolus: release of nitric oxide

• fight or flight • inhibits ENS • decreased peristalsis, blood flow, secretion, absorption

• rest and digest • stimulates ENS • increased peristalsis, blood flow, secretion, absorption

• increased by cholecystokinin, gastrin, motilin, serotonin, insulin: increase in activity in ENS • decreased by secretin and glucagon: decrease in ENS

time taken for something to move through gi tract

more drug absorbed

regulates drug absorption

• Recurring motility pattern • Regulated by electrical activity • Occurrs between feeding (when you haven’t eaten) • Process from stomach to large intestine • Cleansing mechanism (removes bad bacteria/ food particles) • Responsible for “tummy” intestines rumbling

• timing of administration is important • can use control release drugs

• localised contraction + relaxation of haustra • segmentation in haustra allows optimum water absorption • mixes contents • contents moved from intestine to gut to microbiome • stool formation

• coordinated contractions that propel the contents of the colon toward the rectum • contractions that occur in the ascending colon and transverse colon • triggered by the gastrocolic reflex: when take food into stomach, stomach sends signal to intestine to remove waste • defection

• temporarily stored in rectum • activation of stretch receptors • voluntary and involuntary steps

• weak mass movement • increased transit time in gi tract • too much water absorbed in large intestine due to slowed down movement Causes: - lifestyle - medications - neurological issues