[08.24] Hormonal Regulation of Digestion

Autocrine

What type of hormone acts on the same cell that secretes it?

Paracrine

What type of hormone affects neighboring cells?

Endocrine

What type of hormone travels through the bloodstream to reach its target organ?

Neurocrine

What type of hormone is released by nerve terminals?

Gastrin

What hormone is the major endocrine regulator of the secretory response to meals?

G cells

What cells secrete gastrin?

Stomach antrum

Where is the primary site of gastrin secretion?

Amino acids and peptides

What stimulates gastrin release?

Tryptophan and phenylalanine

What are the most potent amino acid stimulators of gastrin release?

Distention of the stomach

What mechanical stimulus promotes gastrin secretion?

Vagus nerve

Which nerve stimulates gastrin release?

HCl secretion

What is the primary function of gastrin?

Parietal cells

What cells in the stomach secrete HCl?

Histamine release from ECL cells

How does gastrin indirectly increase acid secretion?

CCK2 receptor

What receptor does gastrin bind to on parietal cells?

Acidic pH (H+ presence)

What inhibits gastrin secretion?

Secretin and GIP

What hormones inhibit gastrin release?

Gastrocolic reflex

What reflex is stimulated by gastrin, causing movement of the colon?

Cholecystokinin (CCK)

What hormone is the main stimulus for pancreatic enzyme and bile release?

I cells

What cells secrete CCK?

Duodenum and jejunum

Where is CCK primarily secreted?

Amino acids and fatty acids

What stimulates CCK secretion?

Gallbladder contraction

What effect does CCK have on the gallbladder?

Relaxation of the sphincter of Oddi

What effect does CCK have on bile flow into the duodenum?

Slows gastric emptying

What effect does CCK have on stomach motility?

CCK-8

Which form of CCK has the highest receptor affinity?

Sulfation at tyrosine 7

What chemical modification increases CCK-8’s activity?

CCKA receptor

Which receptor preferentially binds sulfated CCK?

Secretin

What hormone is released in response to acidic chyme?

S cells

What cells secrete secretin?

Duodenum

Where is secretin primarily released?

Bicarbonate secretion

What is the primary function of secretin?

Pancreatic ductal cells

What cells secrete bicarbonate in response to secretin?

Liver

Which organ also increases bicarbonate secretion due to secretin?

Inhibition of gastrin release

How does secretin regulate stomach acid secretion?

Glucose-dependent insulinotropic polypeptide (GIP)

What hormone stimulates insulin release in response to nutrients?

K cells

What cells secrete GIP?

Duodenum and jejunum

Where is GIP secreted?

Glucose, amino acids, and fatty acids

What nutrients stimulate GIP release?

Insulin secretion

What is the primary function of GIP?

GLP-1

What hormone enhances insulin secretion and delays gastric emptying?

L cells

What cells secrete GLP-1?

Hexose and fats

What stimulates GLP-1 secretion?

Motilin

What hormone increases gastrointestinal motility during fasting?

Mo cells

What cells secrete motilin?

Proximal small intestine

Where is motilin primarily released?

Migrating motor complex (MMC)

What intestinal motility pattern is regulated by motilin?

90 minutes

How often is motilin released in a fasting state?

Stops when food is ingested

When is motilin secretion inhibited?

Gastrin and CCK

Which two hormones share a common pentagastrin structure?

Secretin and glucagon

Which two hormones share structural similarity?

CCK and secretin

What two hormones work together to stimulate pancreatic secretion?

Parietal cells, ECL cells, and D cells

What three cell types does gastrin affect?

Pancreatic growth

What trophic effect does CCK have?

Enhances satiety

What is an additional function of CCK?

GIP and GLP-1

What two hormones belong to the incretin family?

GLP-2

What hormone stimulates chylomicron release into lacteals?

Stimulation of lipoprotein lipase activity

What metabolic effect does GIP have in adipocytes?

Regulation of hunger and anxiety

What CNS effects does CCK have?

CCK-4

Which form of CCK lacks a sulfate group but remains active?

CCKB receptor

Which receptor binds both gastrin and CCK equally?

Inhibits gastric emptying

What effect does GLP-1 have on stomach motility?

Increases sensitivity of beta cells to glucose

How does GLP-1 enhance insulin secretion?

Secretin and GIP

Which two hormones inhibit gastric acid secretion?

CCK and motilin

Which two hormones slow gastric emptying?

Secretin

What hormone counteracts gastrin’s effects?

Gastroileal reflex

What reflex does gastrin stimulate to empty the small intestine?

Vagus nerve

What nerve mediates neurocrine control of gastrin release?

Proglucagon

What precursor is processed into GLP-1?

Enhances pancreatic growth

What trophic effect does secretin have?

Liver and gallbladder

What two organs increase bicarbonate secretion due to secretin?

Stops gastric acid production

What is the main function of secretin?

CCK slows motility

How does CCK prevent overloading of digestive enzymes?

CCK-8 has higher activity than CCK-4

How do different CCK forms compare in function?

GIP is the only hormone stimulated by all three macronutrients

What is unique about GIP stimulation?

CCK promotes gallbladder contraction

How does CCK help in fat digestion?

CCK enhances secretin function

How do CCK and secretin interact?

GLP-1 and GIP

Which two hormones stimulate insulin release?

Inhibits apoptosis of pancreatic beta cells

What protective effect does GIP have on the pancreas?

CCK increases pancreatic enzyme secretion

What is the primary effect of CCK?

Gastrin is inhibited by acid

What feedback mechanism controls gastrin?

Motilin increases gastric motility

What effect does motilin have?

GIP induces satiety

How does GIP affect appetite?

Secretin is released at pH < 4.5

What pH threshold stimulates secretin?

CCK suppresses appetite

What effect does CCK have on hunger?

GLP-1 delays gastric emptying

How does GLP-1 affect digestion?

Secretin and bicarbonate secretion

What is secretin’s primary function?

CCKA receptors prefer sulfated CCK

How do CCKA and CCKB receptors differ?

GLP-1 enhances insulin secretion

What is GLP-1’s main metabolic effect?

Motilin clears the stomach

What is motilin’s fasting function?

GIP stimulates lipoprotein lipase

What metabolic effect does GIP have?

GLP-1 suppresses appetite

How does GLP-1 affect satiety?

Secretin promotes bicarbonate release

What effect does secretin have on pH?

CCK inhibits motility

How does CCK regulate digestion speed?

Motilin is released every 90 minutes

What is the release cycle of motilin?

GIP protects beta cells

What protective function does GIP have?

Gastrin increases acid secretion

What is gastrin’s primary function?

CCK promotes pancreatic growth

What is a trophic effect of CCK?

Secretin stops acid production

What is secretin’s main role?

GLP-1 reduces gastric motility

How does GLP-1 influence digestion speed?