Hormonal Regulation of Digestion

Autocrine

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

Paracrine

What type of hormone acts on neighboring cells without entering the bloodstream?

Endocrine

What type of hormone is released into the bloodstream to act on distant target cells?

Neurocrine

What type of hormone is released by nerve terminals and acts on target cells?

Gastrin

Which hormone is the primary endocrine regulator of the secretory response to meals?

G-cells

Which cells secrete gastrin in the stomach antrum?

Peptides and amino acids

What are the most potent stimulators of gastrin release?

Tryptophan and phenylalanine

Which amino acids are the strongest stimulators of gastrin secretion?

Stretch receptors

What sensory mechanism triggers gastrin release when the stomach is full?

Gastrin-releasing peptide (GRP)

What neurocrine signal stimulates gastrin secretion via the vagus nerve?

Histamine release from enterochromaffin-like cells (ECLs)

How does gastrin indirectly stimulate acid secretion?

Parietal cells

Which cells secrete hydrochloric acid (HCl) in response to gastrin?

CCK2 receptor

What receptor does gastrin bind to on parietal cells and ECLs?

Acid secretion and trophic effects on gastric mucosa

What are the two main functions of gastrin?

Small intestine, stomach, colon

Which organs experience trophic growth due to gastrin?

Gastrocolic reflex

Which reflex is stimulated by gastrin and promotes colonic contraction?

Secretin

Which hormone inhibits gastrin secretion?

pH < 4.5

At what pH level does secretin secretion increase?

Bicarbonate secretion

What is the primary function of secretin in neutralizing stomach acid?

S cells in the duodenum

Which cells secrete secretin?

CCK (cholecystokinin)

Which hormone enhances the effects of secretin?

GIP (glucose-dependent insulinotropic peptide)

Which hormone inhibits gastric acid secretion along with secretin?

CCK-A receptor

Which receptor slows down motility to allow digestion?

I cells in the small intestine

Which cells secrete cholecystokinin (CCK)?

Pancreatic enzyme release

What is the primary function of CCK?

Gallbladder contraction

What effect does CCK have on bile secretion?

Sphincter of Oddi relaxation

Which physiological change allows bile and pancreatic enzymes to enter the duodenum?

CCK-8 (sulfated form)

Which form of CCK has the highest receptor affinity?

CCK-4 (non-sulfated form)

Which form of CCK is less biologically active?

GLP-1 (glucagon-like peptide-1)

Which hormone decreases gastric emptying and promotes satiety?

L cells

Which cells secrete GLP-1?

Hexose and fat

What stimulates the release of GLP-1?

GLUT4 upregulation

How does GLP-1 enhance insulin secretion?

Motilin

Which hormone is responsible for increasing gastric motility in a fasting state?

Mo cells in the small intestine

Which cells secrete motilin?

Every 90 minutes

How frequently is motilin secreted during fasting?

Gastric phase

During which digestive phase is motilin secretion suppressed?

GIP (glucose-dependent insulinotropic peptide)

Which hormone was formerly called gastric inhibitory peptide?

K cells in the duodenum and jejunum

Which cells secrete GIP?

Fatty acids, amino acids, glucose

What stimulates GIP secretion?

Insulin secretion

What is the primary function of GIP?

Beta-cell sensitivity to glucose

How does GLP-1 enhance insulin secretion?

CCK and GLP-1

Which two hormones induce satiety?

CCK

Which hormone slows gastric emptying by contracting the pyloric sphincter?

Secretin and CCK

Which two hormones work together to neutralize stomach acid?

Secretin

Which hormone has a trophic effect on the exocrine pancreas?

Bicarbonate secretion from the pancreas

What is the primary action of secretin?

Biliary bicarbonate secretion

How does secretin help neutralize acidic chyme?

Secretin inhibition

What effect does gastrin have on secretin secretion?

Parietal cells, ECL cells, and G cells

Which three cell types are directly influenced by gastrin?

Neurocrine hormones

Which hormone type is released from nerve endings to regulate digestion?

Gastrin and CCK

Which hormones share a similar receptor (CCK-B)?

Secretin, CCK, and GIP

Which three hormones inhibit gastric acid secretion?

Enterogastric reflex

Which reflex slows gastric emptying when acidic chyme enters the duodenum?

GLP-1 and GIP

Which two hormones are classified as incretins?

Gastrin and motilin

Which two hormones increase gastric motility?

Secretin and CCK

Which hormones protect the duodenal mucosa from acid damage?

Gastrin

Which hormone is inhibited by high stomach acidity?

GIP

Which hormone primarily responds to glucose intake?

GLP-1

Which hormone promotes insulin secretion and slows gastric emptying?