Gastrointestinal: regulation Flashcards
(36 cards)
What is the role of the lateral hypothalamus?
Feeding centre (promotes eating)
What is the role of the ventromedial hypothalamus?
Satiety centre (inhibits eating)
What are the 4 satiety signals?
Nervous - reflexes initiated by distension
Hormonal - feedback by cholecystokinin
Chemical - glucostatic and lipostatic
Thermal
What is the cycle of leptin? (4)
- Increased food intake, decreased energy expenditure
- Adipose tissue, increased fat deposits, increased leptin synthesis
- Increased plasma leptin conc.
- Hypothalamus, increased activation of leptin receptors
What are the 5 peptides in the hypothalamus that increase food intake?
Neuropeptide Y Orexins Galanin Melanin Ghrelin (stomach)
What are the 6 peptides in the hypothalamus and intestines that decrease food intake?
CCK - small intestine
Corticotropin-releasing hormone - hypothalamus
a-melanocyte-stimulating hormone - hypothalamus
CART - hypothalamus
Glucagon-like peptide-1 - intestines
PYY 3-36 - intestines
What are the 2 paths for GI regulation?
Neural and endocrine
How is food intake regulated? (3)
Not based on homeostasis concept
Maximise absorption - regardless of need
Lumen of GI tract conditions regulated to max. absorption
What neural pathways are the enteric nervous system comprised of? (2)
Submucosal plexus
Myenteric plexus
What is the short reflex pathway? (4)
Stimulus in lumen
GI receptors
Intrinsic nerve plexus
Effector organ in GI tract
What is the long reflex pathway? (5)
Stimulus in lumen GI receptors Central nervous system Intrinsic nerve plexus Effector organ in GI tract
What are the 4 GI hormones?
Gastrin - stomach
Cholecystokinin - duodenum, jejunum
Secretin - duodenum and jejunum
Glucose-dependent insulinotropic peptide - duodenum and jejunum
What is the role of gastrin? (3)
Stimulates gastric secretion and motility
Stimulates ill motility and relaxes ileocecal sphincter
Stimulates mass movement of colon
What is the role of cholecystokinin? (2)
Inhibits gastric secretion and motility
Stimulates gallbladder
What is the role of secretin? (2)
Inhibits gastric secretion and motility
Potentiates actions of CCK on pancreatic enzyme secretion
What is the role of glucose-dependent insulinotropic peptide? (2)
Inhibits gastric secretion and motility
Stimulates insulin secretion by pancreas
What are the 3 phases of gastrointestinal control?
Cephalic phase - thoughts, taste and smell
Gastric phase - stimuli originate in stomach
Intestinal phase - stimuli originate in small intestine
What is involved in short-term regulation: hunger verses satiety? (3)
Insulin
CCK
Neural input from mechano/chemo receptors
What is involved in long-term regulation? (6)
- Leptin = hormone released from adipose cells when calories exceeds demands
- Leptin suppresses hunger and increases metabolism
- Saliva secretion
- Acid and pepsinogen secretion in the stomach
- Secretion of pancreatic juice and bile
- Rates of fluid movement in the digestive tract
What are the steps in saliva secretion? (5)
Taste and texture of food Mechanoreceptors and taste receptors in mouth Salivary centre of medulla Autonomic nervous system Stimulate salivation
What are the 2 types of autonomic input to salivary glands and what do they produce? (3)
Parasympathetic: watery saliva
Sympathetic: more mucus, thick saliva
How is gastric acid secreted and what does it do? (7)
- Parietal cells produce HCl
- Carbonic anhydrase catalyses bicarbonate and H+
- H+ actively secreted into the lumen of the stomach
- Bicarbonate is transported into interstitial fluid for Cl-
- Cl- diffuses into lumen of stomach
- H+ & Cl- secreted into stomach lumen
- bicarbonate enters the interstitial fluid then blood
How are these secretions regulated? (3)
Parasympathetic nervous system
Gastrin
Histamine
What causes an increase in acid and pepsinogen secretion? (5)
Sight of food Taste Smell Chewing Swallowing
