Hormonal Control Of Digestion And Appetite Flashcards
What are the. Phases of secretion
- Cephalic
- Gastric
- Intestinal
Describe the cephalic phase
Cause
-sensations and thoughts
Effect
- parasympathetic impulses increased gastric secretion
Describe the gastric phase
Neural negative feedback
- stretch receptors and chemoreceptors routed via submucosa plexus
-peristalsis stimulated
- food passed on and PH rises, distension lessens, stimulus disappears
Leads to emptying of stomach
- distension, partly digested proteins, caffeine, stimulate G (enteroendocrine) cells which releases gastric
Gastric transported to blood in gastric glands and targets the stomach Which controls HCl secreting parietal cells
When is gastric secretion inhibited/stimulated
Inhibited < PH2
Stimulated when PH increases
Gastrin lowers PH
What does gastric do
- stimulates gastric secretions
- contraction of lower oesophageal (cardiac) sphincter
- increases motility
- relaxes pyloric sphincter
Which three substances control HCl secretion
Gastrin
Acetylcholine
Histamine
(All 3 needed for strong H+ secretion)
Describe intestinal phase (excitatory responses)
Excitatory
- stretch receptors respond
- chemoreceptors detect fatty acids and glucose in duodenum chyme
- enteroendocrine cells in stomach release gastrin
- increases gastric peristalsis and stomach emptying
Describe intestinal phase (inhibitory responses)
Inhibitory -enterogastric reflex -enterogastric secretion Enteroendocrine cells in small intestine release: Cholecystokinin (CCK) Gastric inhibitory peptide (GIP) Secretin - they inhibit gastric secretion
What inhibits stomach emptying
The parasympathetic enterogastric reflex and by GIP, CCK and secretin
What 3 things regulate pancreatic secretion
- nervous control from parasympathetic division of ANS via vagus nerve
- autoregulation by sensing presence of fatty amino acids and amino acids in the acidic chyme (will release enzymes and bicarbonate to neutralise)
- hormonal control by secretion of CCK and secretin from duodenum
What regulates bile production/secretion in the liver
- nervous control parasympathetic division ANS via vagus nerve
- autoregulation by sensing fatty acids and amino acids in the acidic chyme
- hormonal control by secretion CCK (causes release of bile) and secretin (stimulates to make more bile) from duodenum
Production of bile helps to break down food
Describe CCK in control of appetite
- secreted in response to food
- reduces appetite and inhibits eating
- in hypothalamus neurotransmitter to inhibit eating
Describe glucagon-like peptide 1 in control of appetite
- reduces gastric emptying
Describe peptide YY (PYY) in control of appetite
- inhibits pancreatic exocrine secretion
- slows down gastric and small bowl motility
- reduces appetite
What are the 3 long term satiety signals
Leptin
Insulin
- role may be in brain in regulation of energy homeostasis
Oestrogen
- may act to lower body weight
- may target anorexigenic pro-opiomelanocortin (POMC) neuron
What do anorexigenic signals do
Decrease appetite
What do orexigenic signals do
Increase appetite
Describe lectin
Adipose cells
Decreases appetite and increases energy expenditure
Acute changes in food take no effect
If mutated can be obese early in life
Describe ARC
= arcuate nucleus
Contains anorexigenic (POMC/CART neurons) and orexigenic (AGRP/CART neurons) neurons but are separate
Stimulated by leptin
Describe melanocortin system
Peptides adrenocorticotropin and melanocyte stimulating hormones
Anorexigenic
Occurs ARC of hypothalamus
Integrates long and short term signals
May sense blood glucose levels activated by POMC and CART inhibited by NYP and AgRP
Describe ghrelin
Peripheral hunger signals Mediated by grehlin
- only GIT hormone to increase food intake
- secreted endocrine cells of gastric mucosa
- increases hunger, growth hormone secretion and fat stores
- binds to GHSR in hypothalamus
Describe NPY
Neurotransmitter
- activates receptor GPCR
- stimulates eating
Stimulated with reduction of insulin and leptin
Describe AgRP
Neurotransmitter
- binds to and inhibits MC4R
- inhibits anorexigenic effects of a-MSH
Stimulated with reduction of leptin and insulin
