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PRINCIPLE OF SATIATION (FUNCTION (SATIATION (to prevent overconsumption…
PRINCIPLE OF SATIATION
DEFINITION
Satiation : processes that promote meal termination,
thereby limiting meal size
Satiety
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Satiety signal : most of them promote termination of ongoing
meals & do not delay subsequent meal initiation / affect intake if delivered between meals.
FUNCTION
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SATIATION
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satiation signals arise from multiple sites in the GI system
( stomach, proximalsmall intestine, distalsmall intestine,
colon & pancreas)
HINDBRAIN
principal central site receiving input from short-acting satiation signals which are transmitted both neurally
examples
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hormonally (by gut peptides acting directly on the area postrema, which lies outside the blood-brain barrier)
gut-hindbrain communication : sufficient for satiation,
although this normally interacts with higher cognitive centers
to regulate feeding
ADIPOSITY HORMONES
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pathways relaying short-acting satiation signals from the gut
to the hindbrain also interact at several levels with long-acting
adiposity hormones involved in body-weight regulation (leptin & insulin )
GI EFFECTS
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meals stop:warning:
meals are typically stopped long before gastric capacity is reached & when food is diluted with noncaloric bulking agents, the volume
ingested increases to maintain constant caloric intake
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however this observation does not specifically implicate stomach as source of satiation signals**, because the exodus of ingesta through a gastric cannula also precludes meal-related signals that would normally arise from postgastric sites
major gastric distention alone issufficient to terminate ingestion, but the amount of food required for this exceeds that eaten in a typical meals
normal postprandial gastric distention does contribute to satiation when acting in concert with pregastric & postgastric stimuli
pregastric, gastric,& intestinal satiation signals (function in unison)
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stomach can sense nutrients to regulate gastrin release,
stomach wall is endowed with discrete neural sensors of tension, strecth, & volume
Bombesin-related peptides(gastrin-releasing peptide & neuromedin B), - produced by gastric myenteric neurons, can reduce food intake when delivered pharmacologically
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