Question

Multiple peripheral signals provide information to the CNS about food intake and other metabolic processes.  Describe these different signals, and how they are integrated within the hypothalamus to provide overall regulation of body weight.

Answer 1

SIGNAL FOR FOOD INTAKE and feeding

• .The idea was that eating behaviour is stimulated and inhibited by internal signalling systems (for the drive and suppression of eating respectively) in order to regulate the internal environment (energy stores, tissue needs).
• It is also important to note however that day-to-day food involves the co-ordination of both homeostatic and non-homeostatic feedback
• Palatable food induces resistance to several satiety signals, documented for CCK, insulin and leptin, resulting in overeating.
• Food intake is driven by an increased activity in the reward system (dopamine, serotonin and opiates), triggered by the attractiveness of the taste
• FOOD intake is a regulated mechanism, afferent signal provide signal for food to central nervous system (which control satiety or food seeking or food rejection signal)'
• these signal start before food coming by smell. ,seeing, hearing
• Signals from the GI tract and the liver are involved in short-term regulation of feeding.
• Afferent signals travel in vagal nerve fibers from stretch receptors, and chemoreceptors activated by the presence of nutrients in the stomach and proximal small intestine are involved in meal termina- tion.
• Nutrients arriving via the portal vein may also trigger vagal afferent signals from the liver.
• Glucose can modulate food intake by acting on glucose-responsive neurons in the CNS.
• Ketones appear to decrease appetite.
• , the proximal intestine releases cholecystokinin (CCK), which reaches the liver via the portal vein and the CNS via the systemic circulation;
• CCK may act on CCK-A receptors at both sites to inhibit food intake.
• Endocrine L cells in the terminal small intestine (ileum) release glu- cagon-like peptide-1 (GLP-1), which inhibits feeding,

BODY WEIGHT REGULATION

• The brain plays a role in the regulation of physiological processes AND energy homeostasis.
• Central nervous circuits assess and integrate peripheral metabolic, endocrine and neuronal signals, and coordinate a response
• The brain directs, coordinates and integrates circulating hormones and metabolites that signal energy availability.
• Changes in body weight reflect respective changes in energy balance resulting from an imbalance between energy taken up