Regulation of Feeding Flashcards
What does the regulation of body weight require?
A balance between food intake and energy expenditure
Which is stronger? Mechanisms that induce feeding or mechanisms that reduce feeding?
Mechanisms that induce feeding as a result of evolutionary pressures to seek and store food
Which mechanisms control feeding?
Homeostatic and non-homeostatic. The two systems overlap and communicate in different capacities
What is the Prandial State?
The period prior to and during meal consumption (anabolic metabolism)
What is the Post-absorptive State?
The period between meals (catabolic metabolism)
How is glucose used as a primary energy source?
Glucose is converted to adenosine triphosphate (ATP) which is the primary energy source in the cell
How does the body regulate energy homeostasis?
Through distal and proximal cues. Feeding usually ceases before proximal cues peak, indicating that animals use the distal and intermediate cues to estimate food consumption
What are distal cues?
External cues such as grocery store logos or food items
What are proximal cues?
Internal cues such as blood glucose and nutrient levels. They provide the body with feedback about its metabolic and nutritional state
What neural systems or structures are involved in homeostatic mechanisms?
Hypothalamus, Nucleus of the solitary tract (NTS), Adiposity signals (proximal cue, long-term, such as leptin, insulin, etc), Satiation signals (proximal cue, short-term, such as CCK, etc)
What neural systems or structures are involved in non-homeostatic mechanisms?
Amygdala, Accumbens, Paraventricular nucleus of the thalamus (PVT), Ventral tegmental area (VTA), Hedonic stress (distal cue)
How does the brain receive signals about the current energy state of the body?
Through short-term signals (signals rising and falling around meals) such as ghrelin, insulin, PYY, CCK, mechanosensory receptors in the digestive tract; and long-term signals (signals regarding energy stores) such as leptin
What factors affect the short-term regulation of food intake?
Orexigenic factors (appetite stimulant) and anorexigenic factors (appetite suppressant). Blood glucose levels must be well-regulated across the prandial and postabsorptive states (therefore cues must anticipate blood glucose levels)
What are examples of orexigenic factors?
Grehlin, NPY (Neuropeptide Y), AgRP (Agouti-related peptide). Ghrelin stimulates the release of NPY and AgRP which stimulates feeding
What are examples of Anorexigenic factors?
CCK (cholecystokinin), PYY (peptide tyrosine-tyrosine), CART (cocaine and amphetamine-related transcripts), aMSH (alpha melanocyte stimulating hormone), Insulin, Glucagon
How is ghrelin related to the short-term regulation of feeding?
Ghrelin increases with fasting and decreases after a meal. It increases before a meal suggesting a role in initiating eating. Ghrelin antagonists inhibit feeding. Ghrelin injections increase eating and can cause weight gain over time (cause subjects to have increased feelings of hunger). Ghrelin is produced in the stomach
How is CCK related to the short-term regulation of feeding?
CCK is present in cells lining the duodenum. CCK can act as a satiety signal (injections suppress feeding). It acts as both a neuropeptide and a peptide hormone
What is the duodenum?
Beginning of the small intestine, controls bile secretion, monitors presence of fats, releases CCK
How is PYY related to the short-term regulation of feeding?
PYY decreases feeding. It is a hormone released by the gut proportional to the number of calories ingested. Injections can cause subjects to feel less hungry (correlates with levels of satiety)
What is the glucostatic theory?
The hypothesis that low glucose levels trigger eating. However, there is not strong evidence to support it (injections do not have a huge effect on food consumption)
What is hypoglycemia?
When the level of glucose in the blood drops below what is healthy
How is insulin related to the short-term regulation of feeding?
Large injections of insulin cause hypoglycemia and glucoprivation (stimulates eating). Insulin converts and stores glucose and allows non-neural cells to use it (without insulin only brain cells can use glucose).
Is body weight regulated over the long term or short term?
Long-term (bodies will adapt to diets over the long term to stay within a certain weight range)
How is leptin related to the long-term regulation of feeding?
Leptin is secreted by well-nourished fat cells (more fat in fat cells means more leptin signal). Injections of leptin can reduce obesity (however there has been limited impact in treating obesity). High levels of leptin desensitize the brain to hunger signals. Low levels provide a stronger hunger signal. Leptin levels help the body regulate weight.
