Control of food intake Flashcards
What starts to expand when you eat?
→ The fundic area expands to accomodate food
What two hormones are used in accommodation?
→ VIP and NO
What is PYY and what does it do?
→ Is is a satiety factor and increases gut motility
What do you feel when emptying occurs?
→ A sense of hunger (ghrelin)
Where do contractions occur and what are they mediated by?
→ Occur in the antrum
→ Mediated by AcH
What relaxation occurs when food is swallowed?
→ Receptive relaxation
What is receptive relaxation done by?
→ Vagal innervation
What kind of relaxation occurs in the stomach to allow accommodation?
→ adaptive relaxation
What is CCK stimulated by?
→ Lipids
What is affected if you cut vagus nerves?
→ Accommodation
→ Gastric compliance
What is the difference between appetite and hunger?
→ Appetite is a psychological desire
→ Hunger is a physiological craving
What is hyperphagia/polyphagia?
→ Abnormal desire for food
What does the hypothalamus control?
→ Hunger + thirst
Functions of the prefrontal cortex
→ Food seeking
→ Integration of sensory information from inside and outside the body
→ Receives emotional + cognitive information from the limbic system
→ Makes choices by translating the homeostatic and environmental information into adaptive behavioral responses,
What is the limbic system?
→ Complex system of nerves and networks in the brain
associated with instinct and mood
What sites is feeding behavior modulated by?
→ Lateral hypothalamus
→ Ventromedial hypothalamus
What is the role of the lateral hypothalamus?
→Hunger + thirst center
What is the role of the ventromedial nucleus ?
→ Satiety center
What happens if there is a lesion to the VMN?
→ Increased appetite with weight gain
What does the dorsomedial nucleus do?
→ Modulates energy intake (hunger center)
What acts on the dorsomedial nucleus to increase feeding?
→ NPY into the DMN increases feeding
What does the paraventricular nucleus do?
→ Modulates feeding behavior
What does the arcuate nucleus produce?
→ Orexigenic signals
What are the functions of the suprachiasmatic nucleus?
→ Human body clock is here
→Perception of the light-dark cycle
→ Sensation of hunger
What is the ligand of the medial amygdaloid nucleus?
→ 5-HT
→ Regulates appetite and food intake
What are agents that reduce appetite called?
→ Anorexigenic factors
When are carbohydrates and fats metabolized?
→ Carbohydrates during the day
→ Fats during the night
What condition happens if you stimulate the hypothalamus?
→ Aphagia
What condition happens if there are lesions to the hypothalamus?
→ Hyperphagia
What do opioids and growth releasing hormone do to appetite?
→ Increased appetite
What does naltrexone do?
→ Reduce the hedonic valence of food
What do orexigenic and anorexigenic neurotransmitters do?
→ orexigenic = increase appetite
→ Anorexigenic = decrease appetite
What does glucose in the blood stimulate?
→ Gluco-receptors in the hypothalamus
What happens to hunger/appetite when blood glucose increases?
→Up regulation of satiety
What happens to hunger/appetite when blood glucose decreases?
→ Up regulation of hunger
What is the effect of temperature on appetite?
→Hot enivronments stimulate feeding
What are the afferent inputs that affect appetite?
→Distension of a full stomach inhibits appetite
→Contraction of an empty stomach stimulates appetite
→Deposition of fat may control appetite
What hormone is released when fat is ingested and what effect does this have?
→ CCK
→ Slows gastric emptying
What does CCK do?
→ Inhibits further food intake
What happens if CCK is injected in the brain?
→ Appetite is reduced
What does insulin release?
→ Adipokine
What are the two effects that occur when insulin reaches the arcuate nucleus?
→ Stimulates arcuate nucleus
→ Catabolic effect reduces food intake and body fat
→reduces NpY and AgRP
→ Over time there are anabolic effects which increase food intake and body fat
What is the role of glucagon on controlling food intake?
→Acts mainly at the liver where it increases glucose production
→while generating a signal to reduce energy intake that is relayed to the hindbrain.
What is the role of insulin on controlling food intake?
→Insulin: acts at both the liver and the forebrain to reduce energy intake.
→ Suppress hepatic glucose production.
What is the role of amylin on controlling food intake?
→acts directly at the hindbrain to reduce energy intake.
What are the three pancreatic hormones?
→ Glucagon
→ Insulin
→ Amylin
What does white adipose tissue secrete?
→ Leptin
How does leptin control fat stores?
→ Operates a feedback mechanism between adipose tissue and the brain
→ Increases the expression of anorexigenic factors
→ Stimulates metabolic rate
→ Inhibits neuropeptide Y which stimulates feeding
What is ghrelin?
→ Appetite inducing hormone - orexin
→ Fast acting and stimulates food intake
→ Increases central orexins - NPY and AgRP
→ Suppresses the ability of leptin to stimulate anorexigenic factors
Where is ghrelin released from?
→ Stomach, pancreas and adrenals in response to nutritional status
When do circulating ghrelin levels increase?
→ preprandially
When do circulating ghrelin levels decrease?
→ after a meal
What can secretion of ghrelin be inhibited by?
→ Leptin
Where is obestatin produced?
→ The epithelial cells of the stomach
What is obestatin encoded by?
→ The ghrelin gene
WHat does obestatin do?
→ Antagonizes ghrelin induced food intake
→ Imbalance of ghrelin and obestatin may have a role in obesity
→ Suppresses food intake
What is satiation of feeding associated with?
→motor planning and execution
Why can we not modulate mechanisms of reward?
→ Cortico-limbic mechanisms of reward are under executive control so we cannot modulate it
