Behavioral Neuroscience Chapter 12- Ingestive Behavior

what is ingestive behavior?

eating or drinking

What BMI is overweight and what is obese

Above 25 and above 30.

What is adipose tissue?

Fat tissue that serves as our long term resevoir

Which hormone is produced re: low blood volume?

Kidneyrs produce angiotensin

What regions of the hypothalamus regulate ingestive behavior?

Lateral hypothalamus for hunger and ventromedical hypothalamus for satiety

Where are glucose and lipid detectors?

Liver

Where does the last stage of satiety occur?

Liver

What is decerebration?

Surgical procedure severing brain stem, disconnecting hindbrain and forebrain

What are the four essential features of a regulatory mechanism

System variable, set point, detector, and correctional mechanism

Where does brain recieve glucoprivic or lipoprivic hunger signal from?

Vagus nerve from liver

When does volumetric thirst occur?

When intravascular plasma volume decreases

When food is plentiful, when do we eat?

When stomach and upper intestine are empty

What brain regions are involved in thirst

angular cingulate cortex as well as AV3V

Where are the receptors for volumetric thirst?

detector cells in the kidneys and in the atria of the heart

When we have an empty digestive tract, what does CNS live on?

glucose released by liver

____, _______, and _______ are derived from _____, ______, and ________ during the fasting phase

glucose, amino acids, and fatty acids glycogen, protein, and adipose tissue

What is the condition where the intravascular blood volume falls lows and heart can no longer pump blood efficientely?

hypovolemia

What peptides does leptin stimulate?

inhibits NPY and AgRP

2/3 of the body's water is contained where

intracellular fluid

Where are osmoreceptors found?

lamina terminalis, OVLT and SFO In the AV3V of the hypothalamus

What is a satiety mechanism?

A brain mechanism that causes cessation of hunger or thirst, produced by adequate and available supplies of nutrients or water. Cessation occurs in anticipation of replenishment.

What is angiotensin?

A peptide hormone that causes thirst and salt hunger, and reduces blood flow to kidneys so organism can compensate for reduced volume until fluid balance is restored

Explain the characteristics of a regulatory mechanism.

A regulatory system contains four features: a system variable (the variable that is regulated), a set point (the optimal value of the system variable), a detector to measure the system variable, and a correctional mechanism to change it. Physiological regulatory systems, such as control of body fluids and nutrients, require a satiety mechanism to anticipate the effects of the correctional mechanism, because the changes brought about by eating and drinking occur only after a considerable period of time.

Explain how the liver provides late-stage satiety signals.

A satiety signal comes from the liver, which detects nutrients being received from the intestines through the hepatic portal vein.

What is glycerol?

A soluble carbohydrate part of triglycerides

What is the genetic component of obestity?

Additive of a large number of genes

What provides long term satiety signals?

Adipose tissue

Describe how insulin can function as a satiety signal.

Although a high level of insulin in the blood causes glucoprivic eating by reducing blood levels of glucose, moderately high levels, associated with the absorptive phase of metabolism, provide a satiety signal to the brain.

What is a disorder that causes people to eat too little even to the point of starvation?

Anorexia nervosa

What produces NPY and AgRP?

Arcuate nucleus

What parts of the brain receive sensory information regarding taste and satiety?

Area Postrema and nucleus of the solitary tract (AP and NST) in the medulla

What is a disorder characterized by eating binges but not compensatory purging?

Binge eating disorder

Evaluate the roles of reinforcement, stress, surgery, pharmacology, and behavioral interventions in treating obesity.

Both dopamine, which plays an important role in reinforcement, and corticotrophin- releasing hormone (CRH), which plays an important role in stress, are involved with eating. Stress and anxiety can lead to increased eating behavior. Researchers have evaluated many interventions for obesity, but no universally successful program has yet been identified. Successful bariatric surgery is probably effective due primarily to suppression of ghrelin secretion and stimulation of PYY secretion. Two drugs initially appeared to show some promise in the treatment of obesity. Fenfluramine, a serotonin agonist, and rimonabant, a cannabinoid antagonist, suppress appetite, but adverse side effects have prevented their use. Another drug, orlistat, prevents the absorption of calories from fat, but produces significant side effects as well. Behavioral interventions for obesity show modest effects on weight loss.

What is disorder characterized by loss of control of food intake, and usually binging and purging?

Bulimia nervosa

What neurons does leptin activate?

CART/ alpha-MSH neurons, which inhibit MCH and orexin neurons in lateral hypothalamus

Which hormones are involved in reinforcement of food-seeking behavior?

CRH and dopamine

What is the function of CCK?

Causes gallbladder to contract and provides satiety signal through vagus nerve

What is osmometric thirst?

Cellular dehydration. Thirst produced by an increase in osmotic pressure of the interstitial fluid relative to intracellular fluid.

What purpose do the insulin receptors in the brain serve?

Detect insulin present in the body, although they do not need it to process glucose, it may serve as a satiety signal

What area controls ghrelin secretion?

Duodenum, upper part of small intestine

Compare the pathways for the use of glucose, fat, and amino acids by the brain and body in the absorptive phase.

During the absorptive phase we receive glucose, amino acids, and fats from the intestines. The blood level of insulin is high, which permits all cells to metabolize glucose. In addition, the liver and the muscles convert glucose to glycogen, which replenishes the short-term reservoir. Excess carbohydrates and amino acids are converted to fats, and fats are placed into the long-term reservoir in the adipose tissue.

Explain signals from the stomach that help start a meal.

Eating can be initiated when the stomach and upper intestine are empty. Ghrelin, a peptide hormone released by the stomach when it and the upper intestine are empty, is a potent stimulator of food intake. Ghrelin levels are low during the absorptive phase, and increase before a meal. Gastric bypass surgery reduces ghrelin levels and is associated with weight loss.

Discuss the roles of brain changes, starvation, excessive exercise, and genetic factors in eating disorders.

Eating disorders are associated with enlarged ventricles and reduced brain volume. Some research suggests that preoccupation with food and eating, ritualistic eating, erratic mood, excessive exercising, impaired cognitive performance, and physiological changes such as decreased body temperature are symptoms of starvation and not the underlying causes of anorexia. Birth complications are associated with eating disorders. Twin studies support a role for heredity in eating disorders.

Discuss the contributions of environment, physical activity, and genetics to the development of obesity.

Environmental factors can affect how many calories are expended through physical exercise and ingested in calorie-dense foods. Reduced physical activity contributes to obesity, along with less "nonexercise activity thermogenesis," or NEAT. Obesity has a strong hereditary basis as well. Individuals can inherit more efficient metabolisms, making them more likely to gain weight when food is plentiful. Examples of specific genetic contributors to obesity include mutations of the MC4R and the FTO gene. In general however, the high level of heritability of obesity is likely the additive effects of a large number of genes, each of which has a small effect on BMI. Interactions between genetic and environmental factors are illustrated by the example of Pima living in the United States and Mexico. A high percentage of Pima who live in the United States and consume a high-fat diet become obese and, as a consequence, develop diabetes. In contrast, Pima living in Mexico, who engage in subsistence farming and eat a low-fat diet, remain thin and have a low incidence of obesity.

When we have an empty digestive tract, what does most of body live on?

Fatty acids

What are triglycerides?

Form of fat storage in adipose cells that consist of a glycerol molecule and three fatty acids

Explain how the stomach can provide satiety signals.

Gastric satiety factors are activated by the entry of food into the stomach. The stomach possesses nutrient detectors that convey satiety signals. the stomach also secretes ghrelin, and a fall in ghrelin provides a satiety signal to the brain.

What peptide hormone increases eating?

Ghrelin, produced by GI system especially the stomach

What is the response when glucose falls?

Glucagon, a different peptide hormone, is secreted to prompt glygocen to convert to glucose

How does glucose act in the absorptive phase?

Glucose level rises, which causes pancreas to begin secreting insulin, which lets cells use glucose as a fuel. Extra glucose is converted into glycogen, which fills the short-term carbohydrate reservoir. If some glucose is left over, it is converted into fat and absorbed by fat cells.

What is the short term store of nutrients?

Glycogen, stored in liver and muscles

What is a crucial vein in the liver?

Hepatic portal vein

What is leptin?

Hormone secreted by adipose tissue that decreases food intake and increases metabolic rate. Antiobestity hormone

What is the condition that describes a fall in blood glucose level?

Hypoglycemia

Where are ghrelin receptors in the brain?

Hypothalamus

What prompts glucose conversion into glycogen?

Insulin, a peptide hormone produced by pancreas

List strategies used in eating disorder interventions.

Interventions for eating disorders include cognitive behavioral therapy, pharmacological treatments, and alternative therapies. The success rates for most eating disorder treatments are low, however some alternative therapies have shown a higher success rate.

Describe how the intestines can provide satiety signals.

Intestinal satiety factors are activated by the passage of food from the stomach into the duodenum. The intestines possess nutrient detectors that convey satiety signals. Another satiety signal from the intestine is provided by CCK, which is secreted by the duodenum when it receives fat-rich food from the stomach. Information about the secretion of CCK is transmitted to the brain through the afferent axons of the vagus nerve. PYY, a peptide secreted after a meal by the intestines, also acts as a satiety signal. the stomach and intestines also secrete ghrelin and a fall in ghrelin provides a satiety signal to the brain.

What are the extracellular fluids?

Intravascular Blood plasma, cerebrospinal fluid, and interstitial fluid that bathes our cells

What is a correctional mechanism?

Mechanism that changes the value of the system variable

What is the detector?

Mechanism that signals when system variable deviates from the set point

What is the absorptive phase?

Metabolic phase where nutrients are absorbed from the digestive system

What happens when there is decerebration?

Muscles involved in ingestive behavior are only affected by hindbrain

What is elevated in blood of patients with anorexia nervosa?

NPY, stimulating eating

What activates MCH and orexin neurons?

Neuropeptide Y and AgRP

Can leptin treat obestity?

Nope, most obese people already have high lepin levels in blood

Are genes that promote an efficient metabolism always beneficial?

Not if you have low physical demand and high food

What is the fasting phase of metabolism?

Nutrients aren't available from the digestive system, so they are derived from other sources

What is an ob mouse?

Obese mouse with low metabolism that has a mutation that prevents leptin production

Compare osmometric and volumetric thirst.

Osmometric thirst occurs when the interstitial fluid draws water out of cells. This event, which can be caused by evaporation of water from the body or by ingestion of a salty meal, is detected by osmoreceptors in the hypothalamus. Activation of these osmoreceptors stimulates drinking. The sensation of thirst in humans appears to involve the anterior cingulate cortex. Volumetric thirst occurs along with osmometric thirst when the body loses fluid and is often caused by blood loss, vomiting, and diarrhea. The primary stimulus for volumetric thirst is provided by a fall in blood flow to the kidneys and heart. This event triggers the formation of angiotensin, which increases blood pressure and stimulates changes that inhibit the secretion of water and sodium by the kidneys and induce a sodium appetite.

Where does arcuate nucleus project to?

Paraventricular nucleus

What small intestine chemical releases in response to nutrients?

Peptide YY3-36, or PYY

What is negative feedback?

Process where the effect produced by an action lowers or ends that same action

What does the RYGB surgery do?

Produces a small pouch attatched to lower part of intestine, and disrupts ghrelin secretion and increases PYY

What are ingestive behaviors controlled by?

Satiety mechanisms and detectors that monitor system variables

How does duodenum control the rate of stomach emptying?

Secreting Cholecystokinin (CCK) hormone in presence of fats

What provides short term satiety signals?

Sensory info from face as well as GI organs

What do the short and long term reservoirs store?

Short term stores carbohydrates and long term stores fats

What is the primary physical difference between a person who is obese and a person who is not?

Size of fat cells, determined by amount of triglycerides

How do amino acids act in the absorptive phase?

Small portion are protein building blocks, most are stored in adipose tissue as fats

What is an example of a fatty acid?

Stearic acid, oleic acid, or palmitic acid

What is glucoprivation?

Stimulates eating Fall in blood level of glucose or drugs that inhibit glucose metabolism

What is lipoprivation?

Stimulates hunger by depriving cell of lipis Fall in level of fatty acids, caused by drug

Describe how metabolic signals can play a role in starting a meal.

Studies with inhibitors of the metabolism of glucose and fatty acids indicate that low levels of both of these nutrients are involved in hunger; that is, animals will eat in response to both glucoprivation and lipoprivation. These signals are normally present only after more than one meal has been missed. Receptors in the liver detect both glucoprivation and lipoprivation and transmit this information to the brain through sensory axons of the vagus nerve. Glucoprivic eating can also be stimulated by interfering with glucose metabolism in the medulla; thus, the brain contains its own glucose-sensitive detectors.

Identify functions of the brain stem involved in eating regulation.

The brain stem contains neural circuits that are able to control acceptance or rejection of sweet or bitter foods and can even be modulated by satiation or physiological hunger signals, such as a decrease in glucose metabolism or the presence of food in the digestive system. The area postrema and nucleus of the solitary tract (AP/NST) receive signals from the tongue, stomach, small intestine, and liver and send the information on to many regions of the forebrain. These signals interact and help to control food intake. Lesions of the AP/NST disrupt both glucoprivic and lipoprivic eating.

Identify functions of the hypothalamus involved in eating regulation.

The lateral hypothalamus is involved in initiating eating and the ventromedial hypothalamus is involved in regulating satiety. The lateral hypothalamus contains two sets of neurons whose activity increases eating and decreases metabolic rate. These neurons secrete the peptides orexin and MCH (melanin-concentrating hormone). Food deprivation increases the level of these peptides. The axons of these neurons project to regions of the brain involved in motivation, movement, and metabolism. The release of neuropeptide Y in the lateral hypothalamus induces ravenous eating, an effect that is produced by excitatory connections of NPY-secreting neurons with the orexin and MCH neurons. NPY neurons in the arcuate nucleus of the hypothalamus receive input from glucose-sensitive neurons in the medulla. NPY neurons are the primary target of ghrelin in the hypothalamus. Ghrelin also activates the mesolimbic reinforcement system by stimulating dopaminergic neurons in the ventral tegmental area, which increases the release of DA in the nucleus accumbens. When NPY is infused in the paraventricular nucleus, it decreases metabolic rate. Levels of NPY increase when an animal is deprived of food and fall again when the animal eats. Blocking NPY receptors suppresses eating. NPY neurons also release a peptide called AgRP. This peptide serves as an antagonist at MC4 receptors and, like NPY, stimulates eating. Endocannabinoids also stimulate eating, apparently by increasing the release of MCH and orexin. Leptin desensitizes the brain to hunger signals. It binds with receptors in the arcuate nucleus of the hypothalamus, where it inhibits NPY-secreting neurons, increasing metabolic rate and suppressing eating. The arcuate nucleus also contains neurons that secrete CART, a peptide that suppresses eating. These neurons, which are activated by leptin, have inhibitory connections with MCH and orexin neurons in the lateral hypothalamus. CART neurons also secrete a peptide called α-MSH, which serves as an agonist at MC4 receptors and inhibits eating. Ghrelin, which activates NPY/AgRP neurons and stimulates hunger, also inhibits CART/α-MSH neurons and suppresses the satiating effect of the peptides secreted by these neurons. The anorexigenic peptide, PYY, which is released by the gastrointestinal system, suppresses the release of NPY and AgRP.

Describe the function, location, and contents of the long-term reservoir.

The long-term reservoir supplies nutrients to the brain and body during prolonged periods of fasting. It is located in the adipose tissue, where energy is stored in triglyceride molecules until needed.

What is the set point?

The optimal value of the system variable

Describe the function, location, and contents of the short-term reservoir.

The short-term reservoir supplies nutrients to the brain during brief periods of fasting (between meals). It is located in the liver, where energy is stored in glycogen molecules until needed.

Summarize the signals from the environment that help start a meal.

The time of day, presence of groups of people, or cues such as the sensory signals of food can all contribute to initiating a meal.

What is the system variable?

The variable that is controlled by a regulatory mechanism, like temperature in a heating system

Contrast the function of satiety signals from adipose tissue with short-term satiety signals.

Unlike short-term satiety signals that regulate the size of a meal, signals arising from fat tissue affect food intake on a long-term basis, apparently by modulating the effectiveness of short-term hunger and satiety signals. Force-feeding facilitates satiety, and starvation inhibits it. Studies of the ob mouse led to the discovery of leptin, a peptide hormone secreted by well-nourished adipose tissue that increases an animal's metabolic rate and decreases food intake.

Compare the pathways for the use of glucose, fat, and amino acids by the brain and body in the fasting phase.

Unused glucose, fat, and amino acids are stored in the liver and adipose tissues for later use during the fasting phase. During the fasting phase the activity of the parasympathetic nervous system falls, and the activity of the sympathetic nervous system increases. In response, the level of insulin falls, and the levels of glucagon and the adrenal catecholamines rise. These events cause liver glycogen to be converted to glucose and triglycerides to be broken down into glycerol and fatty acids. In the absence of insulin, only the central nervous system can use the glucose that is available in the blood; the rest of the body lives on fatty acids. Glycerol is converted to glucose by the liver, and the brain metabolizes the glucose.

In a study of a short period of fasting, what is the effect on young men and women?

Young men ate more food, and young women ate less food

You're eating a snack before class, where are your brain and body getting energy from?

Your brain will be obtaining energy from glucose, while your body obtains energy from carbohydrates, amino acids, and possibly fats. This is the absorptive phase

You skip breakfast to workout. where are your brain and body getting energy from?

Your brain will be obtaining energy from glycogen or glycerol, while your body obtains energy from adipose tissue.

____ and ______ are the main energy source for cells during absorptive phase, and excess nutrients are stored in _______

glucose and amino acids triglycerids

What brain changes are assosciated with anorexia nervosa?

loss of gray and white brain matter

Which peptide neurotransmitters are produced by lateral hypothalamus and what are their functions?

melanin-concentrating hormone (MCH) and orexin, and they stimulate hunger and decrease metabolic rate to increase and prserve stores

What is the effect of lesions on the area postrema or nucleus of the solitary tract?

no more glucoprivic or lipoprivic feeding

What does gastric bypass do?

reduce ghrelin and prompt weight loss

What are osmoreceptors?

stretch sensitive neurons with a firing rate affected by level of hydration, where if interstitial fluid is more concentrated, they will shrink through osmosis and send signals.

What is homeostasis?

the process by which the body's substances and characteristics are maintained at their optimal level