Ppt Chap 10

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Ppt Chap 10

  1. 1. Chapter 10 Internal Regulation
  2. 2. Temperature Regulation <ul><li>Temperature affects many aspects of behavior. </li></ul><ul><li>Temperature regulation is vital to the normal functioning of many behavioral processes. </li></ul><ul><li>Homeostasis refers to temperature regulation and other biological processes that keep certain body variables within a fixed range. </li></ul>
  3. 4. Temperature Regulation <ul><li>A set point refers to a single value that the body works to maintain. </li></ul><ul><ul><li>Examples: Levels of water, oxygen, glucose, sodium chloride, protein, fat and acidity in the body. </li></ul></ul><ul><li>Processes that reduce discrepancies from the set point are known as negative feedback . </li></ul><ul><li>Allostasis refers to the adaptive way in which the body changes its set point in response to changes in life or the environment. </li></ul>
  4. 5. Temperature Regulation <ul><li>Temperature regulation is one of the body’s biological priorities. </li></ul><ul><ul><li>Uses about two-thirds of our energy/ kilocalories per day. </li></ul></ul><ul><li>Basal metabolism is the energy used to maintain a constant body temperature while at rest. </li></ul>
  5. 6. Temperature Regulation <ul><li>Poikilothermic refers to the idea that the body temperature matches that of the environment. </li></ul><ul><ul><li>Amphibians, reptiles and most fish. </li></ul></ul><ul><li>The organism lacks the internal, physiological mechanisms of temperature regulation. </li></ul><ul><li>Temperature regulation is accomplished via choosing locations in the environment. </li></ul>
  6. 7. Temperature Regulation <ul><li>Homeothermic refers to the use of internal physiological mechanisms to maintain an almost constant body temperature. </li></ul><ul><ul><li>Characteristic of mammals and birds. </li></ul></ul><ul><li>Requires energy and fuel. </li></ul><ul><li>Sweating and panting decrease temperature. </li></ul><ul><li>Increasing temperature is accomplished via shivering, increasing metabolic rate, decreasing blood flow to the skin, etc. </li></ul>
  7. 8. Temperature Regulation <ul><li>Mammals evolved to have a constant temperature of 37 ˚ C ( 98 ˚ F). </li></ul><ul><ul><li>Muscle activity benefits from being as warm as possible and ready for vigorous activity. </li></ul></ul><ul><ul><li>Proteins in the body break their bonds and lose their useful properties at higher temperatures. </li></ul></ul><ul><ul><li>Reproductive cells require cooler temperatures. </li></ul></ul>
  8. 9. Temperature Regulation <ul><li>Body temperature regulation is predominantly dependent upon areas in the preoptic area/ anterior hypothalamus (POA/AH). </li></ul><ul><li>The POA/AH partially monitors the body’s temperature by monitoring its own temperature. </li></ul><ul><ul><li>Heating the POA/AH leads to panting or shivering; cooling leads to shivering. </li></ul></ul><ul><li>Cells of the POA/AH also receive input from temperature sensitive receptors in the skin. </li></ul>
  9. 11. Temperature Regulation <ul><li>Bacterial and viral infections can cause a fever, part of the body’s defense against illness. </li></ul><ul><li>Bacteria and viruses trigger the release of leukocytes which release small proteins called cytokines . </li></ul><ul><li>Cytokines attack intruders but also stimulate the vagus nerve. </li></ul>
  10. 12. Temperature Regulation <ul><li>(Continued) </li></ul><ul><li>The vagus nerve stimulates the hypothalamus to initiate a fever. </li></ul><ul><li>Some bacteria grow less vigorously in warmer than normal body temperature. </li></ul><ul><li>However, a fever of above 39 ˚ C (103 ˚ F) does the body more harm than good. </li></ul>
  11. 13. Thirst <ul><li>Water constitutes 70% of the mammalian body. </li></ul><ul><li>Water in the body must be regulated within narrow limits. </li></ul><ul><li>The concentrations of chemicals in water determines the rate of all chemical reactions in the body. </li></ul>
  12. 14. Thirst <ul><li>Mechanisms of water regulation vary for humans. </li></ul><ul><li>Water can be conserved by: </li></ul><ul><ul><li>Excreting concentrated urine. </li></ul></ul><ul><ul><li>Decreasing sweat and other autonomic responses. </li></ul></ul><ul><li>Most often water regulation is accomplished via drinking more water than we need and excreting the rest. </li></ul>
  13. 15. Thirst <ul><li>Vasopressin is a hormone released by the posterior pituitary which raises blood pressure by constricting blood vessels. </li></ul><ul><ul><li>helps to compensate for the decreased water volume. </li></ul></ul><ul><li>Vasopressin is also known as an antidiuretic hormone because it enables the kidneys to reabsorb water and excrete highly concentrated urine. </li></ul>
  14. 16. Thirst <ul><li>Two different kinds of thirst include: </li></ul><ul><ul><li>Osmotic thirst – a thirst resulting from eating salty foods. </li></ul></ul><ul><ul><li>Hypovolemic thirst – a thirst resulting from loss of fluids due to bleeding or sweating. </li></ul></ul><ul><li>Each kind of thirst motivates different kinds of behaviors. </li></ul>
  15. 17. Thirst <ul><li>Osmotic thirst occurs because the human body maintains a combined concentration of solutes at a fixed level of .15 M (molar). </li></ul><ul><li>Solutes inside and outside a cell produce osmotic pressure , the tendency of water to flow across a semi-permeable membrane from an area of low solute concentration to an area of high solute concentration. </li></ul><ul><ul><li>Occurs when solutes are more concentrated on one side of the membrane. </li></ul></ul>
  16. 19. Thirst <ul><li>Eating salty food causes sodium ions to spread through the blood and extracellular fluid of the cell. </li></ul><ul><li>The higher concentration of solutes outside the cell results in osmotic pressure , drawing water from the cell to the extracellular fluid. </li></ul><ul><li>Certain neurons detect the loss of water and trigger osmotic thirst to help restore the body to the normal state. </li></ul>
  17. 20. Thirst <ul><li>The brain detects osmotic pressure from: </li></ul><ul><ul><li>Receptors around the third ventricle. </li></ul></ul><ul><ul><li>The OVLT (organum vasculosum laminae terminalis) and the subfornical organ (detect osmotic pressure and salt content). </li></ul></ul><ul><ul><li>Receptors in the periphery, including the stomach, which detect high levels of sodium. </li></ul></ul>
  18. 21. Thirst <ul><li>Receptors in the OVLT, subfornical organ, stomach and elsewhere relay information to areas of the hypothalamus including: </li></ul><ul><ul><li>the supraoptic nucleus </li></ul></ul><ul><ul><li>paraventricular nucleus. </li></ul></ul><ul><ul><ul><li>Both control the rate at which the posterior pituitary releases vasopressin. </li></ul></ul></ul><ul><li>Receptors also relay information to the lateral preoptic area which controls drinking. </li></ul>
  19. 23. Thirst <ul><li>When osmotic thirst is triggered, water that you drink has to be absorbed through the digestive system. </li></ul><ul><li>To inhibit thirst, the body monitors swallowing and detects the water contents of the stomach and intestines. </li></ul>
  20. 24. Thirst <ul><li>Hypovolemic thirst is thirst associated with low volume of body fluids. </li></ul><ul><ul><li>Triggered by the release of the hormones vasopressin and angiotensin II, which constrict blood vessels to compensate for a drop in blood pressure. </li></ul></ul><ul><li>Angiotensin II stimulates neurons in areas adjoining the third ventricle. </li></ul><ul><li>Neurons in the third ventricle send axons to the hypothalamus where angiotensin II is also released as a neurotransmitter. </li></ul>
  21. 26. Thirst <ul><li>Animals with osmotic thirst have a preference for pure water. </li></ul><ul><li>Animals with hypovolemic thirst have a preference for slightly salty water as pure water dilutes body fluids and changes osmotic pressure. </li></ul><ul><li>Sodium-specific hunger , a strong craving for salty foods. </li></ul><ul><ul><li>develops automatically to restore solute levels in the blood. </li></ul></ul>
  22. 28. Hunger <ul><li>Animals vary in their strategies of eating, but humans tend to eat more than they need at the given moment. </li></ul><ul><li>A combination of learned and unlearned factors contribute to hunger and eating behaviors. </li></ul>
  23. 31. Hunger <ul><li>The function of the digestive system is to break down food into smaller molecules that the cells can use. </li></ul><ul><li>Digestion begins in the mouth where enzymes in the saliva break down carbohydrates. </li></ul><ul><li>Hydrochloric acid and enzymes in the stomach digest proteins. </li></ul>
  24. 33. Hunger <ul><li>The small intestine has enzymes that digest proteins, fats, and carbohydrates and absorbs digested food into the bloodstream. </li></ul><ul><li>The large intestine absorbs water and minerals and lubricates the remaining materials to pass as feces. </li></ul>
  25. 34. Hunger <ul><li>At the age of weaning, most mammals lose the intestinal enzyme lactase , which is necessary for metabolizing lactose. </li></ul><ul><li>Lactose is the sugar found in milk. </li></ul><ul><li>Milk consumption after weaning can cause gas and stomach cramps. </li></ul><ul><li>Declining levels of lactase may be an evolutionary mechanism to encourage weaning. </li></ul>
  26. 35. Hunger <ul><li>Most human adults have enough lactase to consume milk and other dairy products throughout the lifetime. </li></ul><ul><li>Nearly all people in China and surrounding countries lack the gene that enables adults to metabolize lactose. </li></ul><ul><ul><li>Only small quantities of dairy products can be consumed. </li></ul></ul>
  27. 37. Hunger <ul><li>A carnivore is an animal that eats meat and necessary vitamins are found in the meat consumed. </li></ul><ul><li>Herbivores are animals that exclusively eat plants. </li></ul><ul><li>Omnivores are animals that eat both meat and plants. </li></ul>
  28. 38. Hunger <ul><li>Herbivores and omnivores must distinguish between edible and inedible substances to find sufficient vitamins and minerals. </li></ul><ul><li>Selecting foods to eat is usually accomplished via imitation of others. </li></ul>
  29. 39. Hunger <ul><li>Other strategies of selecting food include: </li></ul><ul><ul><li>Selecting sweet foods and avoiding bitter foods. </li></ul></ul><ul><ul><li>Preferring things that taste familiar. </li></ul></ul><ul><ul><li>Learning from consequences that happen after a food is consumed. </li></ul></ul><ul><li>A conditioned taste aversion is a distaste for food that develops if the food makes one ill. </li></ul>
  30. 40. Hunger <ul><li>The brain regulates eating through messages from the mouth, stomach, intestines, fat cells and elsewhere. </li></ul><ul><li>The desire to taste and other mouth sensations, such as chewing, are also motivating factors in hunger and satiety. </li></ul><ul><li>Sham feeding experiments , in which everything an animals eats leaks out of a tube connected to the stomach or esophagus, do not produce satiety. </li></ul>
  31. 41. Hunger <ul><li>The main signal to stop eating is the distention of the stomach. </li></ul><ul><li>The vagus nerve conveys information about the stretching of the stomach walls to the brain. </li></ul><ul><li>The splanchnic nerves convey information about the nutrient contents of the stomach. </li></ul>
  32. 42. Hunger <ul><li>The duodenum is the part of the small intestine where the initial absorption of significant amounts of nutrients occurs. </li></ul><ul><li>Distention of the duodenum can also produce feelings of satiety. </li></ul><ul><li>The duodenum also releases the hormone cholecystokinin (CCK) , which helps to regulate hunger. </li></ul>
  33. 43. Hunger <ul><li>Cholecystokinin (CCK) released by the duodenum regulates hunger by: </li></ul><ul><ul><li>Closing the sphincter muscle between the stomach and duodenum and causing the stomach to hold its contents and fill faster. </li></ul></ul><ul><ul><li>Stimulating the vagus nerve to send a message to the hypothalamus that releases a chemical similar to CCK. </li></ul></ul>
  34. 44. Hunger <ul><li>Glucose, insulin, and glucagon levels also influence feelings of hunger. </li></ul><ul><li>Most digested food enters the bloodstream as glucose, an important source of energy for the body and nearly the only fuel used by the brain. </li></ul><ul><li>When glucose levels are high, liver cells convert some of the excess into glycogen and fat cells convert it into fat. </li></ul><ul><li>When low, liver converts glycogen back into glucose. </li></ul>
  35. 45. Hunger <ul><li>Insulin is a pancreatic hormone that enables glucose to enter the cell. </li></ul><ul><li>Insulin levels rise as someone is getting ready for a meal and after a meal. </li></ul><ul><li>In preparation for the rush of additional glucose about to enter the blood, high insulin levels let some of the existing glucose in the blood to enter the cells. </li></ul><ul><li>Consequently, high levels of insulin generally decrease appetite. </li></ul>
  36. 47. Hunger <ul><li>Glucagon is also a hormone released by the pancreas when glucose levels fall. </li></ul><ul><li>Glucagon stimulates the liver to convert some of its stored glycogen to glucose to replenish low supplies in the blood. </li></ul><ul><li>As insulin levels drop, glucose enters the cell more slowly and hunger increases. </li></ul>
  37. 48. Hunger <ul><li>If insulin levels constantly stay high, the body continues rapidly moving blood glucose into the cells long after a meal. </li></ul><ul><ul><li>Blood glucose drops and hunger increases in spite of the high insulin levels. </li></ul></ul><ul><ul><li>Food is rapidly deposited as fat and glycogen. </li></ul></ul><ul><ul><li>The organism gains weight. </li></ul></ul>
  38. 50. Hunger <ul><li>In people with diabetes, insulin levels remain constantly low, but blood glucose levels are high. </li></ul><ul><ul><li>People eat more food than normal, but excrete the glucose unused and lose weight. </li></ul></ul>
  39. 52. Hunger <ul><li>Long-term hunger regulation is accomplished via the monitoring of fat supplies by the body. </li></ul><ul><li>The body’s fat cells produce the peptide leptin, which signals the brain to increase or decrease eating. </li></ul><ul><li>Low levels of leptin increase hunger. </li></ul><ul><li>High levels </li></ul>
  40. 53. Hunger <ul><li>High levels of leptin do not necessarily decrease hunger. </li></ul><ul><ul><li>Most people are obese because they are less sensitive to leptin. </li></ul></ul><ul><ul><li>Some people are obese because of a genetic inability to produce leptin. </li></ul></ul>
  41. 54. Hunger <ul><li>Information from all parts of the body regarding hunger impinge into two kinds of cells in the arcuate nucleus. </li></ul><ul><li>The arcuate nucleus is a part of the hypothalamus containing two sets of neurons: </li></ul><ul><ul><li>neurons sensitive to hunger signals. </li></ul></ul><ul><ul><li>neurons sensitive to satiety signals. </li></ul></ul>
  42. 55. Hunger <ul><li>Ghrelin is released as a neurotransmitter in the brain and a hormone in the stomach </li></ul><ul><li>Neurons of the arcuate nucleus specifically sensitive to hunger signals receive input from: </li></ul><ul><ul><li>The taste pathways. </li></ul></ul><ul><ul><li>Axons releasing the neurotransmitter ghrelin. </li></ul></ul><ul><ul><li>also acts in the stomach to trigger stomach contractions. </li></ul></ul>
  43. 56. Hunger <ul><li>Input to the satiety-sensitive cells of the arcuate nucleus include signals of both long-term and short-term satiety: </li></ul><ul><ul><li>Distention of the intestine triggers neurons to release the neurotransmitter CCK. </li></ul></ul><ul><ul><li>Blood glucose and body fat increase blood levels of the hormone insulin. </li></ul></ul><ul><ul><li>Some neurons release a smaller peptide related to insulin as a transmitter. </li></ul></ul><ul><ul><li>Leptin provides additional input. </li></ul></ul>
  44. 58. Hunger <ul><li>Output from the arcuate nucleus goes to the paraventricular nucleus of the hypothalamus. </li></ul><ul><li>The paraventricular nucleus is a part of the hypothalamus that inhibits the lateral hypothalamus which is important for feelings of hunger and satiety. </li></ul><ul><li>Axons from the satiety-sensitive cells of the arcuate nucleus deliver an excitatory message to the paraventricular nucleus which triggers satiety. </li></ul>
  45. 59. Hunger <ul><li>Input from the hunger-sensitive neurons of the arcuate nucleus is inhibitory to both the paraventricular nucleus and the satiety-sensitive cells of the arcuate nucleus itself. </li></ul><ul><ul><li>inhibitory transmitters include GABA, neuropeptide Y (NPY), and agouti-related peptide (AgRP). </li></ul></ul><ul><li>N europeptide Y (NPY) and agouti-related peptide (AgRP) are inhibitory transmitters that block the satiety action of the paraventricular nucleus and provoke overeating. </li></ul>
  46. 60. Hunger <ul><li>Output from the paraventricular nucleus acts on the lateral hypothalamus. </li></ul><ul><ul><li>The lateral hypothalamus controls insulin secretion and alters taste responsiveness. </li></ul></ul><ul><li>Animals with damage to this area refuse food and water and may starve to death unless force fed. </li></ul>
  47. 62. Hunger <ul><li>The lateral hypothalamus contributes to feeding by: </li></ul><ul><ul><li>Detecting hunger and sending messages to make food taste better. </li></ul></ul><ul><ul><li>Arousing the cerebral cortex to facilitate ingestion, swallowing, and to increase responsiveness to taste, smell and sights of food. </li></ul></ul><ul><ul><li>Increasing the pituitary gland’s secretion of hormones that increase insulin secretion. </li></ul></ul><ul><ul><li>Increasing digestive secretions. </li></ul></ul>
  48. 66. Hunger <ul><li>Damage to the ventromedial hypothalamus that extends to areas outside can lead to overeating and weight gain. </li></ul><ul><li>Those with damage to this area eat normal sized but unusually frequent meals. </li></ul><ul><li>Increased stomach secretions and motility causes the stomach to empty faster than usual. </li></ul><ul><li>Damage increases insulin production and much of the meal is stored as fat. </li></ul>
  49. 70. Hunger Left here <ul><li>People with a mutated gene for the receptors melanocortin overeat and become obese. </li></ul><ul><ul><li>Melanocortin is a neuropeptide responsible for limiting food intake </li></ul></ul><ul><li>Prader-Willis syndrome is a genetic condition marked by mental retardation, short stature, and obesity. </li></ul><ul><ul><li>Blood levels of the peptide ghrelin is five times higher than normal. </li></ul></ul>
  50. 71. Hunger <ul><li>Although a single gene can not be identified, a genetic influence has been established in many factors contributing to obesity. </li></ul><ul><li>Most cases relate to the combined influences of many genes and the environment. </li></ul>
  51. 73. Hunger <ul><li>Obesity can also be a function of genes interacting with changes in the environment. </li></ul><ul><ul><li>Example: Diet changes of Native American Pimas of Arizona and Mexico. </li></ul></ul><ul><li>Obesity has become common in the United States and has increased sharply since the 1970’s. </li></ul><ul><ul><li>Attributed to life-style changes, increased fast-food restaurants, increased portion sizes, and high use of fructose in foods. </li></ul></ul>
  52. 74. Hunger <ul><li>Weight-loss is often difficult and specialist rarely agree. </li></ul><ul><li>Successful treatments include change of lifestyle, increased exercise and decreased eating. </li></ul><ul><li>Some appetite-suppressant drugs such as fenfluramine and phentermine block reuptake of certain neurotransmitters to produce brain effects similar to that of a completed meal. </li></ul>
  53. 75. Hunger <ul><li>Sibutramine has replaced fenfluramine and decreases meal size and binge eating by bloking reuptake of serotonin and norepinephrine </li></ul><ul><li>“ Orlistat” is drug that prevents the intestines from absorbing fats. </li></ul><ul><li>Gastric bypass surgery is the removal or sewing off of part of the stomach. </li></ul><ul><li>Decreased stomach size allows greater distention of the stomach to produce satiety. </li></ul>
  54. 76. Hunger <ul><li>Anorexia nervosa is an eating disorder associated with an unwillingness to eat as much as needed. </li></ul><ul><li>Causes and physiological predispositions are not well-understood. </li></ul><ul><li>Associated with a fear of becoming fat and not a disinterest in food. </li></ul><ul><li>Biochemical abnormalities in the brain and blood are probably not the cause, but a result of the weight loss. </li></ul>
  55. 77. Hunger <ul><li>Bulimia nervosa is an eating disorder in which people alternate between extreme dieting and binges of overeating. </li></ul><ul><ul><li>Some force vomiting after eating. </li></ul></ul><ul><li>Associated with decreased release of CCK, increased release of ghrelin, and alterations of several other hormones and transmitters. </li></ul><ul><ul><li>May be the result and not the cause of the disorder. </li></ul></ul><ul><ul><li>Reinforcement areas of the brain associated with addiction also implicated. </li></ul></ul>

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