B&b

• Basal Metabolism


  Energy used to maintain a constant body temperature at rest. Uses about 2/3 of our energy/ kilocalories per day.
• Homeostasis


  Biological processes which keep certain body variables within a fixed range. In mammals, temperature regulation, thirst and hunger are nearly homeostatic and not exactly homeostatic.
• Set point


  Level at which a homeostatic process maintains a variable.
• Negative feedback


  Processes that reduce discrepancies from the set point.
• Allostasis


  The adaptive way in which the body changes its set point in response to changes in life or the environment.
• Poikilothermic (Ectotherms)


  Animals with body temperatures the same as their environment. Amphibians, reptiles and most fish. The organism lacks the internal, physiological mechanisms of temperature regulation. Temperature regulation: choosing locations in the environment.
• Homoeothermic (Endotherms)


  Refers to the use of internal physiological mechanisms to maintain an almost constant body temperature (37˚ C or 98˚ F). Characteristic of mammals and birds. Requires energy and fuel. Sweating and panting decrease temperature. Increasing temperature is accomplished via shivering, increasing metabolic rate, decreasing blood flow to the skin, etc. Muscle activity benefits from being as warm as possible and ready for vigorous activity. Proteins in the body break their bonds and lose their useful properties at higher temperatures. Reproductive cells require cooler temperatures.
• Endotherm's responses to temperature variation


  1. Stimulus

  2. The problem

  3. Behavioral response

  4. Functional response
• Preoptic area / anterior hypothalamus (POA/AH)


  The brain region most critical for temperature control. Monitors body temperature by monitoring its own temperature and by receiving input from temperature-sensitive skin and spinal cord receptors. Receives input from the immune system.
• The body temperature of fish, amphibians, and reptiles match that of their surroundings but rarely fluctuate tremendously because these animals choose their location within the environment. Mammals can also maintain their body temperature by behavioral means.
• Hypothalamus


  • Suprachiasmatic N – circadian
  • Preoptic area – temperature
  • Organum vasculosum laminae terminalis – osmotic pressure
  • Supraoptic and paraventricular N – release of vasopressin
  • Lateral preoptic area – drinking
  • Subfonical organ – stimulated by angiotensin II → drinking
  • Lateral N – increase eating
  • Ventromedial N -- decrease eating
  • Ventral noradrenergic bundle – decrease eating
  • Paraventricular N – decrease eating
• Fever


  1. Bacteria and viruses trigger the leukocytes to release small proteins called cytokines

  2. Cytokines attack intruders but also stimulate the vagus nerve

  3. The vagus nerve stimulates the hypothalamus to initiate a fever

  4. Some bacteria grow less vigorously in warmer than normal body temperature

  5. A fever of above 39˚C (103˚F) does the body more harm than good

  6. Fevers above 41˚ C (109˚ F) are life-threatening
• Infant rat behavioral capacities are poor at room temperature but improve dramatically in temperatures kept above 30˚C.
• The immune system delivers prostaglandins and histamines, which causes shivering, increased metabolism, and fever. The POA/AH is not the only brain area involved in temperature regulation.
• Water


  Constitutes 70% of the mammalian body. Must be regulated within narrow limits. The concentrations of chemicals in water determines the rate of all chemical reactions in the body.
• Vasopressin (ADH)


  Raises blood pressure by constricting blood vessels. Enables the kidneys to reabsorb water and secrete highly concentrated urine.
• Osmotic thirst


  Thirst due to an increase in solute concentrations.
• Hypovolemic thirst


  Thirst due to a loss of overall volume.
• Osmotic pressure


  The tendency of water to flow across a semipermeable membrane from an area of low concentration to areas of high concentration.
• Osmotic thirst


  1. Receptors around the 3rd ventricle

  2. Organum Vasculosum Laminae Terminalis (OVLT) and subfornical organ: around the 3rd ventricle, for detecting osmotic pressure

  3. Receptors in the periphery, including the stomach and intestine, which detect high levels of sodium

  4. Signals relayed to the supraoptic nucleus and paraventricular nucleus of the hypothalamus that control the rate at which the posterior pituitary gland releases vasopressin (ADH)

  5. Signals relayed to the lateral preoptic area, which controls drinking
• Hypovolemic thirst


  1. Baroreceptors: Receptors attached to large veins that determine the pressure of blood returning to the heart

  2. Trigger the release of the hormones vasopressin and angiotensin II

  3. When blood volume decreases, the kidneys release the hormone renin which splits a portion off angiotensinogen to form angiotensin I which is then converted into angiotensin II

  4. Angiotensin II constricts blood vessels in order to reverse the loss of blood volume, and stimulates subfornical organ (SFO) to increase drinking

  5. Angiotensin II stimulates neurons in areas adjoining the 3rd ventricle

  6. Neurons in the third ventricle also send axons to the hypothalamus where angiotensin II is also released as a neurotransmitter
• Sodium-specific cravings

  A strong craving for salty foods (due to bleeding or excessive sweating) caused by the release of aldosterone, a hormone which causes the kidneys, salivary glands, and sweat glands to conserve sodium and excrete more watery fluids than usual.
• A Big Mac is composed of beef patties (largely proteins and triglyceride, or neutral fat), special sauce, lettuce (cellulose), cheese (protein and triglyceride), pickles (cellulose, starch?), onions (cellulose, starch?) on a sesame seed bun (starch).
• A 200 gram Big Mac consists of roughly 25 grams of protein, 28 grams of fat, and 47 grams of carbohydrate, totaling 540 Calories.
• Digestive system or Gastrointestinal tract


  Provides the body with a continual supply of water, electrolytes, and nutrients. Requires movement of food, secretion of digestive juices, absorption of water, various electrolytes, and digestive products, circulation of blood to carry away the absorbed substances, and control of all these functions by local, nervous, and hormonal systems.
• Digestion


  1. Begins in the mouth, where food is broken down by enzymes in the saliva

  2. Food travels down the esophagus to the stomach, where hydrochloric acid and enzymes digest proteins

  3. The pyloric sphincter (located between the stomach and the intestines) allows food to periodically enter the intestines

  4. Food enters the small intestine which is the main site for nutrient absorption into the bloodstream

  5. The large intestine absorbs water and minerals and lubricates remaining materials for excretion
• Many mammals lose their ability to metabolize lactose (sugar found in milk) after infancy due to decreased levels of the intestinal enzyme lactase. Worldwide most adult humans cannot consume large amounts of milk products.
• Carnivore


  An animal that eats meat.
• Herbivore


  An animal that eats plants.
• Omnivore


  An animal that eats both.
• Behavioral strategies for food selection


  • Preference for sweet taste
  • Avoidance of bitter taste
  • Preference for familiar foods
  • Conditioned taste aversions (learned dislike of a food based on past experience with the food)
• Brain regulation of eating


  Messages from the mouth, stomach, intestines, fat cells, and elsewhere.
• Sham feeding


  Experiments in which everything an animal eats leaks out of a tube connected to the stomach or esophagus, do not produce satiety.
• Satiety


  The main signal to stop eating is the distention of the stomach. The vagus nerve (cranial nerve X) carries information to the brain regarding the stretching of stomach walls.
• Splanchnic nerves


  Convey information about the nutrient contents of the intestines to the brain.
• Omnivore


  An animal that eats both
• Behavioral strategies that help determine food selection


  • Preference for sweet taste
  • Avoidance of bitter taste
  • Preference for familiar foods
  • Conditioned taste aversions (learned dislike of a food based on past experience with the food)
• Brain regulates eating


  Through messages from the mouth, stomach, intestines, fat cells, and elsewhere
• Desire to taste and other mouth sensations


  Motivating factors in hunger and satiety
• Sham feeding experiments, in which everything an animal eats leaks out of a tube connected to the stomach or esophagus, do not produce satiety