Study Guide: Chapter 11.docx

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University at Buffalo
PSY 351
Scott Wersinger

Chapter 11 1) What is homeostasis? The process by which the body’s substances and characteristics (such as temperature and glucose level) are maintained at their optimal level. Why is it important? 1) Our body needs to be in a certain temperature range to function normally 2) Too high or low, it could be life threatening 2) Describe osmotic thirst. The changes in the balance of osmotic fluid - E.g. After eating a bag of potato chips and we feel thirsty i. Cause by ingesting or changes in the amount of electrolytes in the blood ii. Occurs when we have too much salt in our bodies  Need water to dissolve the salt content Need just fluid to curb the thirst 3) Describe hypovolemic thirst. Caused by the decrease in fluid and electrolytes (Cause by loss of fluid and blood) i. E.g. If we donate blood Need fluid and nutrients to curb the thirst 4) Understand the concept of a regulatory system, including all of its components. 1. System variable a. A variable that is controlled by a regulatory mechanism b. Eg. Temperature in a heating system c. So that the temperature do not remain too hot or too cold 2. Set point a. The optimal value of the system variable in a regulatory mechanism b. Lower than the point = No effect c. Higher than the point = Cooling effect 3. Detector a. In a regulatory process, a mechanism that signals when the system variable deviates from its set point 4. Correctional mechanism a. In a regulatory process, the mechanism that is capable of changing the value of the system variable b. “Correct” the variable to the optimal value 5. Satiety mechanism a. A brain mechanism that causes cessation of hunger or thirst, produces by adequate and available supplies of nutrients or water 6. Negative feedback a. A process whereby the effect produces by an action serves to diminish or terminate that action b. To know when to shut off the correctional mechanism Stop drinking before the body fluid is back to normal = The satiety mechanism would be activated before the body fluid is back to normal Detectors would sense the loss of fluid level  Correction mechanism induce thirst to motivate drinking  Stomach is filled and send signals to the brain Satiety mechanism inhibits drinking => 5) Know hypertonic, isotonic, hypotonic. Be able predict the direction water moves in response to osmotic pressure. They are all part of the osmotic pressure. Isotonic environment - Same amount of solute and water outside and inside of the cell. - No movement Hypotonic environment - Water outside > Water Inside - Solute inside > Solute outside - Only water flow from outside to inside (Outside  Inside) - Cells would expand Hypertonic environment - Water inside > Water outside - Solute Outside > Solute inside - Only water flow from inside to outside (Inside  Outside) - Cells would shrink 6) What starts a meal? a. Psychological effect i. Sight & smell of food b. Signal from stomach i. Ghrelin  Stimulate our appetite  An increase in ghrelin before we eat c. Metabolic signal i. Detectors of nutrient level  Brain: Detect glucose within the blood-brain-barrier  Liver: Detect nutrient level in the periphery ii. Glucoprivation  Block glucose metabolism (decrease in energy level) iii. Lipoprivation  Block fat metabolism (decrease in energy level) - When we block anyone pathway, our body can detect the decrease in energy level and it would affect our eating behaviour d. Liver i. Detect level of glucose and lipids (regulate the metabolic level) 7) What stops a meal? 1. Gastric factors and intestinal factors a. Sham eating experiment i. Cannot conclude whether is due to the stomach or because of the lack of nutrient that affect a rat’s satiety b. Cues from stomach and intestine trigger satiety i. Stomach stretching stimulates vagus nerve (V) ii. Hormones released by somach:  CCK: Inhibit feeding  PYY 2. Liver factors a. Once the stomach release hormones to stop eating, the liver also releases hormones to continue/maintain the inhibition of appetite. 3. Insulin a. Eat more  More glucose  Insulin release  More glucose taken by cells  Reduced appetite b. Time passes  Reduce blood glucose  Hunger again 4. Long-term satiety a. Leptin (only apply to non-human animal) i. Produced by fat cells (in human and animal) ii. Signal body level of fat supply 1. Low fat = Low leptin level 2. High fat = High leptin level iii. Hunger decrease with high levels of leptin in the blood 1. Leptin increase = Hunger decrease iv. Most overweight people have high levels of leptin b. OB mouse i. Do not make leptin ii. Without leptin gene = Big and fat
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