BIO PSY CHAP 9

• Homeostasis


  Temperature regulation and other biological processes that keep body variables within a fixed range
• Set point


  A single value that the body works to maintain
• Negative feedback


  Processes that reduce discrepancies from the set point
• Allostasis


  The adaptive way in which the body anticipates needs depending on the situation, avoiding errors rather than just correcting them
• Much of the control depends on cells from the hypothalamus
• Breakdowns in homeostatic processes

  • Obesity
  • Anorexia nervosa
  • High blood pressure
  • Diabetes
• An average young adult expends about 2600 kilocalories per day
• Most of that energy goes to basal metabolism - the energy used to maintain a constant body temperature while at rest
• Maintaining body temp requires twice as much energy as do all other activities combined
• Brown adipose cells


  Burn fuel like muscle cells but release it directly as heat instead of as muscle contractions
• Poikilothermic


  Their body temp matches the temp of their environment
• Ectothermic


  Depending on external sources for body heat, "cold-blooded"
• These animals lack physiological mechanisms of temp regulation (shivering, sweating) but they can regulate their body temp behaviourally
• Homeothermic


  Mammals and birds that use physiological mechanisms to maintain a nearly constant core temperature despite changes in their environment
• To cool ourselves when the air is warmer than body temperature we only have one physiological mechanism: evaporation
• You endanger your health if you do not drink enough to replace the water you lose by sweating
• Without drinking you become dehydrated
• Physiological mechanisms to increase your body heat in a cold environment

  1. Shivering

  2. Decreased blood flow to the skin prevents blood from cooling too much

  3. Warm internal organs but cold skin

  4. Fluffing out fur to increase insulation
• Behavioural mechanisms


  1. Finding a cool place on a hot day/ warm place on a cold day

  2. Putting on clothing/ taking it off

  3. Becoming more active to get warmer and vice versa

  4. Huddle with others
• Advantages of constant high body temperature

  • Birds and mammals stay constantly ready for vigorous activity
  • We eat a great deal to support our high metabolism so that even when it is cold out we can still run rapidly without fatigue
• Mammal body temp = 37degrees C (98degrees F)
• Beyond 41 degrees C, proteins begin to break their bonds and loose their useful properties
• Odd microscopic animals called thermophiles can survive in boiling water
• Reproductive cells require a cooler environment than the rest of the body
• Birds lay eggs and sit on them, instead of developing them internally, because the bird's internal temp is too hot for an embryo
• Scrotum hangs outside of the body because the internal temp is too hot for sperm production
• Pregnant woman are advised to avoid hot baths and anything else that might overheat a developing fetus
• Preoptic area/anterior hypothalamus (POA/AH)


  The brain areas that control physiological mechanisms of temperature regulation
• After damage to the POA/AH mammals can still regulate body temp, but only in the same behavioural mechanisms that a lizard might use
• Fever


  An increases set point for body temperature directed by the hypothalamus
• Fever is not something an infection does to the body; it is something the hypothalamus directs the body to produce
• Moving to a cooler room does not lower your fever, your body just works harder to keep its temperature at the feverish level
• Certain types of bacteria grow less vigorously at high temperature than at normal mammalian body temps
• The immune system works more vigorously at an increase temperature
• Vasopressin


  A hormone released by the posterior pituitary that raises blood pressure by constricting blood vessels
• Antidiuretic hormone (ADH)


  Another name for vasopressin, as it enables the kidneys to reabsorb water from urine, thus making the urine more concentrated
• Humans drink more than we need and we excrete the excess
• Osmotic thirst


  Thirst caused by eating salty foods, which increases the osmotic pressure outside cells
• Hypovolemic thirst


  Thirst caused by losing fluid by bleeding or sweating, which induces a drop in blood volume
• Osmotic pressure


  The tendency of water to flow across a semipermeable membrane from the area of low solute concentration to the area of higher concentration