Test 3 Notes Internal Regulation Homeostasis within a fixed range biological processes that keep body variables Best function for us Working hard to maintain the optimal level of functioning Narrow range of measures Set point a single value that the body works to maintain 98 6 degrees basal body temperature Set points for a lot of things levels of water oxygen glucose calcium protein fat acidity Maintained through negative feedback Blood sugar levels get low we eat High enough we stop eating Increase glucose is a signal to stop eating Allostasis the adaptive way in which the body changes its set point in response to changes in life or the environment Adaptive change from homeostasis Way of adapting to changes in the environment Today Body temperature Water balance Energy balance ingestive behavior Controlling Body Temperature Mammals and birds are homeothermic Work to maintain our set point If it gets cold we need a way to generate heat and the brain needs to know about that and if it is being thermically challenged use of internal physiological mechanisms to maintain an almost constant body temperature 37 C or 98 F Requires energy To decrease temperature Sweat pant increase blood flow to skin To increase temperature shiver increase metabolic rate decrease blood flow to the skin etc We know what to do behaviorally as well to protect 98 6 Warm or Cool Why 98 6 Warm and ready for vigorous activity If they get too warm then cells do not function properly Muscle activity benefits from being as warm as possible Muscles work better when they are a little bit warmer Cool Proteins in the body break their bonds and lose their useful Reproductive cells require cooler temperatures properties at higher temperatures Hypothalamus Body temp regulated by different nuclei of hypothalamus o Preoptic area anterior hypothalamus POA AH cools you off when you are hot o Posterior hypothalamus warms you up when you are cold Some neurons of POA are directly warm sensitive activate these cells sweating vasodilation o If blood is warmer than normal they can detect that by sensing the temperature of the passing blood When they detect this they initiate things like sweating the skin Cells of the POA AH also receive input from themoreceptors in Hypothalamus involved in many different things Receptors in skin that detect temperature Hypothalamus knows internal temperature and also Basal dilation blood vessels get bigger temperature of your skin Fever A change in the set point Cytokinds trigger hypothalamus Cranial nerves sensory and motor above the shoulder 10th cranial nerve breaks this rule Cytokines affect the vagas nerve which allows it to signal they Bacteria and viruses trigger the release of leukocytes which Cytokines attack intruders but also stimulate the vagus nerve hypothalamus Increases the set point Hypothalamus makes temperate increase release small proteins called cytokines vagus stimulates hypothalmaus hypothalamus changes increases set point At first you feel cold when fever breaks you feel hot and sweat Cold comes from within You re at 98 6 and your brain says you need to be warmer Shiver to generate heat which warms you up There are benefits to a fever when you re sick Body gets deregulated sometimes Someone who is generally healthy will probably not strike a life What s a fever good for threatening fever 105 and up is very dangerous Some bacteria grow less vigorously in warmer than normal Useful in terms of boosting immune system function Slow progression of bacterial illness Slow virus Wanting to lie in bed all day from feeling crappy allows you Also makes you feel bad so you rest and you energy can Fever helps directly and indirectly fight virus to conserve energy and use your body s full energy towards fighting the illness body temperature Fever enhances activity of the immune system be used for healing Fever of above 39 C 103 F does the body more harm than good Fevers above 41 C 109 F are life threatening These are for healthy young adults Babies and immune compromised people need to get a doctor involved with any type of fever Is a fever dangerous Water constitutes 70 of the mammalian body Fluid balance highly regulated b c the concentrations of solutes in water determines the rate of all chemical reactions in the body Need to maintain solutes in our body Sodium outside cells potassium inside cell Really specific range we need to keep solutes at proper concentration for regular cellular physiology to occur Thirst Water can be conserved by Excreting concentrated urine thank you vasopressin Decreasing sweat and other autonomic responses Most often water regulation is accomplished via drinking more water than we need and excreting the rest Really good at ignoring signals like not stopping eating or not drinking water What can make you feel thirsty Eating salty foods osmotic thirst Increase solute concentration Loss of fluid sweating vomiting bleeding hypovolemic thirst Both types of thirst trigger mechanisms in hypothalamus but we respond to them differently Osmotic drink plain water Hypovolemic thirst Drink Gatorade or something to replenish salts Osmotic Thirst Eat salty foods Osmotic pressure draws water out of cells to normalize solute Occurs when solutes are more concentrated on one side of the Eating salty food causes sodium ions to spread through the blood The higher concentration of solutes outside the cell results in Increased concentration of solutes in extracellular fluid concentration Lots of solutes outside pull it out of the cells Osmotic thirst occurs because the human body maintains a combined concentration of solutes at a fixed level of 15 M molar 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 membrane and extracellular fluid of the cell osmotic pressure drawing water from the cell to the extracellular fluid Blood Vessels supply brain walls have cells that form tight junctions with each other so hard for things to cross also astrocytes to protect neurons from everything that was in the blood Areas also where the BBB is incomplete Most in area of hypothalamus Allows brain to sample blood Detected by neurons in circumventricular organs Windows in BBB so brain can sample blood SFO and OVLT mainly the latter trigger drinking of pure water and stimulates other regions that control vasopressin release The water you drink
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