Chapter 6 Motivation and Regulation of Internal States Pages 158 163 Test 2 moved to March 26th Simple Homeostatic Drives cont Temperature regulation Negative feedback loop feedback stabilizes the system at a given set point Ex thermostat Picture of tank water will come in faster than the hole lets water out the ball attached to the lever will rise as the water does and stop the flow of water the water will flow out and eventually the ball will fall and the water will be able to enter again this will keep the water at a near constant level with small variations negative feedback Most systems work on negative feedback biology technology Positive feedback feedback continues to build the system rather than stabilizing it ex oxytocin released during delivery birth controlled avalanche atomic explosion wild fire Most examples from physics The ability to keep our body centered around an ideal temperature at which it works the best Heterothermic animals reptiles externally regulated body temperature Adjust body temperature by behavioral means such as sunning finding shade going in water etc Homeothermic Endothermic animals mammals birds adjust body temperature internally Act through negative feedback loop in body to regulate temperature to a constant temp within ideal range reflexive Also have behavioral means to adjust temperature like heterothermic animals Sweating cool down evaporation cools down the blood vs shivering warm up uncontrollable muscle spasms release heat The thermostat is the hypothalamus Anterior commissure band of axons that connect the left and right sides of the brain Optic chiasm intersection of peripheral and central nervous system two optic nerves seemingly merge at this point Pituitary gland directly connected to hypothalamus master gland of endocrine system Mamillary body 2 of them named because if you look at it from the outside looks like breasts at least to the person who named it Hypothalamus Preoptic area of hypothalamus called preoptic because it sits in front of optic chiasm contains warmth sensitive and cold sensitive cells Thirst Heat reducing responses sweating and panting and heat conserving responses shivering Two types of physiological thirst but we can t tell the difference between the two Osmotic thirst water content decreases inside the cell intracellular water loss Stimulus ex salty foods sodium and chloride ions can t travel through membrane more ions are outside than inside so the water will leave the cell to balance it out pressure exerted on cell osmotic pressure Hypovolemic thirst blood volume decreases due to loss of extracellular water Ex soldiers bleeding out on battlefield ask for water sweating a lot vomit a lot Signaled by different regions but converge on same part of the hypothalamus Osmotic thirst OVLT Sends signals to the median preoptic nucleus in hypothalamus When this MPON region becomes active you become thirsty Hypovolemic thirst One system Second system Receptors found in the heart baroreceptors blood pressure receptors When blood pressure drops signal is sent through the nucleus of the solitary tract in the medulla Neurons in the medulla relay the signal to the median preoptic nucleus feel thirst In kidneys renin will be released which will cause another hormone to be released angiotensin II Goes to sub fornical organ and activates those neurons Activates median preoptic nucleus feel thirst Know this because if you inject angiotensin II into the sub fornical organ the animal will feel thirsty Hunger More complex drive than temperature regulation and thirst Set point can undergo dramatic and prolonged shifts e g obesity More vulnerable to learning and environment nurture rather than nature Involves the need for a variety of different and specific kinds of nutrients Dietary selection must distinguish between nutritious and non nutritious or toxic foods role of taste Taste 5 primary tastes sweet salty sour bitter umami meaty flavors and certain vegetables like tomatoes born with these receptors and the psychological reactions to these experiences Sweet better correlates with sugar and carbohydrates scarce in environment that s why signal tells us to eat sweet things when we find it Bitter bad many toxins taste bitter can train away like with coffee Salty good not plentiful in environment so when you find it signal tells you to eat it More complex taste sensations are combinations of the 5 primaries Bumps on tongue papilla Look in book on page 162 for better picture Receptors taste buds underside of papilla get chemical signals when they fall in crack Signals from receptors sent to nucleus of the solitary tract medulla Then sent to insula cerebral hemispheres hidden by other lobes Contributes to dietary selection in three additional ways 1 Sensory specific satiety the more of a specific food a person eats the less appealing the food becomes