Brain and Behavior Study Guide for Test 3 Orenda Johnson PSB2000 Circadian Rhythms Circadian Rhythms rhythms that last about a day body regulates sleeping eating urine production sensitivity to drugs Zeitgeber a stimulus that resets the biological clock o Ex light temperature noise meals exercise Purpose of both endogenous rhythms is to prepare for changes in the environment before they actually occur Jet Lag endogenous rhythm doesn t match external time Shift Work people who work out of sync with regular sleep wake cycles o Effects over time some memory loss decreased productivity Suprachiasmatic Nucleus SCN main control center for sleep and temperature circadian rhythms o Lesions disrupt clock total time 24 18 hours o Brain transplants of hamsters showed that SCN holds intrinsic circadian rhythms Ex When 20 hr mutation put in normal SCN tissue changed to 20 hour rhythm Or when normal SCN tissue was put in mutated hamster changed to 24 hr normal rhythm Genes involved in sleep period timeless clock Proteins involved in sleep PER TIM clock o Small amount exists in the morning increase as day goes on High levels negative feedback genes turn off Some sleep disorders are linked with this Retinohypothalamic Pathway projection that goes directly from the retina to the SCN providing it with info about light Affects circadian rhythms by telling a change in light to animals that can t even see the actual light Melatonin gets info about light from SCN feeds back to it o Released hormone by pineal gland to help fall asleep at nigh time 2 3 hours before o Adjusts to seasonal rhythms o Makes SCN more sensitive to zeitgerbers Sleep Possible functions 1 Energy Conservation Probably original purpose Species differ in how much they sleep based on how active they are 2 Restoration GABA released during sleep Brain rebuilds proteins and replenishes glycogen 3 Memory Most evidence for this Brain removes useless daily things and stores more fully learned concepts traces into long term memory Genes for synaptic formation physiology and neurotrophins restored Possible functions of REM sleep o Important for memory storage o Oxidation to cornea of eyeballs o Brain development Four stages of sleep 1 Stage One overall brain activity high but declining 2 Stage Two brain activity still decreasing some wave forms that protect awakening from 3 Stage Three slow wave sleep SWS 4 Stage Four SWS thalamus stops relaying sensory information to cortex brain activity sudden stimuli highly synchronized o Each stage has different waves formed more in order 1 2 3 4 3 2 REM Dreaming activates some parts of parietal and occipital cortexes very active strong emotions in dreams active motivation and drives in dreams o Pons o Amygdala o Hypothalamus o Prefrontal o V1 or 1 degree sensory cortex hallucinations o PGO Waves high amplitude electrical potentials Start in pons then thalamus occipital cortex inactive lack of logic in dreams hard to remember afterwards inactive self generated info can t compete no Insomnia inadequate non restorative sleep causes medical disorders early aging psychiatric disorders Narcolepsy frequent unexpected sleepiness throughout the day o Cataplexy sudden body weakness collapse paralyzed while awake o Some hallucinations after waking up Sleep Apnea inability to breathe while sleeping o Due to genetics aging obesity o Snoring Periodic Limb Movement restless leg syndrome o Leg kicks every 20 30 seconds REM behavior disorder move around vigorously during sleep Night terrors intense anxiety fear screaming or sitting up while still asleep Sleep walking talking causes unknown Internal Regulation Homeostasis biological process that keeps body variables within a fixed range Set Point a single value that the body works to maintain o Often maintained through negative feedback Allostasis The adaptive way the body changes its set point in response to changes in life or the environment Thermoregulation ability to keep body temperature within certain limits o Keep body temperature at 98 degrees because muscles benefit from being warm o Not too hot so don t denature proteins o Reproductive cells require cooler temperatures Hypothalamus regulates body temperature o Preoptic area anterior hypothalamus POA AH cools you off when you re hot sweating and vasodilation o Posterior hypothalamus warms you up when you are cold shivering Fever triggered by release of leukocytes which release proteins cytokines o Stimulates vagus nerve stimulates hypothalamus Increases set temperature point Increases immune system and decreases bacteria virus efficiency Feel cold when temperature first spikes sweat when breaks because body cooling down Osmotic Thirst o Occurs when you eat salty foods o Too much salt outside cells draws water out of cells to normalize solute concentration low high concentration solutes o Detected by neurons in circumventricular organs o SFO and OVLT trigger drinking pure water control vasopressin release Hypovolemic Thirst o Low volume of body fluids general dehydration too much bleeding or sweating o Detected by neurons monitoring blood pressure and SFO o Drinking slightly salty water constrict blood vessels and some vasopressin Hunger and Satiety signals trigger eating short and long term comes from mouth stomach intestines fat cells Signals to eat Signals to stop eating o Desire to taste chew social settings metabolic signals brain signals hormones o Sight of food taste smell stomach digestion CCK nutritional detection insulin secretion leptin control Insulin released by pancreas to help glucose enter cells o Ex Glucose lowers become hungry insulin increases eat food more glucose in cells you feel full insulin lowers glucose stops entering is digested Leptin peptide produced by fat cells o Monitors fat supply in body long term regulation of hunger and energy expidenture o Low levels increase hunger o High levels increase physical immune system activity doesn t necessarily decrease o Obese people are less sensitive too body tells you not to eat doesn t listen hunger Hunger Satiety Signals 1 Arcuate Nucleus receives many signals CCK Leptin taste insulin 2 Lateral Hypothalamus promotes feeding behavior detects hunger a Deals with hunger or satiety a Tells you to go get food 3 Paraventricular Nucleus PVN inhibits lateral hypothalamus slide PVN controls satiety eat normal amounts of meals very large portions Lateral Hypothalamus detects hunger signals brainstem and cortex to enhance taste Ventromedial
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