Exam 3 Brain and Behavior Circadian Rhythm 1 Define circadian rhythm and zeitgeber Know examples of each What is the purpose of endogenous rhythms A circadian rhythm is a rhythm that lasts about a day 24 2hrs waking and sleeping hormone secretion melatonin sleep urine production eating and drinking and sensitivity to drugs Another example is your body temperature reaching a low 2 hours after you fall asleep and peaks about 6 hours prior to falling asleep Zeitgeber is any external cue that synchronizes an organism s internal time keeping system to the earth s 24 hour light dark cycle Strongest zeitgeber is light but temperature social interactions eating and drinking patterns noise and different medications can also be considered zeitgebers Endogenous rhythms allow us to prepare for precise and regular environmental changes They rhythm is important in regulating and coordinating internal metabolic processes 2 What are jet lag and shift work and what are some effects of these situations on people Jet Lag when our endogenous rhythm doesn t match the external time where we are If someone flew to Tallahassee from Los Angeles they would have difficulty waking up at 6am event though they are used to waking up at 6am in LA because their body rhythm is telling them it is actually 3am People that suffer from chronic jetlag like pilots and flight attendants show smaller than average hippocampus stress hormones are released that are toxic to the hippocampus and also can have trouble with memory Shift Work people who work out of synch with regular shift cycle People that work during the night try to sleep during the day but find it very difficult Having a dark room is helpful but it is hard to override the drive to sleep at night and stay awake during the day 3 What is the significance of the suprachiasmatic nucleus SCN What is the behavioral result of a lesion of the SCN How did brain transplants help prove the role of the SCN The SCN is the main control center for sleep and temperature circadian rhythms The neuronal and hormonal activities it generates regulate many different body functions in a 24hr cycle A lesion in the SCN can disrupt rhythms of body temperature sleeping and waking 4 What are some genes and proteins involved in sleep and how are they involved Genes are segments of DNA that contain the instructions for the production of a certain protein The gene period codes for the protein PER timeless codes for TIM and clock codes for CLOCK Period influences the length of the circadian rhythm Timeless functions as a timekeeper in mammals Clock affects both the persistence and length of the circadian rhythm 5 What is the retinohypothalamic pathway In what way does it contribute to circadian rhythms From what retinal cells does it project and where does it go The retinohypothalamic pathway is an input pathway involved in the circadian rhythm of mammals It takes information about external lighting and sends it directly to the SCN The retinohypothalamic pathway is different from regular photoreceptor cells perception of colors and vision at night This has been researched on blind people Even though their photoreceptor cells are nonfunctional they maintain a light influenced circadian rhythm because of the information relayed to SCN by the retinohypothalamic pathway This allows them to have a normal circadian rhythm The retinohypothalamic pathway projects information from intrinsically photosensitive Retinal Ganglion Cells ipRGC to the superchiasmatic nucleus SCN 6 How is melatonin involved in circadian rhythms What structure makes releases melatonin When is it released What brain structure responds to melatonin How do humans respond to melatonin ie does it make us sleepy or awake Melatonin is a hormone released by the pineal gland about 2 3 hours prior to sleep It makes the SCN more sensitive to zeitgebers such as change in light As nights get longer more melatonin is released Melatonin makes us sleepy Sleep 1 We discussed 3 possible functions of sleep in general know those Energy conservation suggests that sleep reduces an individual s energy demand and expenditure during part of the day or night especially when it is least efficient to search for food Restoration the brain rebuilds proteins and replenishes glycogen stores stored energy during sleep Memory brain areas that are active during learning are the same brain areas that are active during the next sleep Short term memory can get rid of unnecessary memories while long term memories can be reinforced and cemented into your brain 2 We also discussed possible functions of REM sleep know those REM is important for memory consolidation and removal of useless connections REM is important in brain development Babies have tons of REM sleep while their brain is still developing REM may be simply for the rapid eye movement allowing the corneas of our eyes to get enough oxygen 3 What are the different stages of sleep In general what is brain activity like in those stages In what order do humans move thru these stages during a night of sleep What do heart rate breathing blood pressure and temperature do during the different stages of sleep Stage 1 brain activity high but declining last 1 5 minutes transition stage between wake and sleep Stage 2 brain activity decreasing 90minute cycle Stage 3 4 slow wave sleep heart rate brain activity and breathing slow Stage 4 thalamus stops relaying sensory information to cortex unless extreme or relevant gunshot or your child s footsteps REM rapid eye movement body is paralyzed deep sleep facial twitches dreaming usually occurs in REM sleep ORDER 1 2 3 4 3 2 REM 4 What is paradoxical about REM sleep What neurotransmitters are involved How is it related to dreams REM sleep is sometimes referred to as paradoxical sleep because it is characterized by rapid periodic twitching of the eye muscles and other changes such as increased breathing heart rate and brain activity It is a mixture of brain states of excitement and muscular immobility Serotonin and Acetylcholine are involved When in REM sleep certain areas of the brain are inactivated and activated Muscles are immobile Hypothalamus is active gives rise to motivation and drive in dreams Amygdala is active explains the high emotional content of dreams 5 When dreaming what brain areas are very active and which ones are inactive What is the functional consequence of that for example the prefrontal cortex being inactive leads to poor memory and logic in dreams
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