Study Guide three Circadian Rhythms Define circadian rhythm and zeitgeber Know examples of each What is the purpose of endogenous rhythms Circadian Rhythms Rhythms that last about a day humans last around 24 2 hours Endogenous Rhythms Purpose to prepare for changes in environment before they occur Examples Activity of flying squirrel kept in total darkness Endogenous Zeitgeber A stimulus that resets the biological clock Waking and Sleeping Hormone Secretion Urine production Eating and drinking Sensitivity to drugs Temperature Exercise Noise Meals Bright light What are jet lag and shift work and what are some effects of these situations on people Problem is that our endogenous rhythm doesn t match external time Easier to travel West stay up later than normal and sleep in than East have to go to bed early and wake up early Flight attendants on long trips across several time zones for greater than five yeats causes smaller than average hippocampus and some memory impairment 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 SCN is the main control center for sleep and temperature circadian rhythems SCN neurons have Aps that peak every 24 hours What are some genes and proteins involved in sleep and how are they involved Proteins per and tim Bright light flash in night inactivates tim and resents clock 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 Retinohypothalamic Pathway Projection that goes directly from the retina to the SCN providing it with info about light 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 Hormone Released by Pineal Gland starting 2 3 hrs before bedtime peaks around bedtime makes us sleepy Pineal gets info about light indirectly from retina SCN and melatonin feeds back on SCN Taken in afternoon melatonin phase advances the biological clock Melatonin seems to make the cells of the SCN more sensitive to zeitgebers Tumor here can make people stay awake for days Pineal is critical for seasonal rhythms As nights get longer releases more melatonin acts on many regions of the brain to change behavior and physiology to prepare for winter As days get longer Spring releases less melatonin Melatonin is antigonadotropic so less of it means more reproductive behavior more important in seasonal breeders than humans Sleep We discussed 3 possible functions of sleep in general know those Energy conservation Restoration Memory We also discussed possible functions of REM sleep know those REM is important for memory consolidation and removal of useless connections Brain development Just for rapid eye movement part of REM 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 overall brain activity is high but declining Stage 2 brain activity still decreasing see wave forms K complexes which serve to protect a person from being awakened by a sudden stimulus Stages 3 4 Slow wave sleep Stage 4 thalamus stops relaying sensory info to cortex unless extreme or relevant From 1 2 3 4 3 2 REM then 2 and 3 predominate w REM interspersed and increasing in early morning hours What is paradoxical about REM sleep What neurotransmitters are involved How is it related to dreams Postural muscles of body are most relaxed actually paralyzed so deep Sleep 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 What are PGO waves Pons activates some parts of parietal temporal and occipital cortex Amygdala is active hence strong emotional content of dreams Hypothalamus is active hence motivations and drives in dreams No activity in V1 or 1 degree sensory cortes so no sensory info to compete with self generated into hallucinations Prefrontal is inactive so memory is weak during and after a dream Know understand some common sleep disorders insomnia narcolepsy sleep apnea periodic limb movement disorder restless leg syndrome REM behavior disorder night terrors sleep walking and sleep talking Insomnia Inadequate non restorative sleep Onset maintenance or termination Causes include medical disorders pain psychiatric disorders aging Sleep apnea Inability to breath while sleeping due to genetics hormones aging obesity Periodic limb movement disorder Legs kick up to once every 20 30 sec Can cause insomnia REM behavior disorder Move around vigorously during REM sleep b c no paralysis Narcolepsy Frequent periods of sleepiness during the day Night terrors sleep talking sleep walking NT experiences of intense anxiety from which person awakens screaming in terror NT SW usually during non REM sleep and usually in children Recent study found that sleep walkers are mimicking that day s activities As we age what changes about overall sleep and the amount of time spent in REM sleep and what happens to the incidence of sleep disorders As we age overall sleep and the amount of time spent in REM sleep increases Sleep disorders also become more prevalent when you age Organizing and Activating Effects of Hormones Know the 3 classes of sex steroid hormones and their synthesis pathway Know examples of each class ie testosterone is an androgen Androgens Testosterone DHT Estrogens Estradiol Progestins Progesterone Start with cholesterol base and various hormones work on that and convert it to progesterone and then there s 3 enzymatic steps and it is converted to testosterone and can be converted into Estradiol with aromatase or dihydrotestosterone with reductase Know the differences between organizational and activational effects of hormones What are some examples of each type of effect in men and in women Organizing Occur mostly during sensitive periods in development well before birth in humans Effects are generally permanent Determine whether brain and body will develop male or female characteristics Activating or behavioral Occur any time in life when a hormone temporarily
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