What does it mean for a pattern of behavior to have an endogenous circadian rhythm? What influence do zeitgebers have on these cycles? Give an example of how behavior can be disrupted in their absence.Endogenous rhythms: internally generated signals preparing behavior that occurs on a cycle – Circannual (annually): migration, hibernation– Circadian (daily): sleep, feedingOccur without environmental prompts, but need to be reset and maintained by zeitgebers (time-keeper), which are stimuli that typically cycle along with our rhythms (e.g., light, temperature, exercise, arousal, meals)– Interrupted in visual impairments and by lifestyle changes like overseas flights and night shift jobsWhat brain area is necessary for the generation of endogenous cycles? In what specific way does it receive input? Describe how this brain area affects a hormone associated with biological clock regulation.Superchiasmatic nucleus ( SCN ) : portion of the hypothalamus just above the optic chiasm– SCN receives info directly via the optic nerves (i.e., retinohypothalamic path), which is why light is the primary zeitgeber in humans– Special retinal ganglion cells that contain the photopigment melanopsin compose this portion of the optic nerve– SCN controls the activity of other areas, such as the endocrine pineal gland, which releases melatonin that is produced at night and promotes sleepinessDefine the stages of sleep. What does the slowing of brain waves as sleep progresses indicate? How is REM sleep paradoxical?– Wakefulness : steady, relatively high frequency of alpha waves– Stage 1 : irregular waves with lower amplitude– Stage 2 : emergence of sleep spindles (waves of activity) and K-complexes (sharp wave associated with temporary inhibition of neuronal firing) – Slow-wave sleep (Stages 3 and 4) : lower frequency waves; sensory input to the recbral cortex is greatly reduced, and the few remaining sources f input can synchronize many cells– Slow, low frequency waves indicative of synchrony of neuronal activity and inhibition of the cortex; brain waves are best way to see if someone is asleep;frequency is different but not necessarily amplitude – Rapid eye movement sleep (REM)– Brain activity similar to Stage 1 (e.g., fast, low amplitude waves)– Muscles completely relaxed to the point of paralysis, although autonomic functioning increases– Some facial twitching and eye movements in humans– Often associated with vivid dreaming, but not necessary for it– It is paradoxical because it is deep sleep but also light; you are sleeping, but there is movement occurringList the areas of the brain involved in arousal and wakefulness and the neurotransmitters that they signal with. What is the main neurotransmitter that maintains sleep?Brain structure Neurochemicals used FunctionsPontomesencephalon - part of reticular formationAcetylcholine and Glutamate Promotes wakefulnessLocus coeruleus - part of ponsNorepinephrine Strengthens storage of recent memories, especially emotional onesHypothalamus Histamine Active during arousalHypocretin (aka, orexin) Necessary for staying awake, but not for wakingBasal forebrain Acetylcholine Shift from non-REM to REM sleepDorsal raphe – part of pons Serotonin Shift out of REM sleep to non-REM sleepGABA is the main neurotransmitter that maintains sleep How can a practitioner diagnose insomnia? What causes narcolepsy? Best way to diagnose insomnia is to see how someone feels during the following day. Causes: nosie, uncomfortable temperatures, stress, pain, diet, medications and can be the result of epilepsy, parkinson’s, brain tumors, depression, anxiety, or other neological or psychiatric conditionsNarcolepsy: condition based by frequent periods of sleepiness during the day; can be in family or not; 4 symptoms: 1. gradual attacks of sleepiness during the day, 2. Occasional cataplexy- attack of muscle weakness wile the person remains awake, 3. Sleep paralysis, 4. Hypnagogic hallucinations- dreamlike experiences that the person has trouble distinguishing from realityWhat functions might sleep play? What about dreaming?during sleep, we rest our muscles, decrease metabolism, rebuild proteins in the brain, reorganize synapses, and strengthen memoiresDescribe the main components of a homeostatic system. Why does fluid balance need to beso tightly controlled?Set point: a single value that the body works to maintain- your body compensates for what is missing or in excess above this set point. Negative feedback: processes that reduce discrepancies from the set point; motivated behavior, Allostasis: the adaptive way in which the body changes its set points depending on the situation Very tightly controlled homeostatic mechanismAttempt to keep a certain variable at a set-point through use of negative feedbackWhat causes the two types of thirst? In which do you need both fluid and salt? Hypovolemic thirst. How does ADH help re-regulate both situations?Osmotic thirst: increased salt content of extracellular fluid– Changes osmotic pressure by drawing fluid out of cells– Dilute extracellular fluid by drinking water and kidneys excrete urine more concentrated with saltHypovolemic thirst: fluid loss (bleeding, sweating, diarrhea)– Not enough fluid to sustain blood pressure and heart function– Also need to restore lost salts to regulate osmotic pressure– aldosteroneADH helps re-regulate because it enables the kidney store reabsorb water from urine and therefore make the urine more concentrated What do angiotensin-II and aldosterone each do? When combined, what type of behavior do they induce?Angiotensin-II: constricts the blood vessels, compensating for the drop in blood pressure, they also help trigger thirst, retain water works with vasopresin Aldosterone: when the body’s sodium reserves are low, the adrenal glands produce this hormone, which causes the kidneys, salivary glands, and sweat glands to retain salt. When combined, the effects is a massive increase in a preference for salt, sometimes producing a preference for salt over sugar or anything elseDetail how insulin and glucagon can be described as a means by which food intake is homeostatically regulated. What are some other peptides that work as negative feedback for promoting satiation?Peptides released by the pancreas influence mobilization and storage of glucose:– Insulin : allows glucose to enter and be used by cells when blood sugar levels are
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