Physiology Exam 3What techniques are used to understand brain and muscle activity during sleep?Electroencephalogram (EEG)Electromyogram (EMG) – an electrical potential recorded from an electrode places on or in a muscle (chin).Electro-oculogram (EOG) – an electrical potential from the eyes, recorded by means of electrodes placed on the skin around them; detects eye movements.Also measure heart rate, respiration, etc.Know the order in which we move thru the stages of sleep, and generally that brain activity slows and becomes more synchronized (from low-amplitude high-frequency activity to high-amplitude low- frequency) as we get into deep sleep, and how REM sleep is different. Know when we would see alpha activity vs beta activity vs delta activity, and what sleep spindles and k-complexes are associated with.AwakeAlpha activity – smooth electrical activity of 8-12 Hz recorded from the brain generally associated with a state of relaxationBeta activity – irregular electrical activity of 13-30 Hz recorded from brain and associated with a state of arousal. Desynchronization; many circuits of the brain are actively processing information.Stage 1 SleepTheta activity – EEG activity of 3.5-7.5 Hz that occurs intermittently during early stages of slow-wave sleep and REM sleep; transition between sleep and wakefulness Stage 2 SleepSleep spindles - play a role in consolidation of memory; 2-5 times per minuteK-complexes- only in stage 2; 1 per minute; triggered by noises to protect person from waking upStage 3 Sleep (Slow Wave Sleep)Delta activity – regular synchronous electrical activity of less than 4 Hz recorded from the brain; occurs during the deepest stages of slow-wave sleepHard to rouse; would be groggy; no dreamingStage 4 SleepMore delta activity in stage 3 than 4, but no other obvious distinctions between the twoREM sleepDesynchronized EEG activity; rapid eye movement; muscle paralysis; dreaming; easy to arouse (would appear alert)Compare and contrast REM sleep and non-REM sleep in terms of functions of each (we spent a bit of time on this), EEG activity, muscle tone, and ability to rouse.Functions of non-REM sleep – rest the brain; cerebral blood flow and cerebral metabolism decline; free radicals are removed from cells Regular synchronous electrical activity of less than 4 Hz Hard to rouse!Functions of REM sleep – brain development; learning; muscle paralysis; dreaming Desynchronized EEG activity; rapid eye movements Would be easy to rouseWhat brain regions are active and inactive during REM sleep (think of this in terms of dreaming)? BTW, can dreams occur in non-REM sleep? What is more common (cognitively) than dreaming in non-REM sleep?Low activity in prefrontal cortex during REM sleep; low activity in V1 (no visual input)High activity in visual association cortex (dreams)Rapid eye movements may reflect scanning the visual imagery of a dreamOther brain regions that may be active - cortical and subcortical movement if dream involves movement; speaking and listening areas; some parts of hypothalamus; amygdala (emotional content of dream)Dreaming can occur in non-REM sleepWhat is evidence that REM and non-REM sleep might be involved in consolidating different types of memories?REM sleep facilitates consolidation of implicit memory. The experiment was as follows:Learn a nondeclarative task in morning then tested in evening with:No nap  test performance worse than at end of trainingNo REM nap  test performance same as at end of trainingREM nap  test performance improved over end of trainingWhat are symptoms of sleep deprivation?Confusion, weight loss, inability to regulate body temperature, and can be fatalWhat is the role of adenosine in sleep?Adenosine is sleep-promoting. The less adenosine, the less time in SWS.What neurotransmitters are “wakefulness promoting”? Neurotransmitters that play a role in wakefulness and/or alertness are: AcetylcholineNorepinephrine – for behavioral arousal and vigilance (higher when awake than asleep)Serotonin – for overall level of consciousness (higher when awake than asleep)HistamineOrexin/Hypocretin - more active when awake than asleep; narcolepsy involves problems with this system; provides stability to wakeful/sleeping flip flopWe discussed 3 general factors controlling sleep: homeostatic, allostatic, and circadian. Understand these, and what chemical signals are important for each.Homeostatic – go without sleep  sleep longer to make up sleep debt (adenosine very important)Allostatic – reactions to stressful factors in the environment that override homeostatic control. Stress hormones very important as well as neuropeptides involved in hunger and thirst. Might stay awake when tired if being threatened for example.Circadian – restrict sleep to certain portions of the day. Suprachiasmatic nucleus (SCN) and melatonin from pineal gland very important.Understand the sleep-wake flip-flop, and the role of orexin in this system. In what major brain region in the “sleep promoting” region?Sleep-wake flip-flop is when either the sleep neurons are active and inhibit the wakefulness neurons or the wakefulness neurons are active and inhibit the sleep neurons. Because the regions are mutually inhibitory, it is impossible for neurons in both sets of regions to be active at the same time. This is advantageous since clearly it is better to either be awake or asleep. How does adenosine affect the sleep-wake flip-flop? How do other things like circadian signals and hunger or satiety signals affect it?Adenosine is produced when neurons are metabolically active, and the accumulation of adenosine produces downiness and sleep. Levels of adenosine increased during wakefulness and slowly decreased during sleep, especially in the basal forebrain. What brainstem regions are important in REM sleep, and what do they do?Thalamic neurons fire in tonic (normal) mode. Reticular neurons near LC inhibit motor neurons  loss of muscle tonePontis oralis: neurons project to extraoccular muscles for REMs.Generally speaking what is insomnia? What are some causes of insomnia?Insomnia is trouble going to sleep or staying asleep. Causes include: psychiatric disorders (depression), chronic medical disorders (sleep apnea), pain, elderly, drug dependency insomnia.What is sleep apnea?Sleep apnea is the cessation of breathing while sleeping. CO2 stimulates chemoreceptors which causes person to wake up gasping for air. O2 returns