Psyc 220 1st EditionExam # 3 Study Guide Chapters: 9, 10, & 12Chapter 9: Wakefulness and Sleep 1. Endogenous circannual and circadian rhythms o Endogenous circannual rhythm Generated within the body, they happen every year  Rhythm that prepares an animal for seasonal changes Ex. Birds migrating South, Squirrels storing nuts for wintero Endogenous circadian rhythms Cycles generated within the body that occur every day Ex. Sleep, hunger, temperature, hormones, urination, drug sensitivity2. Free running rhythms - Free-running (or nonentrained)rhythm - rhythm type characterized by an abnormal sleep-wake rhythm due to a circadian clock that is not in phase with, and cannot be entrained to, the 24-hour light-dark cycleo Seen with damage to the SCN - Suprachiasmatic Nucleus – area of the brain that handles the biological clock 3. What is a zeitgeber? What does it do? - Zeitgeber – “time giver” - The stimulus that resets the circadian rhythmo The main ones is light for land animals, and the tides for marine animals. Also when we exercise, any kind of arousal, when we eat, the temperature, etc. 4. What is jet lag? How do you feel if you travel east to west? West to east? - Jet lag - A disruption of circadian rhythms due to crossing time zoneso If you travel East  West - more time to your day.  Easier to adjust to because we stay awake later at night and then awaken late the next morning, already partly adjusted to the new schedule. We phase-delay our circadian rhythms.o If you travel West  East - you lose time. Going east, we phase-advance to sleep earlier and awaken earlier. Most people find it difficult to go to sleep before their body’s usual time and difficult to wake up early the next day.- Both cases, jetlag results in sleepiness, depression, impaired concentration, and impaired memory. Worse when traveling East.5. What and where is the SCN? How do we know it’s the biological clock? How does light rest it?- SCN (the Suprachiasmatic Nucleus)- aka our biological clock. Part of the hypothalamus that gets its name from its location just above (supra) the optic chasm. o Provides the main control of the circadian rhythms for sleep and body temperature (important for regulating wakefulness and sleep cycles), and damage to it can cause the body’s rhythms to become erratic. Also regulates drinking, locomotor behavior, hormone secretion- How do we know it’s the biological clock?o Lesions to the area result in more sporadic cyclic activity (free rhythm sleep)and scientists saw from an SCN transplant in hamsters  hamsters typically have a free-running period just over 24 hr., but a certain mutation causes a hamster to have a 20 hr. rhythm. The hamster that received the SCN transplant from the one with the mutation followed the rhythm pattern of the donor.- How does light reset it?o The SCN is located just above the optic chiasm. A small branch of the optic nerve, known as the retinohypothalamic path, extends directly from the retina to the SCN. Axons of that path alter the SCN’s settings.  Most of the input to that path does not come from normal receptors, but from a special population of retinal ganglion cells that have their own photopigment called melanopsin, unlike the ones found in rods and cones.  These special ganglion cells receive some input from rods and cones, but even if they do not receive that input, they respond directly to light. They’re located mainly near the nose, not evenly throughout the retina, respond to light slowly, and turn off slowly when the light ceases  they respond to the overall average amount of light, not to instantaneous changes in light.- The average intensity over a period of minutes or hours is the info the SCN needs to gauge the time of day.o6. Genetic basis of the circadian rhythm: which proteins fluctuate (and how?)- Studies on the fruit fly Drosophila found several genes responsible for a circadian rhythm. Main 2: period (abbreviated per) and timeless (tim), which produce the proteins PER and TIM. - The concentration of these 2 proteins, which promote sleep and inactivity, oscillates over a day, based on feedback interactions among several sets of neurons. o Early in the morning, the messenger RNA levels responsible for producing PER and TIM start at low concentrations. - As they ↑ during the day, they ↑ synthesis of the proteins but the process takes time so the protein concentrations lag hours behind, as shown in the figure above. - As the PER and TIM protein concentrations ↑, they feed back to inhibit the genes that produce the messenger RNA molecules.- So during the night, the PER and TIM concentrations are ↑, but the messenger RNA concentrations are declining. By the next morning, PER and TIM protein levels are ↓, the flies awaken, and the cycle restarts. Bc the feedback cycle takes ~ 24 hours, the flies generate a circadian rhythm even in an unchanging environment. - In addition to the automatic feedback, light activates a chemical that breaks down the TIM protein, thereby increasing wakefulness and synchronizing the internal clock to the external world7. Melatonin- The SCN regulates waking and sleeping by controlling activity levels in other brain areas, including the pineal gland (an endocrine gland located just posterior to the thalamus.) The pineal gland releases the melatonin  a hormone that influences circadian and circannual rhythms. - The pineal gland secretes melatonin mostly at night, making us sleepy. Secretion startsto increase ~2-3 hours before bedtime.- When people shift to a new time zone and start following a new schedule, they continue to feel sleepy at their old times until the melatonin rhythm shifts. Melatonin also feeds back to reset the biological clock through its effects on receptors in the SCN8. How do we measure sleep? - Sleep has moderate decrease in brain activity, moderate decrease in responsiveness, and lasts a few hours- We measure it using: o Electroencephalograph (EEG) To measure sleep cycles, rods attached to the head recording potentials in the braino Polysomnograph Combination of EEG and eye-movement records9. What are the stages of sleep, and what do they look like? How do we progress throughthe stages? What happens during REM? Why is REM paradoxical?- Stages of sleep & what they look like:o Slow Wave Sleep (3-4 stages) and Rapid Eye Movement Stage 1- Irregular, jagged, low amplitude waves- Brain activity