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TAMU PSYC 311 - Biological Rhythms and Sleep
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PSYC 311 1st Edition Lecture 7 I. Biological Rhythms – cyclical activities/behaviors that are related to distinct environmental features a. Importance of timing i. Enable ecological adaptation to season temperature/humidity changes ii. Critical for timing of hibernation/migration iii. Optimize seasonal aspects of mating (spring lambs) 1. Need baby birds to mature enough to be able to migrate iv. Important for minimizing predation (fdon’t go out when predators are out) v. Maximizing success of predation b. Stonehenge – development of early clocks and calendars i. Farmer’s Almanac – average first kill frost (November 19) 1. When/how to prepare/plant/store food c. Types of Biological Rhythms i. Based on the moon 1. Lunar – phases of the moon (28 day cycle) 2. Tidal – tides occur approximately every 12.4 hours (peak topeak) a. Timing of fishing (when the tides are changing) 3. Semi-annual lunar cycles – seasonal tides a. Neap tides – highest low tides, lowest high tides (tides minimized) b. Spring tides – highest high tides, lowest low tides (tides maximized)r ii. Circadian Rhythm (around a day) 1. Diurnal clock – 24 hour clock a. Diurnal vs. nocturnal – hearing vs. smell iii. Free-running rhythms 1. Test without Zeitgaber (presence of sun) 2. Ashoff’s Rule – deep cave study a. Steady temperature and humidity b. Maintain 24 hour cycle i. Nocturnals decrease length (-1 hour) ii. Diurnals increase length (+1 hour) iv. Crepuscular animals – active at dawn and dusk 1. Both predator and prey species 2. Rabbit, hare, deer v. Circannual Rhythm – yearly cycles 1. Hibernation, migration, mating a. Young born when resources are maximized and environment is optimalvi. Intermittent 1. Based on flooding, rainfall, hunger vii. Epicycles – various cycles; minutes to hours d. BR Control Mechanisms i. Endogenous: internal pacemaker 1. CNS: higher mammals a. Suprachiasmic nucleus in hypothalamus (SCN) 2. Non-visual cones in retina connect to SCN a. Help reset diurnal clock b. Help overcome jet lag! 3. Pineal gland in animals – can be close to surface at back of head a. Third eye – melotonin ii. Exogenous zeitgebers = environmental cues 1. Day length, geomagnetic forces, tidal changes, temperature changes, variations in food availablity, etc. 2. Many biological cycles in the body – all geared to SCN – may use temperature as a secondary ZG as an adjunct to SCN rhythms II. Sleep (1/3 of your day, 1/3 of your life) a. Adaptive proccess – quiet – we sleep when it’s dark and dangerous b. Restorative force c. Conservation of energy (doesn’t really apply) – not burning calories when you sleep (saving 110) i. Your brain is still active durin sleep d. Sleep research i. 1920s – EEG (electroenccephalogram) 1. measures electrical activity in brain 2. waves vary in wavelength/frequency a. different waay to look at the same phenomena i. Beta – high frequency (> 13 Hz) ii. Alpha – 8-13 Hz iii. Theta – 4-7 Hz (slow waves) iv. Delta - <1-4 Hz (slow waves) 3. Vary in amplitude a. Beta = low amplitude – “working brain” i. Out of phase firings cancelling eacch other out b. A, T, D, higher amplitude 4. Vary in synchrony – whether neurons fire at the same time a. Beta = asynchronous e. Stages of Sleep (90 minute sleep cycles) i. Stage 1 – Twilight sleep, shallow sleep 1. Some alpha, more theta ii. Stage 2 – squelch what might wake you up (itch, noise) – lasts the longest1. Lots of theta, spindles and k-complexes iii. Stage 3 – theta, less than 50% delta iv. Stage 4 – greater than 50% delta v. Stage 5 – paradoxical sleep, REM sleep, Dream sleep 1. High Beta and muscule paralysis 2. Brain highly active, deeply asleep f. Types of Sleep i. Slow wave – alpha, theta, delta (stages 3 and 4) 1. Decrease in heart rate, body temperature, brain activity 2. Parasympathetic NS very ctive ii. REM – Beta 1. Increase in HR, SNS very active 2. Found in all higher animals a. “dream sleep” – do animals dream? g. Evolutionary Aspects of Sleep i. Occurs in most vertebrates 1. Sleep/wake states part of metabolic cycle 2. Time for replenishment of essential molecules and construction of cellular components a. Cholesterol, heme, enzymes, NTs, become active (genes involved in making large molecules) 3. Babies/infants sleep the most and dream the most 4. CNS flushes out metabolic byproducts (toxins, waste) via cerebrospinal fluid a. Slow wave sleep ii. Predator-prey 1. Predators generally sleep more than prey a. Exceptions: predator-proof shelters (underground burrows), armor plated (armadillos) 2. Predators show more REM than prey a. As CNS matures, %REM decreases i. Related to periods of growth ii. Geriatric humans sleep/dream the least iii. REM sleep and synaptic homeostasis 1. Neuronal Darwinism – only the shortest synapses survive SW sleep 2. Mice – brain cells fire rhythmic patters while awake/active a. While sleeping, overall brain activity decreases i. Ripples of very high activity 1. Specific place-denoting neurons occur in same pattern as awake 2. Time distorted, but in sequence (SW) 3. Real time, out of sequence (REM)3. Humans – studies using students playing maze-like video games a. Some nap, others watch regular videos h. Sleep deprivation i. Brain: cognitive impairments, decline in memory/judgment ii. Heart: higher risk of cardiac disease iii. Immune system: i. Restorative theory i. Growth Hormone – released during stages 3&4 (slow wave) ii. Superoxide radicals: toxic byproducts iii. Supplies of ATP/mitochondria must be replaced j. REM deprivation – inverted flowerpot i. Rebound: after deprivation, spend more time than normal in REM sleep ii. Anxiety decresed after REM – depression is more likely if REM deprived - Sleep is found in animals that would seem better off without sleep o Marine mammals o Dolphins of the Indus live in very muddy water, and are blind (good sonar)  Dangerous to sleep in river – vicious current, debris  Microsleeps – 4-60 seconds - Pilleri (1979) report that these dolphins sleep 7 hours per day in microsleep naps o Bottlenose dolphins and common porpoises sleep by alternating cerebral hemispheres (unilateral sleep)  Mukhametov (1984) - True of fur seals and killer whales  Flocking birds (chickens, ducks) often sleep with one eye open - Some parts of the brain are monitoring environment, other parts are sleeping


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TAMU PSYC 311 - Biological Rhythms and Sleep

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