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Simon Fraser University
PSYC 388
Ralph Mistlberger

Rhythms of life - Time embedded in our genes; Biological clocks found everywhere (bacteria, worms, us) - Biological clock regulate sleeping, most of what happens in our bodies, our physiology + biochemistry = shows strong day-night differences (heart beat, blood pressure, liver function, metabolizing alcohol, generation of new cells, body temperature, production of many hormones) ~ rhythmic - Biological clock medical implication = action of drugs vary depending on time of day - No time cues our rhythms slowly drift out of alignment with outside world - Natural world= fully of daily, monthly, annual rhythms - Daily circadian rhythms are orchestrated by a central clock to keep our bodily systems working in harmony, but if disrupted = suffer mild symptoms of jet lag to serious conditions such as depression and sleep disorders - Clock keep ensemble of body beating to a collective time = keeps everything from happening all at once and ensures biochemistry of body runs on time and in order - Biological clocks synchronise times of activity and rest of both diurnal (daytime) and nocturnal (nighttimes) organisms and those that are crepuscular (active at dusk and dawn) to ensure peak activity occurs when food, sunlight or prey is available = enable us, etc. to anticipate the predictable rhythmic changes in environment: light, temperature, humidity, UV radiation - Biological clock impose structure that enables organisms to change their behavioural priorities in relations to time of day, month, or year = reset at sunrise and sunset each day to link astronomical time with organisms internal time - Today; 24/7 society = employed in utilities, transport, retail, etc. = imposed structure conflict with our basic biology - Most of what we know about the genetic basis of behaviour comes from study of Drosophila, fruit-fly; = Pittendrigh = study biological rhythms Chapter 1: The day within and The Day Without - Rhythm any process that repeats itself at regular intervals - Oscillator device that produces a rhythm; 1. Can measure duration/elapsed time by counting cycles or portions of a cycle and triggering events at certain intervals 2. Can be synchronized to an external cycle and then consult as clock to recognize local time (ex. Arbitrary time of day) - Pacemaker the oscillator that ultimately sets the rhythms long-term periodicity if more than one oscillator is involved in regulation of a rhythm - Entrainment process of matching the phase and period of an endogenously rhythmic circadian clock to an environmental cycle - Clocks rule our lives = instruct us when to sleep, wake, and work, eat, etc. - Modern world = need to now time to tell us what to do = unnatural - Our basic internal clocks are often masked by artificial timing of modern world (inventions), but notice if travel to different time zones - Believe there no connection between internal clocks and rhythmic cycles of nature (dawn/dusk, lengthen days, shorten night) but could be wrong - Internal daily rhythms (biology) isolate individual from environment reveals it = study: underground in constant light; RESULT: body rhythms start to drift out of synchronisation with outside world than about a month = back in synchrony with outside world then drift again - Almost everything we do shows circadian (day) rhythms = time for everything = regularity stop everything from happening at once ( separate bodily events from time) - Kidney function and urine produce reduced at night because sleep cycles out of phase; body temperature + heart beat + blood pressure higher in day, cognitive abilities change rhythmically over 24 hour period, tooth pain lowest after lunch, proof reading + sprint swimming best in evening, labour pains mostly begin at night, most natural births in early hours, sudden cardiac death mostly I morning - Variations in physical, emotional, cognitive performance therefore depending on task performance change between daily high point and daily low point. complex problem solving or reasoning good at noon, physical coordination best in early evening - Most vulnerable in early morning hours (internal clock disrupted) = symptoms Low point of circadian cycles, body least able to resist cardiac or respiratory difficulties = accidents, etc - Modern world = people knew time by what they were doing = harmony between daily bodily rhythms and external world ( holistic conception of time) constant repetition of day and night, cyclic patterns of seasons and harvest - Sundials measure time by position of sun (shadow)/track slow motion of sunlight across a dial Mesopotamia (Iraq) = plot rotation of earth by follow shadow Tower of Winds in Athens (astronomical observatory for sundial, weather vane and compass, water clock for cloudy days) - First mechanical clocks = 1300 AD modern clocks controls us = race against clock; work-life balance - Rhythmic cycles in plant behaviour - Alexander the Great >>tamarind tree opening and closing its flowers in synchrony with the day - Floral horologue clock made of plants that opened their flowers at different times of day - Carl von Linne formalised idea of floral clock 2 species of daisy (1. Hawks beard 2. Hawkbit) opened and closed with period within half-hour each day (plants many species in circle = hands of clock) - Many plants open leaves in day and close at night + energy of sunlight to drive photosynthetic reaction = converts CO2+ H 2 into sugars, and process release oxygen - Each leaf cell must be exposed to surrounding air for efficient gas-water exchange and light for photosynthesis - Plants: leaves droop if very hot - Plants cant move so circadian clock vital to ensure many physiological activities, ex. Related to photosynthesis, occur in right sequence at optimal time - Tobacco plants, stocks, evening primroses release scent as sun go down = attract pollinating moths and night insects; plant cant release scent in timely manner in response to environmental cue because need time to produce oils = need to anticipate nocturnal insects, and sunset to produce scent on circadian schedule - Nocturnal animals = rhythms diametrically out of phase with diurnal animals - Crepuscular active at twilight or just before dawn - All organisms need to somehow anticipate coming sunset and rise in order to be in right state and right place at right time; different species use same space but divided by time - some species of fish and insects live in caves (no light) retained circadian rhythms of ancestors that lived in light place assumption: clocks used to keep some sense of internal order = = stopping everything from happening at once - rhythm any sequence of regularly recurring functions or events - biological rhythm living world, regular recurrence of an event through time ; ubiquitous (found everywhere) - intertidal (about 12.8 days) - heart beat: rhythmic but not constant same with blood pressure because varies with demands (ex. Run) + underlying circadian rhythm blood pressure lowest at about 4-6:00 a, and rises steadily from then on and peaks in early afternoon before starting to fall - Jean Jacques Ortous de Mairan: first to study biological rhythms scientifically interested in earths rotation and why leaves of plants rigid during day and drooped at night with this rotation >> put mimosa in cupboard and observe = found leaves still opened and closed rhythmically even in dark + (seemed had own representation of day and night) = subjective night drooped, subjective day stiffened up and leaves move at same time = identified first circadian rhythm (still move under constant conditions) www.notesolution.com~ Experiment first show daily rhythms were not response to changing light levels but were internal (endogenous) - Henri duhamel reasoned mimosa leaf movements might have been response to changes in temperature so put plants in constant-temperature environment + constant darkness >> RESULTS: still show regular pattern of leaf movements - Alphonse de Candolle found period of leaf movement rhythm in constant conditions wasnt exactly 24 hours = varied slightly from plant to plant = provide evidence clock is internal, if its due to environmental cue than plants would move at same time - Free-running daily pattern of an organism kept in constant conditions of darkness or light; rhythm innate, hard-wired into genome - Light/dark cycle or other cues can synchronise rhythms but dont cause them - Free-running rhythm = ticking of genetically programmed clock - Aperiodic environment constant temperature and illumination - Erwin Bunning(lead to rigorous investigation of biological rhythms) >> found leaf movements of common bean Phaseolus oscillated in constant darkness with mean period 24.4 hours Established salient property of circadian clocks: when kept in constant conditions they run with period close to, but never exactly, 24 hours - Pittendrigh father of circadian research found fruit fly Drosophila kept in constant conditions, free-running rhythm not quite 24 hours (varies 22-28 hours for different species) + pulled into synchrony by specific signal, usually rise and set of sun = suggest independent, self-sustaining endogenous clock - Limulus crab with ancient daily rhythms >> unchanged for 350 million years but have 1000 photoreceptors clusters (ommatidia) in eye Barlow found circadian clock in crabs brain that transmits nerve signals to its eyes + eyes
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