Transcript Slide 1
Biorhythm From Wikipedia, the free encyclopedia Biorhythm (from Greek βίος - bios, "life"[1] and ῥυθμός rhuthmos, " any regular recurring motion, rhythm"[2]) is an attempt to predict various aspects of a person's life through simple mathematical cycles. Most scientists believe that the idea has no more predictive power than raw chance,[3] and consider the concept an example of pseudoscience. Biological Rhythms • Chronobiology is a field of biology that examines periodic cycles known as biological rhythms in living organisms as an adaptation to solar- and lunar-related rhythms. • Circadian rhythm: “about one day” is a 24-hour cycle – sleep-wake cycle – body temperature – melatonin • Ultradian rhythm: more then once a day – 3 hour cycle of growth hormone production – appetite – sleep stages; for example REM • Infradian rhythms: less then once a day – annual migrations – reproductive cycles; i.e. breeding seasons – menstrual cycle A Hamster for All Seasons seasonal changes in coat color of Siberian hamsters How Activity Rhythms Where Measured A Long Time Ago are measured today voluntary wheel running is one of the most widely used indicators of activity, waketime in research on circadian rhythms and other aspects of chronobiology. How Activity Rhythms where Measured a long time ago Lights on later The Effects of Lesions in the SCN Lesion - Brain Transplants Prove That the SCN Contains a Clock Fetal SCN cells with tau mutation The Retinohypothalamic Pathway in Mammals Components of a Circadian System Note: the eye part of this image is anatomically wrong Intrinsically photosensitive Retinal Ganglion Cells (ipRGCs), also called photosensitive Retinal Ganglion Cells (pRGC), or melanopsin-containing retinal ganglion cells, have slow response and signal the presence of light over the long term. An Unobstructed View A Molecular Clock in Flies and Mice input from retina Molecular components of the mammalian circadian clock Caroline H. Ko and Joseph S. Takahashi Hum. Mol. Genet. (2006) 15 (suppl 2): R271-R277. Gene Average circadian time at peak transcript level Allele Mutant phenotype SCN Periphery Bmal1 (Arntl) 15–21 22–02 Bmal1−/− Arrhythmic Clock Constitutive 21–03 ClockΔ19/Δ19 4-h longer pd/arrhythmic Clock−/− 0.5-h shorter pd Per1brdm1 1-h shorter pd Per1ldc 0.5-h shorter pd/arrhythmic Per1−/− 0.5-h shorter pd Per2brdm1 1.5-h shorter pd/arrhythmic Per2ldc Arrhythmic Per1 Per2 4–8 6–12 10–16 14–18 Per3 4–9 10–14 Per3−/− 0–0.5-h shorter pd Cry1 8–14 14–18 Cry1−/−a 1-h shorter pd Cry2 8–14 8–12 Cry2−/−a 1-h longer pd Rev-erbα (Nr1d1) 2–6 4–10 Rev-erbα−/− 0.5-h shorter pd/disrupted photic entrainment Rorα 6–10 Arrhythmic/variousb staggerer 0.5-h shorter pd/disrupted photic entrainment Rorβ 4–8 18–22 Rorβ−/− 0.5-h longer pd Rorγ N/Ac 16–20/variousb Rorγ−/− Unknown NPAS2 N/Ac NPAS2−/− 0.2-h shorter pd CK1ε (Csnk1ε) Constitutive Constitutive CK1εtaud 4-h shorter pd CK1δ (Csnk1δ) Constitutive Constitutive Csnk1δ−/+ 0.5-h shorter pd 0–4 When the Endogenous Clock Goes Kaput Mouse with clock/clock mutation SCN Output Regulates Many Functions • SCN sends information to other hypothalamic areas – Pre-optic Area (POA) – Para Ventricular Nucleus (PVN) – Dorsal Medial Hypothalamus (DMH) • Organizes the time course of metabolic events – Physiological • body temperature • blood pressure • metabolism – Hormonal: see next slide – Behavioral processes • • • • sleep/wake cycle rest/activity cycle reproductive eating SCN Regulates Hormones Thyroid via POA - TRH – TSH Adrenal Corticosterone DMH - CRH – ACTH pathway PVN – sympathetic pathway to adrenal cortex Melatonin via PVN - sympathetic pathway to pineal gland Sex steroids via POA - GnRH – LH or FSH Leptin via PVN – autonomic innervation of adipose tissue Insulin via PVN – autonomic innervation of pancreas Pineal Gland produces Melatonin • Light Signal Circuit – – – – – special cells in retina detect light signals and entrains the suprachiasmatic nucleus (SCN) Axons from the SCN to the paraventricular nuclei (PVN) PVN to the spinal cord superior cervical ganglia (SCG) SCG connects into the pineal gland • Production of melatonin – stimulated by darkness – inhibited by light • Melatonin (5-methoxy-N-acetyltryptamine) – hormone found in all living creatures from algae to humans – levels vary in a diurnal cycle Regulation of the Pineal Gland Functions of Melatonin • • • • Timing of hibernation, changes in metabolism Timing of (seasonal) breeding Timing of sexual maturity Timing of sleep – promotes drowsiness – increase REM sleep time and vividness of dreams – counteract immunodeficiences • cell-protective “antiapoptotic” for immune cells – a powerful antioxidant to reduce free radicals Cell-autonomous Circadian Oscillator • Most peripheral organs and tissues can express circadian oscillations in isolation such as liver, pancreas, skeletal muscle, intestine, and adipose tissue • Receive, and may require, input from the SCN in vivo • Can generate behavioral rhythms in vivo in the absence of the SCN • Control rhythms of gene transcription for metabolic pathways, glucose homeostasis and lipogenesis • Interact with each other and with the system as a whole. Electrophysiological Correlates of Sleep and Waking A Typical Night of Sleep in a Young Adult Typical: a regular sleep wake pattern with ~ 8 hours of sleep Oh, How I Hate to Get Up in the Morning Sleep We Have Lost: Pre-industrial Slumber in the British Isles • “Sleep We Have Lost: Pre-industrial Slumber in the British Isles” by A. Roger Ekirch (2001) • "first sleep" and “second sleep” • Interrupted by up to an hour or more of quiet wakefulness midway through the night • Sleep's principal contribution was not merely physiological but psychological. • http://ahr.oxfordjournals.org/content/106/2/343.full.pdf+html