Biorhythm From Wikipedia the free encyclopedia Biorhythm from

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. Ry Cooder Get Rhythm

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: “around once per day” is a 24 -hour cycle • sleep-wake cycle • body temperature • melatonin • Ultradian rhythm: more than once per day (< 24 -hour cycle) • 3 hour cycle of growth hormone production • appetite • sleep stages (figure 14. 12) • Infradian rhythms: less than once per day (>24 -hour cycle) • menstrual cycle • reproductive cycles; i. e. breeding seasons • annual migrations

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 in research on circadian rhythms and other aspects of chronobiology.

Phase Shift during Activity Rhythms Each line from left to right is a single day Lights turned off later and turned on later zeitgeber Entrainment is the process of shifting the rhythm free-running hamster becomes active a few minutes later each day

The Effects of Lesions in the SCN

Brain Transplants Prove That the SCN Contains a Clock A wild-type hamster, when kept in constant dim light, displayed an endogenous circadian rhythm 24. 05 hours in duration (top). After the SCN was lesioned, the animal became arrhythmic. Later, an SCN from a fetal hamster with two copies of the tau mutation was transplanted into the lesioned adult hamster (circle). Soon thereafter, the adult hamster began showing a freerunning activity rhythm of 19. 5 hours, matching the SCN of the donor animal. This response to the transplant showed that the period of the clock is determined within the SCN

The Retinohypothalamic Pathway in Mammals Special ganglion cells with melanospin This pathway carries information about the light-dark cycle in the environment to the SCN. For clarity of synaptic connections, the SCNs are shown proportionally larger than other features.

Hypothalamic Nuclei Details not on the exam

Components of a Circadian System Note: the eye part of this image is anatomically wrong Intrinsically photosensitive Retinal Ganglion Cells (ip. RGCs), also called photosensitive Retinal Ganglion Cells (p. RGC), or melanopsin-containing retinal ganglion cells, have slow response and signal the presence of light over the long term.

The Hypothalamus Houses a Circadian Clock Molecular studies in fruit fly Drosophila using mutations of the period (per) gene helped to understand the circadian clock in mammals. SCN cells in mammals make two proteins: – Clock – Cycle (in Drosophila; called Bmal 1 in mammals) Clock and Cycle proteins bind together to form a dimer. The Clock/Cycle dimer promotes transcription of two genes: – Period (per) – Cryptochrome (cry) Per and cry proteins then dimerize. The Per/Cry protein complex enters the nucleus and inhibits the transcription of the Clock/Cycle genes. No new Clock/Cycle proteins are made until the Per/Cry proteins degrade; the cycle takes approximately 24 hours.

A Molecular Clock in Flies and Mice input from retina Period (per), Cryptochrome (cry)

Circadian System SCN Output Regulates Many Functions SCN sends information to other hypothalamic areas – – Para Ventricular Nucleus (PVN) Subparaventricular region Pre-optic Area (POA) 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 Details not on the exam Adrenal Corticosterone DMH - CRH – ACTH pathway PVN – sympathetic pathway to adrenal cortex Melatonin via PVN - sympathetic pathway to pineal gland Sex steroids via POA - Gn. RH – LH or FSH Leptin via PVN – autonomic innervation of adipose tissue Insulin via PVN – autonomic innervation of pancreas

Details not on the exam Figure 1. Challet (2015) Keeping circadian time with hormones. Diabetes, Obesity and Metabolism 17 (Suppl. 1): 76– 83, 2015.

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 SCN PVN

Functions of Melatonin Timing of hibernation, changes in metabolism Timing of (seasonal) breeding Timing of sexual maturity Timing of sleep – promotes drowsiness (in diurnal) – increase REM sleep time and vividness of dreams Counteract immunodeficiences – cell-protective “antiapoptotic” for immune cells – a powerful antioxidant to reduce free radicals which reduces the incidence of cancer

Sleeping and Waking • Sleep is synchronized to external events • • • including light and dark for all animals For humans: Stimuli such as lights, food, jobs, and alarm clocks entrain us to be awake or to sleep. In the absence of cues, humans have a free-running period of approximately 25 hours that varies with age.

Human Sleep Exhibits Different Stages • • • Electrical brain potentials can be used to classify levels of arousal and states of sleep. Electroencephalography (EEG) records electrical activity in the brain. Electro-oculography (EOG) records eye movements. Electromyography (EMG) records muscle activity. • Two distinct classes of sleep stages : • • Slow-wave sleep (SWS) can be divided into three stages and is characterized by slow-wave EEG activity. • Rapid-eye-movement sleep (REM) is characterized by small amplitude, fast-EEG waves, no postural tension, and rapid eye movements.

Electrophysiological Correlates of Sleep and Waking Details not on the exam

A Typical Night of Sleep in a Young Adult Typical: a regular sleep wake pattern with ~ 8 hours of sleep Awake REM

Dreams & Nightmares • Vivid dreams occur mostly during REM sleep, characterized by: • Visual imagery, story • Sense that the dreamer is “there” • Nightmares are long frightening dreams that awaken the sleeper from REM sleep. • Night terrors are sudden arousals from NREM sleep, marked by fear and autonomic activity.