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: “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– menstrual cycle– reproductive cycles; i.e. breeding seasons– annual migrations

A Hamster for All Seasonsseasonal changes in coat color of Siberian hamsters

How Activity Rhythms Where Measured A Long Time Agoare measured todayvoluntary wheel running is one of the most widely used indicators of activity, wake-time in research on circadian rhythms and other aspects of chronobiology.

How Activity Rhythms where Measured a long time ago

Lights on later

free-running

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

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.

Note: the eye part of this image is anatomically wrong

An Unobstructed View

A Molecular Clock in Flies and Miceinput from retina

GeneAverage circadian time at peak transcript

levelAllele 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

Per1 4–8 10–16 Per1brdm1 1-h shorter pd

Per1ldc 0.5-h shorter pd/arrhythmic

Per1−/− 0.5-h shorter pd

Per2 6–12 14–18 Per2brdm1 1.5-h shorter pd/arrhythmic

Per2ldc Arrhythmic

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  0–4 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

Molecular components of the mammalian circadian clockCaroline H. Ko and Joseph S. Takahashi

Hum. Mol. Genet. (2006) 15 (suppl 2): R271-R277.

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 such as liver, pancreas, skeletal muscle, intestine, and adipose tissue can express circadian oscillations in isolation

• Most common is Per gene for Per protein• 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 AdultTypical: a regular sleep wake pattern with ~ 8 hours of sleep

Oh, How I Hate to Get Up in the Morning

Historical Changes in Sleep Patterns

• “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

• Natural Sleep and Its Seasonal Variations in Three Pre-industrial Societies

– Yetish et al., 2015, Current Biology 25, 1–7, November 2, 2015– The Hadza in northern Tanzania, the Kalahari San, the Tsimane in Bolivia– Sleep periods, the times from onset to offset, averaged 6.9–8.5 hour, with sleep

durations of 5.7–7.1 hour,– Sleep duration was strongly linked to time of sleep onset, on average, 3.3 hr after sunset– Sleep offset “Awakening” was very regular and usually before sunrise– During summer one hour less sleep then during winter sleep– Sleep period was not interrupted by extended periods of waking– Sleep terminated with vasoconstriction near the nadir of daily ambient temperature