CIRCADIAN RHYTHMS
Circadian rhythms are physical, mental and behavioral changes that follow a roughly 24-hour
cycle, responding primarily to light and darkness in an organism's environment. They are found
in most living things, including animals, plants and many tiny microbes. The study of circadian
rhythms is called chronobiology.
Our biological clocks drive our circadian rhythms. The biological clocks that control circadian
rhythms are groups of interacting molecules in cells throughout the body. A "master clock" in the
brain coordinates all the body clocks so that they are in synch.
The "master clock" that controls circadian rhythms consists of a group of nerve cells in the brain
called the suprachiasmatic nucleus, or SCN. The SCN contains about 20,000 nerve cells and is
located in the hypothalamus, an area of the brain just above where the optic nerves from the eyes
cross.
Circadian rhythms have a genetic component. Researchers have identified genes that direct
circadian rhythms in people, fruit flies, mice, fungi and several other model organisms used for
studying genetics.
Circadian rhythms are produced by natural factors within the body, but they are also affected by
signals from the environment. Light is the main cue influencing circadian rhythms, turning on or
turning off genes that control an organism's internal clocks.
Circadian rhythms can influence sleep-wake cycles, hormone release, body temperature and
other important bodily functions. They have been linked to various sleep disorders, such as
insomnia. Abnormal circadian rhythms have also been associated with obesity, diabetes,
depression, bipolar disorder and seasonal affective disorder.
Sleep and Circadian Rhythms
Circadian rhythms are important in determining human sleep patterns. The body's master clock,
or SCN, controls the production of melatonin, a hormone that makes you sleepy. Since it is
located just above the optic nerves, which relay information from the eyes to the brain, the SCN
receives information about incoming light. When there is less light—like at night—the SCN tells
the brain to make more melatonin so you get drowsy.
Circadian rhythms and jet lag?
Jet lag occurs when travelers suffer from disrupted circadian rhythms. When you pass through
different time zones, your body's clock will be different from your wristwatch. For example, if
you fly in an airplane from California to New York, you "lose" 3 hours of time. So when you
wake up at 7:00 a.m., your body still thinks it's 4:00 a.m., making you feel groggy and
disoriented. Your body's clock will eventually reset itself, but this often takes a few days.
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How do researchers study circadian rhythms?
Scientists can learn about circadian rhythms by studying humans or by using model organisms
that have similar "clock" genes. Basic researchers doing these experiments can control the
subject's environment by altering light and dark periods and then look for changes in gene
activity or other molecular signals.
How does circadian rhythm research contribute to human health?
Understanding what makes biological clocks tick may lead researchers to treatments for sleep
disorders, jet lag and other health problems. Learning more about the genes responsible for
circadian rhythms will also enhance our understanding of biological systems and the human
body.
Biological markers and effects
The classic phase markers for measuring the timing of a mammal's circadian rhythm are:
melatonin secretion by the pineal gland,
core body temperature minimum and
plasma level of cortisol.
For temperature studies, subjects must remain awake but calm in near darkness while their rectal
temperatures are taken continuously. Though variation is great among normal chronotypes, the
average human adult's temperature reaches its minimum at about 05:00 (5 a.m.), about two hours
before habitual wake time. Baehr et al.,(2000) found that, in young adults, the daily body
temperature minimum occurred at about 04:00 (4 a.m.) for morning types but at about 06:00 (6
a.m.) for evening types. This minimum occurred at approximately the middle of the eight hour
sleep period for morning types, but closer to waking in evening types.
Melatonin is absent from the system or undetectably low during daytime. Its onset in dim light,
dim-light melatonin onset (DLMO), at roughly 21:00 (9 p.m.) can be measured in the blood or
the saliva. Its major metabolite can also be measured in morning urine. Both DLMO and the
midpoint (in time) of the presence of the hormone in the blood or saliva have been used as
circadian markers. However, newer research indicates that the melatonin offset may be the more
reliable marker. Benloucif et al.,(2005) found that melatonin phase markers were more stable and
more highly correlated with the timing of sleep than the core temperature minimum. They found
that both sleep offset and melatonin offset are more strongly correlated with phase markers than
the onset of sleep. In addition, the declining phase of the melatonin levels is more reliable and
stable than the termination of melatonin synthesis.
Other physiological changes that occur according to a circadian rhythm include heart rate and
many cellular processes "including oxidative stress, cell metabolism, immune and inflammatory
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responses, epigenetic modification, hypoxia/hyperoxia response pathways, endoplasmic reticular
stress, autophagy, and regulation of the stem cell environment.
In contradiction to previous studies, it has been found that there is no effect of body temperature
on performance on psychological tests. This is likely due to evolutionary pressures for higher
cognitive function compared to the other areas of function examined in previous studies.
Human health and circadian rhythms
Timing of medical treatment in coordination with the body clock may significantly increase
efficacy and reduce drug toxicity or adverse reactions.
A number of studies have concluded that a short period of sleep during the day, a power-nap,
does not have any measurable effect on normal circadian rhythms but can decrease stress and
improve productivity.
Health problems can result from a disturbance to the circadian rhythm. Circadian rhythms also
play a part in the reticular activating system, which is crucial for maintaining a state of
consciousness. A reversal in the sleep–wake cycle may be a sign or complication of uremia,
azotemia or acute renal failure.
Obesity and diabetes
Obesity and diabetes are associated with lifestyle and genetic factors. Among those factors,
disruption of the circadian clockwork and/or misalignment of the circadian timing system with
the external environment (e.g., light-dark cycle) might play a role in the development of
metabolic disorders.
Shift-work or chronic jet-lag have profound consequences on circadian and metabolic events in
the body. Animals that are forced to eat during their resting period show increased body mass
and altered expression of clock and metabolic genes.[medical citation needed] In humans, shift-work that
favors irregular eating times is associated with altered insulin sensitivity and higher body mass.
Shift-work also leads to increased metabolic risks for cardio-metabolic syndrome, hypertension,
inflammation.
Airline pilots
Due to the work nature of airline pilots, who often cross several timezones and regions of
sunlight and darkness in one day, and spend many hours awake both day and night, they are
often unable to maintain sleep patterns that correspond to the natural human circadian rhythm;
this situation can easily lead to fatigue. The NTSB cites this as contributing to many accidents]
and has conducted several research studies in order to find methods of combating fatigue in
pilots.
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Disruption
Disruption to rhythms usually has a negative effect. Many travellers have experienced the
condition known as jet lag, with its associated symptoms of fatigue, disorientation, and insomnia
A number of other disorders, for example bipolar disorder and some sleep disorders such as
delayed sleep phase disorder (DSPD), are associated with irregular or pathological functioning of
circadian rhythms.
Disruption to rhythms in the longer term is believed to have significant adverse health
consequences on peripheral organs outside the brain, in particular in the development or
exacerbation of cardiovascular disease. LED lighting suppresses melatonin production five times
more than a high-pressure sodium light.[medical citation needed] Depression symptoms from long term
nighttime light exposure can be undone by returning to a normal cycle.[medical citation needed]
Effect of drugs
Studies conducted on both animals and humans show major bidirectional relationships between
the circadian system and abusive drugs. It is indicated that these abusive drugs affect the central
circadian pacemaker. Individuals suffering from substance abuse display disrupted rhythms.
These disrupted rhythms can increase the risk for substance abuse and relapse. It is possible that
genetic and/or environmental disturbances to the normal sleep and wake cycle can increase the
susceptibility to addiction.
It is difficult to determine if a disturbance in the circadian rhythm is at fault for an increase in
prevalence for substance abuse or if other environmental factors such as stress are to blame.
Changes to the circadian rhythm and sleep occur once an individual begins abusing drugs and
alcohol. Once an individual chooses to stop using drugs and alcohol, the circadian rhythm
continues to be disrupted.
The stabilization of sleep and the circadian rhythm might possibly help to reduce the
vulnerability to addiction and reduce the chances of relapse
Circadian rhythms and clock genes expressed in brain regions outside the suprachiasmatic
nucleus may significantly influence the effects produced by drugs such as cocaine. Moreover,
genetic manipulations of clock genes profoundly affect cocaine's actions
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IMMUNE SYSTEM PSYCHOPHYSIOLOGY
Our emotional and mental health are entwined with our physical health. In order to boost
physical healing, we need to reduce the amount of stress, fear, and conflict and increase the
amount of love, pleasure and laughter in our lives. Pursuing even the best of therapeutic supports
in a life that is saturated with stress could be seen as analogous to eating wonderfully healthy
foods but failing to drink.
Pleasure, love, social connection, harmony, and self-regulation techniques like meditation, all
fuel happiness and have been scientifically proven to have a powerful positive impact on our
immune health and healing. However many of us don't prioritize these pleasant parts of our lives.
In fact, a low sense of self worth may prevent some of us from seeking the very relaxing and
happy activities that could relieve the physical ailments that amplify suffering. This is a difficult
trap to escape from. The good news is that even if this is the case and at first we're not fully at
ease with the pursuit of emotional happiness, we can just keep practicing it until it becomes
comfortable.
Even a dutiful pursuit of happiness can have the desired effect eventually. When happiness
seeking behaviour is repeated often enough it becomes a natural survival habit. Regardless of
whether we "throw ourselves into it" fully, we can't help but feel an increase in positive feelings.
These good feelings exponentially reinforce our drive to pursue more fun and they also enhance
our self worth and encourage social behavior. Eventually the practice just becomes a natural part
of who we are as happier, healthier people surrounded by a nourishing social environment.
The Chemistry of Emotions
Emotions trigger a cascade of biochemical changes in our bodies that affect the way our bodies
function and how we feel. Our nervous and endocrine systems communicate bi directionally with
our immune system in the "language" of hormones and neuropeptides. This means that our
emotions can induce health or illness and, in turn our state of health can induce emotions. Armed
with this information we can begin to understand answers to questions like:
Why do optimists live longer? How does happiness improve immune function: Why do stress
and depression slow healing and the immune defense against cancer? Discoveries in the
fascinating fields of applied psychophysiology, health psychology, biopsychiatry and
psychoneuroimmunology have documented many of the biochemical intersections of the body
and mind in terms of immune health. Here are some examples.
Natural killer blood cells (NK cells) work to destroy tumour cells, diseased tissue or invading
viruses, bacteria etc. As a first defense role in controlling infection in the early stages of infection
or damaged, the levels of NK cells are considered indicative of immune strength. Psychological
stress reduces our Natural Killer cells and can increase disease severity. Stressed medical
students tested on the day of their exams showed significantly lowered immune markers
including lowered NK cell. Lack of social bonding also impacts the levels of these cells as was
shown in a study that observed that lonely medical students had lower levels of NK cell activity
than socially active students.
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Oxytocin, is a hormone released during emotional bonding, sexual intimacy, as well as during
childbirth and in preparation for breast feeding. Scientists think it supports maternal behaviors as
well as social recognition, trust, and bonding. It also regulates blood pressure, body temperature,
wound healing and even relief from pain. So we only get to receive the full benefits of this
beautiful hormone when we are celebrating love in one of its many forms.
Cortisol is also a hormone that is excreted during stress. Along with adrenaline, during stress, it
plays an important part of the "fight or flight" response, helping prepare the body for emergency
action. Too much cortisol for too long contributes to high blood pressure, reduced mental
performance, blood sugar problems, thyroid suppression, "bad" cholesterol build up and
increased abdominal fat. Low saliva levels are interpreted to mean the subject is experiencing
little stress and high levels are correlated with high stress. Grief suppresses immune health. A
study of bereaved spouses showed that they had elevated cortisol and decreased NK cell lysis.
Grief, separation, heartbreak and divorce have also been proven to increase cortisol secretions.
Interestingly, the body cannot decipher true threats from imagined. Our body will respond with
cortisol and other toxic biochemical stress reactions in a similar manner whether we are worrying
and imagining a danger or stressful event or actually experiencing it. Here's a strong point to
keep in mind when choosing our thoughts!
Immunoglobin A is a specialized protein called an antibody that is produced by white blood cells
to battle foreign pathogens such as bacteria. It supports the immune system of the mucous
membranes and is the bodies most prolific and important anti body. Similar to NK cells, the
more Immunoglobin A measured through the blood, the stronger immune function is. Studies
show that when we are calm and happy, this chemical is at its highest levels and when we are
frightened or angry, it is reduced.
Rate of Healing and Overall Resilience
Conflict and lack of anger control can reduce our ability to heal. For example, couples in conflict
were shown to have slower healing blisters than those in harmony. In another study, children
exposed to psychosocial stress suffered more illness and more fevers. The children of parents
exhibiting stress symptoms also suffered more illness.
Neuropeptides are another category of specialized protein. They have a particularly interesting
role in the transmission of emotional reactions within the body. Neuropeptides received attention
because their discovery by Candice Pert in the 1970's amplified our scientific mind body
understanding. Their discovery raised the legitimacy of mind body research significantly. This
was because these messengers of emotion were discovered throughout the body, not just in the
brain as previously thought. Neuropeptides create the experience of moods, pain and pleasure
and are found in every part of our bodies. Neuropeptides are believed to facilitate an intimate
communication between the immune system and our emotions. If our body is experiencing
emotional sensations like tightness in the chest or an upset stomach it is not just because our
brains signal the stress alert. We literally feel stress (and pleasurable emotions) throughout our
body!
Bowel Immune Function
Bowel health is another crucial, though little understood measure of immune health. According
to and article in the British Journal of Clinical Pharmacology, bowel biology is made up of
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"microflora, a large bacteria community that colonizes the gut with metabolic activity equal to an
organ." This microflora plays a significant role in our immune function at least partially via our
intestinal mucous membrane.
Our immune health is strongly influenced by our digestive and bowel health, which are
themselves affected by stress in a couple of ways. Negative emotions trigger the release of pro-
inflammatory agents that worsen intestinal conditions such as colitis, Crohns and irritable bowel
syndrome. Inflammatory bowel conditions such as these may also irritate the immune mucosa
lining of the gut and may result in frequent elimination which can lower populations of
beneficial bacteria which play a large role in immune function.
Sleep Derived Immune Strength
Sleep health, like bowel health, is also related to immune function. Unlike bowel health, sleep is
well known by most of us for its importance for both happiness and health, perhaps because the
effects of sleep loss can be felt so immediately. There is no shortage of science supporting the
relationship between sleep and stress. Studies have shown that deprivation of REM (rapid eye
movement) sleep causes psychological disturbances, such as apathy, depression, irritability,
confusion, disorientation, hallucinations, impaired memory, and paranoia. As most of us know,
sleep also has a paradoxical relationship with stress. Too much stress interrupts sleep which then
causes more stress.
Sleep loss lowers immune function too. Even just one night of disturbed sleep can decrease
production and activity of white blood cells and T cells. One study showed that chronic sleep
deprivation can leave children at a higher risk of catching colds, flu, and other infectious
diseases. Sleep shortages increase daily stress (and therefore immunity) by interfering with
memory and focus and the ability to organize information.
