What Are Biological Rhythms

What Are Biological Rhythms?

The human body contains many different kinds of cells which perform various functions. These cells have their own internal clocks. They are called “biological” because they are controlled by chemical signals from the brain rather than being driven by external environmental factors such as light or food. Most biological rhythms occur within the cell itself, but some may also occur outside it (for example, in other organs).

There are two main classes of biological rhythms: those that control how long certain parts of the body work at a particular time, and those that regulate when these same parts start working again. The former type is known as a “homeostatic” rhythm; the latter as a “photic” one.

Both types are regulated by hormones released into our blood stream during sleep and wakefulness respectively.

In humans, there are three major types of biological rhythms: melatonin secretion, cortisol release and the circadian rhythm. Melatonin is secreted by pineal gland in the center of your brain.

Cortisol is produced mainly by adrenals and pituitary glands. The circadian rhythm occurs throughout all 24 hours of the day and night in most mammals including humans.

The main driving force behind all biological rhythms in humans is the circadian rhythm. It not only affects the sleep wake cycle, but also our body temperature, hormone production and many other functions.

When we travel across time zones our circadian rhythm gets confused. Usually it takes one full day for each time zone changed to fully adjust to the new time. Until that happens, a person temporarily experiences insomnia, disorientation, and general malaise.

In addition to the circadian rhythm, melatonin and cortisol levels also affect sleep patterns. In the evening, cortisol levels drop and melatonin levels increase in preparation for sleep.

In the early morning hours melatonin secretion drops and cortisol rises. This process prepares you for wakefulness. However, in people who work at night, melatonin levels stay high throughout the night and only start decreasing in the morning. This may be why many night-shift workers complain of tiredness during the day.

In addition to affecting the wake-sleep cycle, biological rhythms also determine other functions in your body such as body temperature, stomach acid production and even blood pressure. The importance of maintaining the biological rhythm was first realized by farmers who began using artificial light in chicken coops.

Fertility increased ten-fold when the chickens were exposed to light during their natural night time.

If you have to travel across time zones, try to move your body clock ahead or behind the new time as quickly as possible. If you are flying west, start shifting your bedtime one hour earlier for each time zone you cross.

For example, if you are flying from Los Angeles to London which is seven hours difference, you should go to bed seven hours earlier each night until you reach the new destination.

In a similar manner when traveling east add hours to your bedtime. If you are traveling from Los Angeles to Moscow which is ten hours difference, go to bed ten hours later each day until you reach your destination.

Of course if you have to change your internal clock in this manner, it will take some time to adjust once again when you return to your home time zone.

Try to minimize the adverse effects of jet lag by flying during the day and night. If you fly west, try to travel during the day.

If you fly east, fly at night. When you reach your destination try to stick as close as possible to your new time zone’s “normal” sleeping patterns.

Finally, don’t forget that exercise and a healthy diet are always important, but even more so when traveling across time zones in order to adjust internal body rhythms.

Some travelers experience severe disorientation when they visit other countries and try to adjust their sleep habits and wakefulness times to match the local environment. This can lead to considerable fatigue and even a complete breakdown in one’s ability to think clearly.

As a result, it is important that travelers know how to adjust their internal body rhythms to those of the new location.

Again, if you are going east, you should stay up later each night and sleep in later each morning. If you are going west, do exactly the opposite: Go to bed earlier and get up earlier.

It is important to remember that these are only general guidelines. Some people may find that they adjust more quickly by following the guidelines strictly (even if it seems unnatural at first), while others will find that they need to adjust differently.

There is no right or wrong way to do it, but you need to find out what works for you.

If you are a morning person traveling to the east, you’ll probably want to keep getting up at your normal time (if not earlier), even though the sun is rising much later. If you are a night person traveling to the east, you’ll want to stay up later each evening and wake up later each morning.

Here are some other tips that may help you during your trip:

If you are going to a popular destination at about the same time every year, you can set your watch (and body) to the new time zone before you leave. This will make the transition much easier when you arrive.

Also, try to get as much sleep as you can on the plane (but don’t take a sleep pill — they tend to make you feel groggy). If you are really tired when you arrive, try to take a nap during the day so your body can continue to adjust. If you have trouble sleeping at night when you first arrive, try going for a walk during the day (if visiting in the summer).

Some people can reset their body clock by using light as a cue. If you want to try this technique, get to your destination at least a day before you need to be awake and alert according to the local time.

The first night, stay up until you would normally go to sleep at home. Then, in the morning get some direct sunlight — sitting near a window or going for a walk — for at least an hour. Each day you will get sleepy earlier and sleepy faster. Continue to do this until you can fall asleep at your normal bedtime at home (but don’t take any sleep aids).

If your trip is only a few days long, try to spend at least one full “day” at your destination. It may take a full day at the destination for your body to realize that it needs to sleep according to the new time zone (this also works for the flight home).

If you’re going somewhere exotic, take a digital camera with you. This will help your brain activate more memory centers and make the experience seem more real.

You may even want to take pictures of yourself at different locations so you can create a “memory album” when you get home.

Relax before going to bed. Take a warm bath or read a book in your hotel room (reading in bed can cause you to fall asleep while reading).

If you don’t fall asleep immediately, get up and do something relaxing until you feel sleepy again. Then go back to bed.

Take your sleep aids at home so you don’t forget them when you pack for your trip.

When you get back home, it may take a few days to readjust to your old sleeping habits. Remember to keep busy during the day so you will be too tired to stay up late.

Also, try taking naps during the day for a few days.

If you have trouble sleeping at home, you may want to take a trip “home” so you can fall asleep at night. It may also help to set your watch and calendar at home to match the time at your destination.

For example, if you went to a location six hours ahead, set your watch and calendar ahead six hours when you get home. You can do the same thing when you arrive (set your watch and calendar back six hours). The change in time should help your body adjust faster.

Remember that jet lag tends to affect people differently. What helps one person might not help another.

The key is to keep trying different things until you find out what works best for you.

Remember that jet lag is usually temporary and goes away within a few days or weeks. You shouldn’t let it get in the way of your trip.

After all, that’s why you’re taking the trip in the first place!


Hypoglycemia (hye-poe-glis-e-me-ah) is a condition in which the body has too little glucose (a type of sugar). Glucose gives you energy, and when you don’t have enough, you get hungry, tired, and moody.

You may also feel shaky, sweaty, dizzy, and lightheaded.

There are different types of hypoglycemia. Ingestion of too much alcohol or a big meal may cause temporary hypoglycemia.

Fasting (not eating) or starvation can cause temporary or permanent hypoglycemia. Too much exercise without eating enough food can also cause temporary hypoglycemia.

If you have this condition, you should always carry a snack with you in case you get hungry. Do not let yourself get hungry, and do not engage in strenuous activities until the symptoms go away.


Hypotonia (hi-po-toe-nee-ah) is a decrease in muscular tone. The opposite condition is hypertonia (hi-per-toe-nee-ah).

If you have hypotonia, your muscles are “loose.” You may have a hard time doing some movements because the muscles are not working together in a normal way.

Newborns often have hypotonia. This is normal in these young babies and usually goes away when a baby reaches two to three months of age.

There are several causes of hypotonia. It can be caused by a head injury, infection, or brain tumor.

Medicines such as anti-seizure drugs or any medicine that affects the nervous system may cause hypotonia. Hypothyroidism (an underactive thyroid gland), certain types of muscular dystrophy, and a lack of oxygen during labor and birth may also cause hypotonia.

A doctor must determine the exact cause of hypotonia. The doctor will give you an exam and ask you questions about your baby’s medical history and your own.

Sometimes, the doctor may request tests such as blood tests or scans.

There is no cure for hypotonia. Treatment depends on the cause.

For example, medicines may help if the hypotonia is caused by medicine, infection, or illness. If the hypotonia is caused by birth problems or a head injury, the baby may need physical therapy.


Internal absorption is when something from the outside of the body absorbs into the body.

For example, a woman wearing an underwire bra and goes for a run may feel some “digging in.” This is because of the pressure of the underwire on her ribcage.

This can lead to increased sweating and ultimately internal absorption.

Internal absorption can also affect people who live or work in poorly ventilated areas. People who wear medical masks for allergic reactions are also susceptible to internal absorption due to the underchin area being covered.

The body absorbs these materials over time, and this can lead to serious health concerns. If you notice any physical symptoms such as a rash on the skin or breakouts, you should seek medical attention immediately.


If you have iron deficiency anemia (a lack of iron in the body that causes fewer red blood cells), you may experience:


*Pale skin

*Shortness of breath

*Brittle nails


If you have severe iron deficiency anemia, you may experience:

immune system problems, which can increase your risk of infection.

In women, iron deficiency anemia has been linked to problems during pregnancy.

Your doctor can diagnose iron deficiency anemia with a blood test. After that, the doctor will prescribe an iron supplement and dietary changes.

The two main ways to get the proper amount of iron are through food and dietary supplements.


*Beef – 3 oz = 6.45 mg

*Tofu – 1 cup = 2.4 mg

*Lentils – 1 cup = 8.1 mg

*Black Beans – 1 cup = 11.3 mg

*Dark Chocolate (70% cocoa) – 1 oz = 3.2 mg

*Spinach – 1 cup = 6.4 mg

Often, people take iron supplements to help with anemia and iron deficiencies in general. Iron supplements can interact with certain medicines (like Tylenol) and should be avoided by those with rare iron storage diseases.


The most common sign of vitiligo is the appearance of white spots on the skin. These spots are areas of damaged skin, caused by a lack of cells that produce color (melanocytes).

If you have vitiligo, you may notice one or more white patches on your skin. The patches may appear suddenly or they may appear gradually over time. The affected skin may or may not be itchy. The patches are permanent and will not get better without treatment.

Treatment for vitiligo usually involves medicines to increase the amount of pigment-producing cells (melanocytes). A doctor can help you develop a treatment plan based on the severity of your symptoms, your skin type, and other factors.

If you have vitiligo, it is very important to avoid direct sunlight (including from tanning beds) as this can lead to sunburn and increase your risk of skin cancer. Also, some people with vitiligo are prone to skin infections or eczema.

You should also be aware that vitiligo can affect your self esteem and mental health. There are support groups and counselors who can help you cope with the emotional effects of vitiligo.

You should see a doctor if you notice a change in the color or appearance of your skin. This includes changes in normal moles or birthmarks as well.

It is also important to see a doctor if you notice any open sores, scabs, or rashes that do not heal after several weeks. Early detection and treatment is the best way to prevent serious health concerns.


Lead poisoning is caused by heavy metals, including lead. Lead poisoning can happen in children if they accidentally chew on painted toys or swallow (ingest) paint chips.

Lead poisoning can also happen to adults who work with lead on a regular basis.

Young children are especially at risk of severe lead poisoning and the long term health effects that come with it. These effects can include permanent intellectual disability, brain damage, and behavioral problems.

You should always try to prevent your child from putting things in their mouth and make sure to keep a clean environment for them to play in. With older houses, it is important to make sure that the house is free of peeling paint as this is a large risk factor.

If you have concerns about lead poisoning or suspect that a person has been exposed, you should see a doctor right away.

Lead poisoning in adults can cause a decrease in mental capacity, including memory loss, as well as difficulty concentrating. It can also cause fertility problems and increased excretion of blood in the urine.

Although lead poisoning is treatable, there are a number of permanent effects that come with it.

You should seek medical attention if you work around lead on a regular basis or if you experience symptoms such as abdominal pain, confusion, constipation, headaches, or trouble concentrating.


Most motorcycle crashes are the result of rider error and not problems with the motorcycle or road conditions. Crashes can result in multiple types of injuries.

These can include traumatic brain injury, spinal cord injury, and fractures. It is important to wear a helmet whenever you ride a motorcycle. This will decrease your risk of head injury if you are in an accident. A helmet should fit tightly on your head and should not move when you try to twist or tilt it.

If you ride a motorcycle, it is important to wear the right gear. This includes a DOT-approved helmet, boots, jacket, pants, gloves and eye protection.

Even if you wear the right gear, you can still get hurt in an accident. If someone else caused the crash, you may be able to get compensation for your medical bills and other losses.

The insurance company will probably try to blame the crash on you. It is important that you find a lawyer who can help you through the details of your case.


Parkinsons disease is a degenerative brain disorder that results in the loss of muscle control. The most common symptoms are tremors, slow movement, rigid posture and difficulty with walking.

The exact cause of parkinsons disease is not known but factors that increase the risk of the disease include age, genetics and environmental toxins. There is no cure for parkinsons disease but symptoms can be managed with medication and therapy.

Parkinsons disease results in a loss of dopaminergic neurons in the substantia nigra region of the brain. These neurons produce a neurotransmitter called dopamine which is responsible for muscle control.

If you have been diagnosed with parkinsons disease you can expect the following symptoms:

Tremor in hands, arms, legs, jaw or tongue.

Muscle stiffness.

Muscle loss.

Difficulty with walking or moving.

Impaired balance and coordination.


If you experience a rapid heart rate that occurs without any physical exertion, you should seek medical attention. While a rapid heartbeat by itself is not life-threatening in most cases, it can be a symptom of other conditions that could cause serious health problems.

There are a number of factors that can cause a rapid heartbeat. These can include smoking, caffeine intake, stress, anxiety and sleep deprivation.

In some cases, an underlying heart condition can be the cause of the rapid heart rate. It is important to determine if the rapid heartbeat is caused by an underlying condition because this condition could become life-threatening without treatment.

A rapid heartbeat from an underlying condition is typically not caused by physical exertion and is usually unrelated to anxiety. It can also occur at rest.

Some of the common causes of a rapid heartbeat include:

Heart problems such as an irregular heartbeat or heart valve disease.

Heart attack.

Heart muscle disease.

If you experience a rapid heartbeat, it is important to see a doctor. The doctor will perform a physical examination and ask you questions about your medical history and your symptoms.

A physical examination will be performed to check for any heart conditions, and you may be given a blood test to check the levels of certain minerals and hormones in your body.

The above medical tests can help determine if you have an irregular heartbeat or a heart problem. In some cases, electrocardiograms and echocardiograms may also be used.

If the cause of the rapid heartbeat is an underlying heart condition, lifestyle changes and medication can help prevent or control further complications. Patients with heart conditions are also advised to quit smoking, reduce stress and maintain a healthy weight.

In some cases, surgery may be necessary to solve the problem.

If the rapid heartbeat is caused by stress or anxiety, behavior therapy and counseling can help ease the symptoms. These techniques can also be used to help prevent the condition from recurring in patients with a history of rapid heartbeat caused by stress or anxiety.

If the rapid heartbeat is caused by an overactive thyroid, hormone-replacement therapy can help alleviate the symptoms. In some cases, surgery may be necessary to remove part of the thyroid gland.

In some cases, a rapid heartbeat is related to a life-threatening condition in which the heart contracts so fast that it stops pumping blood effectively. This condition is called ventricular fibrillation, and the patient will experience sudden paleness, dizziness and nausea.

These patients are in a critical condition and require immediate medical attention to avoid death.


A resting heart rate is the number of heart beats per minute when the body is at rest. This rate is different for everyone and decreases with age.

The average resting heart rate is between 60 to 100 beats per minute. It can increase if a person is anxious or excited.

It can also increase with exercise.

A slow resting heart indicates a calm and relaxed person while a fast resting heart indicates an energetic and excitable person.

When the body is at rest, the heartbeat should be regular. Irregular heartbeats can be caused by a number of factors and should always be discussed with a doctor.

These irregular heartbeats are called arrhythmias.

Some factors that can cause an irregular heartbeat include:

1. Stress

2. Aneurysm

3. High blood pressure

4. Congenital heart defect

5. Electromagnetic fields

6. Drinking alcohol

7. Pregnancy

8. Certain drugs such as cocaine, caffeine, nicotine, ephedrine and excessive consumption of tea, coffee and energy drinks

The most common cause of an irregular heartbeat is high blood pressure, which should be controlled through a healthy diet and regular exercise. An ECG (electrocardiogram) can help determine if high blood pressure is the cause of an irregular heartbeat.

Sources & references used in this article:

Biological rhythms and the behavior of populations of coupled oscillators by AT Winfree – Journal of theoretical biology, 1967 – Elsevier

A survey on biological rhythms by J Aschoff – Biological rhythms, 1981 – Springer

Biological rhythms and animal behavior by B Rusak, I Zucker – Annual review of psychology, 1975 – annualreviews.org

Light, timing of biological rhythms, and chronodisruption in man by TC Erren, RJ Reiter, C Piekarski – Naturwissenschaften, 2003 – Springer

Handbook of behavioral neurobiology. Volume 4. Biological rhythms. by J Aschoff – 1981 – cabdirect.org

Food availability and daily biological rhythms by Z Boulos, M Terman – Neuroscience & Biobehavioral Reviews, 1980 – Elsevier

Cycles of Nature. An Introduction to Biological Rhythms. by A Ahlgren, F Halberg – 1990 – ERIC

Social zeitgebers and biological rhythms: a unified approach to understanding the etiology of depression by CL Ehlers, E Frank, DJ Kupfer – Archives of general psychiatry, 1988 – jamanetwork.com

Biological rhythms in terrestrial arthropods by AS Danilevsky, NI Goryshin… – Annual review of …, 1970 – annualreviews.org