Human Biological Clock

The picture above is a diagram of the human biological clock that I got from Wikipedia. I think is very important to know. Activities that we do on the right biological clock would be more efficient and quality. Even this will affect our health tremendously. For example, if we reverse use to work night and day to sleep, believe me, your face will look like a zombie. That’s not good thing, right?
Here, I’m not going to explain many things about this cycle. I believe just by looking at the picture above you already know what it is the human biological clock. For those of you who might be a little confused by some of terms in the picture, I will try to help by giving some definitions that I got from several resources.

Human Biological Clock is a roughly 24-hour cycle in the biochemical, physiological or processes of living entities, including plants, animals, fungi and cyanobacteria.

Melatonin also known chemically as N-acetyl-5-methoxytryptamine, is a naturally occurring compound found in animals, plants, and microbes. In animals, circulating levels of melatonin vary in a daily cycle, thereby regulating the circadian rhythms of several biological functions. Many biological effects of melatonin are produced through activation of melatonin receptors, while others are due to its role as a pervasive and powerful antioxidant, with a particular role in the protection of nuclear and mitochondrial DNA. Production of melatonin by the pineal gland is inhibited by light and permitted by darkness. For this reason melatonin has been called "the hormone of darkness" and its onset each evening is called the Dim-Light Melatonin Onset (DLMO). Secretion of melatonin as well as its level in the blood, peaks in the middle of the night, and gradually falls during the second half of the night, with normal variations in timing according to an individual's chronotype. Besides its function as synchronizer of the biological clock, melatonin also exerts a powerful antioxidant activity. The discovery of melatonin as an antioxidant was made in 1993. In many lower life forms, it serves only this purpose. Melatonin is an antioxidant that can easily cross cell membranes and the blood-brain barrier. Melatonin is a direct scavenger of OH, O₂⁻, and NO. Unlike other antioxidants, melatonin does not undergo redox cycling, the ability of a molecule to undergo reduction and oxidation repeatedly. Redox cycling may allow other antioxidants (such as vitamin C) to regain their antioxidant properties. Melatonin, on the other hand, once oxidized, cannot be reduced to its former state because it forms several stable end-products upon reacting with free radicals. Therefore, it has been referred to as a terminal (or suicidal) antioxidant.While it is known that melatonin interacts with the immune system, the details of those interactions are unclear. There have been few trials designed to judge the effectiveness of melatonin in disease treatment. Most existing data are based on small, incomplete clinical trials. Any positive immunological effect is thought to result from melatonin acting on high affinity receptors (MT1 and MT2) expressed in immunocompetent cells. In preclinical studies, melatonin may enhance cytokine production, and by doing this counteract acquired immunodeficiences. Some studies also suggest that melatonin might be useful fighting infectious disease including viral, such as HIV, and bacterial infections, and potentially in the treatment of cancer.Some supplemental melatonin users report an increase in vivid dreaming. Extremely high doses of melatonin (50 mg) dramatically increased REM sleep time and dream activity in both people with and without narcolepsy. Many psychoactive drugs, such as cannabis and lysergic acid diethylamide (LSD), increase melatonin synthesis. It has been suggested that nonpolar (lipid-soluble) indolic hallucinogenic drugs emulate melatonin activity in the awakened state and that both act on the same areas of the brain.Individuals with autism spectrum disorders (ASD) may have lower than normal levels of melatonin. A 2008 study found that unaffected parents of individuals with ASD also have lower melatonin levels, and that the deficits were associated with low activity of the ASMT gene, which encodes the last enzyme of melatonin synthesis. 

Testosterone is a steroid hormone from the androgen group. In mammals, testosterone is primarily secreted in the testes of males and the ovaries of females, although small amounts are also secreted by the adrenal glands. It is the principal male sex hormone and an anabolic steroid. Testosterone is evolutionarily conserved through most vertebrates, although fish make a slightly different form called 11-ketotestosterone. 

Cardiovascular: The circulatory system comprising the heart and blood vessels which carries nutrients and oxygen to the tissues of the body and removes carbon dioxide and other wastes from them.