What physiological processes in the human body change during the day?

Changes in the intensity of vital processes occurring in the body are called biological rhythms.
Their example is daily rhythms. An important role in them is played by a change in illumination. The organs of vision perceive light signals and send them to the hypothalamus, which performs complex coordination of the functions of internal organs. In turn, the hypothalamus is associated with the pituitary gland – the main regulator of the endocrine glands. As a result of interaction, the work of many organs is changing. In habitats where light does not penetrate, changes in illumination have almost no effect on the body.
More than 300 physiological processes in humans are subject to daily rhythms. Their intensity is most maximum in the daytime and minimal at night. One of the main ones is the rhythm of body temperature, as it determines the metabolic rate. By the end of the day, a person has a maximum frequency, depth and volume of breathing, the contractile function of the heart muscle reaches its highest values. Blood circulation is most intense during the day in the brain and muscles, and at night in the vessels of the hands and feet. The bone marrow is most active in the morning, so in the morning hours the largest number of young red blood cells enters the bloodstream. Daily rhythms are associated with the work of the stomach, liver, kidneys, etc.

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