The Physiology of the Lungs. The brain

The Physiology of the Lungs

The physiology of the lungs is associated with their structure. There are over700, 000, 000 alveoli in the lungs.

The total surface of the alveoli is about 90 sq. m (square metres). Elastic fibers of connective tissue enable the lungs to dilate. When one breathes normally not all the alveoli and capillaries of the lungs are opened. When respiration becomes deep, the number of the opened alveoli and capillaries increases. In the adult the vital capacity of the lungs is about 3-4 litres. When the depth of respiration increases the vital capacity may be 6 litres and even more. The lungs take part in the production of physiologically in the metabolism of proteins, fats and carbohydrates.

The brain

The brain is the most complicated mechanism. The weight of the human brain is from one to two kg (kilograms). It has a volume of only about 3. 21 litres, but it consists of about 12 billion cells. The brain is the centre of a wide system of communication. The stimuli comes into the brain through the spinal cord. The stimuli come to the brain from our eyes, ears, and other sense organs for pain, temperature, smell and other feelings. The brain sends orders through the nerve fibers in the spinal cord to different parts of the human body. It is due to these orders that one eats, moves, hears, sees and does many other things. That the motor cortex becomes tired rapidly. The hypothalamus is almost never tired.

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