Earth Science: Human beings
The human body is an exquisitely complex mechanism. Its tissues and organ systems constantly work together to carry out the functions necessary to support life. The body’s form and function are the result of a long evolutionary process, which is still ongoing today.
We perceive our environment through our sense organs.
Stimuli reaching our eyes, ears, nose, skin, and tongue are translated into electrical nerve impulses and sent along to the brain. Far more flexible and powerful than any artificial intelligence system, the human brain processes a vast range of stimuli, organizes our thoughts and behavior, and coordinates our bodily functions.
Thanks to increasingly refined imaging technologies, scientists can now observe the activity in various brain regions during dreams, intense emotions, and sensations of pain. An intricate network of nerves branching out from the brain and spinal cord coordinates our muscles, joints, and bones to produce both consciously and unconsciously directed movements, such as breathing, facial expressions, or sports activity.
The musculoskeletal system gives the body form and stability, while also helping to protect the sensitive internal organs. Alongside the nerves, other systems serve to ensure balance and harmony among different parts of the body. An arsenal of hormones and messenger substances coordinates the complex processes of growth, reproduction, and everyday metabolism.
All of this requires energy, which is provided by our food and made available by the digestive system. Nutritional substances enter the bloodstream over the convoluted surface of the small intestine. The blood supplies all of the body’s cells with energy from food, while also transporting life-giving oxygen, which we breathe in through our lungs.
The blood and lymphatic vessels also help the body dispose of carbon dioxide and other waste products. Through the lungs, liver, kidneys, skin, and intestine, they are metabolized and excreted from the body. Improved living conditions and the enormous advances in medical science have led to significant extensions of the human lifespan in the industrialized world.
This progress has come at a price, however; as the body ages, its genetic and biochemical repair systems function less effectively, and tissues and organs begin to deteriorate. “Diseases of civilization,” such as an unhealthy diet, obesity, lack of exercise, and substance abuse, also prevent the body from functioning optimally.
Among the elderly in wealthy countries, numerous medical conditions, such as diabetes, arthritis, circulatory problems, and even cancer, are appearing more frequently.