HOW ORGAN SYSTEMS WORK TOGETHER
To get an idea of how various body systems work together to accomplish a common activity, consider the complex orchestration that occurs every morning when we wake up and eat breakfast. While asleep, the major organ systems are already working in concert, albeit at a low, basal level. The circulatory band pulmonary systems are providing the oxygen and other nutrients needed by every cell to function.
Together, the complex communications networks of the endocrine and nervous systems are regulating heart rate, blood pressure, body tempreture, and other involuntary or autonomic processes. Metabolism continues at a slowed pace, involving virtually every body organ. As down approaches, the body begins to wake up. Complex circadian rhythms accelerate; hormone levels change; sleep becomes lighter; heart and respiratory rates begin to increase. Finally, we awaken, somtimes prompted by an alarm clock but often without any external stimuli. Since it has been 8 or more hours since our last meal, one of the first things we feel is hunger.
The appetite centre, located in the hypothalamus area of the brain, works through an intricate feedback system involoving hormones, nerves, and sensory organs to ensure that we eat enough. It’s also usual to awaken to a full bladder. The nervous system conveys the message that the bladder is full, prompting the urge to urinate. To ensure that this urge doesn’t awaken us in the middle of the night, the kidneys process fluid differently while we sleep so that the urine is concentrated and therefore of lower volume. That’s why morning urine is darker in colour than that produced while we’re awake.
Even before breakfast is on the table, the major sense organs – the eyes, ears, nose, and then the tongue and mouth – begin preparing the body to receive food. The aroma of, say, eggs sizzling in a frying pan reaches the mucous membranes lining the nose and stimulates olfactory nerve receptors, which transmit the impulse to the brain, where it is recognised as an odor and even just the thought of food, the brain, working through the endocrine and nervous systems, transmits mesages to glands in the mouth and stomach, which increase the flow of digestive juices in anticipation.
The message also may prompt a physical response; if the smell says the eggs are burning, we quikly act (requiring the coordinated effort of the nervous ands muscvle sstems) to remove the pan from the stove. If the pan handle is too hot, the nerve endings in the skin trigger an automatic protective reaction; wothout thionking, the hand is jerked from the pan even before the pain sensation is perceived.
The sense of hearing also comes into play. Familiar sounds associated with a meal, for example, juice being poured into a glass or cereal into a bowl, are carried as vibrations through the outer ear and then finally to the brain, where the sound is perceived and registered. If the sound says the coffee is boiling over, the body responds with a coordinated, concious action: we turn off the coffeepot.
Sight is yet another important sensory. It response in readying the body for a meal. Light from an object such as a glass of juice, strikes the lens of the eye and is directed to the retina. The impulse generated by the retina travels along the optic nerve to the brain, where it is perceived. If the image shows a favourite food, our appetitecentre and digestive system will be further stimulated.
With the first bite of breakfast, two of our senses are stimulated; taste and touch. In the mouth, food comes in contact with the tiny taste buds on the tongue, nerve receptors in these taste organs are transmitted to the brain. All the taste sensations of only four basic responses: sweet, sour, salty or bitter, these plus the food’s odor produce its unique and recognizable flavour.
Touch is also involoved in eating. As the food touches nerve endings in the tongue and palate, its texture and tempreture further stimulate circulation of blood in the entire digestive system and also help increase the secretion of digestive enzymes.
In a marvelously coordinated, highly complex process that requires little or no concious effort aside from chewing or swallowing, our breakfast is transformed into the fuel and other nutroents required by all of our individual cells. Along the way, our food passes through distinctive body structures.