Among the most important features of the human body that we must be aware of is homeostasis.
Homeostasis is not a collection of organs, but a synthesis of bodily functions that collectively keeps the entire body stable. In order to keep homeostasis at optimum it must have access to an adequate supply of energy.
Our body’s energy comes from the sun. We can take energy directly from it or from any of its storage media, e.g. farm produce, seafoods, water.
In order to keep our body’s health at optimum, we need to maintain a sense of balance between energy acquisition and utilization. An oversupply of energy could affect the whole system just the same as the inadequacy of it. Overworking or excessive stress is another.
The types of food that we eat should not only provide the energy but must strike a balance between acidity and alkalinity, too. This is obviously hard to accomplish for the fast food fanatics, but that is plain, hard truth, i.e. fast food stuffs are not healthy. However, you cooked it, homemade meals are still better.
The amount of water that our body must be nourished with should not fall below a level which hampers the liver and kidneys from flushing those toxins out. Please refer to our homepage for the minimum amounts.
Being conscious of what we do and take in make homeostasis perform a lot better. And when it is functioning properly, the chemical balance would surely reflect into our positive physical and psychological dispositions.
But the most important thing to understand is that homeostasis itself will do the balancing act internally for you, and you don’t need to be an “expert” or you don’t need to know exactly how it’s done. It’s completely automatic just like your own auto-immune system.
But as always, it is to your advantage that you have some level of understanding what it is.
What is homeostasis?
January 3, 2000
Emeritus Professor Kelvin Rodolfo of the University of Illinois at Chicago’s Department of Earth and Environmental Sciences provides this answer:
Homeostasis, from the Greek words for “same” and “steady,” refers to any process that living things use to actively maintain fairly stable conditions necessary for survival. The term was coined in 1930 by the physician Walter Cannon. His book, The Wisdom of the Body, describes how the human body maintains steady levels of temperature and other vital conditions such as the water, salt, sugar, protein, fat, calcium and oxygen contents of the blood. Similar processes dynamically maintain steady-state conditions in the Earth’s environment.Homeostasis has found useful applications in the social sciences. It refers to how a person under conflicting stresses and motivations can maintain a stable psychological condition. A society homeostatically maintains its stability despite competing political, economic and cultural factors. A good example is the law of supply and demand, whereby the interaction of supply and demand keeps market prices reasonably stable.
Homeostatic ideas are shared by the science of cybernetics (from the Greek for “steersman”), defined in 1948 by the mathematician Norbert Wiener as “the entire field of control and communication theory, whether in the machine or in the animal.” Cybernetic systems can “remember” disturbances and thus are used in computer science to store and transmit information. Negative feedback is a central homeostatic and cybernetic concept, referring to how an organism or system automatically opposes any change imposed upon it.
For example, the human body uses a number of processes to control its temperature, keeping it close to an average value or norm of 98.6 degrees Fahrenheit. One of the most obvious physical responses to overheating is sweating, which cools the body by making more moisture on the skin available for evaporation. On the other hand, the body reduces heat-loss in cold surroundings by sweating less and reducing blood circulation to the skin. Thus, any change that either raises or lowers the normal temperature automatically triggers a counteracting, opposite or negative feedback . Here, negative merely means opposite, not bad; in fact, it operates for our well being in this example. Positive feedback is a response to change from the normal condition that increases the departure even more.
For example, if a person’s temperature is raised to about 107 degrees Fahrenheit, the negative feedback systems stop operating. A person with a high fever has hot, dry skin if they do sweat to help cool it. Not only have the negative feedback systems shut down in such a case; the increased temperature speeds up the body chemistry, which causes the temperature to rise even more, which in turn speeds up the body chemistry even more, and so forth. This vicious cycle of positive feedback, a “runaway” process, can only end in death if not stopped.
It is important to emphasize that homeostatic reactions are inevitable and automatic if the system is functioning properly, and that a steady state or homeostasis may be maintained by many systems operating together. For example, flushing is another of the body’s automatic responses to heating: the skin reddens because its small blood vessels automatically expand to bring more heated blood close to the surface where it can cool. Shivering is another response to chilling: the involuntary movements burn body tissue to produce more body heat.
Negative feedback arises out of balances between forces and factors that mutually influence each other. To illustrate several of its important characteristics, we can regard a car and its driver as a unified, complex, homeostatic or “goal-seeking” system–a cyborg, or “cybernetic organism,” in that it seeks to keep the car moving on track. The driver does not steer by holding the wheel in a fixed position but keeps turning the wheel slightly to the left and right, seeking the wheel positions that will bring the naturally meandering car back on track. Disturbance, or departure from equilibrium, is every bit as important as negative feedback: Systems cannot correct themselves if they do not stray.
Oscillation is a common and necessary behavior of many systems. If the car skids, the driver automatically responds by quickly steering in the opposite direction. Such abrupt negative feedback, however, usually over-corrects, causing the car to move toward the other side of the road. A negative feedback, if it is as large as the disturbance that triggered it, may become an impressed change in the direction opposite to that of the original disturbance. The car and driver recovers from the skid by weaving from side to side, swerving a little less each time. In other words, each feedback is less than the last departure from the goal, so the oscillations “damp out.” Negative feedback takes time and such a time lag is an essential feature of many natural systems. This may set the system to oscillating above and below the equilibrium level.
Cells depend on the body environment to live and function. Homeostasis keeps the body environment under control and keeps the conditions right for cells to live and function. Without the right body conditions, certain processes (eg osmosis) and proteins (eg enzymes) will not function properly.
Why is homeostasis important for cells?
Living cells depend on the movement of chemicals around the body. Chemicals such as oxygen, carbon dioxide and dissolved food need to be transported into and out of cells. This is done by the processes of diffusion and osmosis, and these processes depend on the body’s water and salt balance, which are maintained by homeostasis.
Cells depend on enzymes to speed up the many chemical reactions that keep the cell alive and make it do its job. These enzymes work best at particular temperatures, and so again homeostasis is vital to cells as it maintains a constant body temperature.
Particles in liquids and gases move about randomly in all directions.
In an area of high concentration, particles will escape from the concentrated area to places where there are fewer or no particles. Very few particles leave an area of low concentration to go to an area where the concentration is higher.
Diffusion is the movement of particles from an area of high concentration to an area of low concentration. This is described as moving down a concentration gradient.
Examples of diffusion
Here are some examples of diffusion across concentration gradients:
Examples of diffusion in the body
Particles which move
digested food products
blood in capillary of villus in small intestine
air spaces between mesophyll cells
alveolar air space
blood circulating around the lungs
blood circulating around the lungs
alveolar air space
Homeostasis maintains the correct body conditions in order for diffusion to take place.
Remember: Particles continue to move from a high to a low concentration until all the particles are evenly and randomly distributed.
Diffusion in the lungs
In the lungs, the blood will continue to take in oxygen from the alveolar air spaces, provided there is more oxygen in the air spaces than in the blood. The oxygen diffuses across the alveolar walls into the blood. The circulation takes the oxygen-rich blood away and replaces it with blood that is low in oxygen.
In the exam, you may be asked to give two examples of diffusion in organisms. Make sure you know an example from plants as well as from animals.
Osmosis is simply a special type of diffusion. It occurs when water molecules pass through a partially permeable membrane.
Some membranes in plant and animal cells allow certain particles to pass through them but not others. They are partially permeable membranes.
During osmosis, more water molecules pass from the pure water into the dilute solution than pass back the other way. This is because there is a higher concentration of water molecules in the pure water than in the solution. This results in more water molecules diffusing across the concentration gradient from the water to the solution. Eventually, the level on the more concentrated side of the membrane will rise, while that on the less concentrated side falls.
Osmosis is the overall movement of water from a dilute solution to a more concentrated solution through a partially permeable membrane. This is still like diffusion, as the water is moving from a higher concentration of water to a lower concentration of water.
When the concentration of water is the same on both sides of the membrane, the movement of water will be the same in both directions. At this point, the net exchange of water is zero, and the system is in equilibrium.
If red blood cells are placed in pure water, water enters them by osmosis and the red blood cells swell up and burst.
If cells are placed in a concentrated solution, water leaves them by osmosis and they are unable to function.
Enzymes are proteins that speed up chemical reactions in our cells.
Enzymes work best at their optimum temperature. This is why homeostasis is important – to keep our body temperature at a constant 37°C.
As the temperature increases, so does the rate of chemical reaction. This is because heat energy causes more collisions, with more energy, between the enzyme molecules and other molecules. However, if the temperature gets too high, the enzyme is denatured and stops working.
A common error in exams is to write that enzymes are killed at high temperatures. Since enzymes are not living things, they cannot be killed.
Graph showing the effect of temperature on enzyme reactions
One enzyme – one job
Enzymes are specific. Only molecules with the correct shape can fit into the enzyme. Just like only one key can open a lock, only one type of enzyme can speed up a specific reaction. This is called the lock and key model.
The important part of an enzyme is called the active site. This is where specific molecules bind to the enzyme and the reaction occurs.
Anything that changes the shape of the active site stops the enzyme from working. This is similar to a key that opens a door lock. It does not matter what a key handle looks like, but if you change the shape of the ‘teeth’ the key no longer works.
The shape of the active site is affected by pH. This is why enzymes will only work at a specific pH, as well as a specific temperature. Change the pH and the enzyme stops working.
Increasing the temperature to 60°C will cause a permanent change to the shape of the active site. This is why enzymes stop working when they are heated. We say they have become denatured.
Active transport – Higher
Active transport is the process by which dissolved molecules move across a cell membrane from a lower to a higher concentration. In active transport, particles move against the concentration gradient – and therefore require an input of energy from the cell.
Sometimes dissolved molecules are at a higher concentration inside the cell than outside, but, because the organism needs these molecules, they still have to be absorbed. Carrier proteins pick up specific molecules and take them through the cell membrane against the concentration gradient.
In humans, active transport takes place during the digestion of food in the small intestine. Carbohydrates are broken down into simple sugars such as glucose. The glucose is absorbed by active transport into the villi, to be passed into the bloodstream and taken around the body.
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