Why do We Respire?

Every part of our body undoubtedly needs oxygen for our survival. Everyday functions of our body, such as moving the muscles, digesting the food, or even thinking that the body needs oxygen. When these processes occur, as a waste product, carbon dioxide is produced. Our lungs' job in this entire system is to get rid of the waste gas, carbon dioxide, and provide these processes with oxygen.

Our brains continually get signals from our bodies that detect the amount of oxygen and carbon dioxide in our blood. Also, our brain will pass signals to the muscles involved in breathing and adjust our breathing rate based on how active we are.

When we're active, our breathing can increase to about 40-60 times in a minute to cope with the additional demand. The delivery of oxygen to our muscles also speeds up, and by doing so, they can perform their job efficiently. Also, the increase in our breathing makes sure there's no carbon dioxide build-up in our bloodstream.

How do We Respire?

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Healthy lung tissue is elastic and springy, so, our muscles need to work to expand our chest and draw air into the lungs.

The respiratory centre signals in our brain travel down nerves to the diaphragm and other muscles. The diaphragm is flat pulled, pushing out the lower ribcage and abdomen. Similarly, the muscles between our ribs pull the rib cage up and out. This makes the chest expand and draws air into the lungs.

Air is pulled into our mouth or nose and the windpipe. This divides into airways supplying the right and left lungs. The air then passes down the airways, which divide another 15 to 25 times, and finally into the thousands of smaller airways until the air reaches the air sacs.

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Breathing out is mostly a passive process in the rest position. The muscles we use to breathe in now relax, and our elastic lungs push the air out. When we exercise, and the body needs to move air more quickly, our abdominal muscles provide the main drive for exhaling, and also, the intercostal muscles help.

The system works so that we comfortably breathe in and out at rest, where minimal effort is required to move air, and we're not probably conscious of our breathing. When we exercise, we need to move excess air. To do this, we can take bigger breaths or breathe more promptly, or both usually.

Although breathing is automatic, we can control it if we want to, for example, when we sing or talk.

Why do We Respire?

We know that all organisms are made of small microscopic units known as cells. The cell is the smallest functional and structural organism’s unit. Each organism cell performs specific functions such as transport, nutrition, excretion, and reproduction. The cell needs some energy to perform these functions. Even when we are eating, reading, or sleeping, we require energy.

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But, the ultimate question is, where does all this energy come from? Can we say why our parents insist that we should eat regularly? The food has stored energy released at the time of respiration. Thus, all living organisms respire to get energy from food. 

During breathing, we breathe in the air. We also know that air contains oxygen. The air we release is rich in carbon dioxide. Whereas the air we respire in (oxygen-rich) is transported to all the body parts and each cell ultimately. For the cells, oxygen present in the air helps in the food breakdown. This breakdown process of food in the cell with the release of energy in the form of ATP is known as cellular respiration. Cellular respiration occurs in the cells of all organisms.

In the cell, the food or glucose is broken down into carbon dioxide and water using oxygen. When the breakdown of glucose occurs with the use of oxygen, it is known as aerobic respiration. The food can also be broken down, in the absence of oxygen. This method is called anaerobic respiration. Breakdown of food will release energy.

Glucose   \[\overset{\text{With the use of Oxygen}}{\rightarrow}\]   Carbon dioxide + Water + Energy

We also should know, there are a few organisms like yeast that can survive in the absence of air. They are known as anaerobes. They get energy via anaerobic respiration. In the lack of oxygen, the glucose breaks down into carbon dioxide and alcohol, as represented in the below chemical equation.

Glucose \[\overset{\text{With the use of Oxygen}}{\rightarrow}\] Alcohol + Carbon dioxide + Energy

Also, our muscle cells can respire anaerobically, but only for less time, when there is a temporary deficiency of oxygen. During fast running, cycling, heavy exercises, heavy weightlifting, or walking for many hours, the energy demand is high. But the oxygen supply to produce the energy will be limited. Then, anaerobic respiration occurs in the muscle cells to fulfil the demand of energy as given in the below chemical equation.

Glucose \[\overset{\text{In the absence of Oxygen}}{\rightarrow}\] Lactic Acid + Energy

In Muscles

We might have wondered why we get muscle cramps after heavy exercise? It is because the cramps occur when muscle cells anaerobically respire. The partial breakdown of glucose forms lactic acid. The accumulation of lactic acid causes muscle cramps. We get relief from cramps either after a massage or a hot water bath. It is so because the massage or hot water bath improves blood circulation. Resultantly, the oxygen supply to the muscle cells increases. This results in the complete breakdown of lactic acid into water and carbon dioxide.

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The Process of Respiration

Respiration is the process of getting oxygen into the body and releasing carbon dioxide, whereas, breathing is only the movement of oxygen into the body and carbon dioxide out of the body. The process of respiration also includes the exchange of oxygen and carbon dioxide between the blood and the cells of the body.

The cells in our body need oxygen to create energy efficiently. The cells when they  create energy, however, make carbon dioxide. We get oxygen by breathing in the fresh air, and we remove carbon dioxide from the body by breathing out stale air. The blood also gives the carbon dioxide a ride back to the lungs. All the living things perform respiration of some kind that keeps them alive. 

Respiration in Animals

Different organisms have different respiratory systems. Some of the examples are: 

• Through Plasma Membrane: In unicellular animals, such as amoeba, the exchange of gases takes place through the cell surface.

• Through Body Wall or Skin: Tapeworms, earthworms, and leeches use their skin for the exchange of gases.

• Through the Tracheal System: Insects, centipedes and arachnids.

• Through Gills: Fishes 

• Through lungs: Human beings