Tag: zoology

During inspiration external intercoastal muscles and diaphragm contract because it allows air to be moved into the lungs and requires the contraction of various musceles; the diaphragm and external intercoastal muscles contract.

Inspiration is primarily initiated by the contraction of the diaphragm, which increases the thoracic cavity volume vertically.

Sum of the partial pressure of all gases is 760 mm of Hg.

The amount gases in exhaled air are 4% to 5% by volume more carbon dioxide and 4% to 5% by volume less oxygen than was inhaled. This expired air typically composed of: 78.04% nitrogen; 13.6% - 16% oxygen; 4% - 5.3% carbon dioxide; 1% other gases.

When the diaphragm relaxes, air is exhaled by elastic recoil of the lung and the tissues lining the thoracic cavity in conjunction with the abdominal muscles which act as an antagonist paired with the diaphragm's contraction. The internal intercostals assist in expiration by pulling the ribcage down.

When we breathe in, or inhale, the diaphragm contracts (tightens) and moves downward. This increases the space in the chest cavity, into which the lungs expand. The intercostal muscles between the ribs also help enlarge the chest cavity. They contract to pull the rib cage both upward and outward when we inhale. As the lungs expand, air is sucked in through the nose or mouth. The air travels down the windpipe and into the lungs. After passing through the bronchial tubes, the air finally reaches and enters the alveoli (air sacs).

Carbon dioxide can bind to plasma proteins or can enter red blood cells and bind to hemoglobin. This form transports about 10 percent of the carbon dioxide. When carbon dioxide binds to hemoglobin, a molecule called carbaminohemoglobin is formed. Binding of carbon dioxide to hemoglobin is reversible. Therefore, when it reaches the lungs, the carbon dioxide can freely dissociate from the hemoglobin and be expelled from the body. About 30% of CO$ _2$ is transported as carbamino haemoglobin. 

Internal respiration refers to gas exchange across the respiratory membrane in the metabolizing tissues. External respiration refers to gas exchange across the respiratory membrane in the lungs. Pulmonary ventilation is the process by which oxygen enters and carbon dioxide exits the alveoli. Respiration is the process by which oxygen and carbon dioxide diffuse in and out of the blood. 

What most people don’t know is that it is, in fact, the level of CO$ _2$ rather than oxygen that usually drives breathing rate. Your body’s ability to detect specific concentrations of CO$ _2$ is extremely sensitive. If the level of CO$ _2$ in your blood increases by a mere 10%, your rate of breathing will double. The answer comes from the way CO$ _2$ is transported. Instead of being bound to hemoglobin, the CO$ _2$ mostly just dissolves in your blood. When the CO$ _2$ dissolves, it combines with the water in your blood to form carbonic acid. As this acid builds up, it dramatically decreases the pH of your blood, throwing it out of balance. Your brainstem detects this pH change, and speeds up your breathing rate in order to to get rid of the extra CO$ _2$.