The respiratory rate and depth of inspiration are regulated by the oblong marrow and pons; However, these brain regions do this in response to systemic stimuli. It is a dose-response relationship, a positive feedback relationship in which the larger the stimulus, the greater the response. Thus, the increase in stimuli leads to forced breathing. Several systemic factors are involved in stimulating the brain to create pulmonary ventilation. Breathing usually occurs without thinking, although sometimes you can control it consciously, like. B when swimming underwater, singing a song or blowing bubbles. Respiratory rate is the total number of breaths or breathing cycles that occur each minute. Respiratory rate can be an important indicator of a disease, as it can increase or decrease during an illness or in a medical condition. Respiratory rate is controlled by the respiratory center in the elongated marrow of the brain, which mainly reacts to changes in the levels of carbon dioxide, oxygen and pH in the blood. Then the breathing movements during heavy or laborious breathing are described. During deep breathing, the external intercostal muscles and diaphragm work as hard as possible, while a number of other muscles called accessory respiratory muscles help. Accessory respiratory muscles that support the work of the external intercostal muscles include the scalene, sternocleidomastoid, levatores costarum, leectoral major and pectoral minor. These contract during inspiration to widen the ribs.
The elevation of the ribs is also supported by the erector muscles of the spine, which bend the spine in the posterior direction. Accessory respiratory muscles that act during breathing include the internal intercostal and abdominal muscles. The effect of the abdominal muscles is much greater than that of the internal intercostal muscles. Ventilation control is a complex interaction of several brain regions that signal that the muscles used in pulmonary ventilation are contracting (Table 2). The result is usually a rhythmic and uniform aeration rate that provides the body with sufficient amounts of oxygen while sufficiently removing carbon dioxide. The main inspiratory muscles are the diaphragm and the external intercostal muscles. The normal relaxed procedure is a passive process that occurs due to the elastic recoil of the lungs and surface tension. However, some muscles help with vigorous drainage and include the internal intercostals, the intimidating intercostalis, the subcostals, and the abdominal muscles.  These muscles have exactly the same basic structure as all other skeletal muscles and work together to dilate or compress the chest cavity.  There are different types or modes of breathing that require a slightly different process to allow for inspiration and decomposition.
Calm breathing, also known as eupnea, is a type of breathing that occurs at rest and does not require the individual`s cognitive thinking. With calm breathing, the diaphragm and external intercostals should contract. Both sternocleidomastoideus muscles originate from the mastoid process of the temporal bone and the upper line of the neck of the occipital bone. By attaching them to the manubrium, that is, to the sternum, via their sternal head and to the collarbone via their collarbone head, these muscles can lift the bones and then lift the front ribs. Therefore, they are used as accessory muscles in pulmonary ventilation. Breathing is something most of us take for granted, and the muscles and mechanisms involved in this life-sustaining process are often overlooked. Some muscles are responsible for dilating the chest cavity and sucking air into the lungs. Others are responsible for the collapse of the chest cavity and the expulsion of air from the lungs. These muscles can be divided into a primary group and a secondary group. The primary muscles are the diaphragm and the intercostal. The secondary muscles are the sternocleidomastoid, scalenes and minor pectorals. After all, the abdominal muscles contribute to the process of deep breathing.
Respiratory system: When the diaphragm relaxes, the pleural cavity contracts, which puts pressure on the lungs, which reduces the volume of the lungs because the air is passively pushed out of the lungs. Although the chest provides a resilient but flexible framework, it would be impossible for you to breathe without the action of the chest muscles. More details are given below, but ventilation is done by stretching and contracting the lungs. One way to do this is to change the anteroposterior diameter of the chest cavity by lifting or pressing on the ribs. The main muscles that lift the chest are the external intercostal muscles. These muscles are part of the intercostal muscle group, which is located in the intercostal spaces between the ribs. The outer intercostals are the most superficial layer of this group, while the other two deeper layers are the inner intercostal layers and the innermost intercostals. There are 11 pairs of external intercostals that extend between the tubers of the ribs and the costochondral joints. They run in an infero-anterior direction between the edges of two adjacent ribs. Competing forces in the chest cause the formation of negative intrapleural pressure. One of these forces refers to the elasticity of the lungs themselves – the elastic tissue pulls the lungs inward, away from the chest wall.
The surface tension of the alveolar fluid, which is mainly water, also creates inward pulling of the lung tissue. This tension of the lungs that turns inwards is counteracted by opposing forces of the pleural fluid and the chest wall. The surface tension inside the pleural cavity pulls the lungs outward. Too much or too little pleural fluid would hinder the development of negative intrapleural pressure; Therefore, the level must be closely monitored by mesothelial cells and drained by the lymphatic system. Since the parietal pleura is attached to the chest wall, the natural elasticity of the chest wall counteracts the inward attraction of the lungs. Ultimately, the outward pull is slightly greater than the inward-facing traction, creating an intrapleural pressure of –4 mm Hg relative to the intraalveolar pressure. Transpulmonary pressure is the difference between intrapleural and intraalveolar pressure and determines the size of the lungs. A higher transpulmonary pressure corresponds to a larger lung.
As already mentioned, there is a surface tension in the alveoli caused by the water present in the mucosa of the alveoli. This surface tension tends to inhibit the expansion of the alveoli. However, the pulmonary surfactant secreted by type II alveolar cells mixes with this water and helps reduce this surface tension. Without pulmonary surfactant, the alveoli would collapse on exhalation. Calm breathing: (also eupnea) a type of breathing that occurs at rest and does not require the individual`s cognitive thinking During exercise, however, many other muscles become important for breathing. During inspiration, the outer intercostals lift the lower ribs upwards and outwards, increasing the lateral and anteroposterian dimensions of the thorax. Dandruff muscles and sternomastoids are also involved and serve to lift and push the upper ribs and sternum. They are of three types: the external intercostal muscles (the most superficial muscle of the intercostal muscles), the internal intercostal muscles and the innermost intercostal muscles. Exhalation begins at the end of inhalation. Just as the increase in the negative pressure of the lung cavity during inhalation leads to an aerial view, the pleural cavity contracts during exhalation (due to the relaxation of the diaphragm), which puts pressure on the lungs and makes the pressure inside the cavity less negative. An increase in pressure leads to a decrease in volume in the lungs and air is pushed into the airways when the lungs return to their smallest size.
The pleural cavity is so important for breathing because its pressure changes the volume of the lungs and provides the lungs with a frictionless space where it can expand and contract during breathing. To initiate breathing, the dorsal respiratory group sends impulses through the phrenic nerve to the diaphragm and through the intercostal nerves to the external intercostal muscles. In order for drainage to take place, the group of dorsal airways stops triggering impulses so that the muscles can relax. .