Breathing and Asthma



Breathing and Asthma

Question 1

a) Effects on His Mechanics of Breathings

Firstly, breathing is not something we have to consciously remember to do. Respiration is controlled by nerve cells in the reticular formation of the brain stem (the main concentration of these is in the medulla). These cells send impulses down the spinal cord and then via the phrenic nerve to the diaphragm and via the Intercostal nerves to the Intercostal muscles (Garg, 2005).

Air is drawn into the body as a result of the contraction of the diaphragm and external intercostal muscles (and consequent fall in air pressure in the lungs) This results in the ribs moving upwards and outwards, with the sternum moving upwards and forwards. As the air passes through the nasal cavity it is warmed, moistened and cleaned by the various paranasal sinuses, it then passes through the pharynx (throat) on its way to the respiratory passageways. The main passageway is the trachea (the windpipe) which takes the air into the lungs (the bronchi)

As this is happening, the chest (thorax) expands in three directions. This sees the lungs expanding with air rushing into the body, as the air pressure in the lungs falls below the normal external air pressure (Kajstura, 2006). The air enters the lungs (the bronchi) and then divides into smaller passageways called secondary bronchi; these repeatedly divide and become smaller bronchioles which contain no supporting cartilage. These thin walled respiratory bronchioles end in clusters of thin walled sacs called the alveoli.

The alveoli are in contact with air and blood across their thin walls; it is here that the exchange of gases by diffusion occurs. A flap of cartilage called the epiglottis guards the opening to the larynx. This structure prevents food from entering the respiratory passage way and directs it to the esophagus. By contrast the expiration of air from the body is a passive exercise involving the relaxation of the muscles used during inspiration.

b)Changes in Intrapulmonary Pressure

The changes in respiration under elevated intrapulmonary pressure, which take the form of an initial respiratory arrest, a subsequent retardation of respiration rate, and disruption of the normal relationships of the time and character of inhalation and exhalation (activation and intensification of exhalation), result principally from stimulation of the vagus receptors located in the pulmonary tissue (Benjamin, 2005). The extent and character of the respiratory changes depend on the exhalation and inhalation pressure. The principal role in exhalation during respiration under pressure is played by the muscles of the prelum abdominale. The coordination of the functioning of the abdominal muscles and the true respiratory musculature during respiration under pressure is disrupted after bilateral vagotomy in the cervical region (Kitsis, 2010). At identical elevated intrapulmonary pressures the changes in circulation depend on the character of the pressure. In contrast to intermittent pressure, constant pressure causes more substantial circulatory disturbances, as manifested in a greater decrease in arterial pressure and a larger increase in venous pressure.

c) Physical Factors Influencing Pulmonary Ventilation

Lung compliance

The ease with which lungs can be ...