Lungs Disease : Tuberculosis (TB), Herring - Breuer reflex, Acute and Chronic Bronchitis
It is an infections disease, caused in humans by the bacterium Mycobacterium tuberculae. It was once common world wide and was a killer disease. People infected with HIV are highly susceptible to tuberculosis and the disease is becoming more common again in communities with high rates of HIV infection.
Bronchitis is the inflammation of the bronchi, the air ways that connect the trachea (wind pipe) to the lungs, resulting in cough that may produce considerable quantities of sputum (Phlegm). Two forms, of the disease are recognized as acute bronchitis (sudden onset and short duration) and chronic bronchitis (Persistent over a long period and recurring over several years). Both are more common in smokers and in areas with high atmospheric pollution.
It is a form of bronchitis in which sputum is coughed up on most days for atleast three consecutive months. The disease results in narrowing and obstruction of the air - ways in the lungs. It often coexists with another form of lung disease, emphysema (widening of alveoli). Chronic bronchitis and emphysema together are called chronic obstructive lung disease (COLD) or chronic obstructive airways disease.
When the alveoli are stretched at the height of inspiration the receptors send stimuli to the expiratory center of the medulla through the vagus nerve which inhibits further inspiration. This sequence of events is called Herring - Breuer reflex.
In addition the medulla contains a pneumotaxic center which is connected to the breathing centre and helps to ensure rhythmic breathing. During inspiration, the inspiratory part of the respiratory center sends impulses to the pneumotaxic center which responds by sending impulses to the expiratory part of the respiratory center. The expiratory center is then activated and so the inspiratory center is inhibited reflexly, respiratory rhythm is controlled in this manner by these centers in the brain.
Inflammation of the lungs due to infection is called pneumonia. Pneumonia is caused by viruses or bacteria.Viral pneumonia is due to adenovirus, respiratory syncytial virus or a coxsackie virus. The most common bacterial pneumonia is Pneumococcal pneumonia. Pneumonia may also be caused by a mycoplasma (an organism that is intermediate between a bacterium and a virus)