Body’s Amazing Fighting Forces

A sneeze. A scratch. A tear. Typically, these reflexes barely register on your consciousness or, if they do, it’s as an annoyance. In reality, however, each is an unconscious action that, in its own way, provides essential protection against disease-causing microbes or toxins before they can do harm.

• Scratching

Scratching is a natural reaction to itching, which is triggered by tiny receptors (called nociceptors) in the skin’s nerve endings. The job of these receptors is to warn you that something – perhaps a mosquito – is putting pressure on your skin.

• Coughing

Coughing helps to clear the mouth, throat and lung tissues of foreign invaders, such as moulds, pollen, dust mites and petdefine dander, as well as mucus laden with microbes. In fact, coughing is an important defense mechanism. Although, one may not notice, but one coughs normally once or twice an hour. However, the irony of this is tat many respiratory infections may be spread by droplets of the pathogens put into the air by the cough.

• Sneezing

Sneezing is like coughing but directed through the nose. For example, when dust blows in your face, nerve cells in the nose signal the brain to expel it. We also sneeze to get rid of microbes that multiply in the nasal passageways, as the result of having a cold or the flu.

• Vomiting

Vomiting occurs when harmful substances in the stomach or the duodenum (the upper segment of the small intestinedefine) are identified by receptors in the walls of the digestive tract. The brain signals the digestive tract to stop, reverse itself and squeeze the stomach’s contents past the muscle that separates it from the oesophagus, up and out through the mouth.

• Tearing

Tearing keeps the surface of the eyes moist and sterile, with the help of lysozyme, an enzyme in tears that destroys bacteria by dissolving a chemical bond in the cell membrane, causing the cell wall to collapse. Tears also protect the eye when dust or debris irritate it; tear production increases until the fluid overflows the eyelids and washes away the irritant. Crying a natural response to stress flushes away certain harmful chemicals produced by anxiety.

Despite this impressive range of barriers, reflexes and chemicals, dangerous invaders do occasionally manage to penetrate the body.