Explain the Respiratory Centre
The respiratory centre consists of two main parts - inspiratory centre and the expiratory centre. The inspiratory centre is dominant. A reciprocal relationship exists between these two parts. When the inspiratory muscles are active, expiratory muscles are inhibited. The respiratory centre initiates nerve impulses which pass out from the brain in the phrenic nerves to the diaphragm and intercostal nerves to the intercostal muscles. These impulses stimulate the muscles to contract. This increases the capacity of the thoracic cavity and inspiration occurs. A second group of neurons in the medulla, the expiratory center appears to function mainly during forced expiration, stimulating the internal intercostal and abdominal muscles to contract.