Regulation of breathing mechanism

The breathing control centres are stimulated in the medula oblongata

The breathing controls send more nerve impulses via phrenic nerve and thoracic nerve to the thoracic cavity and receive nerve impulse from the chemoreceptors in carotid bodies and aortic bodies

During vigorous exercise , the partial pressure of carbon dioxide (CO2) in the blood increases and the blood pH drops

This is detected by chemoreceptors in the carotid artery and impulses are sent to stimulate the inspiratory and the cardiovascular centre in the brain

The inspiratory nerve to stimulate the contraction of the external intercostal muscles of the rib cage

The phrenic nerve to stimulate the contraction of radial muscles of the diaphragm

Both contractions bring the rib cage outward and upward to increase the volume of the lungs and decrease its pressure

Atmospheric air is forced or inhaled into the lungs

As the bronchial tree of the lungs is stretched, it stimulates the stretch receptors which then send impulses to the expiratory centre through the vagus nerve

The expiratory centre inhibit inspiration amd stimulate expiration

During expiration, the rib cage and the diaphragm fall back to their original positions (due to natural recoiling) decreasing the lung volume but increasing its pressure

Air is forced or exhaled out of the lungs

During forced exhalation, the internal intercoastal muscles will contract to bring the rib cage downwards and inwards

The expiratory centre then become inactive and inspiration begins again

Inspiration and expiration are carried out more frequently to increase the rate of alveolar ventilation for faster gaseous exchange in the body

At the same time, cardiovascular centre sends impulse throughthe sympathetic nerve to the heart to increase the cardiac frequency

High levels of CO2 also causes the blood pressure to increase

This will cause the walls of carotid arteries to stretch and stretch receptors are stimulated

Impulses are sent to the cardiovascular centre through the afferent nerves

The cardiovascular centre will then respond by stimulating the heart to reduce its cardiac frequency and the blood vessels tp.dilate thus lowering the blood pressure.