Your breathing rate is primarily regulated by neural and chemical mechanisms. Respiration is controlled by spontaneous neural discharge from the brain to nerves that innervate respiratory muscles. The primary respiratory muscle is the diaphragm, which is innervated by the phrenic nerve. The rate at which the nerves discharge is influenced by the concentration of oxygen, carbon dioxide and the acidity of the blood.
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Normal Respiratory Rate
The normal respiratory rate in adults is between 14 and 18 breaths per minute.on average. Newborns breathe much faster at about 44 breaths per minute on average. Over time, the respiratory rate gradually decreases to the adult rate.
There are chemoreceptors in the brain and the heart that sense the amount of oxygen, carbon dioxide and acid present in the body. As a result, they modulate the respiratory rate to compensate for any disruptions in balance of any of these chemicals. Too much carbon dioxide or acidity and too little oxygen cause the respiratory rate to increase and vice versa. Carbon dioxide chemoreceptors are much more sensitive than oxygen chemoreceptors and, thus, exert an effect with smaller changes.
There are two neural mechanisms that govern respiration -- one for voluntary breathing and one for automatic breathing. The voluntary impulse originates in the cerebral cortex region of the brain and the automatic impulse originates in the medulla oblongata.
Respiratory rate is also regulated by lung stretch receptors. The stretch receptors sense the over-inflation of the lungs, which leads to decreases in the respiratory rate. Additionally, irritant receptors in the mucous membrane lining of the respiratory tract, which are stimulated by respiratory irritants, cause increases in the depth and rate of breathing. Blood pressure receptors in the aorta and carotid arteries also influence breathing rate. Low blood pressure causes an increase in breathing rate and vice versa.