Respiratory center

The respiratory centers (RCs) are located in the medulla oblongata and pons, which are parts of the brainstem. The RCs receive controlling signals of neural, chemical and hormonal nature and control the rate and depth of respiratory movements of the diaphragm and other respiratory muscles. Injury to these centers may lead to center respiratory failure, which necessitates mechanical ventilation; usually associated with a poor prognosis.

In healthy individuals the presence of elevated carbon dioxide levels in the blood lowers the blood pH, and this lowered blood pH is the stimulant that the RC responds to in order to signal the respiratory muscles to breathe. Chemoreceptors found in carotid bodies and aortic bodies are responsible for detecting decrease in blood pH by this carbon dioxide.

Groups

A diagram of the respiratory centers

The respiratory centers are divided into four major groups, two groups in the medulla and two in the pons. The two groups in the medulla are the dorsal respiratory group and the ventral respiratory group. The two groups in the pons are the pneumotaxic center also known as the pontine respiratory group, and the apneustic center.

Inspiratory center (Dorsal respiratory group)

• Location: Dorsal portion of medulla
• Nucleus: Nucleus tractus solitarius

Expiratory center (Ventral respiratory group)

• Location: Antero- lateral part of medulla, about 5 mm anterior and lateral to dorsal respiratory group
• Nucleus: Nucleus ambiguus and nucleus retro ambiguus.
• Function: It generally causes expiration but can cause either expiration or inspiration depending upon which neuron in the group is stimulated. It sends inhibitory impulse to the apneustic center.

Pneumotaxic center

• Location: Pons (upper part )
• Nucleus: Nucleus parabrachialis
• Function: It controls both rate and pattern of breathing. Limit inspiration.

Apneustic center

• Location: Pons (lower part)
• Functions:

1. It discharges stimulatory impulse to the inspiratory center causing inspiration.
2. It receives inhibitory impulse from pneumotaxic center and from stretch receptor of lung.
3. It discharges inhibitory impulse to expiratory center.

Respiratory center depression

Depression of a respiratory center can be a result of the following reasons:

• medical drug action (μ-opioids, sedatives, etc.)
• sudden cessation of blood circulation in brain
• severe brain trauma
• brain tumors
• damage of a brainstem

Respiratory center stimulation

Amphetamine stimulates the medullary respiratory centers, producing faster and deeper breaths.^[1] In a normal person at therapeutic doses, this effect is usually not noticeable, but when respiration is already compromised, it may be evident.^[1]

See also

• Control of respiration
• Cough center
• Pre-Bötzinger complex

References

1. Westfall DP, Westfall TC (2010). "Miscellaneous Sympathomimetic Agonists". In Brunton LL, Chabner BA, Knollmann BC. Goodman & Gilman's Pharmacological Basis of Therapeutics (12th ed.). New York, USA: McGraw-Hill. ISBN 9780071624428.