Respiratory Centers in the Brainstem

Respiratory Centers in the Brainstem

• Three main respiratory control centers:

  • Ventral respiratory group (VRG)

  • Dorsal respiratory group (DRG)

  • Pontine respiratory center (pneumotaxic center)

• VRG and DRG are located in the medulla oblongata.

• The pontine respiratory center is located in the pons.

• These centers control the rate, depth, and pattern of breathing by sending signals to respiratory muscles.

Ventral Respiratory Group (VRG)

• Main group that sends impulses to respiratory muscles.

• Contains:

  • Inspiratory neurons (VRGI)

  • Expiratory neurons (VRGE)

• VRGI stimulates the:

  • Diaphragm

  • External intercostal muscles

  • Accessory muscles during forced inhalation

• VRGE becomes especially active during forced exhalation, stimulating:

  • Internal intercostal muscles

  • Abdominal muscles

Dorsal Respiratory Group (DRG)

• Located behind the VRG.

• Provides the VRG with information about the rate and depth of breathing.

• Does not directly send the main motor impulses to the diaphragm and external intercostals.

Normal Breathing Cycle

• VRGI stimulates inhalation for about 2 seconds.

• Then VRGI activity stops for about 3 seconds, allowing the diaphragm and intercostals to relax.

• Relaxation causes exhalation.

• This 2-second inhalation + 3-second exhalation pattern produces about 12 breaths/minute.

Pontine Respiratory Center

• Also called the pneumotaxic center.

• Helps stop inhalation by inhibiting VRGI neurons.

• Helps create a smooth transition between inhalation and exhalation.

Forced Breathing

• Forced inhalation: VRGI increases stimulation of the diaphragm, external intercostals, and accessory muscles.

• Forced exhalation: VRGE activates the internal intercostal and abdominal muscles, making exhalation an active process.

Why It Matters

Damage or illness affecting the brainstem respiratory centers can cause:

• Abnormal breathing patterns

• Changes in respiratory rate or depth

• Poor ventilation

• Reduced gas exchange

• Cellular hypoxia

The patient may then require ventilatory support.