Where it is
Midbrain, pons and medulla oblongata, from the base of the brain down to the foramen magnum.
What it does
Contains centers for breathing, heart rate and blood pressure, the nuclei of most cranial nerves (III–XII), and the reticular activating system that keeps us awake. All signals between brain and body pass through it.
Clinical relevance
- Brain herniation compresses the brainstem: changes in pupils, posturing, abnormal breathing and loss of consciousness.
- Fixed and dilated pupils are an ominous sign.
- Brain death testing includes absence of brainstem reflexes.
Nursing focus
- Report new pupil asymmetry, a pupil that reacts sluggishly, or decorticate or decerebrate posturing immediately.