brainstem

American  

[breyn-stem] / ˈbreɪnˌstɛm /

Or brain stem

noun

1. the portion of the brain that is continuous with the spinal cord and comprises the medulla oblongata, pons, midbrain, and parts of the hypothalamus, functioning in the control of reflexes and such essential internal mechanisms as respiration and heartbeat.

---

brainstem British  

/ ˈbreɪnˌstɛm /

noun

1. the stalklike part of the brain consisting of the medulla oblongata, the midbrain, and the pons Varolii

---

brainstem Scientific  

/ brān′stĕm′ /

1. The part of the vertebrate brain located at the base of the brain and made up of the medulla oblongata, pons, and midbrain. The brainstem controls and regulates vital body functions, including respiration, heart rate, and blood pressure.

2. See also reticular formation

---

Etymology

Origin of brainstem

First recorded in 1875–80; brain + stem ¹

Example Sentences

Once growth hormone is released, it activates neurons in the locus coeruleus, a brainstem region involved in alertness, attention, thinking, and responding to new experiences.

From Science Daily • Jul. 5, 2026

Once growth hormone enters the system, it activates the locus coeruleus, a brainstem region that controls alertness, attention, and cognitive function.

From Science Daily • Mar. 30, 2026

To investigate hedgehog hearing, researchers at the University of Oxford worked with collaborators in Denmark to measure the auditory brainstem response of 20 rehabilitated hedgehogs from Danish wildlife rescue centers.

From Science Daily • Mar. 12, 2026

This area of the brainstem receives interoceptive input, or signals from the body about its internal state, like hunger, pain and fullness.

From Salon • Feb. 6, 2025

Capping the brainstem is the R-complex, the seat of aggression, ritual, territoriality and social hierarchy, which evolved hundreds of millions of years ago in our reptilian ancestors.

From "Cosmos" by Carl Sagan