Plural of brainstem; the parts of the brain that connect the brain to the spinal cord and control basic functions like breathing and heart rate.
Compound of 'brain' (from Proto-Germanic 'bragno') and 'stem' (from Old English 'stemn'). The term emerged in medical terminology in the early 20th century as neuroscience advanced.
The brainstem is sometimes called your 'lizard brain' because it's the oldest part of our brain evolutionarily—even snakes and fish have one! It keeps you alive without you even thinking about it.
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