Nucleus · one in each half of the brain

Centromedial amygdala

Also called Central and medial nuclei, CeA and MeA, Centromedial group

The amygdala's alarm switch: triggers the racing heart and frozen body of fear.

Open in 3D

The centromedial nuclei are the main output side of the amygdala. Once the basolateral part decides something is dangerous, the central nucleus sends orders to the hypothalamus and brainstem. These areas then create the body's fear response: a pounding heart, fast breathing, freezing in place and a rush of stress hormones. It all happens automatically, often before you have decided anything at all.

Where it is

The upper, inner part of each amygdala, closest to the middle of the brain.

What it does

Think of it as the fire alarm panel: once smoke is detected, it rings the bells, calls the fire trucks and unlocks the exits all at once.

Works with

• Basolateral amygdalaThe basolateral complex feeds it the decision "this is dangerous", which it turns into action.
• HypothalamusIt triggers the hypothalamus to start the stress hormone chain and raise heart rate and blood pressure.
• MidbrainIt drives a region of the midbrain, around the cerebral aqueduct, that produces freezing and can dull pain during danger.
• Medulla oblongataIts signals reach centers in the medulla that control heart rate and blood pressure.
• Locus coeruleusIt activates the locus coeruleus, which releases noradrenaline across the brain to make you alert.
• Medium spiny neuronMany of its neurons resemble the medium spiny neurons of the striatum and use GABA, the brain's main "stop" signal.

When it goes wrong

For learning only, not medical advice. If you have a health concern, talk to a doctor.

Surprising facts

• Many body signs of a scare, like a pounding heart, fast breathing and sweaty palms, are set in motion by orders that pass through here.
• Freezing is not a choice. It is an automatic reaction shared by many animals, and it helps prey avoid being noticed by predators.
• The amygdala is often called the fear center, but this small part is more like the button that launches the response than the part that decides.

Where the name comes from

Named after its two main members: the central nucleus ("centro") and the medial nucleus ("medial", meaning toward the middle).

Sources

1. Neuroanatomy, Amygdala, StatPearls, NCBI Bookshelf
2. 12.2 Neural Mechanisms and Circuitry of the Stress Response, OpenStax, Introduction to Behavioral Neuroscience
3. Neuroanatomy, Periaqueductal Gray, StatPearls, NCBI Bookshelf

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