Fright in the flesh

Alarm strikes your body within sec­onds of rec­og­niz­ing a threat. Here’s what’s go­ing down.

Popular Science - - CHARTED -

1 Amyg­dala

Be­fore you con­sciously process a prob­lem, this al­mond-shaped brain re­gion ac­ti­vates and begins to amp up the sym­pa­thetic ner­vous sys­tem’s fight-or-flight re­sponse.

2 Hip­pocam­pus and frontal cor­tex

The ra­tio­nal cen­ters of our brain kick in, an­a­lyz­ing whether the per­ceived visual or au­di­tory in­put shows a true dan­ger.

3 Car­dio­vas­cu­lar sys­tem

Stress hor­mones in­crease your heart­beat and breath­ing rate while di­lat­ing the tiny air­ways in your lungs. This al­lows more oxy­gen to reach your mus­cles.

4 En­docrine glands

Sig­nals from the amyg­dala hit the hy­po­thal­a­mus, which starts a cas­cade of ac­tiv­ity through­out the en­docrine sys­tem. The re­sult: a surge of adrenaline and cor­ti­sol.

5 Gas­troin­testi­nal sys­tem

Fear re­ally can make you poop your pants. That and retch­ing may be side ef­fects of shrink­ing blood ves­sels in the GI tract—di­vert­ing re­sources to give you strength.

6 Mus­cu­loskele­tal sys­tem

En­docrine sig­nals push glu­cose and other en­ergy-stor­ing mol­e­cules out of re­serve and into the blood, which rushes in to fuel mus­cles should you need to es­cape or fend off a threat.

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