Chuck encountered a growling dog on his way home. Immediatel…

Chuck encountered a growling dog on his way home. Immediately he felt his heart rate and his breathing speed up, his eyes dilated and blood pumped to his extremities (i.e. arms and legs). Chuck had no idea why these reactions occurred as he didn’t think about them. However, we know that these reactions, known as the fight-or-flight response was the result of activating the _____________.