Hello! Socratic's Terms of Service and Privacy Policy have been updated, which will be automatically effective on October 6, 2018. Please contact hello@socratic.com with any questions.

Question #0a05a

1 Answer
Jun 24, 2017


sympathetic nervous system


The sympathetic nervous system initiates the flight-or-flight response in response to a perceived threat or harmful event.

During this response, the adrenal gland sends out signals to secrete norepinephrine and epinephrine. These hormones have many effects on the body during the fight-or-flight response, including:

  • increase of blood flow to muscles
  • pupil dilation
  • increase in blood pressure
  • increased awareness
  • release of glucose into the blood stream