What Is Norepinephrine? - Effects, Function & Definition Video

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Lesson Transcript
Instructor: Laura Enzor

Laura has a Master's degree in Biology and is working on her PhD in Biology. She specializes in teaching Human Physiology at USC.

Norepinephrine is a neurotransmitter that is secreted in response to stress. Learn about what norepinephrine is and how it affects the body. Additionally, discover what drug contains norepinephrine and if it is safe to use.

Definition of Norepinephrine

Have you ever wondered why your heart beats faster and your palms get sweaty when you're scared? Those are both caused by the release of norepinephrine in your body.

Norepinephrine is a chemical released from the sympathetic nervous system in response to stress. It is classified as a neurotransmitter, a chemical that is released from neurons. Because the release of norepinephrine affects other organs of the body, it is also referred to as a stress hormone.

The effect of stress hormones
Effects of Stress Hormones

The sympathetic nervous system triggers a response that is commonly referred to as our 'fight or flight response.' When we are faced with a situation that is potentially dangerous, we need to make a decision to either stay and face whatever we find intimidating or scary or to turn and run away as fast as we can! Both of these options require our body to work faster and better. This is where norepinephrine comes in.


In order to make our body work as efficiently as possible, norepinephrine causes several changes in our body function. These include the following:

  1. An increase in the amount of oxygen going to our brain - this helps us think clearer and faster.
  2. An increase in our heart rate - this pumps more blood around our body, helping our muscles work faster and more efficiently.
  3. An increase in glucose (or sugar) release - this additional sugar gives our muscles something to 'feed on,' which helps them work better and faster.
  4. An increase in breathing rate - when we breathe faster, we are delivering more oxygen to the body and brain. This helps our entire body work better.
  5. A shutting down of metabolic processes - shutting down processes, like digestion and growth, allows blood and energy that would normally go to these functions to be shunted to our muscles and brain.

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