Epinephrine (Adrenaline)

Epinephrine is both a hormone and a neurotransmitter. It is also called adrenaline. As a hormone, it is made and released by the hat-shaped glands on top of each kidney called the adrenal glands. As a neurotransmitter in the central nervous system, it is a chemical that helps nerve signals get from one nerve cell, muscle cell, or gland cell to another nerve cell, muscle cell, or gland cell.

It is a key part of the "fight or flight" response in your body. It's also used as medicine to treat a lot of conditions that could kill you. The "fight or flight" response is called the "acute stress response" in medicine. Epinephrine, norepinephrine, and dopamine are all called catecholamines. The name comes from a certain molecule in their structure. Inside your adrenal gland, norepinephrine is turned into the hormone epinephrine. Epinephrine doesn't do much as a neurotransmitter. Your nerves only make a small amount of it. It has something to do with the body's metabolism, attention, focus, panic, and excitement. A lack of sleep, anxiety, high blood pressure, and a weaker immune system are all linked to levels that aren't normal. Epinephrine's most important job is as a hormone. When you're stressed, your adrenal glands let out epinephrine. The fight-or-flight response is the name for the changes in your body that happen because of this response. The fight-or-flight response is how your body reacts to a stressful situation, like when you need to get away from a growling dog or when you're afraid of something (giving a speech for school or work). Our ancestors had to decide whether to stay and fight or run away when they were in a dangerous situation. During the fight-or-flight response, your brain tells you that something bad is happening. Then, nerves in a part of your brain called the hypothalamus send a message down your spinal cord and out to the rest of your body. Norepinephrine is the neurotransmitter that tells your nervous system what to do when your brain tells it what to do (noradrenaline). The neurotransmitter noradrenaline goes to these organs and tissues and causes these quick reactions in the body. 

The pupils get bigger to let in more light so you can see more of what's around you. Your skin goes pale when your blood vessels get a message to send blood to places that need it more, like your muscles, so you can fight or run away. The heart beats harder and faster to get more oxygenated blood to places like your muscles that need it most. Also, blood pressure goes up. The muscles get more blood flow and oxygen, they can move and work faster and with more strength. Your liver turns the glycogen you have stored into glucose, which gives you more energy. People breathe faster and deeper. Your airways widen, which lets more oxygen into your blood, which then goes to your muscles. Your adrenal gland also gets the neurotransmitter noradrenaline, which tells it to make the hormones adrenaline (epinephrine) and noradrenaline (norepinephrine). These hormones get to every part of your body through your blood. They go back to your eyes, heart, lungs, skin, blood vessels, and adrenal gland. The "message" to these organs and tissues is to keep reacting until the body is no longer in danger.This is an easy way to explain the fight-or-flight response. There are also other parts of your nervous system, other organ systems, hormones, and neurotransmitters that play a role.