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Catecholamines: Definition & Function

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  • 0:04 Fight or Flight
  • 0:47 Characteristics and Release
  • 1:55 The Brain
  • 2:15 The Blood
  • 2:37 Functional Outcomes
  • 3:31 Lesson Summary
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Lesson Transcript
Instructor: Meghan Greenwood

Meghan has taught undergraduate and graduate level science courses and has a PhD in Immunology.

This lesson describes what a catecholamine is and what receptors it binds. It will also detail the function(s) of catecholamines within the human body.

Fight or Flight

Imagine driving down a city street. You approach a stop sign and press your foot down on the brakes. As you are looking both ways, a car nears your back bumper. SLAM! The car behind you did not notice your brake lights and hit you. Unfortunately, you are driving a brand new car. You feel your palms start to sweat. Anger may start to boil up inside of you. How did the driver not see that you were stopped?!

Those feelings of rage are the end result of chemicals called catecholamines. Catecholamines are the substances responsible for the fight-or-flight response to stressful situations. They are the chemicals that cause your heart to beat faster, sweat to coat your palms, and your emotions to change in an instant.

Characteristics and Release

As members of both the neurotransmitter and hormone families, catecholamines are made by nerve tissue, the brain, and the adrenal glands located on top of your kidneys. The name catecholamine comes from the chemical structures of a benzene ring (termed catechol) and a nitrogen-containing group (amine). They can be neurotransmitters, which transmit signals through your nervous system, as well as hormones, which transmit signals from your blood to your organs and tissues. Three of the most recognizable catecholamines are epinephrine (aka adrenaline), norepinephrine, and dopamine.

If we were to follow dopamine along its normal route, it would first be formed in the brain. It would then travel through the nervous system, being released from vesicles in one nerve cell into the synapse and almost immediately binding to a dopamine receptor on the adjacent nerve cell. This neurotransmission leads to different feelings, such as motivation. Eventually, the vesicles release dopamine into the bloodstream. It then binds to receptors on many different tissues, causing decreases in blood pressure and kidney excretion.

Now let's take a closer look at that process, naming some more specific terms to go along with it.

The Brain

Let's start with the brain. As a neurotransmitter, each catecholamine is released into the synapse between neurons, or nerve cells, and then binds to the subsequent neuron via specific receptors. Dopamine is released into the synapse and binds to the dopamine receptor. This binding to the downstream neuron is the vehicle for signal transfer.

The Blood

Eventually, catecholamines are released from the neuronal vesicles into the blood. Once in the blood, they act as hormones, binding to another family of receptors on organs and tissues. These receptors are called alpha-adrenergic and beta-adrenergic receptors. Binding to these receptors leads to various different reactions in the body, as will be discussed.

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