Nervous system: Emotions

Learning Objectives

  1. How do your emotions come about?
  2. How do biological systems as well as past experiences shape emotion processing? 

Today, we will not only discuss how that made you feel, but also how it made you feel; that is, by what mechanism, how your brain processes stimuli to produce what we experience as feelings, EMOTIONS.

Emotions are a difficult topic to study. Anger, love, happiness, these are vague, fuzzy words whose meanings aren’t really quantifiable. There’s no meter stick for joy. But through careful analysis of brain chemistry, neuroscience, and human behavior, we can learn a lot about how our brains create feelings, and how those feelings in turn affect us.

Emotions are universal among humans. No matter where you were born or what culture you come from, we all experience the same emotions. If you were to visit an island completely isolated from your native culture and language, the people there may not be able to understand a word you say, but no matter how little you had in common, you could still recognize each other smile. In fact, there are believed to be about seven universal simple emotions that are directly tied to facial expressions: Happiness, surprise, sadness, fright, disgust, contempt, and anger.


The images shows the seven universal facial expressions. Tell a story about an emotional event in a way that lets a student witness their own emotion. Talk about what part of the brain processes, and how past experience and practice shapes that processing.
Fig. 1 Seven universal facial expressions of emotions by PhD.Paul Ekman. The top row from left to right: happiness, sadness, and contempt. The bottom row from left to right: fright, disgust, and anger. Finally on the far right is surprise.

Facial responses like these are called Inherent Behaviors; even people who are born blind and have never seen another face, make these faces when experiencing an emotion. Just like you never have to learn how to breathe or blink or pull your hand away when you touch a hot stove, you never learn emotions. They’re hardwired into your brain.

Several of these simple emotions are tied to chemicals in your brain, which serve as a system of reinforcing or discouraging certain behaviors that natural selection has deemed valuable or dangerous. Eat a snack when you’re hungry, especially something with lots of energy-rich sugar or fat, and boom, your brain gets a hit of DOPAMINE, a neurotransmitter which triggers the neurons in your brain’s reward center. That’s why ice cream is so delicious, and why you feel happier when you have a full belly. On the other hand, when your brain is low on dopamine, you tend to be irritable, easy to upset, and motivated exclusively to seek whatever your brain is telling you you need.

Of course, there are also more complex emotions. There’s no chemical you can inject into someone’s brain to make them feel jealousy or love.

Such higher level emotions are not merely the result of chemical balance in the brain; they are complex down to the neuron. Think of your brain as a computer; it’s job is to tie certain inputs, such as a scream from the other room, a plump, juicy red apple, or a bully calling your best friend names, into appropriate behavior, like sweaty palms, a watering mouth, or increased blood flow to your muscles. When it has to tie together more complex situations with several variables, it needs a more sophisticated program. Sometimes, for more logical problems, this “program” is conscious thought.

But your brain is also constantly running programs under the hood that influence your behavior: we call them emotions. And just like your conscious thought changes and grows over time, so do your feelings. The part of your brain that processes emotions is called the LIMBIC SYSTEM, and the HIPPOCAMPUS, the memory center of your brain, is a part of that system. As you encounter new experiences and create new memories, your brain is literally rewiring the way it processes emotions. It’s why memories and nostalgia hold so much emotional weight.

So the next time you just can’t help singing and crying along to Adele’s “Someone Like You”, or are overwhelmed with bittersweet memories of your friends who’ve moved away, you can thank your limbic system, because it quite literally gives you the feels.

Figure 1. Icerko Lýdia / CC BY (


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