Your brain is made up of many different parts that all work together to process the information it receives. The main part of the brain responsible for processing emotions, the limbic system, is sometimes called the "emotional brain" [source: Brodal].
Part of the limbic system, called the amygdala, assesses the emotional value of stimuli. It's the main part of the brain associated with fear reactions -- including the "fight or flight" response. A person who has a seizure in the temporal lobe (the location of the amygdala) sometimes reports an intense feeling of fear or danger [source: Fiori].
The part of the brain stretching from the ventral tegmental area in the middle of the brain to the nucleus accumbens at the front of the brain, for example, has a huge concentration of dopamine receptors that make you feel pleasure [source: Banich]. The hypothalamus is in charge of regulating how you respond to emotions. When excitement or fear causes your heart to beat faster, your blood pressure to rise and your breathing to quicken, it's the hypothalamus doing its job. The hippocampus turns your short-term memory into long-term memory and also helps you retrieve stored memory [source: BBC]. Your memories inform how you respond to the world around you, including what your emotional responses are.
Because different parts of the brain process different emotions in different ways, injury to any part of the brain can potentially change your moods and emotions.