In many religious scriptures, novels, fictions you read about this battle between heart and brain. If till date we are using this in our daily conversations and history is full of these examples then there must be some origin of this concept?
In the 4th century B.C., Aristotle identified the heart as the most important organ of the body, and claimed that it was the seat of intelligence and sensation. Aristotle described it as a three-chambered organ that was the center of 'vitality' in the body. Other organs surrounding it (e.g. brain and lungs) simply existed to cool the heart (source: Stanford University). Since then it has been associated with emotions, although in the middle ages during the Enlightenment it already became clear that he heart was a pump, and not the seat of emotions.
A fact, however, is that intense emotions, such as love, fear and anger have pronounced effects on heart rate, mainly because of the release of adrenaline and other (stress) responses regulated by the hypothalamic–pituitary–adrenal axis (HPA) axis (source: Penn State University). The brain sends signals to the adrenal gland, which then secretes hormones and then they go to the heart which causes the heart to beat faster.