Arnold, good evening I hope you are well and having a great night. With regard to your question, consider the following as it pertains to caffeine in the body. To a nerve cell, caffeine looks like adenosine. This is relevant because normally as adenosine is created in the brain, it binds to adenosine receptors. The binding of adenosine causes drowsiness by slowing down nerve cell activity. However, since caffeine looks like adenosine it binds to the adenosine receptor but instead of slowing down the cell's activity like adenosine would the cells speed up. So now you have increased neuron firing in the brain. The pituitary gland sees all of the activity and thinks some sort of emergency must be occurring, so it releases hormones that tell the adrenal glands to produce adrenaline (epinephrine). Adrenaline is the "fight or flight" hormone, and it has a number of effects on your body: • Your pupils dilate. • Your breathing tubes open up (this is why people suffering from severe asthma attacks are sometimes injected with epinephrine). • Your heart beats faster. • Blood vessels on the surface constrict to slow blood flow from cuts and also to increase blood flow to muscles. Blood pressure rises. • Blood flow to the stomach slows. • The liver releases sugar into the bloodstream for extra energy. • Muscles tighten up, ready for action. This explains why, after consuming a big cup of coffee or can of soda you can feel your heart beat increasing.
We hope this helps. Take care and have a great night.
