Noradrenaline tends to be associated with more pleasant kinds of arousal. Adrenaline can also be pleasant, but too much is likely to produce anxiety and jittery feelings. Adrenaline also helps you breathe more easily, fighting symptoms of asthma and allergies. In the movie Pulp Fiction , a character whose heart has stopped gets a jump start from a shot of adrenaline directly into the heart. Having too little, you're likely to feel underaroused, unmotivated, or sleepy, and will be susceptible to headaches.
Caffeine speeds up the release of both, especially adrenaline .
This is why too much coffee can make you jittery. Some individuals with anxiety disorders have too much adrenaline. Even if they do not, they should avoid caffeine intake to keep from compounding their anxious symptoms. As mentioned above, drugs like morphine mimic the actions of the endorphins. The body releases endorphins when you laugh, when you're sexually excited, and when you experience many other kinds of pleasurable sensations.