The first neurotransmitter ever identified was acetylcholine, a chemical transmitter in both the central and parasympathetic nervous system in humans and many other organisms. It was discovered by Henry Hallett Dale and Otto Loewi in 1914; this discovery earned them the Nobel Prize in Physiology or Medicine in 1936. Chemically, acetylcholine is an ester of acetic acid and choline with the very long chemical formula CH3COOCH2CH2N+(CH3)3. It is a very effective deliverer of sodium ions, which stimulate muscle contractions and excites nerves. An increase in acetylcholine causes a decreased heart rate and increased production of saliva, as well as readying the muscles for work. In high doses, it can cause convulsions and tremors. In deficient levels, it can contribute to motor dysfunction.