Glutamate is used at the great majority of fast excitatory synapses in the brain and spinal cord. It is also used at most synapses that are "modifiable '', i.e. capable of increasing or decreasing in strength. Modifiable synapses are thought to be the main memory - storage elements in the brain. Excessive glutamate release can overstimulate the brain and lead to excitotoxicity causing cell death resulting in seizures or strokes. Excitotoxicity has been implicated in certain chronic diseases including ischemic stroke, epilepsy, amyotrophic lateral sclerosis, Alzheimer 's disease, Huntington disease, and Parkinson 's disease. GABA is used at the great majority of fast inhibitory synapses in virtually every part of the brain. Many sedative / tranquilizing drugs act by enhancing the effects of GABA. Correspondingly, glycine is the inhibitory transmitter in the spinal cord. Acetylcholine was the first neurotransmitter discovered in the peripheral and central nervous systems. It activates skeletal muscles in the somatic nervous system and may either excite or inhibit internal organs in the autonomic system. It is distinguished as the transmitter at the neuromuscular junction connecting motor nerves to muscles. The paralytic arrow - poison curare acts by blocking transmission at these synapses. Acetylcholine also operates in many regions of the brain, but using different types of receptors, including nicotinic and muscarinic receptors. Dopamine has a number of important functions in the brain; this includes regulation of motor behavior, pleasures related to motivation and also emotional arousal. It plays a critical role in the reward system; Parkinson 's disease has been linked to low levels of dopamine and schizophrenia has been linked to high levels of dopamine. Serotonin is a monoamine neurotransmitter. Most is produced by and found in the intestine (approximately 90 %), and the remainder in central nervous system neurons. It functions to regulate appetite, sleep, memory and learning, temperature, mood, behaviour, muscle contraction, and function of the cardiovascular system and endocrine system. It is speculated to have a role in depression, as some depressed patients are seen to have lower concentrations of metabolites of serotonin in their cerebrospinal fluid and brain tissue. Norepinephrine which focuses on the central nervous system, based on sleep patterns, focus and alertness. It is synthesized from tyrosine. Epinephrine which is also synthesized from tyrosine takes part in controlling the adrenal glands. It plays a role in sleep, with ones ability to become and stay alert, and the fight - or - flight response. Histamine works with the central nervous system (CNS), specifically the hypothalamus (tuberomammillary nucleus) and CNS mast cells.
what is the most abundant neurotransmitter in the nervous system
Serotonin serotonin