Brain chemistry or neurochemistry is the complex system which allows the brain to function with the use of chemicals known as neurotransmitters which move information around in the brain. Every person's brain chemistry is slightly different, and a number of things can play a role in the levels of various neurotransmitters in the brain, and how those chemicals affect the brain's function. It is believed that difference in brain chemistry may explain a variety of behavioral disorders and phenomena.
The synapse is the connection between nerve cells (neurons) in animals including humans. The synapse joins the axons in one neuron to the dendrites in another. The diagram shows how the synapse connects axons to dendrites:
* Properties of neurotransmitters:
1) Synthesized in the presynaptic neuron
2) Confined to a small area to vesicles in the presynaptic neuron
3) Released from the presynaptic neuron under physiological conditions
4) Rabidly removed from the synaptic cleft by uptake or degradation
5) Presence of receptor on the post-synaptic neuron.
6) Binding to the receptor makes a biological response
Neurotransmitters found in the nervous system:
Excitatory increases the likelihood of the cell firing an action potential. Inhibitory decreases the likelihood
1) Acetylcholine (Ach):
Acetylcholine is an ester of acetic acid and choline with chemical formula CH3COOCH2CH2N+(CH3)3
Synthesis and degradation:
Acetylcholine is synthesized in certain neurons by the enzyme choline acetyltransferase from the compounds choline and acetyl-CoA. The enzyme acetylcholinesterase converts acetylcholine into the inactive metabolites choline and acetate. This enzyme is abundant in the synaptic cleft, and its role in rapidly clearing free acetylcholine from the synapse is essential for proper muscle function. Certain neurotoxins work by limiting acetylcholinesterase, thus leading to surplus of acetylcholine at the neuromuscular junction, which causes paralysis of the muscles needed for breathing and stops the beating of the heart. In the peripheral nervous system, acetylcholine activates muscles, and is a major neurotransmitter in the autonomic nervous system. In the central nervous system, ACh has a variety of effects as a neuromodulator upon plasticity, arousal and reward. ACh has an important role in the enhancement of sensory perceptions when we wake up and in sustaining attention. 2) Serotonin:
Serotonin or 5-Hydroxytryptamine (5-HT) is a monoamine neurotransmitter that is primarily found in the gastrointestinal (GI) tract and central nervous system (CNS) of humans and animals. Approximately 80 percent of the human body's total serotonin is located in the enterochromaffin cells in the gut, where it is used to regulate intestinal movements. The remainder is synthesized in serotonergic neurons in the CNS where it has various functions, including the regulation of mood, appetite, sleep, muscle contraction, and some cognitive functions including memory and learning Transition of serotonin at synapses is thought to be a major action of several classes of pharmacological antidepressants. Break down of serotonin
GABA is the chief inhibitory neurotransmitter in the central nervous system. It plays a role in regulating neuronal excitability throughout the nervous system. In humans, GABA is also directly responsible for the regulation of muscle tone. In insect species GABA acts only on excitatory nerve receptors. GABA's role changes from excitatory to inhibitory as the brain develops into adulthood. In the developmental stages preceding the formation of synaptic contacts, GABA is synthesized by neurons and acts both as an autocrine (acting on the same cell) and paracrine (acting on nearby...