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The Brain, Neurons and Brain Chemistry

Author(s): Nancy P. Moreno, PhD, Barbara Z. Tharp, MS, and Tadzia GrandPré, PhD

Crossing the Synaptic Gap

Most neurons in the brain communicate with each other by releasing chemical messengers called neurotransmitters. Neurotransmitters cross the gaps between neurons or between neurons and other cells, such as muscle, and match up with specific receptors. Chemical signaling between neurons allows different kinds of messages to be sent. For example, some chemical messengers stimulate neurons to fire, while other messengers make it harder for an electrical impulse to be generated in the receiving neuron. Since one neuron can share synapses with thousands of other neurons, the combined effects of different messages ultimately determine whether a signal will be triggered or not. 

Many drugs interfere with communication between nerve cells. Some drugs act directly on neurons, neurotransmitters and receptors. Curare, for example, is a deadly poison used by South American Indians. It causes death from paralysis by blocking receptors on muscle cells. Since the receptors are blocked, the real chemical messenger for muscle contraction (acetylcholine) can no longer stimulate the muscles to contract. 

Drugs also can interfere with communication between neurons in other ways, such as by preventing the manufacture or release of neurotransmitters, by causing excessive firing of neurons by stimulating massive releases of neurotransmitters, by mimicking the effects of chemical messengers, or by preventing the normal breakdown and recycling of chemical messengers.

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Funded by the following grant(s)

NIH Blueprint for Neuroscience Research Science Education Award, National Institute on Drug Abuse, and NIH Office of the Director

The Learning Brain: Interactive Inquiry for Teachers and Students
Grant Number: 5R25DA033006

Science Education Partnership Award, NIH

Filling the Gaps: K-6 Science/Health Education
Grant Number: 5R25RR013454