ABSTRACT
Study objectives Describe the mechanism by which chemical synapses function Describe the effects of neurotransmitter binding to its receptors on the postsynaptic neuron Compare and contrast excitatory synapses and inhibitory synapses Distinguish between an excitatory postsynaptic potential (EPSP) and an inhibitory postsynaptic potential (IPSP) Describe how neurotransmitters are removed from the synaptic cleft Explain how temporal summation and spatial summation take place Distinguish between convergence and divergence Understand how pH and hypoxia affect synaptic transmission Describe the potential mechanisms by which drugs, toxins, and diseases affect synaptic transmission Explain why synaptic transmission is unidirectional Distinguish between an agonist and an antagonist
. Introduction The function of a neuron is to communicate or relay information to another cell by way of an electrical impulse. A synapse is the site where the impulse is transmitted from one cell to the next. A neuron may terminate on a muscle cell, a glandular cell, or another neuron. The discussion in this chapter will focus on neuron-to-neuron transmission. At these types of synapses, the presynaptic neuron transmits the impulse toward the synapse, and the postsynaptic neuron transmits the impulse away from the synapse. Specically, the axon terminal of the presynaptic neuron comes into contact with the cell body or the dendrites of the postsynaptic neuron. Most neurons, particularly in the central nervous system (CNS), receive thousands of inputs. As will become evident, the transmission of the impulse at the synapse is unidirectional, and the presynaptic neuron inuences the activity of the postsynaptic neuron only.
