Anatomy & Physiology I and II

Anatomy & Physiology Study Guide

The Synapse Each synaptic terminal is part of a synapse, a specific area where the neuron connects with another cell. Two cells are involved in every synapse: the presynaptic cell that contains the synaptic terminal sending the communication, and the postsynaptic cell, which receives the message. The message between cells at a synapse includes the release of chemicals by the synaptic terminal called neurotransmitters . Neurotransmitters are chemicals packaged in synaptic vesicles . These chemicals, discharged by the presynaptic cell, influence the activity of the postsynaptic cell. A synapse between a neuron and a muscle cell is called a neuromuscular junction , and a synapse between a neuron and a gland cell is called a neuroglandular junction .

©2018 Achieve Test Prep Page 145 of 367 13.4 Structural Classification Neurons are classified by the relationship of the dendrites to the cell body and the axon. They can be anaxonic, bipolar, unipolar, or multipolar. Anaxonic neurons are little and have no structural features that distinguish dendrites from axons; all the cell processes look alike. Anaxonic neurons are located in the brain and in special sense organs. Bipolar neurons have two distinct processes—one dendrite that branches out at its tip, and one axon—with the cell body between the two. Bipolar neurons occur in special sense organs, where they relay information about sight, smell, or hearing from receptor cells to other neurons. In a unipolar neuron , or pseudounipolar neuron, the dendrites and axon are merged, and the cell body lies off to one side. Many sensory neurons of the peripheral nervous system are unipolar. Their synapses end at the CNS and their axons may extend a meter or more to reach it. The longest are those carrying sensations from the tips of the toes to the spinal cord. Multipolar neurons have two or more dendrites and a single axon. These are the most communal neurons in the CNS. All the motor neurons that control skeletal muscles are multipolar neurons. The axons of