synaptic
Secretory Vesicles contain materials that are to be excreted from the cell, such as wastes or hormones . Secretory vesicles include synaptic vesicles and vesicles in endocrine tissues. Synaptic vesicles store neurotransmitters. They are located at presynaptic terminals in neurons. When a signal reaches the end of an axon, the synaptic vesicles fuse with the cell membrane and release the neurotransmitter. The neurotransmitter crosses the synaptic junction, and binds to a receptor on the next cell. Some cells also produce molecules, such as hormones produced by endocrine tissues, needed by other cells. These molecules are stored in secretory vesicles and released when needed. Secretory vesicles also hold enzymes needed to make extracellular structures, such as the extracellular matrix of animal cells.