Exocytosis

Vesicle exocytosis, the fusion of a vesicle with the plasma membrane, releases vesicular contents to exert various functions - for example, the secretion of transmitters from neurons mediates synaptic transmission essential for brain functions, the neuronal secretion of peptides (e.g., neuropeptide Y) and hormones (e.g., vasopressin, oxytocin) regulates labour and mental state, the secretion of insulin from pancreatic cells regulates blood glucose level (critical in diabetes), the secretion of catecholamine and peptides from adrenal chromaffin cells is involved in the stress response, and blood cell exocytosis is involved in immune responses.

Following exocytosis, vesicular membrane and proteins are retrieved from the plasma membrane through endocytosis, which recycles vesicles, maintains exocytosis, and prevents secretory cells from swelling or shrinking.

Reference

1. Wu L et al. Exocytosis and Endocytosis: Modes, Functions, and Coupling Mechanisms. Annu Rev Physiol. 2013 Nov 20;76:301–331