Question #198584
what would happen if each vesicle does not fuse with the plasma membrane
Expert's answer
These vesicles do not fuse with the plasma membrane once they arrive there, unlike the constitutive pathway; they are carried by microtubules on the cells' cytoskeleton to near the surface of the membrane. The vesicles only fuse with the membrane once they receive a signal from a receptor after a messenger (e.g. a hormone) has successfully bonded to the receptor. This complex activates intracellular signals that cause the vesicles to fuse with the membrane and release their contents into the environment. A good example is in nerve cells in the pre-synaptic membrane, when an action potential reaches the pre-synaptic membrane and causes a flow of calcium ions into the cell, these ions then allow the vesicles to fuse with the membrane and release their contents; in the case with neurons it is usually neurotransmitters such as acetylcholine and dopamine released[5].
