Axon terminals contain synaptic vesicles that store the neurotransmitter for release at the synapse. The postganglionic neuron will then synapse at the target organ. Alpha motor neurons send fibers that mainly synapse on extrafusal muscle fibers. Purkinje neurons feed back into the deep nuclei via a potent inhibitory synapse. Tethering interactions are likely to be involved in concentrating synaptic vesicles at the synapse. These axons also synapse with lower motor neurons in the ventral horns. At this point, the axons synapse with lower motor neurons. Rod bipolar cells do not synapse directly on to ganglion cells. Neurons in V2 then synapse onto cells in the extended V4. Rather, they only synapse on VM lower motor neurons ipsilaterally. Once released, a neurotransmitter enters the synapse and encounters receptors. The transmitter at this synapse is acetylcholine. An example of this mechanism is found in the receiving cell of a neural synapse. The greater palatine parasympathetic synapse on the hard palate and regulate mucus glands located there. They are dependent on serotonin availability in the synapse.