Histology. Nerve synapses. Colored scanning electron micrograph (SEM) of the junctions between a nerve cell (green) and a muscle fiber (red). Such junctions are known as synapses. The nerve cell (motor neuron) ends in a group of pads called end plates. The end plate holds neurotransmitter chemicals. When activated, the end plate releases a neurotransmitter, which is taken up by receptors on the muscle's side of the synapse. This makes the muscle contract. In neuromuscular synapses such as this, the neurotransmitter is the chemical acetylcholine. Magnification unknown.