Wow, what a fascinating take on the synapse! Compare these two images of the active zone of a synapse. One (Figure 2 below) is easily recognized as a typical textbook rendition of a synapse, but the other not (Figure 1). The image that looks like hallucinatory spaghetti comes from a relatively recent paper and depicts our current understanding the appearance of the active zone of a synapse. Astonishing!!
Published in 2014 by Wilhelm et al in Science, I don’t know why it took me so long to encounter this paper 😊. Their research is a revelation in terms of the physical structure and complexity of the synapse.
Structure of the Synapse
An average synaptosome (synaptic bouton) is made up of about 300,000 proteins, far more than we ever thought. The bouton only has a volume of about 0.37 µm3; it’s miniscule, yet packed into that space are about 350-400 tiny vesicles that contain neurotransmitters, waiting to be released and to play their role in the persistence of consciousness and mental life. Estimates of the number of synapses in the human brain vary considerably, ranging between about 100 trillion to around 1,000 trillion. There are more synapses in your brain than stars in the Milky Way. Without synapses, you wouldn’t be reading this. In fact, you wouldn’t exist.
The researchers identified about 65 major proteins that play a major role in the functioning of the synapse, as illustrated in Figure 4. The colours in the Figure 4 map onto the colours used in Figures 1 and 3.
This research comes from the Rizzoli Lab, headed up by a genius in neurobiology, Prof Silvio O. Rizzoli from the Department of Neuro- and Sensory Physiology at the University of Göttingen Medical Center. Have a look at his movie of a 3D reconstruction of the contents of a typical synaptosome available on the Rizzoli Lab website.