Science has known, for at least 30 years, that the synapses in our ears are faster than normal, something important for us to be able to maintain our balance and fall infrequently. We just didn’t know the processes involved at that speed, a mystery recently unraveled by scientists, after 15 years of simulations and a lot of research: get to know the non-quantal transmissions.
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The structures responsible for our balance are complex and delicate, called the vestibular system. When there are problems with it, we run the risk of suffering from vertigo and constant falls, which can be very dangerous, especially for the elderly. The superior reflexes of this system can bypass the 0.5 millisecond delay that neurotransmitters normally experience. But how?
The secrets of non-quantal transmission
Non-quantal transmission, despite being named, was a mystery to scientists. It has to do, we now know, with the structure of the ear. We have capillaries in the inner ear, clusters of hair-like sensors that detect the movement of the human head through the fluid surrounding them. Local information is transmitted directly to the brain, allowing it to align the body and vision accordingly, ensuring balance.
The neurons connected to the capillaries have a structure similar to that of a wine glass, called the Cup of Held, or vestibular cup. It surrounds the capillaries and leaves only a small gap, called the synaptic cleft, as it allows synapses to flow. Ions flow through the channels of this slit, creating an electrical potential that accelerates the flow of information to incredible speeds. The cup shape is unique in the entire nervous system, whose workings were also mysterious.
With computational models, the scientists simulated non-quantal transmission, seeking to understand in detail what was happening in the synaptic cleft. Changes in electrical potential, then, were shown to be responsible. This was discovered by tracking the flow of potassium ions in the capillary and slit channels.
The mechanism was described as being very subtle, full of dynamic interactions that allow to slow down or speed up the transmission of information. The key to the success of this speed was the ability to identify the potassium level and electrical potential at each exact location within the rift. This is only possible because of the goblet shape, a mechanism for electrical transmission between cells that the researchers suspect is present in other synapses.