![]() ![]() Now director of the Center for Neuroscience at the University of California, Davis, McAllister continues to investigate how the brain’s nerve cells - called neurons - find each other, connect and disengage. As a graduate student in the 1990s studying developmental neurobiology, she was drawn to the question of how the brain is built: how individual brain cells in a growing fetus somehow organize themselves into an organ capable one day of pondering the mysteries of life. Kimberley McAllister has been fascinated by the human brain since college. By sending electrical signals from nerve cell to nerve cell within a great network of connections, the brain creates thoughts as mundane as “Where are my keys?” or as profound as “I think, therefore I am.” ![]() That’s because it’s the connections between those cells that make the brain so amazing. No thoughts, no worries, no wonder or awe. The post-synaptic cell will only send the message along if it gets enough excitatory input to depolarize across the threshold, and open the voltage-gated ion channels in its axon.If you were to take a human brain and toss it in a blender - not that you should - the resulting slurry of cells wouldn’t be special in the way that the human brain is. There might even be competition among the neurons, with a single post-synaptic neuron receiving glutamate from one pre-synaptic neuron and GABA from its neighbor. ![]() This is why the brain uses neuron networks to send many signals to a single cell, or why a neuron may have to fire a couple times before it can pass the message along. Most of the time, all the vesicles released from an action potential aren’t enough to trigger an action potential in the following cell. However, a single vesicle of neurotransmitter isn’t enough to depolarize the cell body. If the neurotransmitter is inhibitory, it will hyperpolarize the cell body. If the neurotransmitter is excitatory, the influx of positive ions will depolarize (bring closer to zero) the cell body. Each vesicle packet released from the pre-synaptic neuron will contain a set amount of neurotransmitters, which will then bind to some of the receptors on the post-synaptic cell. ![]()
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