The brain is by far the most intriguing organ in our body. It perceives the world around us, allows us to learn new skills, forms and retrieves our memories and holds the key to our very selves. Everything that we know about the world is filtered through and depends upon the structure of our sensory receptors and the processing of that information through the communication of neurons in the brain. Understanding the brain is a daunting and intimidating task and yet the principles underlying brain function depend on the physical properties of cell membranes, ion channels and the physical connections between cells.
The whole trick of the neuron comes down to the properties of the cell membrane. The membrane is a physical barrier between the inside and the outside of the cell; some types of molecules can pass through easily other types of molecules cannot. Ions are charged particles that cannot pass through the lipid membrane. So how do ions get in and out of the cell? Through ion channels which create actual pores in the membrane that allow different types of ions to pass through. Ion channels act as gate keepers that open or close based on the physical surroundings. Ion channels undergo conformational changes to open or close in response to different cues some ion channels open in response to an increase in voltage while others open when they bind a particular type of molecule. All of these properties of ion channels are determined by their physical shape which is determined by the sequence of amino acids that makes up the protein, which is encoded in our DNA.
So far so good, right? Easy! We have a physical barrier between the inside and the outside of the cell and a series of transmembrane protein that act as gate keepers to either let ions in or keep them out. Coming up: how do neurons take advantage of this arrangement to create the electrical signals that serve as the communication signal throughout the brain?
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