How do nerves work? Are nerves simply the wires in the body that conduct electricity, like the wires in the walls of your home or in your computer? This is an analogy often made, but the reality is that nerves have a much more complex job in the body. They are not just the wires but the cells that are the sensors, detectors of the external and internal world, the transducers that convert information to electrical impulses, the wires that transmit these impulses, the transistors that gate the information and turn up or down the volume, and finally, the activators that take that information and cause it to have an effect on other organs.
Consider this. Your mother gently strokes your forearm and you react with pleasure. Or a spider crawls on your forearm, you startle and slap it off. Or you brush your forearm against a hot rack while removing a cake from the oven, and you immediately recoil. Light touch produced pleasure, fear, or pain. How can one kind of cell have so many functions? Nerves are in fact bundles of cells called neurons and each of these neurons is highly specialized to carry nerve impulses, their form of electricity, in response to only one kind of stimulus, and in only one direction.
The nerve impulse starts with the a receptor, a specialized part of each nerve, where the electrical impulse begins. One nerve's receptor migh be a thermal receptor, designed only to respond to a rapid increase in temperature.
Another receptor type is attached to the hairs of the forearm, detecting movement of those hairs, such as when a spider crawls on your skin.
Yet another kind of neuron is Low-Threshold mechanoreceptor, activated by light touch. Each of these neurons then carry their specific information: pain, warning, pleasure. And that information is projected to specific areas of the brain and that is the electrical impulse.
The inside of a nerve is a fluid that is very rich in the ion potassium. It is 20 times higher than in the fluid outside the nerve while that outside fluid has 10 times more sodium than the inside of a nerve. This imbalance between sodium outside and potassium inside the cell results in the inside of a nerve having a negative electrical charge, relative to the outside of the nerve, about equal to minor 70 or minor 80 miliVolts. This is called the nerve's resting potential. But in response to that stimulus the nerve is designed to detect, pores in the cell wall near the receptor of the cell open. These pores are specialized protein channels that are designed to let sodium rush into the nerve.
analogy (n): sự tương tự, sự giống nhau
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