{"id":1980,"date":"2016-10-20T03:06:01","date_gmt":"2016-10-20T03:06:01","guid":{"rendered":"https:\/\/courses.lumenlearning.com\/waymaker-psychology\/?post_type=chapter&p=1980"},"modified":"2024-05-17T02:18:35","modified_gmt":"2024-05-17T02:18:35","slug":"reading-neural-communication","status":"publish","type":"chapter","link":"https:\/\/courses.lumenlearning.com\/waymaker-psychology\/chapter\/reading-neural-communication\/","title":{"raw":"How Neurons Communicate","rendered":"How Neurons Communicate"},"content":{"raw":"
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Learning Objectives<\/h3>\r\n
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  • Describe how neurons communicate with each other<\/li>\r\n \t
  • Explain how drugs act as agonists or antagonists for a given neurotransmitter system<\/li>\r\n<\/ul>\r\n<\/div>\r\n<\/section>
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    Now that we have learned about the basic structures of the neuron and the role that these structures play in neuronal communication, let\u2019s take a closer look at the signal itself\u2014how it moves through the neuron and then jumps to the next neuron, where the process is repeated.<\/p>\r\n

    We begin at the neuronal membrane. The neuron<\/span><\/strong> exists in a fluid environment\u2014it is surrounded by extracellular fluid and contains intracellular fluid (i.e., cytoplasm). The neuronal membrane keeps these two fluids separate\u2014a critical role because the electrical signal that passes through the neuron depends on the intra- and extracellular fluids being electrically different. This difference in charge across the membrane, called the membrane potential<\/strong>, provides energy for the signal.<\/p>\r\n

    The electrical charge of the fluids is caused by charged molecules (ions) dissolved in the fluid. The semipermeable nature of the neuronal membrane somewhat restricts the movement of these charged molecules, and, as a result, some of the charged particles tend to become more concentrated either inside or outside the cell.<\/p>\r\n

    Between signals, the neuron membrane\u2019s potential is held in a state of readiness, called the resting potential<\/strong>. Like a rubber band stretched out and waiting to spring into action, ions line up on either side of the cell membrane, ready to rush across the membrane when the neuron goes active and the membrane opens its gates (i.e., a sodium-potassium pump<\/span> that allows movement of ions across the membrane). Ions in high-concentration areas are ready to move to low-concentration areas, and positive ions are ready to move to areas with a negative charge.<\/p>\r\n

    In the resting state, sodium (Na+<\/sup>) is at higher concentrations outside the cell, so it will tend to move into the cell. Potassium (K+<\/sup>), on the other hand, is more concentrated inside the cell, and will tend to move out of the cell (Figure 1). In addition, the inside of the cell is slightly negatively charged compared to the outside. This provides an additional force on sodium, causing it to move into the cell.<\/p>\r\n\r\n<\/section>\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"975\"]\"A Figure 1<\/strong>. At resting potential, Na+<\/sup> (blue pentagons) is more highly concentrated outside the cell in the extracellular fluid (shown in blue), whereas K+<\/sup> (purple squares) is more highly concentrated near the membrane in the cytoplasm or intracellular fluid. Other molecules, such as chloride ions (yellow circles) and negatively charged proteins (brown squares), help contribute to a positive net charge in the extracellular fluid and a negative net charge in the intracellular fluid.[\/caption]\r\n\r\nFrom this resting potential state, the neuron receives a signal, and its state changes abruptly (Figure 2). When a neuron receives signals at the dendrites\u2014due to neurotransmitters from an adjacent neuron binding to its receptors\u2014small pores, or gates, open on the neuronal membrane, allowing Na+<\/sup> ions, propelled by both charge and concentration differences, to move into the cell. With this influx of positive ions, the internal charge of the cell becomes more positive. The process of when the cell's charge becomes positive, or less negative, is called depolarization<\/strong>.\u00a0If the charge reaches a certain level, called the threshold of excitation<\/strong>, the neuron becomes active and the action potential begins.\r\n\r\nMany additional pores open, causing a massive influx of Na+<\/sup> ions and a huge positive spike in the membrane potential, the peak action potential. At the peak of the spike, the sodium gates close and the potassium gates open. As positively charged potassium ions leave, the cell quickly begins repolarization. At first, it hyperpolarizes<\/strong>, becoming slightly more negative than the resting potential, and then it levels off, returning to the resting potential.\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"487\"]\"A Figure 2<\/strong>. During the action potential, the electrical charge across the membrane changes dramatically.[\/caption]\r\n\r\nThis positive spike constitutes the action potential<\/strong>: the electrical signal that typically moves from the cell body down the axon to the axon terminals. The electrical signal moves down the axon like a wave; at each point, some of the sodium ions that enter the cell diffuse to the next section of the axon, raising the charge past the threshold of excitation and triggering a new influx of sodium ions. The action potential moves all the way down the axon to the terminal buttons.\r\n

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    Watch It<\/h3>\r\nThe process of neural communication is explained in the following video.\r\n\r\n