{"id":3041,"date":"2020-12-13T21:20:17","date_gmt":"2020-12-13T19:20:17","guid":{"rendered":"https:\/\/meddists.com\/learn\/pre-clinical\/histology\/neurohistology\/introduction\/the-neuron\/"},"modified":"2020-12-13T21:52:07","modified_gmt":"2020-12-13T19:52:07","slug":"the-neuron","status":"publish","type":"page","link":"https:\/\/meddists.com\/learn\/pre-clinical\/histology\/nervous-system\/introduction\/the-neuron\/","title":{"rendered":"The Neuron"},"content":{"rendered":"\n<div class=\"wp-block-image\"><figure class=\"aligncenter\"><a href=\"https:\/\/meddists.com\/wp-content\/uploads\/2020\/02\/neuron.png\" target=\"_blank\" title=\"The Neuron\" rel=\"noopener noreferrer\"><img decoding=\"async\" src=\"https:\/\/meddists.com\/wp-content\/uploads\/2020\/02\/neuron-600x437.png\" alt=\"\" class=\"wp-image-25577\"\/><\/a><figcaption><strong>The structure of a neuron<\/strong><\/figcaption><\/figure><\/div>\n\n\n<span class=\"block-heading\" id=\"header_1\">\n<h4 class=\"wp-block-heading\" class=\"wp-block-heading\" class=\"title_collection title2\">Description<\/h4>\n<\/span><span class=\"block-content\" id=\"contents_1\">\n\n\n<p class=\"wp-block-paragraph\">Neurons are the functional units of the nervous system.<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>They are one of the most active cell groups in our body &#8212; consuming a lot of energy (the brain uses up to 20% of daily energy usage) in the form of glycogen, however, they <strong>do not store it<\/strong>.<\/li><li>Neurons have the characteristics of protein-producing cells, therefore, their nucleus is euchromatic and they contain a lot of ribosomes &#8212; both free and bound to rER.<ul><li>Usually, a large nucleolus will also be visible.<\/li><\/ul><\/li><li>Neurons cannot divide, however, in some areas of the brain, neuronal stem cells are capable of replacing damaged cells.<\/li><\/ul>\n\n\n<\/span><span class=\"block-heading\" id=\"header_2\">\n<h3 class=\"wp-block-heading\" class=\"wp-block-heading\" class=\"title_collection title1\">Parts<\/h3>\n<\/span><span class=\"block-content\" id=\"contents_2\">\n\n\n<ul class=\"wp-block-list\"><li>The <strong>cell body<\/strong> is the major part of the neuron, containing basophilic aggregations called <strong>Nissl bodies<\/strong> that are clusters of ribosomes in the rER.<\/li><li>Extending from the cell body there are several processes that usually include one or more <strong>dendrites<\/strong> and a single <strong>axon&nbsp;<\/strong>that forms a&nbsp;<strong>synapse&nbsp;<\/strong>at its end.<\/li><\/ul>\n\n\n\n<div class=\"wp-block-image\"><figure class=\"aligncenter\"><a href=\"http:\/\/meddists.com\/wp-content\/uploads\/2019\/01\/Screenshot_4.png\" target=\"_blank\" title=\"The Neuron\"><img decoding=\"async\" src=\"https:\/\/meddists.com\/wp-content\/uploads\/2019\/01\/Screenshot_4-300x226.png\" alt=\"\" class=\"wp-image-8540\"\/><\/a><figcaption><strong>Nissl bodies&nbsp;(basophilic spots marked with arrows)<\/strong>&nbsp;(Credit: Michael Bonert, CC BY-SA 3.0)<\/figcaption><\/figure><\/div>\n\n\n<\/span><span class=\"block-heading\" id=\"header_3\">\n<h4 class=\"wp-block-heading\" class=\"wp-block-heading\" class=\"title_collection title2\">Dendrites<\/h4>\n<\/span><span class=\"block-content\" id=\"contents_3\">\n\n\n<p class=\"wp-block-paragraph\">Dendrites are branch-like projections of the neuron that receive information from other neurons or the environment.<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>Their diameter is larger than that of axons, and they are <strong>unmyelinated&nbsp;<\/strong>(not covered by myelin sheath &#8212; will be discussed in the Myelin lesson).<\/li><li>Not all neurons carry dendrites.<\/li><\/ul>\n\n\n<\/span><span class=\"block-heading\" id=\"header_4\">\n<h4 class=\"wp-block-heading\" class=\"wp-block-heading\" class=\"title_collection title2\">Axons<\/h4>\n<\/span><span class=\"block-content\" id=\"contents_4\">\n\n\n<p class=\"wp-block-paragraph\">Axons are long tube-like projections of the neuron that transmit stimuli to neighboring neurons or effector cells (muscles, glands).<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>As mentioned above, each neuron carries a <strong>single axon.<\/strong><\/li><li>Axons originate from a region called the <strong>axon hillock<\/strong>; this landmark usually lacks large cytoplasmic organelles.<\/li><li>Distally from the hillock, we can find the <strong>initial segment<\/strong>, which is the site where the action potential is generated.<\/li><li>Some axons may be myelinated; depending on the location of the neuron, engulfed by different types of cells.<\/li><\/ul>\n\n\n<\/span><span class=\"block-heading\" id=\"header_5\">\n<h4 class=\"wp-block-heading\" class=\"wp-block-heading\" class=\"title_collection title2\">Synapses<\/h4>\n<\/span><span class=\"block-content\" id=\"contents_5\">\n\n\n<p class=\"wp-block-paragraph\">Synapses are chemical connections between the axon of one neuron and a dendrite of the next neuron (or a set of receptors on a non-neuronal cell, such as muscles or glands).<\/p>\n\n\n\n<div class=\"wp-block-image\"><figure class=\"aligncenter\"><a href=\"https:\/\/meddists.com\/wp-content\/uploads\/2020\/02\/neuron-2.png\" target=\"_blank\" title=\"The Neuron\"><img decoding=\"async\" src=\"https:\/\/meddists.com\/wp-content\/uploads\/2020\/02\/neuron-2-600x403.png\" alt=\"\" class=\"wp-image-25579\"\/><\/a><figcaption><strong>The structure of a neuron (simplified)<\/strong> (Credit: OpenStax, CC BY-SA 4.0)<\/figcaption><\/figure><\/div>\n\n\n<\/span><span class=\"block-heading\" id=\"header_6\">\n<h3 class=\"wp-block-heading\" class=\"wp-block-heading\" class=\"title_collection title1\">Types of neurons<\/h3>\n<\/span><span class=\"block-content\" id=\"contents_6\">\n\n\n<p class=\"wp-block-paragraph\">Neurons can be classified in different ways and can carry different names based on their location, function, and morphology.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The most basic classification of neurons is based on their activity in the nervous system:<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li><strong>Sensory neurons<\/strong><\/li><li><strong>Motor neurons<\/strong><\/li><li><strong>Interneurons<\/strong><\/li><\/ul>\n\n\n<\/span><span class=\"block-heading\" id=\"header_7\">\n<h4 class=\"wp-block-heading\" class=\"wp-block-heading\" class=\"title_collection title2\">Sensory neurons<\/h4>\n<\/span><span class=\"block-content\" id=\"contents_7\">\n\n\n<p class=\"wp-block-paragraph\">Sensory neurons receive information from the environment (such as vibration, touch, smell, taste, light) and translate it into an electrical signal. They send these signals to other components of the nervous system in the spinal cord and brain.<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>Sensory neurons usually have an axon that branches into two segments: one segment attaches to dendrites that receive sensory information and another that transmits this information to the spinal cord.<ul><li>This type of morphology is known as&nbsp;<strong>pseudounipolar.<\/strong><\/li><\/ul><\/li><\/ul>\n\n\n<\/span><span class=\"block-heading\" id=\"header_8\">\n<h4 class=\"wp-block-heading\" class=\"wp-block-heading\" class=\"title_collection title2\">Motor neurons<\/h4>\n<\/span><span class=\"block-content\" id=\"contents_8\">\n\n\n<p class=\"wp-block-paragraph\">Motor neurons transmit signals from the central nervous system onto muscle cells.<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>The connection between the motor neuron and the muscle cell is known as the&nbsp;<strong>neuromuscular junction<\/strong>.<\/li><li>Motor neurons usually have multiple dendrites and a single axon.<ul><li>This type of morphology is known as&nbsp;<strong>multipolar<\/strong>.<\/li><\/ul><\/li><li>Motor neurons carry <strong>Golgi type I axons.<\/strong><\/li><\/ul>\n\n\n<\/span><span class=\"block-heading\" id=\"header_9\">\n<h4 class=\"wp-block-heading\" class=\"wp-block-heading\" class=\"title_collection title2\">Interneurons<\/h4>\n<\/span><span class=\"block-content\" id=\"contents_9\">\n\n\n<p class=\"wp-block-paragraph\">Interneurons form a connection between nearby neurons and are not considered as sensory or motor.<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>Interneurons usually have multiple dendrites and a single axon.<ul><li>This type of morphology is known as&nbsp;<strong>multipolar<\/strong>.<\/li><\/ul><\/li><li>Interneurons carry&nbsp;<strong>Golgi type II axons<\/strong>.<\/li><\/ul>\n\n\n\n<div class=\"wp-block-image\"><figure class=\"aligncenter\"><a href=\"https:\/\/meddists.com\/wp-content\/uploads\/2020\/02\/neuronal-types.png\" target=\"_blank\" title=\"The Neuron\"><img decoding=\"async\" src=\"https:\/\/meddists.com\/wp-content\/uploads\/2020\/02\/neuronal-types-600x450.png\" alt=\"\" class=\"wp-image-25593\"\/><\/a><figcaption><strong>Neuron morphologies<\/strong> (Credit: Miguel Iglesias, CC BY-SA 4.0)<\/figcaption><\/figure><\/div>\n<\/span><div id=\"the_titles\" style=\"display:none;\"><h4 class=\"wp-block-heading\" class=\"wp-block-heading\">Description<\/h4><h3 class=\"wp-block-heading\" class=\"wp-block-heading\">Parts<\/h3><h4 class=\"wp-block-heading\" class=\"wp-block-heading\">Dendrites<\/h4><h4 class=\"wp-block-heading\" class=\"wp-block-heading\">Axons<\/h4><h4 class=\"wp-block-heading\" class=\"wp-block-heading\">Synapses<\/h4><h3 class=\"wp-block-heading\" class=\"wp-block-heading\">Types of neurons<\/h3><h4 class=\"wp-block-heading\" class=\"wp-block-heading\">Sensory neurons<\/h4><h4 class=\"wp-block-heading\" class=\"wp-block-heading\">Motor neurons<\/h4><h4 class=\"wp-block-heading\" class=\"wp-block-heading\">Interneurons<\/h4><\/div>","protected":false},"excerpt":{"rendered":"<p>Description Neurons are the functional units of the nervous system. They are one of the most active cell groups in our body &#8212; consuming a lot of energy (the brain uses up to 20% of daily energy usage) in the form of glycogen, however, they do not store it. Neurons have the characteristics of protein-producing [&hellip;]<\/p>\n","protected":false},"author":23,"featured_media":0,"parent":3028,"menu_order":1,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-3041","page","type-page","status-publish","hentry"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v28.0 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>The Neuron &#8211; Meddists<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/meddists.com\/learn\/pre-clinical\/histology\/nervous-system\/introduction\/the-neuron\/\" \/>\n<meta name=\"twitter:label1\" content=\"Est. reading time\" \/>\n\t<meta name=\"twitter:data1\" content=\"3 minutes\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\\\/\\\/schema.org\",\"@graph\":[{\"@type\":\"WebPage\",\"@id\":\"https:\\\/\\\/meddists.com\\\/learn\\\/pre-clinical\\\/histology\\\/nervous-system\\\/introduction\\\/the-neuron\\\/\",\"url\":\"https:\\\/\\\/meddists.com\\\/learn\\\/pre-clinical\\\/histology\\\/nervous-system\\\/introduction\\\/the-neuron\\\/\",\"name\":\"The Neuron &#8211; 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