Written by Arda Kizilkaya
Neurons are nerve cells that make up the brain and the nervous system, neurons also send messages all over your body to allow you to do everything from breathing to talking, eating, walking, and thinking. The reason for that is that our roughly 100 billion neurons do interact closely with other cell types broadly classified as glia , with that interaction our cells do what the neurons ordered them to do. Neurons also help with our immune system. Dendritic cells move to the lymph nodes to find the right T-cell, and dendritic cells arrive at the lymph nodes with the help of neurons.
How a Neuron Function:
Neurons have multiple different factors that affect how they function. For example:
A Neuron's Structure:
A neuron's role and location change according to size and structure, but nearly all neurons have three essential parts: a cell body, an axon, and dendrites.
Cell body:
The cell body, also known as soma, is the core section of the neuron. The cell body contains the neuron's genetic information, maintains the neuron’s structure, and provides the energy to drive activities. Similar to other cell bodies, a neuron’s soma contains a nucleus and specialized organelles. The cell body is enclosed by a membrane that both protects it and allows it to interact with its immediate surroundings.
Axon
A neuron's axon is a long, tail-like structure. It joins the cell body at a specialized interchange called the axon hillock. Most of the axons are insulated with a fatty substance called myelin. Myelin helps the axons to conduct an electrical signal. Neurons mostly have one main axon.
Dendrites
Dendrites are fibrous roots that branch out from the neuron's cell body and the axon of the neuron. Dendrites receive and process electrochemical signals from the axons of other neurons. Neurons can have multiple sets of dendrites, which is known as dendritic trees. How many sets of dendrites a neuron has generally depends on their role. For instance, Purkinje cells are a special type of neuron found in the brain's cerebellum. These cells have highly developed dendritic trees which allow them to receive hundreds of thousands of signals.
Types of Neurons:
Neurons are different from other neurons' structure, function, and genetic makeup. There are many different types of neurons, much like there are thousands of species of living organisms on Earth. However, there are five major neuron forms. Each of them combines several elements from the basic neuron shape:
Multipolar neurons: These neurons have a single axon and symmetrical dendrites that extend from the neuron's cell body. This is the most common type of neuron in the central nervous system.
Unipolar neurons: Usually only found in primitive-like species, these neurons have a single axon.
Bipolar neurons: Bipolar neurons have two extensions that extend from the cell body. On one side of the neuron is the axon, and the dendrites are on the other side. These types of neurons are usually found in the retina of the eye, but they can also be found in parts of the nervous system that help the nose and ear function.
Pyramidal neurons: These neurons have one axon but several dendrites that form a pyramid shape. These are the largest neuron cells and they are mostly found in the cortex. The cortex is responsible for conscious thoughts.
Purkinje neurons: Purkinje neurons have multiple highly developed dendrites that fan out from the cell body. These neurons are inhibitory neurons, which means they release neurotransmitters that keep other neurons from firing.
The Functions of the Types of Neurons:
Sensory neurons
Sensory neurons help you with taste, smell, hearing, sight, and touch. Sensory neurons are triggered by physical and chemical inputs from the environment around you. For example, touching on a hot pan activates sensory neurons in the soles of your fingers. Those neurons send a message to your brain, which makes you aware of the heat of the pan.
Motor neurons
Motor neurons' role is in movement, including voluntary and involuntary movements. These neurons allow the central nervous system (the brain and spinal cord) to communicate with muscles, organs, and glands all over the body.
Motor neurons are in two types: lower and upper. Lower motor neurons carry signals from the spinal cord to the smooth muscles, like our stomach and intestines, and skeletal muscles, like Tibialis anterior and Gastrocnemius. Upper motor neurons carry signals between your central nervous system. When you eat, for instance, lower motor neurons in the spinal cord send signals to the smooth muscles in your esophagus, stomach, and intestines. These muscles contract, and that allows food to move through the digestive tract.
Interneurons:
Interneurons are neural intermediaries found in your central nervous system. They’re the most common type out of all the neuron types. They pass the signals from sensory neurons and other interneurons to motor neurons and other interneurons. Usually, they form complex circuits that help you to react to external stimuli. For instance, when you touch something sharp like a knife, sensory neurons in your fingertips send a signal to interneurons in your spinal cord. Some interneurons pass the signal on to your motor neurons in your hand, which allows you to move your hand away. Other interneurons send a signal to the pain center in your brain, and after that you experience pain.
How do neurons work?
Neurons send signals by using action potentials. An action potential is a shift in the neuron’s potential electric energy caused by the constant flow of charged particles in and out of the membrane of the neuron. When it's generated, it’s carried along the axon to a presynaptic ending. Action potentials can be triggered by both chemical and electrical synapses. Synapses are locations where neurons can pass these electrical and chemical messages between neurons. They are made up of a presynaptic ending, a synaptic cleft, and a postsynaptic ending.
Chemical synapses
In a chemical synapse, the neuron releases chemical messengers called neurotransmitters. Neurotransmitters cross the synaptic cleft and bind to receptors in the postsynaptic ending of a dendrite. Neurotransmitters can trigger a response in the postsynaptic neuron that causes it to generate an action potential of its own,or they can prevent activity in the postsynaptic neuron. If that's the case, the postsynaptic neuron doesn’t generate an action potential.
Electrical synapses
Electrical synapses can only provoke. Electrical synapses form when two neurons are connected by a gap junction. This gap is much smaller than a chemical synapse and is made up of ion channels, which help transmit a positive electrical signal. Signals move much faster across electrical synapses than chemical synapses because of the way these signals travel. However, these signals can diminish from one neuron to the other. This makes electrical synapses less effective at transmitting repeated signals.
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