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Our nervous system is divided in two components: the central nervous system (CNS), which includes the brain and spinal cord, and the peripheral nervous system (PNS), which encompasses nerves outside the brain and spinal cord. These two components cooperate at all times to ensure our lively functions: we are nothing without our nervous system! Unlike the brain and the spinal cord of the central nervous system that are protected by the vertebrae and the skull, the nerves and cells of the peripheral nervous system are not enclosed by bones, and therefore are more susceptible to trauma. If we consider the entire nervous system as an electric grid, the central nervous system would represent the powerhouse, whereas the peripheral nervous system would represent long cables that connect the powerhouse to the outlying cities (limbs, glands and organs) to bring them electricity and send information back about their status. Image credit: Alessandra Donato Basically, signals from the brain and spinal cord are relayed to the periphery by motor nerves, to tell the body to move or to conduct resting functions (like breathing, salivating and digesting), for example. The peripheral nervous system sends back the status report to the brain by relaying information via sensory nerves (see above image). As with the central nervous system, the basic cell units of the peripheral central nervous system are neurons. Each neuron has a long process, known as the axon, which transmits the electrochemical signals through which neurons communicate. Axons of the peripheral nervous system run together in bundles called fibres, and multiple fibres form the nerve, the cable of the electric circuit. The nerves, which also contain connective tissue and blood vessels, reach out to the muscles, glands and organs in the entire body Nerves of the peripheral nervous system are classified based on the types of neurons they contain - sensory, motor or mixed nerves (if they contain both sensory and motor neurons), as well as the direction of information flow – towards or away from the brain. The afferent nerves, from the Latin "afferre" that means "to bring towards", contain neurons that bring information to the central nervous system. In this case, the afferent are sensory neurons, which have the role of receiving a sensory input – hearing, vision, smell, taste and touch - and pass the signal to the CNS to encode the appropriate sensation. The afferent neurons have also another important subconscious function. In this case, the peripheral nervous system brings information to the central nervous system about the inner state of the organs (homeostasis), providing feedback on their conditions, without the need for us to be consciously aware. For example, afferent nerves communicate to the brain the level of energy intake of various organs. The efferent nerves, from the Latin "efferre" that means "to bring away from", contain efferent neurons that transmit the signals originating in the central nervous system to the organs and muscles, and put into action the orders from the brain. For example, motor neurons (efferent neurons) contact the skeletal muscles to execute the voluntary movement of raising your arm and wiggling your hand about. Peripheral nervous system nerves often extend a great length from the central nervous system to reach the periphery of the body. The longest nerve in the human body, the sciatic nerve, originates around the lumbar region of the spine and its branches reach until the tip of the toes, measuring a meter or more in an average adult. Importantly, injuries can occur at any point in peripheral nerves and could break the connection between the "powerhouse" and its "cities", resulting in a loss of function of the parts of the body that nerves reach into. So, it of great interest for scientists to understand how the nerves, or even how the axonal structure within the nerves, are protected from the constant mechanical stresses exerted on them. Work in this area of biology is carried out by Dr. Sean Coakley, in the laboratory of Prof Massimo Hilliard. The peripheral nervous system can be divided into somatic, autonomic and enteric nervous systems, determined by the function of the parts of the body they connect to. Author: Alessandra Donato from the Hilliard Lab OverviewThe central and peripheral nervous systems. The peripheral nervous system branches outward from the spinal cord and brain to reach every part of your body.What is the peripheral nervous system?Your peripheral nervous system (PNS) is that part of your nervous system that lies outside your brain and spinal cord. It plays key role in both sending information from different areas of your body back to your brain, as well as carrying out commands from your brain to various parts of your body. Some of those signals, like the ones to your heart and gut, are automatic. Others, like the ones that control movement, are under your control. What’s the difference between the peripheral and central nervous systems?Your nervous system consists of two main parts: your central nervous system and your peripheral nervous system. Your central nervous system includes two organs, your brain and spinal cord. Your peripheral nervous system is everything else and includes nerves that travel from your spinal cord and brain to supply your face and the rest of your body. The term “peripheral” is from the Greek word that means around or outside the center. FunctionWhat does the peripheral nervous system do?Your peripheral nervous system has two main subsystems: autonomic and somatic.
Those two subsystems are how your peripheral nervous system does its three main jobs:
SensesYour brain is like a powerful supercomputer. However, it knows nothing about the world outside your body without outside input. That’s why your peripheral nervous system is so important. A computer needs peripheral devices like a camera, microphone or keyboard to give it information from outside itself, and your brain is the same. Your peripheral nervous system is how your brain gets information about the outside world. Most of your peripheral nervous system travel to the rest of your body by exiting or entering your spinal cord. Your cranial nerves are unlike other peripheral nerves in that these very special nerves connect directly to your brain. These nerves carry signals from your nose, ears and mouth, as well as many other organs. Your cranial nerves also give you a sense of touch in the skin of your face, head and neck. Other peripheral nerves intertwine throughout every part of your body. They stretch out everywhere, including to the tips of your fingers and toes. The sensory nerves in your hands and feet are also part of your brain’s ability to get information from the outside world. The motor nerves allow you to move various parts of your body. MovementYour peripheral nerves that branch outward throughout your body deliver command signals from your brain to your muscles. That allows you to move around and do all kinds of tasks, ranging from simple ones, like scratching your nose, to complicated ones, like juggling. Unconscious processesYour autonomic nervous system functions without you thinking about it. Part of your brain is always working, managing processes that keep you alive. Your brain needs your peripheral nervous system to control those functions. Examples of these processes include your heart rate, breathing, blood pressure and your gut’s digestion of food. Types of nerve signalsYour nerves consist of bundles of nerve cells, which have long, arm-like extensions called axons. The nerve cells and their axons twist and intertwine together to form nerve fibers. This is similar to how multiple strands of spun cloth fibers twist together to form sewing thread. Some of the nerves in that bundle carry information into your brain, while others carry information out of your brain.
How does the peripheral nerve system help with other organs?Your autonomic nervous system, which is a part of your peripheral nervous system, helps your brain control all of the vital organs in your body. That also helps your brain care for itself. An example of this is your brain controlling your heartbeat, which ensures your heart pumps blood to your body and brain. Without that blood flow, your brain would die in minutes. Your peripheral nervous system also relays nerve signals from those organs to your brain. Examples include feeling warmth inside of your stomach when you drink a hot beverage or feeling full after a meal. AnatomyWhere is the peripheral nervous system located?Your peripheral nervous system extends everywhere in your body that isn’t your spinal cord or brain. It includes:
The above nerves all branch out and become smaller nerves that spread throughout your body. They eventually end at places like the tips of your fingers and toes or just underneath the surface of your skin. What does it look like?One way to imagine the nervous system is like an upside-down tree, with your brain as the root of the tree and your spinal cord as the tree’s trunk. Your peripheral nervous system spreads out through the rest of your body like limbs, branches and twigs of the tree. What is it made of?Your peripheral nervous system consists of various types of nerve cells and structures. Peripheral nerves and cranial nerves have command centers that are neurons as well as highways that send information called axons and dendrites. The cell types are as follows, with more about them listed below: NeuronsNeurons are the cells that send and relay signals through your nervous system, using both electrical and chemical signals. Each neuron consists of:
Neuron connections are incredibly complex, and the dendrites on a single neuron may connect to thousands of other synapses. Some neurons are longer or shorter, depending on their location in your body and what they do. Glial cellsGlial (pronounced glee-uhl) cells have many different purposes, helping develop and maintain neurons when you’re young and managing how the neurons work throughout your entire life. They also protect your nervous system from infections, control the chemical balance in your nervous system and create the myelin coating on the neurons’ axons. Your nervous system has 10 times more glial cells than neurons. Conditions and DisordersWhat are the common conditions and disorders that affect this body system or organ?There are many conditions and causes of peripheral neuropathy, which means disease or damage of your peripheral nervous system. Some of the most common examples include:
Your peripheral nerves may also show effects of conditions that affect any part of your central nervous system. While these don’t directly affect your peripheral nervous system, they can still disrupt how it works. Common signs or symptoms of peripheral nervous system conditions?The symptoms of peripheral nervous system problems depend on the types of nerves affected. Damage to motor nerves affects your muscles by causing:
Damage to sensory nerves causes the following symptoms:
Damage to your autonomic nerves can affect the following organs and systems:
Common tests to check the health of the body organ?Many tests can help diagnose conditions that affect your peripheral nervous system. The most common starting point is a neurological exam, where your healthcare provider has you use different parts of your body, especially arms, hands, legs and feet, in certain ways. Some of the most common tests include:
Common treatments for the body organ?The treatments for peripheral nervous system problems are as varied as the problems themselves. In many cases, treating the underlying cause of peripheral nervous system issues can relieve the effects on that system. It’s also common that treatments for a condition (or similar conditions) won’t work for other kinds of problems. Potential treatments include, but aren’t limited to, the following:
CareHow can I prevent peripheral nervous system conditions and problems?Prevention is key for many of the conditions that can cause peripheral nervous system damage. Some of the most important things you can do include:
A note from Cleveland Clinic Your peripheral nervous system is a key part of your life. It helps you move around and delivers vital information from your senses to your brain. Prevention is key when caring for this part of your nervous system. If you have conditions that affect your peripheral nerves, there’s a wide range of ways healthcare providers can diagnose and treat these conditions. Even with incurable conditions, it’s usually possible to limit how the symptoms of these conditions affect your life. Which of the following are true about the peripheral nervous system?The correct answer is (D): It includes a sensory division and a motor division. The peripheral nervous system includes all nervous tissue located outside the brain and the spinal cord. It contains two main divisions: sensory and motor.
Which of the following is a true statement about the peripheral nervous system quizlet?Which of the following is a true statement about the peripheral nervous system? It connects the brain and spinal cord with receptors which detect sensations.
Which of the following statements best describes the peripheral nervous system?Which best describes the central and peripheral nervous systems? The central nervous system processes stimuli information the body receives, and the peripheral nervous system senses stimuli and carries out the reaction.
Which of the following is a function of the peripheral nervous system quizlet?Solution. The primary function of the peripheral nervous system is to relay between the CNS and the rest of the body.
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