What is Nervous system: Definition and 22 Discussions

In biology, the nervous system is a highly complex part of an animal that coordinates its actions and sensory information by transmitting signals to and from different parts of its body. The nervous system detects environmental changes that impact the body, then works in tandem with the endocrine system to respond to such events. Nervous tissue first arose in wormlike organisms about 550 to 600 million years ago. In vertebrates it consists of two main parts, the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS consists of the brain and spinal cord. The PNS consists mainly of nerves, which are enclosed bundles of the long fibers or axons, that connect the CNS to every other part of the body. Nerves that transmit signals from the brain are called motor nerves or efferent nerves, while those nerves that transmit information from the body to the CNS are called sensory nerves or afferent. Spinal nerves are mixed nerves that serve both functions. The PNS is divided into three separate subsystems, the somatic, autonomic, and enteric nervous systems. Somatic nerves mediate voluntary movement. The autonomic nervous system is further subdivided into the sympathetic and the parasympathetic nervous systems. The sympathetic nervous system is activated in cases of emergencies to mobilize energy, while the parasympathetic nervous system is activated when organisms are in a relaxed state. The enteric nervous system functions to control the gastrointestinal system. Both autonomic and enteric nervous systems function involuntarily. Nerves that exit from the cranium are called cranial nerves while those exiting from the spinal cord are called spinal nerves.
At the cellular level, the nervous system is defined by the presence of a special type of cell, called the neuron, also known as a "nerve cell". Neurons have special structures that allow them to send signals rapidly and precisely to other cells. They send these signals in the form of electrochemical impulses traveling along thin fibers called axons, which can be directly transmitted to neighboring cells through electrical synapses or cause chemicals called neurotransmitters to be released at chemical synapses. A cell that receives a synaptic signal from a neuron may be excited, inhibited, or otherwise modulated. The connections between neurons can form neural pathways, neural circuits, and larger networks that generate an organism's perception of the world and determine its behavior. Along with neurons, the nervous system contains other specialized cells called glial cells (or simply glia), which provide structural and metabolic support.
Nervous systems are found in most multicellular animals, but vary greatly in complexity. The only multicellular animals that have no nervous system at all are sponges, placozoans, and mesozoans, which have very simple body plans. The nervous systems of the radially symmetric organisms ctenophores (comb jellies) and cnidarians (which include anemones, hydras, corals and jellyfish) consist of a diffuse nerve net. All other animal species, with the exception of a few types of worm, have a nervous system containing a brain, a central cord (or two cords running in parallel), and nerves radiating from the brain and central cord. The size of the nervous system ranges from a few hundred cells in the simplest worms, to around 300 billion cells in African elephants.The central nervous system functions to send signals from one cell to others, or from one part of the body to others and to receive feedback. Malfunction of the nervous system can occur as a result of genetic defects, physical damage due to trauma or toxicity, infection, or simply senesence. The medical specialty of neurology studies disorders of the nervous system and looks for interventions that can prevent or treat them. In the peripheral nervous system, the most common problem is the failure of nerve conduction, which can be due to different causes including diabetic neuropathy and demyelinating disorders such as multiple sclerosis and amyotrophic lateral sclerosis. Neuroscience is the field of science that focuses on the study of the nervous system.

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  1. D

    Biology The cell bodies of which of the neurons are present in the spinal cord

    TL;DR Summary: Location of cell bodies of neurons. ***The cell bodies of which of the following neurons are present in the grey matter of the spinal cord?*** *(a) Motor neuron and Sensory neuron (b) Association neuron and Motor neuron (c) Sensory neuron and Association neuron (d) Sensory...
  2. samy4408

    Medical The impact of the sympathetic nervous system on blood vessels

    Hello, I have some trouble understanding the role of the sympathetic nervous system in vasoconstriction and vasodilatation of blood vessels, I searched and found contradicting resources, does anyone have the right answer?
  3. Wrichik Basu

    How do different retinal ganglion cells send distinct signals to the brain?

    I was thinking how nerve impulses may differ from each other, if at all they do differ. I searched on Google, but the answers didn't provide a satisfactory answer to my question. Take, for example, the human eye. The cone cells are responsible for vision on bright light, and they have the...
  4. lekh2003

    B Is it possible to use technology from a nervous system?

    Is it in anyway possible to use the "propagation of action potential" and an artificial myelin sheath in modern technology? Would this method overcome the problem of resistance? I found that superconductors have zero resistance but are too expensive. So ceramic can be used, but that is brittle...
  5. I

    Un-involvement of the nervous system in the body?

    This might be an obvious question, but is there any tissue functionality in the body that the nervous system is not involved or implicated in? What I mean is, is there any process that doesn't need the nervous system's involvement and does its functionality independently and not related to it...
  6. F

    Medical Can the Nervous System Be Manipulated to Control Inflammation?

    http://www.nature.com/nature/journal/v421/n6921/full/421328a.html Would you know other researches about this? the connection between inflammation and the nervous system?
  7. I

    Influence of the nervous system on the endocrine system

    In explanations of the nervous and endocrine systems, so far, I have only heard that they influence each other or work together in some way. Can anyone give me an example or two on how exactly the nervous system would influence/activate/stimulate the endocrine system? And if vice versa? Many...
  8. I

    Is reflex considered a function of autonomic nervous system?

    I was wondering if reflex is exclusively under the umbrella of the autonomic nervous system, or are there some reflexes that for some reason or definition, that would be associated with another nervous system? I did find in some articles that somatic nervous system also has its own types of...
  9. E

    Magnetic Field affecting the nervous system

    I recently learned about Magnetic fields and the force they apply on moving charged particles.I had read in biology that the nervous system works on electrical impulses.My question is,do magnetic fields affect the nervous system?Do they apply a force on the nerves? I know this may not be the...
  10. Pythagorean

    Gap junction function in the nervous system

    In part branching off a discussion here, but also a discussion I've always been interested in having. I also want to take some time to answer the question in that thread: axo-axonic gap junctions in the hippocampus are thought to play a role in generating ultra-fast oscillations that have a...
  11. J

    Sympathetic nervous system activates major skeletal muscle?

    Is is true that "Sympathetic nervous system activates your heart and major skeletal muscles? Thank you for your help!
  12. C

    Signal processing in the nervous system?

    How does body motion control occur? For example, walking on high heels during a strong wind is pretty hard. There is a compressible fluid flow across the body, the center of mass is changing all the time, you have to balance on a tiny surface area, sensor data from the skin, eyes, ears, etc...
  13. C

    Books (or any information material) about the nervous system?

    I appear to have a very specific need, I require some sort of a book that covers the human nervous system from a to z, I need to know everything about it, what it's made of, what each part's function are, how the nerves behave at each particular sections of the body, the calculations that are...
  14. M

    Paralysing the somatic nervous system

    In the movie Law Abiding Citizen, there's a scene where a guy gets paralysed by a puffer fish toxin I think it was (maybe tetrodotoxin) and the guy who paralysed him explained that "the toxin completely disables your ability to move your muscles but it leaves all the other neurological functions...
  15. S

    Neurophysiology homework question- nervous system of a fictional sea creature.

    [b]1. Create the nervous system of a simple fictional sea creature which is round with a single tail controlled by two antagonistic muscles. You may only use two light-sensitive neurons, but as many excitatory and/or inhibitory neurons as you wish. Each neuron used must be either entirely...
  16. B

    Effects of static electricity on nervous system

    Maybe this should be posted in biology but it seems more like an electricity question to me: I've read that static electricity increases in the cold because of lower relative humidity. This seems to mean that it is more difficult for things to dissipate/ground their electric charge to the...
  17. S

    Medical Supporting cells of the nervous system

    Hello everyone, I have a quick question. Ok the endoneurium is a layer of delicate connective tissue that encloses the myelin sheath of a nerve fiber within a fasciculus. Now my question is supporting cells of the nervous system like glial cells usually connect two nerve fibres together, so...
  18. M

    Medical Pain in the peripheral nervous system

    To my (limited) understanding, the peripheral nervous system sends messages of pain in the form of electrical impulses to the brains. But what's the difference between signals of extreme pain and mild pain/touch?
  19. E

    Medical Nervous System Problems/Diseases and multiple sclerosis

    Hi, my AP bio class is going over the nervous system, and brain structure and eventually will be discussing diseases that attack the nervous system. Does anyone have any good examples I could bring up? I also am looking for an answer as to why in multiple sclerosis the myelin sheaths are...
  20. P

    What is the Role of Schwann Cells in Speeding Up Nervous System Signals?

    Would someone explain me, please, the sentence in bold? My doubt is why signals jumping from node to node travel hundreds of times faster than signals traveling along the surface of the axon.
  21. S

    Cocaine and the nervous system

    Can anyone hook me up with some good sites that describe the science behind how cocaine affects the human nervous system? I've searched by found little quality I'll be grateful is you can procide me with any sites/info.
  22. C

    Exploring Development of Human Nervous System

    I have some questions : :smile: 1> Would you please tell me what slows down the development of human nervous system ? 2> A situation: A very cute two year old baby was playing with his toys: I let him see a pink ball, ten times. Then let him see a blue ball. I tried to observe his actions and...