What is Neurons: Definition and 62 Discussions

A neuron or nerve cell is an electrically excitable cell that communicates with other cells via specialized connections called synapses. It is the main component of nervous tissue in all animals except sponges and placozoa. Plants and fungi do not have nerve cells.
Neurons are typically classified into three types based on their function. Sensory neurons respond to stimuli such as touch, sound, or light that affect the cells of the sensory organs, and they send signals to the spinal cord or brain. Motor neurons receive signals from the brain and spinal cord to control everything from muscle contractions to glandular output. Interneurons connect neurons to other neurons within the same region of the brain or spinal cord. A group of connected neurons is called a neural circuit.
A typical neuron consists of a cell body (soma), dendrites, and a single axon. The soma is usually compact. The axon and dendrites are filaments that extrude from it. Dendrites typically branch profusely and extend a few hundred micrometers from the soma. The axon leaves the soma at a swelling called the axon hillock, and travels for as far as 1 meter in humans or more in other species. It branches but usually maintains a constant diameter. At the farthest tip of the axon's branches are axon terminals, where the neuron can transmit a signal across the synapse to another cell. Neurons may lack dendrites or have no axon. The term neurite is used to describe either a dendrite or an axon, particularly when the cell is undifferentiated.
Most neurons receive signals via the dendrites and soma and send out signals down the axon. At the majority of synapses, signals cross from the axon of one neuron to a dendrite of another. However, synapses can connect an axon to another axon or a dendrite to another dendrite.
The signaling process is partly electrical and partly chemical. Neurons are electrically excitable, due to maintenance of voltage gradients across their membranes. If the voltage changes by a large enough amount over a short interval, the neuron generates an all-or-nothing electrochemical pulse called an action potential. This potential travels rapidly along the axon, and activates synaptic connections as it reaches them. Synaptic signals may be excitatory or inhibitory, increasing or reducing the net voltage that reaches the soma.
In most cases, neurons are generated by neural stem cells during brain development and childhood. Neurogenesis largely ceases during adulthood in most areas of the brain.

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  1. Sibilo

    I Can EM waves stimulate neurons?

    I'm posting this topic after an invitation to do so. So considering that transcranial magnetic stimulation which operates in frequencies and therefore through EM induction can excite neurons, then can an EM wave also excite neurons?
  2. O

    Radio Wave Induced Firing Of Neurons Through Ca2+ Channel Manipulation

    I’ve read that the Ca2+ channels in neurons can be manipulated through the use of certain radio wave frequencies. And the resulting internal/external charge differential will cause the neurons to fire. Does anyone have any more insight into that?
  3. T

    Patterns in dendritic tree branches of neurons

    I am looking for a study/ressearch that my have been done concerning patterns found in the dendritic tree branching of Neurons.
  4. J

    Uncovering the Link Between Anger and Crime: Neurological Insights and Solutions

    Many crimes and murder were committed because of uncontrollable anger. For example, I heard the news the other day about an ex-cop who shot a mother and his son because of argument. He will spend time in jail, but just before committing the crime couldn't he have thought he would live the rest...
  5. A

    Cumulative DNA damage in active vs. less active neurons?

    Hi all, In light of recent findings about Topoisomerase-mediated DNA double strand breaks, I have been looking for a study out there that compares cummulative DNA damage in active neurons vs. less active counterparts. So far I have not been able to find anything - this would hopefully be over a...
  6. mktsgm

    Medical Exploring the Physiology of Hunger: Hormones, Neurons, and Energy Levels

    I have been studying about the physiology of hunger. I have studied about the hormones that are involved in the process of hunger, like ghrelin, leptin, pancreatic polypeptide, cholecystokinin, cholecystokinin (CCK) and the neurons like AgRP, POMC and neuropeptide Y (NPY) etc. I understand...
  7. BillTre

    Did Neurons Evolve from Secretory Cells?

    People in this Science magazine news article argue yes. The idea that the neuron cell type was in some way derived from secretory cells has been around for a while (1970's at least). The new findings involve finding similarities in how nerve cells and particular secretory cells shared an...
  8. BillTre

    Thermo Activation of Individual Neurons in Live Vertebrates

    A very cool new molecular neuro trick Here's some background and a loose summary. Here is the main reference (surprisingly openly available!). In recent years, neurobiologists have been able to get neurons to make particular proteins by various means (such as filling the cells or in someway...
  9. I

    Do cells in the body stay in one place once they have found their position?

    Once cells in the body "find their place" between other neighboring cells, do they stay there touching each other in the same way or do they move around, migrating, sliding around with their membranes? Can a cell just "take off"? I wonder the same about neuron cells and their axons and...
  10. I

    Are neurons that have been used for years ever re-delegated?

    I'm not sure if this specific question has been already covered. If a person in his 60s who had been say, a painter all his life, decides to instead learn to play an instrument, what happens to the neural processes in his brain? Will the brain use brand-new neurons to create a brand new...
  11. M

    A Three lines two neurons and M×M receptors.

    Dear all, I have lately been interested in AI. One of my thoughts has been as follows: What if we have two 'neurons' and the world consists of vertical, horizontal and diagonal lines. How would we go about making sure only one neuron is assigned to either vertical or horizontal lines and...
  12. I

    How many neurons fire in an eye blink?

    I am wondering how many neurons would need to fire approximately in a human brain in order for the eye to blink, or for example, for a head to nod? And I am referring directly to just the motor act, not all the internal brain processes that might lead to an eye blink. And I am not necessarily...
  13. Q_Goest

    Ion channels enable electrical communication in bacteria

    Here’s an interesting bit of research regarding how bacteria communicate through ion channels. It talks about biofilms which I understand as being thin films of bacteria that colonize the surface of teeth for example: The bacteria then communicate using what sounds like a 2 dimensional EM wave...
  14. Thinkor

    What are prefrontal pyramidal neurons doing?

    I've been reading up on neurology lately and I'm mystified by pyramidal neurons. The pyramidal neurons in the prefrontal cortex, for example, have maybe 20,000 inputs through their dendritic trees and 1 output through the axon. The output is an action potential that always has the same...
  15. Eagle9

    Handbook describing the various types of neurons in rat’s brain

    Good day guys! I am looking for the handbook describing the various types of neurons in rat’s brain. Have you got something like this? I tried to find in google this information with these key words: nissl stain rat brain Accumbens neurons types and number of neurons in rat brain and...
  16. R

    DNA code for human brain neurons

    Hello; First of all I apologize in advance if I make any wrong quotes as I am a Mech engineering and has nothing to do with biology and DNA. I wish to know the entire code or the program of the DNA structure in human brain. As I understood DNA is made up of Adenine, thymine, cytosine and...
  17. N

    Equation from neuroscience textbook, regarding modeling neurons

    Hello, I am trying to understand an equation from the textbook "Theory of neural information processing systems" by Coolen, Sullich and Kuhn. The book states that "the evolution in time of the postsynpatic potential V(t) can be written as a linear differential equation of the form: \frac...
  18. Superposed_Cat

    Does the Encog framework add extra neurons automaticly?

    I recently started using Encog and used BasicNetwork network = new BasicNetwork(); network.AddLayer(new BasicLayer(new ActivationSigmoid(), true, 1)); network.AddLayer(new BasicLayer(new ActivationSigmoid(), true, 2)); network.AddLayer(new BasicLayer(new ActivationSigmoid(), true, r.Length))...
  19. I

    Neurons, DNA, Memory and Learning

    Hello I am not an expert in this field but I am really hoping to understand as much as I can about the concepts described in my questions below. I might be using some improper jargon and expressions, so I apologize if some things are incorrect or confusing. #1 Do all the neurons have the same...
  20. G

    Where does the presynaptic membrane shrink

    During a synapse, a synaptic vesicle fuses with the presynaptic membrane releasing whatever neurotransmitters it contains. Neurotransmitters are then taken in through transport proteins during re-uptake. Stimulation occurs on a regular basis for some neurons and since the neurotransmitters are...
  21. R

    What are the functions of sensory, motor and relay neurons?

    What are the functions of sensory,motor and relay neurons?
  22. J

    Information Representation in Neurons

    Hello everybody, So I've been studying how the brain represents and encodes information. There is ample evidence/info showing that neurons adjust their firing rates and strengths of their synapses in order to encode information and form accessible neural pathways. However I am having trouble...
  23. David Carroll

    Do Neurons Change Fire Rate Over Time?

    I have a question for those who are in the know: Do neurons fire at the same rate throughout a person's life or does the average rate change over time? I ask this because - and this, of course, is speculative - it could figure into why time seems to speed up as one ages, i.e. by anecdote I know...
  24. G

    Whats Carrying the Current in Neurons?

    I was wondering what carries the current between two nodes of ranvier (under the myelin sheath) in a neuron. Books and sources say that the impulse jumps between nodes, but I have not found one that tells me how! Is it through the membrane, across microtubules, through the cytoplasm, or...
  25. J

    Why do big neurons have lower threshold potentials than small neurons?

    Why is that large neurons have smaller threshold potentials than small neurons during external stimulation? My confusion is because the time constant should be larger, right? tau = (r_m) * (c_m). where r_m is membrane resistance and c_m is membrane capacitance Capacitance increases...
  26. P

    Neurons and neurotransmitters. The bigger picture?

    I am trying to learn about neuroscience on my own but every book I have picked up goes so much into details for every single thing that I tend to miss the bigger picture. I have some questions that I can't seem to find answers on, mainly about how neurons work. Keep in mind that I have a...
  27. U

    Modelling of population of neurons

    I am a bit confused between single neuron models and population of neuron models. If we have single neuron models (Integrate and fire model etc) then why we want to develop models for population of neurons? Although single neuron models are ordinary differential equations (easy to analyze) and...
  28. F

    Neurophysics: speed of neurons

    I think this is more of a Neurophysics question and I am just asking a question with no experience in this field. I know the consciousness works because the neurons can send electrical signals within the brain. If I assume the right and left brain is apart from each other and the right brain is...
  29. R

    Do neurons actually die within 5 minutes of anoxia?

    Anoxia is a condition in which there is no delivery of oxygen to tissues of the body. Generally it occurs in cardiac arrest or upon termination of access of air into the lungs. Different tissues have different degrees of resistance to anoxia. It is thought that the least stable are neurons, the...
  30. K

    Medical Do neurons communicate with magnetism ?

    Magnetic effects on the brain are well known, as are magnetic brain scans, but I'm having difficulty finding anything to say magnetism has a function within the brain. I can find electrical communication, but not magnetic. Am I missing something ? Folk, do say if so.
  31. fluidistic

    Medical Are neurons in humans different of the ones of other animals?

    Are neurons in humans different of the ones of other animals like spiders for example? In other words if one shows you a neuron under the microscope, can you identify from which animal it comes from?
  32. mrspeedybob

    Uncovering the Complexity of Single Neurons: A Look into Homoclinic Orbits

    A brief internet search revealed that the number of neurons in a human brain is in the 85 - 100 billion ballpark. (reference) What I could not find was any clear indication of how complex a single neuron is. Is the brain like a network of 85 - 100 billion transistors or 85 - 100 billion...
  33. S

    Why should potassium ions leak from neurons?

    In terms of neurons, the outside is more positive than the inside. Thus, a potassium ion trying to make an escape (due to it's concentration gradient) should be deflected/repelled back into the neuron. Those ions should be bounced back in when they reach close to the surface. But since not, this...
  34. S

    How don't neurons get enough K+ to balance out their inner negative charge?

    If resting potential is negative, then K+ ions shouldn't be passively exiting the cell. It doesn't make sense for a male that is attracted to females to leave a club full of females and go outside where there are lots of males. There are females to be had!
  35. A

    Quantum Information and Brain neurons

    Hello, i want to know if there is any way we can describe the way our brain transfers information using Quantum Information theory. I have been looking at Quantum Information theory for some time now and would want to know if it will ever be possible to transfer information directly from the...
  36. M

    Medical Dielectric constant of neurons

    Hello! First time poster. I hope this is not a wrong sub-forum for this kind of question. Can anyone tell me where can I find values for dielectric constants of neurons and nerve fibers for frequencies in the range of 1e12 - 1e14 Hz (optical and RF part of the spectrum)? I have found data...
  37. Pythagorean

    Coevolution of spatial and synaptic distribution of neurons in C elegans

    1) Original Article: http://www.sciencemag.org/content/298/5594/824.short 2) Comment on Article: http://www.sciencemag.org/content/305/5687/1107.3.full 3) Rebuttal: http://www.sciencemag.org/content/305/5687/1107.4.full Summary of above: 1) Original authors (Milo, et al) create a random...
  38. L

    Telomeres of neurons: Do they also become more short?

    Hello all! During mitosis the telomeres reduced. But neurons do not divide during postnatal period (neural stem cells are exclusion). So - does Hayflick limit exist for neurons? Thanks
  39. rhody

    TED Video: Ed Boyden: A light switch for neurons

    Interesting http://www.ted.com/talks/ed_boyden.html?utm_source=newsletter_weekly_2011-05-17&utm_campaign=newsletter_weekly&utm_medium=email", I thought I would pass it on. Ed Boyden shows how, by inserting genes for light-sensitive proteins into brain cells, he can selectively activate or...
  40. D

    What factors influence the differentiation of neurons?

    Of late, I have been self-learning about the underlying biology behind neurons; saltatory conduction; electrotonic and action potentials. I have (at least for the most part) surmised a basic understanding of how most of this works. What I don't understand, is how do the neurons differentiate...
  41. Femme_physics

    Can Sensors be Attached to Neurons in the Human Body?

    Wasn't sure where to post it as there is no medical engineering forum but... Is it possible to attach a sensor to a neuron in a human body and get the human's neuron to react to the sensor being stimulated?
  42. J

    Neurons would need energy to generate those pain 'signals'

    Hi A human body is a chemical machine. Every process, such as walking, sleeping, thinking, etc., consumes energy but rate of energy consumption varies from one activity to another. I have been told that when some body part such as forehead, hand, is experiencing, a lot of energy is consumed...
  43. M

    What would it feel like if your neurons fired more slowly?

    I am assuming this would have the effect of causing things to appear to move faster, thus remaining in view for shorter subjective periods of time (if crossing your field of view perpendicularly). I think the more you slowed thought, the more the objects would "stutter" as they moved, skipping...
  44. Pythagorean

    Medical Using light to manipulate neurons

    neat trick: http://www.hhmi.org/bulletin/may2010/features/moves3.html
  45. M

    Optogenetics and neurons firing

    Optogenetics is the combination of deep brain stimulation with fiber optics and gene therapy. I have read that there can be two way traffic (http://www.wired.com/magazine/2009/10/mf_optigenetics/all/1") I know that there are no big or small firing of neurons - all firings are the same size...
  46. Simfish

    Summation of reversal potentials in neurons

    Homework Statement Consider a neuron with resting potential of -65 mV and threshold of -55 mV. It receives two synaptic inputs with similar synaptic conductances, one with reversal potential of -10 mV and the other with reversal potential of -58 mV. Draw the predicted postsynaptic...
  47. Pythagorean

    Medical What is Computing with Real Neurons and What Research Exists in This Field?

    Is there a name for this or any research in it? I remember this: http://www.wired.com/wiredscience/2008/08/how-to-train-yo/ but I can't find anything else like it.
  48. M

    Is Muscle Memory tied to Mirror Neurons?

    Just wondering: I know that your mirror-neurons strengthen connections simply by watching someone perform an action. My question is, is muscle memory tied to mirror neurons? Or is this not yet known? Can you gain muscle memory simply by thinking about a certain motion, rather than...
  49. Q_Goest

    Medical Saving Your Brain: How Learning Keeps Neurons Alive

    Not sure if this is the best spot for this, but thought it might be of interest to some folks here. Free seminar open to the public. Where: Lehigh University, Bethlehem, PA Date: Thursday, September 24, 2009 Time: 4:10 PM Loc: Iacocca Hall, B-023; Mountaintop Campus Host...
  50. B

    Medical Question about saltatory conduction in neurons

    I’ve been trying to understand salutatory conduction in myelinated axons and want a better understanding of how depolarization at one node of Ravier causes an action potential at the next. Is it caused by the actual mechanical movement of sodium ions through the axon? There is an animated...