Neurons Definition and 63 Threads

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. 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...
  2. I

    Are neurons sensitive to quantum effects?

    How sensitive are neurons and chemical receptors like olfactory receptors to the chemicals that stimulate them? Can a single molecule stimulate a nerve? How many photons does it take to stimulate a rod or a cone in the eye? I ask because I'm curious as to whether or not human thought and...
  3. Q_Goest

    Medical Is There Any Evidence of Classical Interaction Between Neurons?

    I'm looking for a published paper I can reference that indicates neurons interact classically (ie: no quantum entanglement between neurons). Is there any such reference?
  4. B

    Neurons & Cell Repair: Understanding the Repair Process

    I'm confused about the ability of neurons to repair themselves. My understanding was that most tissue was repaired not by 'mending' individual cells but by creating new cells by cell division (and that most types of neurons don't actually do this) and that cells just became more worn until...
  5. S

    Are Our Moral Values Hardwired in the Brain?

    Lots of current research showing that primates have hard coded values in the neurons of their prefrontal cortexes. See costs and benefits in the brain http://www.nature.com/neuro/journal/vaop/ncurrent/abs/nn1756.html Cardinal utility in the brain...
  6. M

    Medical Neurons & Brain: Exploring the Familiarity Connection

    Can familiarity be explained by neurons or the brain ? how can that be ?
  7. E

    Neurons, Axons & Athletic Injury: Overcoming Problems & Repair Process

    What problems does a neuron need to overcome to maintain the health and growth of the axon? I thought it has a problem with axon's length? Another question is: How would you estimate the muscle mass of a person? I know that muscle does not float, but adipose tissue does. Would I just...
  8. N

    Medical Dielectropharetic control of neurons

    In what ways, if any, is it possible to purposely control neurons? Thanks
  9. S

    Medical Stimulating neurons via magnetic fields

    I ran across this article in "Newsweek-Next Frontiers" about stimulating neurons directly by firing large magnetic pulses to specific locations in the brain: Address: http://www.msnbc.msn.com/id/9557716/site/newsweek/ Well, I can imagine a much more "accurate" device which can affect...
  10. J

    The Unique Shape of Neurons: Exploring Their Form & Function

    Why are neurons shaped the way they are?
  11. Jeebus

    Neurons, Memory & Long-Term Potentiation

    How does the brain knows when and where to store memories—memories such as a car accident? And how does it know whether to place the memories in long-term or short-term memory? Plus doesn't one hypothesis called: long-term potentiation (or LTP) have any basis on how the brain is stimulated...
  12. S

    1st In Vivo Evidence for Quantum Neurons

    This paper on the new quantitative biology section of the preprint arxiv claims evidence in brains of living rats of chaotic behavior matching that of a well known theoretical model of chaotic quantum mechanics. If verified, a true breakthrough.
  13. G

    How do sensory neurons share information in the brain?

    I am trying to find out some information about the nerves that deliver sensory inputs into the brain. I understand that neurons in the brain itself share thousands of connections to other neurons. The neurons that deliver sensory information into the brain at some point meet the ones in the...
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