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| Chemboy |
 Posted: Tue Apr 22, 2008 9:42 am Post subject: firing nerves |
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Forum Ph.D.
Joined: 01 Jul 2006
Posts: 954
Location: NY
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Do nerves ever randomly fire, or if a person experiences a pain or other kind of sensation is it always caused by something affecting a nerve?
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| Robbie |
| Posted: Tue Apr 22, 2008 10:14 am Post subject: |
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Forum Bachelors Degree
Joined: 08 Aug 2006
Posts: 484
Location: Dublin
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Yes but there are mechanisms to prevent this being brought to the attention of the brain. a certain amount of firing is required which prevents "misfires" being interpretted/causing movement.
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| Chemboy |
| Posted: Tue Apr 22, 2008 10:24 am Post subject: |
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Forum Ph.D.
Joined: 01 Jul 2006
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Location: NY
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| Robbie wrote: |
| Yes but there are mechanisms to prevent this being brought to the attention of the brain. a certain amount of firing is required which prevents "misfires" being interpretted/causing movement. |
So is that to say that when a nerve randomly fires or "misfires," there won't be any kind of sensation associated with it and it'll go unnoticed?
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| Robbie |
| Posted: Tue Apr 22, 2008 11:13 am Post subject: |
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Forum Bachelors Degree
Joined: 08 Aug 2006
Posts: 484
Location: Dublin
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ok, I'll try and explain (wish I had diagrams!!!)
You've probably heard of synapses at least.
In a sensory pathway, there are two synapses, one at the spinal cord and another at the thalamus.
primarily at the spine, around the level where the nerve enters the cord, there is a synapse, lets pretend there is a pain nerve fired, this arrives at the spinal cord, if one pain nerve ending arrives at the synapse and fires once, no signal with be gereated at the postsynaptic neuron, if it fires rapidly a successive amount, there will be sufficient depolarisation of the postsynaptic neuron to generate an action potential and propagate the signal. Similarly, if multiple pain fibres reached the same nerve and fired once, this may cause sufficient depolarisation to make an action potential.
This whole process is called temporal summation,
The other factor that matters is the site of the synapse, if the synapse is along a dendrite spatially distant from the body of the neuron, it will have lesser an effect than if it were closer, so it will cause less net depolarisation of the neuron. This is called spatial summation.
Finally, the other issue is whether the presynaptic neuron is excitatory or inhibitory, if inhibitory (e.g. GABA), it will prevent an action potential, if excitatory, it will produce one. So in total, the action potential in the postsynaptic neuron is the net effect of multiple excitatory and inhibitory neurons acting together.
The signal must be generated at the synapse in the spine to pass up to the brain to the next synapse at the thalamus and be recognised.
(Im pretty sure Ive also just explained part of the foundation of gate control theory.)
If that's too technical I can explain stuff from basics, not too sure what you already know!
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