Triggering Neurons

[HelloSkitty]

I know that signals are received using dendrites and sent via axons. But how is the original signal created? Every signal has to start somewhere, so how to the neurons originally fire? Does a sensory stimulus automatically create a pattern of signals to represent the incoming information, which subsequently trigger other neurons which allows for reactions? But if somebody were to be totally deprived of all sensory input, would they be unable to function? Being blind, deaf, numb, and olfactory deprived, would they still be conscious and capable of thought?

 

Also, neurons fires using a chain of chemical reactions along the axon to pass a charge down a line. Supposing somebody were too close to an EMP. Would this cause all of the neurons to fire simultaneously? Or is this what the sheath around the axon is for? Otherwise, then during the refractory period, would a person be unable to function for that split second?

 

It the original signal triggered chemically or electromagnetically? I know this is sort of a mix among physics, molecular biology, and neuroscience, and I though that this was the most suitable location.

[CharonY]

The signal itself are action potentials. You need to understand membrane potentials and depolarization mechanisms (check out wiki and other sites, should be fairly well explained). These signals do not cross synaptic gaps (as the way they are generated prevents this). Instead the arriving action potentials result in the release of metabolites (neutransmitters) that travel the synaptic gap towards receptors. These can then trigger the formation of a new action potential that travels along the new (postsynaptic) neuron.

[Ahsan Iqbal]

Neurons of the nervous system are just conductive pathways for the signals. The sensory neurons convey signals towards the brain and the motor neurons carry them away from the brain. Associative neurons form the brain tissue where information is relayed and saved etc. This is the function of neurons. The generation of impulse in not the function of neurons, (though they can do it in certain conditions). You must have been hearing that human have five senses from childhood. You got to think about it. What does a sense means. What is a sensory organ. Let me explain it to you. Sensory organ of human body is the organ that converts signal of some type into electrical stimulus that can be conveyed to brain. The eye for example convertes light into electrical stimulus, the ear converts sound into electrical stimulus, the nose converts smell into electrical stimulus and so on. Each of these organs have their own separate mechanism to convert corresponding signal into electrical stimulus and if you want further details, I can provide them to you.

The neurons just carry this electrical signal to brain be a wave of polarization and depolarization. So now you can understand the a person having absolutely functional neurons and nervous system can be blind because the organ which transmits light into electrical stimulus is not working. There is no stimulus for neurons to carry to the brain and in simple words, the person is true. The other possibility is also true where the eye is functioning properly but the optic nerves are damages and there is no route to carry the electrical impulse generated by light to the brain. So both a generator and a carrier are necessary.

 

The signal itself are action potentials. You need to understand membrane potentials and depolarization mechanisms (check out wiki and other sites, should be fairly well explained). These signals do not cross synaptic gaps (as the way they are generated prevents this). Instead the arriving action potentials result in the release of metabolites (neutransmitters) that travel the synaptic gap towards receptors. These can then trigger the formation of a new action potential that travels along the new (postsynaptic) neuron.

Charony, I think you have fallen in some other discussion. He is just asking from where does the starting impulse come. All that polarization and depolarization mechanism including the role of neurotransmitters works in conduction of impulse from sensory organs to brain or from brain to the effector. It has nothing to do with the absolute starting point of an impulse.