1.4 An interesting feature of the action potential is this: the amplitude is alw

Question

1.4 An interesting feature of the action potential is this: the amplitude is always the same. That is, whether the nerve is communicating something important or boring, complicated or simple, the amplitude of the pulse moving down the axon is exactly the same. The shape and speed of the pulses are also always the same! Given these constraints, how might action potentials be used to convey more than one piece of information?

1.5 The membrane of the axon cell controls the action potential and therefore determines what we sense, how we think, and much more. The membrane potential is an example of a Nernst potential, described by the equation: delta V = (kB T / q) ln (c1/c2). How might the cell membrane actually control the electric potential that exists between the inside and outside of the cell and what quantities could be measured to test your proposed mechanism? Your answer should refer explicitly to the physics of the Nernst potential. The best answers will relate the state of the membrane to one or more of the phases of the action potential, but please do not write a book. No more than one paragraph is called for here.

1.6 Nerve impulses are transmitted from the end of one axon to the beginning of the next by the release ofneurotransmitters. These are chemicals that cause a modest change in the potential across any nearby axon membrane, including that of the signaling nerve. Consider the features of the action potential. The neurotransmitters released by the signaling nerve do not trigger a return action potential that would run back along the same axon from which the signal came. In light of this observation, how much of a change in potential can these neurotransmitters induce, and for how long? Your answer should be based solely on the model and information provided here, and not from the much more complicated scenarios described on the internet, in articles, and in books.

Explanation / Answer

Answer 1.4

Suppose an action potential is carry information to the hand to sense a heated cup. Action potentials need only threshold potential to be fired. When it gets the threshold, it is fired, and allows the heat sensation to the hand.

At the same time, the person may shout for which the same action potential will pass the same threshold potential to a (vocal) nerve that is going towards the à brain-à motor nerve -à vocal cord. So, the same action potential potential will be traversed via synapse to the nerve that is going toward the vocal cord.

Now, let us consider that the same person perspires at the same time. For this fight and flight hormone, adrenaline should be produced. So, either the heat sensation of the hand or the shout sensation of vocal cord will transfer the same action potential to the nerve going towards the adrenals. The process will be same as explained in the above paragraph. First the signal will go to the brain and then the motor nerve will bring the signal to the adrenals.

So, an action potential can convey more than one piece of information at a time.

Note that in the above case the same action potential is conveying three messages at a time: heat sensation, shouting, and perspiration.

** Kindly post the other questions separately.

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