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Neuron function question

David Todtman dtodtmanREMOVETHHIS at shaw.ca
Fri Oct 24 10:22:36 EST 2003


I am trying to understand an element of neuron action.

At the outset, I want to thank anyone who takes the time to help me out
here.

The text I am using notes two types of neuronal action:  ionic and
metabolic.  An ionic action occurs when enough neurotransmitter molecules
(or other ligands) bind with postsynaptic cell receptors.  I gather that the
binding is an electro-chemical bond and when enough electro-chemical bonds
occur, the electrical potential of the postsynaptic cell changes rapidly and
the cell is said to "fire."  Is this more or less the general idea?  I do
not have to understand this process in a deeply technical way.

Now for a second question.  The text says that metabolic actions occur
gradually--hours, days, weeks, or months.  Then, the text says, "When
ligands bind to these receptors, they operate by activating what are
referred to as _second messenger systems_ within the cytoplasm of the cell."
What is not explained in the text is "these receptors."  Are there a
specific class of receptors that are 'metabolic receptors' as opposed to
'ionic receptors'?

Now, here is another query.  The text says that the second messenger systems
within the alter the cell's internal chemical environment.  Okay but what
specifically are the "messengers"?   Particular molecules?  Do the these
ligands pass into the cell thus altering the internal environment?

And finally, one result of metabolic action can be alteration in the number
of receptor cites.  In simple terms, what are some ways that this may occur?
I.e., I believe that receptors are protein structures and does it happen
that a type of metabolic action results in reductions in the cell's ability
to manufacture the receptors?

Thank you again.

With all good wishes,
David





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