Capacitative current through cell membrane

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Discussion Overview

The discussion revolves around the concept of capacitative current through a neural membrane, particularly how ions move through a capacitor-like structure in the context of neural activity. Participants explore the relationship between ion channels, the plasma membrane, and the flow of current in a steady state.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant expresses confusion about how ions can flow through a capacitor when the plasma membrane acts as a barrier.
  • Another participant clarifies that ion channels are openings in the membrane that allow ions to flow through.
  • A different participant suggests that current does not actually flow through a capacitor but rather builds up charge, proposing that the plasma membrane can be viewed as a dielectric material.
  • This participant also draws an analogy between the behavior of ions in neurons and the charging and discharging of a capacitor, suggesting a similarity to digital signal states.
  • Another comment notes that the principle of current in equals current out applies, but also highlights that neurons can continue to function for a time even without a current input due to the availability of ions.

Areas of Agreement / Disagreement

Participants exhibit a range of views on the nature of current flow through the membrane and the role of ion channels, with no clear consensus reached on the interpretation of the original question or the underlying physics.

Contextual Notes

There are assumptions regarding the definitions of current flow and the behavior of capacitors that remain unresolved. The discussion also touches on the analogy between biological processes and electrical concepts, which may not be universally accepted.

boltdude
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Hello,

I'm having a lot of trouble understanding/visualizing the movement of ions through a capacitor. My book says the total current flowing through a neural membrane (that is in steady state) is equal to the current flowing through ion channels (rm) and the capacitor. However, how can ions flow through a capacitor if the plasma membrane is in the way? Thanks - I'll probably need a dummied down explanation to understand this.
 
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I'm not what you are asking- ion channels/transporters etc. are quite literally little holes in the membrane through which ions flow.
 
Welcome to PF!

boltdude said:
I'm having a lot of trouble understanding/visualizing the movement of ions through a capacitor. My book says the total current flowing through a neural membrane (that is in steady state) is equal to the current flowing through ion channels (rm) and the capacitor. However, how can ions flow through a capacitor if the plasma membrane is in the way?

Hi boltdude! Welcome to PF! :smile:

I know nothing about the subject :rolleyes:, but I remember seeing (but not reading :wink:) a thread in the Biology sub-forum, which may help you: https://www.physicsforums.com/showthread.php?t=258168 :smile:
 
The grammar in which the question was asked is slippery..Because first off current doesn't flow through or across a capacitor,it just builds up,charge is stored...If this is a problem from a physics textbook then revisit the account taking in mind the plasma could just be another dielectric material...If it is from a biology book which i think has something to do with neurons,synapses,the central nervous system,reflex actions and the like then just consider what another had said,plasma membrane has pores through which ions can pass through...The text account I think,was demonstrating the analogy between message transfer in neurons due to ions getting in and out of the membrane as the charging and discharging of the capacitor...You can even consider analogy between this and digital signals because the states are virtually the same,either ON or OFF!Am sure you mistook the book's statement,revisit it again,with consideration of what others have said here at PF!
 
current in = current out

but even with no current in at all the neuron can continue to fire thousands of tumes before it runs out of ions.
 
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