Dear All,
Can anyone help me with this problem?
Nerve and muscle cell membranes depolarise and repolarise
by about 120 mV up to 100 times per second.
The depolarisation of the plasma membrane is very rapid
(a few microseconds) and results in the extracellular
medium gaining a more negative electrical potential,
while the intracellular, cytosolic medium becomes more
positive due to the entry of positive ions. The abrupt
increase in the positive potential of the cytosol must
immediately cause an increase in the transmembrane
potential of intracellular organelles by up to 100 mV.
For example the transmembrane potential of the mitochondria
must increase by up to 100mV. This hyperpolarisation of
intracellular organelles will disipate as ions move across
the membranes in response to the increased potental. And
the hyperpolarisation will be reversed (1 to 2 milliseconds
later) when the plasma membrane is repolarised.
But if this is true there will inevitably be massive
perturabtions of energy metabolism and intracellular
ion fluxes up to 100 times per second!
How large the perturbations will be depends on the relative
electrical capacity and conductance of the extracellular and
intracellular media.
Does anyone know whether the spread of the intracellular
potential change has been measured or modelled (other than
in the squid axon)? Any references, ideas, or previous
thought on this subject would be appreciated.
Guy Brown
