Page 144 - The Miracle in the Cell Membrane

Voltage-Gated
Ion Channels

The move ment of ion chan -
nel in the form of gates
depends upon the elec tri cal
charge of the cell mem brane.
For exam ple, when a strong
neg a tive charge exists on the
inner side of the cell mem -
brane, the sodi um chan nels'
outer sides are tight ly closed.
When the inner side of the
mem brane loses its neg a tive
charge, these gates sud den ly
open and large amounts of
sodium enter the cell.
Potassium gates, on the other
hand, open when the inner side
of the cell mem brane becomes
pos i tive ly charged.
You might com pare the
gates open ing and clos ing to
doors that are opened and
closed under the con trol of a
secu ri ty offi cer. In the same
way that the offi cer opens the
door only when he rec og niz es
peo ple or approves their
iden ti ty cards, so the ion

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