367
CHAPTER TEN
Nervous System I
+
+
+
+
+
+
+
+
+
+
+
+ –
+
+
+
+
–70 mV
Low Na
+
Low K
+
High K
+
High Na
+
Na
+
K
+
(c)
Pump
Cell
membrane
Gatelike mechanism
Protein
Fatty acid
tail
Phosphate
head
(b)
Channel open
(a)
Channel closed
FIGURE 10.14
The resting potential. (
a
)
Conditions that lead to the resting potential. (
b
)
In the resting neuron, the inside of the membrane
is negative relative to the outside. (
c
) The Na
+
/K
+
pump maintains the concentration gradients for
Na
+
and K
+
ions.
FIGURE 10.13
A gatelike mechanism can (
a
) close or (
b
) open some of the channels in cell membranes through which ions pass.
Axon
Cell body
Low Na
+
Axon terminal
Low K
+
High K
+
High Na
+
Impermeant
anions
(a)
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
–70 mV
(b)
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