↑
Neurones
m
The most important parts of system the
m
a nervous are
cell
nerve cells also called neurones These
. cells can produce,
process and transmit electrical impulses. The specialisation Fold of Schwann cell
fibre
of the various neurone types can be seen in their shape
,
branching and degree of extension (see margin) .
Their len-
Nerve fibre
gut can vary from a few micrometers to more than one
meter. However, neuron diversity can be traced back to a
uniform and typical building plan.
Nerve Impulse
A
propagating of electrical RMP -70mV polarised
=
nerve Impulse is a self wave
=
Axon is
↳
disturbance that travels
along the sur face of the axon membrane. stimulus arrives via dendrites= depolarisation (Axon becomes less negative
Tonpotentia
+ 30mV
It is not , however , an electrical current , but a
temporary reversal
RMP
=I V
T
of the electrical potential dience across the axon membrane . stimulus
+
+ + + +
1
------
This reversal is between 2 states called the resting potential refractory
period
and the action potential .
time
Resting Potential
The inside of an axon is negatively charged relative to the outside
(extracellular fluid
In this condition the axon is said to be polarised .
Sodium-potassium pump cycle close and
lon - -
lons
In phase b transport three sodium
In phase a, 3
sodium"go into the sodium-potassium pump .
,
ATP separates into ADP and Energy .
This Energy leads the Pump to the into
lons lons
the polar extracellular space in phase c . Also in phase c ,
when the sodiumTeaves the pump , the shape of the places where the sodium
were inside the pump
In phase d two Potassium lons get pulled into the pump and
Squeeze together because they push out the sodium lons . , the
Energy ,
which closed the
inner side of the pump leaves , so that the pump opens into the
negative charged intracellular space in phase e .
Now in phase f the , same thing happens
to the sodium lon but in the other around. The potassium lons get pushed out of the pump and the shape of the inner
potassium lon , than to the , way
pump changes again. The places for the Potassium lons Squeeze together and the places for the sodium lons open
again. I
·
The neurone is not resting ! The maintenance of the resting potential requires energy. The Term resting potential
is used to describe a neuron that is not transmitting an impulse
#S