6.5.5 Explain how a nerve impulse passes along a non-myelinated neuron

1. 6.5.5
Explain how a nerve impulse passes
along a non-myelinated neuron

2. NERVE IMPULSE
• An electrical current which carry information
that travels along dendrites and axons of a
neuron

3. NON-MYELINATED NEURON
• Neuron without myelin sheath

5. RESTING POTENTIAL
• The potential difference across a nerve cell membrane
when it is not stimulated. (-70mV)
• A nerve impulse is an electrical current that travels
along dendrites or axons due to ions moving through
voltage-gated channels in the neuron’s plasma
membrane.
• The voltage-gated channels are the sodium and
potassium channels, which means that they can open
and close depending on the voltage across the
membrane.

6. • When the neuron is not sending an impulse,
the charge difference is maintained inside and
outside of the axon cell. This is called the
resting potential where it is polarized.

7. • The resting potential is due to the active
transport of Na+ ions and K + ions through
sodium-potassium pumps.
• The pumps sends Na+ ions out of the axon cell
and brings K + ions in.
• There are negatively charged ions (Cl-) located
permanently in the cytoplasm of the axon.
This leads to the net positive charge outside
the axon membrane and a net negative charge
inside the axon membrane.

9. ACTION POTENTIAL
• The potential difference produced across the
plasma membrane of nerve cell when it is
stimulated.
• Due to the diffusion of ions from outside the
axon to the inside and from the inside of axon
to the outside.

10. • Action potential is triggered by a stimulus
received at a receptor or sensitive nerve ending
causes a sodium channel to open.
• The Na+ ions which is actively transported out
diffused into the membrane. This causes the local
region inside the membrane to have net positive
charge while the outside having net negative
charge.
• The membrane is said to be “depolarized”. The
resting potential is reversed from -70mV to
+40mV. ~

11. • This area of axon then initiates the next area
of the axon to open up the other sodium
channels. (Domino effect)
• Therefore, the moving depolarization is called
an action potential.
• After a short while, the sodium channels
closed, and the potassium channels are
opened.

12. • This causes the rapid flow of K + ions out of the
membrane and thus, “repolarizing” the
membrane.
• So, the inside is again negatively charged and
the outside is positively charged.
• The resting potential of the membrane is
restored.