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

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

• 1.
  6.5.5 Explain how anerve impulse passes along a non-myelinated neuron
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  NERVE IMPULSE • Anelectrical current which carry information that travels along dendrites and axons of a neuron
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  NON-MYELINATED NEURON • Neuronwithout myelin sheath
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  RESTING POTENTIAL • Thepotential 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.
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  • When theneuron 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.
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  • The restingpotential 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.
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  ACTION POTENTIAL • Thepotential 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.
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  • Action potentialis 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. ~
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  • This areaof 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.
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  • This causesthe 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.