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In myelinated axons where are the voltage gated sodium channels concentrated?
Wiki User
∙ 12y ago
In myelinated axons, the voltage gated sodium ions are located along the nodes of Ranvier, the exposed places between the myelin segments. The gates here, however, are not particularly more concentrated than on other un-myelinated axons.
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Wiki User
∙ 12y ago
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Where are voltage gated sodium channels concentrated in myelinated axon?
In myelinated axons, the voltage gated sodium ions are located along the nodes of Ranvier, the exposed places between the myelin segments. The gates here, however, are not particularly more concentrated than on other un-myelinated axons. TRUE
What is The region of a neuron with voltage-gated sodium channels?
soma
Where is the density of voltage gated sodium channels the greatest?
Perhaps the neuromuscular junction (NMJ).
What cell gates open immediately after action potential peak?
Sodium and potassium voltage gated ion channels.
What does TTX do to voltage-gated Na channels?
Tetrodotoxin (TTX) is a natural inhibitor and blocks single sodium channels in an all-or-none manner.
How does myelin increase the speed of nerve impulse conduction?
The way an action potential propagates is by opening voltage-gated sodium channels which depolarize the cell. Think about how long it would take to conduct an action potential if you had to open channels along the entire length of the axon and wait for sodium influx. In the case of the myelinated nerve fibers, the myelin sheath covers large portions of the axon, leaving uncovered spaces known as nodes of Ranvier. The sodium channels in a myleinated nerve fiber are only at the nodes of Ranvier. So one sodium channel opening depolarizes a much greater length of the axon until it reaches the next node of Ranvier, where the voltage-gated sodium channels open and this cycle continues. In essence the AP "hops" around, covering much greater distance in a shorter amount of time.
Which ion channel opens in response to a change in membrane potential and participates in the generation and conduction of action potentials?
Sodium channels. A neuron's membrane potential may depolarize for many reasons (neurotransmitters, mechanical deflection, electrical synapse, etc). When that membrane depolarizes to the point of its threshold of activation, then voltage gated channels open up an allow an influx of sodium into the cell. This rapidly depolarizes the cell's membrane, causing that upward peak or rising phase to occur.
What type of channels that are present within the varicosities of autonomic neurons are absent from the axon terminal of other neurons?
Voltage-gated Sodium ions and Potassium ions channels
A nerve impulse results from?
It results from the opening of voltage-gated sodium ion channels, causing an influx of sodium ions (influx of positively-charged ions), depolarizing the neuronal membrane.
Do potassium channels open and sodium channels close during repolarization phase of the action potential?
They both stay open.If sodium channels were to remain closed, there wouldn't be any repolarization. The Potassium concentration gradient would keep pumping Potassium ions out of the cell and the Potassium electrical gradient would drive Potassium ions into the cell, thus maintaining the equilibrium potential of -90 mV.No repolarization would occur if the sodium channels are closed.The above is not correct.During the depolarization phase, BOTH VOLTAGE-GATED SODIUM & POTASSIUM channels open.Once the cell reaches close to sodium's equilibrium potential, the VOLTAGE-GATED sodium channel closes.The VOLTAGE-GATED potassium channel opens around this time(The voltage gated potassium channel is very slow to open; it fully opens around the same time the voltage gated sodium channel closes) causing repolarization.The cell experiences hyperpolarization because the voltage gated potassium is also slow to close.Once fully closed, the cell depolarizes back to resting potential.Also, the picture is a picture of the AP in cardiac muscle which differ from skeletal muscle.The plateau is due to voltage-gated calcium channel that opens during the AP.
The axons of some neurons have an insulating coating called?
This is called myelin or myelin sheath. It's made mainly from fat with a few proteins in it, and is produced by oligodendrocyte cells in the CNS and schwann cells in the peripheral nervous system. It speeds up nerve signalling by allowing action potentials (the electric currents that make up nerve impulses) to skip between the gaps in the myelin (nodes of ranvier). In unmyelinated axons, sodium and potassium channels have to create the voltage differences at every single step along the nerve. (Say for example 100 times per nerve). Myelinated neurones only need to create these voltage differences at the nodes of ranvier (where sodium and potassium ion channels are located on myelinated neurones) Say for example there are 10 nodes of ranvier on a myelinated axon. The unmyelinated axon must create this voltage difference 10 times more frequently than the myelinated axon, hence the nerve impulse travels 10 times faster in a myelinated axon. (Based on the random numbers I used. In real life the numbers may be wildly different, but they still work in this way).
How is an action potential propagated down an axon after voltage-gated sodium channels open in a region of the neuron's membrane?
The entry of sodium ions into the neuron and their diffusion to adjacent areas of the membrane causes those portions of the membrane to become depolarized and results in the opening of voltage-gated sodium channels farther down the axon, which release potassium ions to the outside, returning the charge to its previous state
