Sage-Tips

What type of a gate the Na+ channel has?

Voltage-gated sodium channels have two gates: an activating gate that is voltage-dependent and an inactivating gate that is time-dependent. The opening of the activating gate allows the influx of sodium and cell depolarization.

What is the role of sodium ion gated channels in the generation transmission of an action potential?

Voltage-gated Na+ channels initiate action potentials in neurons and other excitable cells, and they are responsible for propagation of action potentials along nerves (axons), muscle fibers and the neuronal somato-dendritic compartment 1.

Why is it important for voltage-gated sodium channels to have 2 gates?

Voltage-gated Na+ channels have two gates: an activation gate and an inactivation gate. Therefore, it is not possible for the sodium channels to open again without first repolarizing the nerve fiber. When the Na+ channels are open at the axon hillock, the local membrane potential quickly becomes positive.

How did Hodgkin and Huxley measure potassium conductance?

Hodgkin and Huxley used the equations (2.7) and (2.8) to work the other way round. After blocking the sodium channel with appropriate pharmacological agents, they applied a voltage step and measured the time course of the potassium current.

Which part of the action potential occurs when the Na+ channels are inactivating and K+ channels open?

depolarization
Although the Na+ channel is closed, the localized depolarization causes the local voltage-gated K+ channels to open; K+ passively diffuses out of the axon. When this occurs, action potential is locally restored to near-resting state.

Why is it important that Na+ channels inactivate during an action potential?

Role in action potential Voltage-gated sodium channels play an important role in action potentials. The ability of these channels to assume a closed-inactivated state causes the refractory period and is critical for the propagation of action potentials down an axon.

What is the purpose of sodium ion channels in neurons?

Sodium channels play a central role in physiology: they transmit depolarizing impulses rapidly throughout cells and cell networks, thereby enabling co-ordination of higher processes ranging from locomotion to cognition. These channels are also of special importance for the history of physiology.

How many gates do voltage-gated potassium channels have?

two
Potassium channels are presumed to have two allosterically coupled gates, the activation gate and the selectivity filter gate, that control channel opening, closing, and inactivation.

What is true about the opening of voltage-gated Na+ and K+ channels?

What is TRUE about the opening of voltage-gated Na+ and K+ channels? Voltage-gated K+ channels open more slowly than voltage-gated Na+ channels, even though they are activated at the same time.

What could Hodgkin and Huxley do to study just the role of K+ during action potentials?

Hodgkin and Huxley used the voltage clamp while also manipulating the levels of different ions in the extracellular fluid. In this way they were able to determine the exact contribution of sodium and potassium (and chloride and organic) ions to the action potential.

What did Hodgkin and Huxley discover?

Hodgkin and Huxley’s work with the giant squid axon was the first to use mathematical models to represent biological systems. Due to Hodgkin and Huxley’s findings, we are able to understand how an action potential propagates along a nerve and the functions of their associated ion channels.

What causes Na+ channels gates to open quizlet?

This inward movement of positive charge makes the membrane potential more positive (less negative). The depolarization phase is a positive feedback cycle where open Na+ channels cause depolarization, which in turn causes more voltage-gated Na+ channels to open.

What is the difference between Na channel and K channel?

The K channel is somewhat simpler. It contains a single class of gate consisting of 4 individual activation gates (the n -gates ), which respond more slowly than the activation gates of the Na channel. Thus if the membrane is depolarised, the n-gates open (slowly), and the K channel opens.

How many activation and inactivation gates are in a Na channel?

The HH model proposes that each Na channel contains a set of 3 identical, rapidly-responding, activation gates (the m-gates), and a single, slower-responding, inactivation gate (the h-gate).

What is the function of the m and H Gates?

The m and h gates control sodium flow, while the n gate controls potassium flow. In the resting phase of the action potential, the m gate is closed, while the h gate is open. Therefore, sodium is neither leaving or entering the cell. The n gate is also closed, so potassium can neither leave nor enter the cell.

What is the function of the voltage-gated Na+ channels?

Voltage-gated Na+ channels initiate action potentials in neurons and other excitable cells, and they are responsible for propagation of action potentials along nerves (axons), muscle fibers and the neuronal somato-dendritic compartment .