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What has to be crossed before the neuron fires?
The threshold potential must be reached for the neuron to fire. This is the level of depolarization that triggers an action potential to be generated and propagated along the neuron.
A neuron will generate action potentials when it?
reaches a certain threshold level of depolarization, typically around -55 mV. This threshold is reached when excitatory signals outweigh inhibitory signals received by the neuron. Once the threshold is reached, voltage-gated sodium channels open, allowing a rapid influx of sodium ions and causing depolarization of the cell membrane, leading to an action potential.
What ion is rapidly moving into the cell during the depolarization period of an action potential?
Sodium.A positive ion (cation) that enters the cell (influx) rapidly when the membrane threshold is reached and the voltage gated sodium channels open.This occurs during the rising phase of an action potential, i.e. membrane depolarization beyond the threshold for activation.
What effect of the action potential if sodium channels are kept closed?
The action potential will not generate if the sodium channels are kept closed.This is because the sodium channels are responsible for the dramatic rising phase of membrane depolarization that occurs when the threshold of activation is reached. As a membrane potential gradually depolarizes (which can occur for a variety of reasons such as neurotransmitter stimulation, mechanical deformation of the membrane, etc), that membrane potential gradually comes closer to that threshold of activation. Once that threshold is reached, the voltage gated sodium channels open and allow for a dramatic influx of sodium ions into the cell. This results in a rapid depolarization which is seen as the rising phase of that upward spike noted in an action potential. Without the ability to open these sodium channels we may reach the threshold of activation, but the actual action potential will not occur.
Why don't the terms depolarization and action potential mean the same thing?
Depolarization occurs when a stimulus opens sodium channels which allow more sodium to go into the membrane making it less negative and more positive (toward reaching threshold). An action potential can only occur once the membrane reaches threshold which means it has reached the level needed through depolarization. An action potential is a brief reversal in polarity of the membrane making the inside more positive and the outside more negative, the reverse occurs again once the membrane reaches resting potential.
What has to be crossed before the neuron fires?
The threshold potential must be reached for the neuron to fire. This is the level of depolarization that triggers an action potential to be generated and propagated along the neuron.
A neuron will generate action potentials when it?
reaches a certain threshold level of depolarization, typically around -55 mV. This threshold is reached when excitatory signals outweigh inhibitory signals received by the neuron. Once the threshold is reached, voltage-gated sodium channels open, allowing a rapid influx of sodium ions and causing depolarization of the cell membrane, leading to an action potential.
What ion is rapidly moving into the cell during the depolarization period of an action potential?
Sodium.A positive ion (cation) that enters the cell (influx) rapidly when the membrane threshold is reached and the voltage gated sodium channels open.This occurs during the rising phase of an action potential, i.e. membrane depolarization beyond the threshold for activation.
What effect of the action potential if sodium channels are kept closed?
The action potential will not generate if the sodium channels are kept closed.This is because the sodium channels are responsible for the dramatic rising phase of membrane depolarization that occurs when the threshold of activation is reached. As a membrane potential gradually depolarizes (which can occur for a variety of reasons such as neurotransmitter stimulation, mechanical deformation of the membrane, etc), that membrane potential gradually comes closer to that threshold of activation. Once that threshold is reached, the voltage gated sodium channels open and allow for a dramatic influx of sodium ions into the cell. This results in a rapid depolarization which is seen as the rising phase of that upward spike noted in an action potential. Without the ability to open these sodium channels we may reach the threshold of activation, but the actual action potential will not occur.
Why don't the terms depolarization and action potential mean the same thing?
Depolarization occurs when a stimulus opens sodium channels which allow more sodium to go into the membrane making it less negative and more positive (toward reaching threshold). An action potential can only occur once the membrane reaches threshold which means it has reached the level needed through depolarization. An action potential is a brief reversal in polarity of the membrane making the inside more positive and the outside more negative, the reverse occurs again once the membrane reaches resting potential.
What determines whether a neuron has an action potential?
A neuron will have an action potential if the stimuli it receives are strong enough to reach its threshold level. Once the threshold is reached, voltage-gated channels open, allowing an influx of sodium ions which triggers depolarization and leads to the generation of an action potential.
When threshold is reached at the SA node what channels open causing further depolarization of the membrane?
Fast Calcium
A common feature of action potentials?
A common feature of action potentials is their all-or-nothing nature, meaning once the threshold is reached, the action potential will always fire at full amplitude. Additionally, action potentials are propagated in one direction, from the cell body down the axon to the axon terminal. They have a consistent shape and duration, regardless of the stimulus strength.
Triggering of the muscle action potential occurs after?
depolarization of the cell membrane reaches a threshold level. This threshold is usually around -55mV. Once threshold is reached, voltage-gated sodium channels open, allowing sodium ions to rapidly enter the cell and generate an action potential.
What does threshold mean in a muscle or nerve cell membrane?
Threshod is the amount of force or exertion that a muscle or nerve cell can withstand at the peak of stimulation. Extending over a threshold can lead to cell over-exertion and possible damage to the internal structures.
What is the response if you increase the stimulus intensity past the threshold level for a neuron?
Increasing the stimulus intensity past the threshold level for a neuron will not further increase the action potential generated. Once the threshold is reached, the neuron will fire an action potential at its maximum intensity.
What principle states that the properties of the action potential are independent of the relative strength of the depolarizing stimulus?
The all-or-none principle states that the properties of an action potential, such as amplitude and duration, are independent of the intensity of the stimulus that triggers it. This means that once a threshold stimulus is reached, the action potential will fire at maximal strength regardless of the strength of the initial stimulus.
