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An action potential occurs regardless of the amount of stimulation received by the cell.
An action potential occurs regardless of the amount of stimulation received by the cell.
True
During an action potential, the membrane potential can remain at a negative value regardless of stimulation.
During an action potential, the membrane potential can remain at a negative value regardless of stimulation.
False
The amplitude of an action potential is lower than that of graded potentials.
The amplitude of an action potential is lower than that of graded potentials.
False
The time course of an action potential is directly influenced by the duration of the stimulus.
The time course of an action potential is directly influenced by the duration of the stimulus.
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Action potentials exhibit decremental conduction, meaning they diminish in strength over distance.
Action potentials exhibit decremental conduction, meaning they diminish in strength over distance.
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The absolute and relative refractoriness characteristics of an action potential allow the cell to respond to new stimuli immediately after firing.
The absolute and relative refractoriness characteristics of an action potential allow the cell to respond to new stimuli immediately after firing.
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Hyperpolarization can occur during the process of an action potential.
Hyperpolarization can occur during the process of an action potential.
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The resting membrane potential is considered an electrical signal.
The resting membrane potential is considered an electrical signal.
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A threshold value of membrane potential is necessary to trigger the occurrence of an action potential.
A threshold value of membrane potential is necessary to trigger the occurrence of an action potential.
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Depolarization occurs when the membrane potential goes from -70mV to -40mV.
Depolarization occurs when the membrane potential goes from -70mV to -40mV.
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Hyperpolarization refers to the membrane potential becoming more positive than the outside environment.
Hyperpolarization refers to the membrane potential becoming more positive than the outside environment.
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Repolarization is the process of returning the membrane potential to its resting state after depolarization.
Repolarization is the process of returning the membrane potential to its resting state after depolarization.
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The inside of a cell becomes positively charged compared to the outside during reverse polarization.
The inside of a cell becomes positively charged compared to the outside during reverse polarization.
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Active responses of the membrane are organized by the muscle cells themselves without any neural translation.
Active responses of the membrane are organized by the muscle cells themselves without any neural translation.
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Electrodes are used to measure changes in potential across the membrane during fluctuations.
Electrodes are used to measure changes in potential across the membrane during fluctuations.
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A big axon is not suitable for exciting and analyzing membrane properties due to its shape.
A big axon is not suitable for exciting and analyzing membrane properties due to its shape.
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In an unmyelinated axon, the action potential is regenerated at every patch of membrane, leading to a higher velocity of conduction.
In an unmyelinated axon, the action potential is regenerated at every patch of membrane, leading to a higher velocity of conduction.
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The diameter of an axon does not affect the velocity of conduction of the action potential.
The diameter of an axon does not affect the velocity of conduction of the action potential.
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Saltatory conduction occurs in myelinated axons, where action potentials are generated only at the nodes of Ranvier.
Saltatory conduction occurs in myelinated axons, where action potentials are generated only at the nodes of Ranvier.
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In conditions like multiple sclerosis, corrupted myelination prevents action potentials from reaching the effector.
In conditions like multiple sclerosis, corrupted myelination prevents action potentials from reaching the effector.
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A myelinated axon always conducts action potentials faster than an unmyelinated axon regardless of axon size.
A myelinated axon always conducts action potentials faster than an unmyelinated axon regardless of axon size.
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The axon hillock is referred to as the trigger zone where action potentials originate.
The axon hillock is referred to as the trigger zone where action potentials originate.
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An action potential is a digital signal and can be generated anywhere along the neuron's dendrites.
An action potential is a digital signal and can be generated anywhere along the neuron's dendrites.
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The size of axons has no influence on the ability to conduct an action potential.
The size of axons has no influence on the ability to conduct an action potential.
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The action potential of skeletal muscle fibre lasts longer than that of motor neurons.
The action potential of skeletal muscle fibre lasts longer than that of motor neurons.
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Dissipation of graded potentials occurs mainly due to the current lost through the axoplasm.
Dissipation of graded potentials occurs mainly due to the current lost through the axoplasm.
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In a parallel RC circuit model, the capacitor represents the membrane lipids.
In a parallel RC circuit model, the capacitor represents the membrane lipids.
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Action potentials are continuously regenerated due to the voltage gated sodium channels located near the stimulating site.
Action potentials are continuously regenerated due to the voltage gated sodium channels located near the stimulating site.
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As a capacitor becomes charged, its resistance decreases over time.
As a capacitor becomes charged, its resistance decreases over time.
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Graded potentials can be observed far from their stimulating site due to their strong dissipation characteristics.
Graded potentials can be observed far from their stimulating site due to their strong dissipation characteristics.
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Myelinated axons exhibit decremental conduction of action potentials due to the presence of channels in the myelin sheath.
Myelinated axons exhibit decremental conduction of action potentials due to the presence of channels in the myelin sheath.
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When current is injected, there is initially no change in membrane potential because the ion channels are open.
When current is injected, there is initially no change in membrane potential because the ion channels are open.
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The flow of ions after they enter the intracellular fluid (ICF) is towards the more positive regions.
The flow of ions after they enter the intracellular fluid (ICF) is towards the more positive regions.
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If axoplasmic resistance is high compared to membrane resistance, it would be easier for current to move along the axon.
If axoplasmic resistance is high compared to membrane resistance, it would be easier for current to move along the axon.
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The electrical field outside the cell changes as the membrane potential alters, influencing resting potential.
The electrical field outside the cell changes as the membrane potential alters, influencing resting potential.
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Current always flows through both arms of the circuit simultaneously when the circuit is closed.
Current always flows through both arms of the circuit simultaneously when the circuit is closed.
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The voltage gated Na channels contain only an activation gate.
The voltage gated Na channels contain only an activation gate.
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Na channels are responsible for repolarization and hyperpolarization during the action potential.
Na channels are responsible for repolarization and hyperpolarization during the action potential.
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Na conductance increases sharply when the threshold value is reached.
Na conductance increases sharply when the threshold value is reached.
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The time course of K channel conductance is faster than that of Na channel conductance.
The time course of K channel conductance is faster than that of Na channel conductance.
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During the action potential, the membrane potential can reach +70mV.
During the action potential, the membrane potential can reach +70mV.
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Afterhyperpolarization occurs as K channels return to 0 conductance.
Afterhyperpolarization occurs as K channels return to 0 conductance.
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Both Na and K ions can reach their equilibrium potential during an action potential.
Both Na and K ions can reach their equilibrium potential during an action potential.
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A positive feedback loop occurs during the opening of Na channels in response to depolarization.
A positive feedback loop occurs during the opening of Na channels in response to depolarization.
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The activation gate of voltage gated Na channels is open when the cell is at rest.
The activation gate of voltage gated Na channels is open when the cell is at rest.
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The inactivation gate opens immediately after the cell reaches the threshold potential.
The inactivation gate opens immediately after the cell reaches the threshold potential.
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Both the activation gate and the inactivation gate can be open at the same time.
Both the activation gate and the inactivation gate can be open at the same time.
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Once the inactivation gate starts closing, the cell can immediately elicit another action potential.
Once the inactivation gate starts closing, the cell can immediately elicit another action potential.
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An action potential can be elicited when the inactivation gate is open and the activation gate is closed.
An action potential can be elicited when the inactivation gate is open and the activation gate is closed.
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The sodium channel transitions from a closed to an open conformation solely based on internal cellular conditions.
The sodium channel transitions from a closed to an open conformation solely based on internal cellular conditions.
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As membrane potential reaches +30 mV, the inactivation gate begins to close.
As membrane potential reaches +30 mV, the inactivation gate begins to close.
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The cycle of sodium channel activation directly determines the time course of action potentials, making them variable.
The cycle of sodium channel activation directly determines the time course of action potentials, making them variable.
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When the membrane potential goes from -50 mV to -49 mV, sodium channels begin to close.
When the membrane potential goes from -50 mV to -49 mV, sodium channels begin to close.
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Hyperpolarization results from an increase in the membrane potential above the threshold.
Hyperpolarization results from an increase in the membrane potential above the threshold.
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During action potential, there is a window when the sodium can enter the cell due to both gates being open.
During action potential, there is a window when the sodium can enter the cell due to both gates being open.
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During absolute refractoriness, a new action potential can be elicited regardless of the intensity of the current.
During absolute refractoriness, a new action potential can be elicited regardless of the intensity of the current.
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Relative refractoriness allows a new action potential to be triggered, but requires an increased stimulus strength compared to a typical situation.
Relative refractoriness allows a new action potential to be triggered, but requires an increased stimulus strength compared to a typical situation.
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Changes in the interstitial fluid's potassium concentration have no impact on the membrane potential.
Changes in the interstitial fluid's potassium concentration have no impact on the membrane potential.
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Action potentials in different excitable cells, such as myocardial muscle cells and motor neurons, exhibit identical time scales and courses.
Action potentials in different excitable cells, such as myocardial muscle cells and motor neurons, exhibit identical time scales and courses.
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During the process of generating an action potential, hyperpolarization makes it easier for the cell to trigger another action potential.
During the process of generating an action potential, hyperpolarization makes it easier for the cell to trigger another action potential.
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If an excitable cell reaches the threshold spontaneously, it will not elicit an action potential.
If an excitable cell reaches the threshold spontaneously, it will not elicit an action potential.
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The ability of the action potential to communicate effectively is dependent on its precise sequence of events.
The ability of the action potential to communicate effectively is dependent on its precise sequence of events.
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An action potential can occur randomly, resulting in random excitations of cells.
An action potential can occur randomly, resulting in random excitations of cells.
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Both sodium and potassium conductance are key factors influencing the property of refractoriness in excitable tissues.
Both sodium and potassium conductance are key factors influencing the property of refractoriness in excitable tissues.
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The Nernst equation is irrelevant when discussing changes in membrane potential.
The Nernst equation is irrelevant when discussing changes in membrane potential.
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Study Notes
Membrane Excitability: Action Potential
- Resting membrane potential is a constant membrane potential when a cell is at rest.
- Neurons and muscle cells can have rapid fluctuations in their membrane potentials, creating electrical signals.
- Passive membrane properties trigger an active response, triggered by specific stimuli.
- The neuron organizes active responses, translating incoming messages into outgoing ones.
- Active responses are transmitted along the membrane.
Depolarization and Hyperpolarization
- Resting membrane potential is -70mV, meaning the membrane is polarized (excess of negative charges inside, positive outside).
- Depolarization occurs when membrane potential changes from -70mV to -40mV, reducing polarization.
- Depolarizing currents drive membrane potential towards 0mV.
- Hyperpolarization occurs when the membrane potential moves towards more negative values.
- Repolarization is when the membrane returns to resting potential after depolarization.
- Reverse polarization is when the inside of a cell becomes more positive than the outside
Passive Response of Plasma Membranes
- A big axon can be excited and easily analyzed, using intracellular and extracellular electrodes and a voltmeter.
- Stimulating current, either inward or outward, causes changes in membrane potential.
- Inward current causes depolarization; outward current causes hyperpolarization
- The response depends on the stimulus intensity. The higher the stimulus, the higher the resulting graded potential.
Action Potential
- Action potential is an active response of the membrane, is an all-or-none response.
- It has a specific time course that doesn't depend on the stimulus duration. Its amplitude is greater than graded potentials.
- Action potential has absolute and relative refractoriness.
- It does not undergo decremental conduction, meaning it is transmitted without loss of amplitude.
Voltage Gated Na Channels
- Voltage-gated Na channels have activation and inactivation gates.
- At rest, the activation gate is closed and the inactivation gate is open.
- Above threshold, the activation gate opens and the inactivation gate closes.
- The opening of Na channels is a positive feedback loop.
- Inactivation gate close to prevent further Na influx and thus rapid repolarization.
- Channels open based on voltage, not on stimulus intensity.
Voltage Clamp Experiments: Ionic Currents
- Action potential is mainly dependent on sodium and potassium currents. The initial (spike) is due to sodium current, while repolarization depends mainly on potassium.
Refractoriness
- Refractoriness is a property of excitable tissues, determining how closely action potentials can occur.
- There are absolute and relative refractory periods.
- During the absolute refractory period, no new action potential can be elicited regardless of stimulus intensity.
- During the relative refractory period, a new action potential can be elicited but with a need for a stronger stimulus.
The Importance of Ions in Interstitial Fluids
- The concentration of potassium affects the resting membrane potential.
- Action potentials are meaningful signals that have consequences (communication with other cells, triggering of devices such as muscles).
Excitable Cells Show Different Action Potentials
- Various excitable cells have different time scales and courses for action potentials (e.g., motor neuron, skeletal muscle, myocardial).
Myelinated and Unmyelinated Axons
- Myelination of axons increases conduction velocity (saltatory conduction).
- Action potential are regenerated only at nodes of Ranvier.
- Axon diameter also affects conduction speed. Larger diameter axons are faster.
Sensory Neurons and Receptor Potential
- Sensory neurons convert stimuli, converting them into receptor potentials (graded potentials).
- These potentials lead to the generation of an action potential at the axon hillock of the neuron.
- The action potential is transmitted to the central nervous system.
- Sensory transduction converts stimuli into receptor potentials
Adaptation
- Adaptation is the neuron's ability to adjust to a continuous stimulus.
- Receptors may adapt quickly (phasic) or slowly (tonic) to a stimulus.
Multiple Sclerosis (MS)
- Multiple sclerosis is a neurological disorder where nerve fibers lose their myelin sheath.
- Loss of myelin slows down impulse transmission and can disrupt the propagation of action potentials.
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Description
Explore the concepts of membrane excitability, resting membrane potential, and the processes of depolarization and hyperpolarization. This quiz delves into how neurons and muscle cells utilize electrical signals to respond to stimuli and the mechanisms involved in action potentials. Test your understanding of these vital physiological processes.
