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Sub threshold depolarisation of nerves, would be the influx of sodium (and maybe efflux of potassium depending) that doesn't cause enough depolarisation for an action potential to be fired. The summation of sub threshold depolarisations may cause an AP to be released. if they 'tip the balance' far enough.
Hope this helps
Edit: Above answer is vague. Sub threshold depolarizations do not occur as a result of efflux of potassium, which hyperpolarizes a neuron. They can be generated as EPSPs at the post synaptic membrane or result from persistant sodium channels, which do not completely inactivate (contributing to pacemaking activity). In both cases, gradual depolarization can lead to action potential generation.
What else can I help you with?
Can action potentials be summated?
Yes, action potentials can be summated when multiple sub-threshold stimuli are received in rapid succession, causing the neuron to reach threshold and fire an action potential. This process of summation can lead to greater depolarization and stronger signals being sent along the neuron.
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.
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.
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.
Why are most action potentials generated in response to a long stimulus that is above threshold?
Action potentials are generated in response to a long stimulus above threshold because it allows for the full development of the depolarization phase. This prolonged depolarization leads to the activation of voltage-gated sodium channels, triggering the rapid influx of sodium ions and initiating the action potential. A sustained stimulus ensures that the membrane potential remains above threshold for a sufficient time to generate an action potential.
Can action potentials be summated?
Yes, action potentials can be summated when multiple sub-threshold stimuli are received in rapid succession, causing the neuron to reach threshold and fire an action potential. This process of summation can lead to greater depolarization and stronger signals being sent along the neuron.
When threshold is reached at the SA node what channels open causing further depolarization of the membrane?
Fast Calcium
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.
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.
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.
When does a neuron reach the threshold of response?
A neuron reaches the threshold of response when the depolarization of its membrane potential exceeds a critical level, typically around -55 mV, due to the influx of sodium ions. This depolarization is often initiated by excitatory inputs from other neurons or stimuli. Once the threshold is crossed, an action potential is generated, allowing the neuron to transmit an electrical signal along its axon. This all-or-nothing response is crucial for effective neuronal communication.
How does a threshold prevent a neuron from generating too many action potential?
A threshold in a neuron represents the critical level of depolarization needed to trigger an action potential. When the membrane potential reaches this threshold, voltage-gated sodium channels open, allowing an influx of sodium ions that leads to rapid depolarization. If the membrane potential does not reach this threshold, the neuron will not fire, thus preventing excessive or spontaneous action potentials. This mechanism ensures that action potentials are generated only in response to sufficient stimuli, maintaining proper signaling in the nervous system.
Why are most action potentials generated in response to a long stimulus that is above threshold?
Action potentials are generated in response to a long stimulus above threshold because it allows for the full development of the depolarization phase. This prolonged depolarization leads to the activation of voltage-gated sodium channels, triggering the rapid influx of sodium ions and initiating the action potential. A sustained stimulus ensures that the membrane potential remains above threshold for a sufficient time to generate an action potential.
What causes Local depolarization that leads to generate action potential?
Local depolarization is caused by the opening of voltage-gated sodium channels in response to the binding of neurotransmitters or other stimuli. This influx of sodium ions results in membrane depolarization, reaching the threshold potential needed to generate an action potential.
When ACh receptors open what ion causes depolarization of the postsynaptic membrane?
When acetylcholine (ACh) receptors open, sodium ions (Na+) primarily flow into the postsynaptic membrane. This influx of positively charged sodium ions leads to depolarization, making the inside of the cell more positive. If the depolarization reaches a certain threshold, it can trigger an action potential in the postsynaptic neuron.
What is the reversal of the resting potential owing to an influx of sodium ions called?
The reversal of the resting potential owing to an influx of sodium ions is called depolarization. This occurs when the membrane potential becomes less negative, bringing it closer to the threshold for action potential initiation.
When several neurons are stimulated equally which one will fire first?
The neuron with the lowest threshold potential will fire first when several neurons are stimulated equally. Threshold potential is the minimum level of depolarization needed to trigger an action potential in a neuron. Neurons with lower threshold potentials are more excitable and will fire before neurons with higher threshold potentials.
