What are action potentials triggered by?

Action potentials are caused when different ions cross the neuron membrane. A stimulus first causes sodium channels to open. Because there are many more sodium ions on the outside, and the inside of the neuron is negative relative to the outside, sodium ions rush into the neuron.

What happens when an action potential is triggered in a neuron?

Once the action potential is triggered, the depolarization (2) of the neuron activates sodium channels, allowing sodium ions to pass through the cell membrane into the cell, resulting in a net positive charge in the neuron relative to the extracellular fluid.

What would cause an action potential to not occur?

Sufficient current is required to initiate a voltage response in a cell membrane; if the current is insufficient to depolarize the membrane to the threshold level, an action potential will not fire. Examples of cells that signal via action potentials are neurons and muscle cells.

What blocks an action potential?

Action potentials are propagating signals that are transmitted by neurons and can be initiated by natural or artificial inputs to their neuronal membrane. The conduction of this signal can be prevented by rendering a section of the axon unresponsive to this traveling wave of depolarization.

Is there a maximum number of action potentials a neuron can send?

There is a maximum frequency at which a single neuron can send action potentials, and this is determined by its refractory periods. Absolute refractory period: during this time it is absolutely impossible to send another action potential.

When does the excitable cell cannot produce an action potential?

The refractory period is the time after an action potential is generated, during which the excitable cell cannot produce another action potential. There are two subphases of this period, absolute and relative refractoriness. Absolute refractoriness overlaps the depolarization and around 2/3 of repolarization phase.

How does the neurotransmitter affect the action potential?

The neurotransmitter can either help (excite) or hinder (inhibit) neuron B from firing its own action potential. In an intact brain, the balance of hundreds of excitatory and inhibitory inputs to a neuron determines whether an action potential will result. Neurons are essentially electrical devices.

How are graded potentials produced in the neuron?

Graded potentials are brought about by external stimuli (in sensory neurons) or by neurotransmitters released in synapses, where they cause graded potentials in the post-synaptic cell. Action potentials are triggered by membrane depolarization to threshold.