"An action potential occurs when the membrane potential of a specific cell rapidly rises and falls."
The electrical signals that neurons use to communicate with each other.
Cell membrane structure and function: Understanding the composition and function of the cell membrane is crucial for understanding how action potentials work.
Ion channels and pumps: Ion channels and pumps are molecules that allow ions to flow in and out of cells. They play a key role in generating and regulating action potentials.
Resting membrane potential: The resting membrane potential is the electrical potential difference across the cell membrane of a neuron when it is not receiving any signals. This is the starting point for action potentials.
Depolarization and hyperpolarization: Depolarization and hyperpolarization are changes in the membrane potential that occur during an action potential. Depolarization makes the membrane potential more positive, while hyperpolarization makes it more negative.
Threshold: The threshold is the membrane potential at which an action potential is triggered.
Action potential initiation: Action potentials are initiated when the membrane potential reaches the threshold. This is a critical step in the process.
Propagation: Once an action potential is initiated, it propagates down the length of the neuron. Understanding how this works is important for understanding how signals are transmitted in the nervous system.
Myelination: Myelin is a fatty substance that coats the axons of some neurons. It helps to speed up action potential propagation and is an important aspect of nervous system function.
Synaptic transmission: Synaptic transmission is the process by which signals are transmitted between neurons. Understanding this process is important for understanding how neurons communicate with each other.
Neurotransmitters: Neurotransmitters are molecules that are released by neurons and help to transmit signals across synapses. Understanding the different types of neurotransmitters is important for understanding how the nervous system works.
Resting potential: This is the electrical potential of a neuron at rest, before it receives any signals.
Threshold potential: This is the minimum level of stimulation required to trigger an action potential.
Depolarization: When a neuron is stimulated, positively charged ions rush into the cell, changing the electrical state of the cell from negative to positive. This change is known as depolarization.
Repolarization: Once an action potential has been triggered, the neuron must return to its resting state. This process is known as repolarization.
Hyperpolarization: In some cases, the electrical potential of a neuron can become more negative than its resting potential. This is known as hyperpolarization.
All-or-nothing principle: Once an action potential has been triggered, it always follows the same sequence of events and reaches the same magnitude. It either happens fully or not at all.
Action potential frequency: The rate at which action potentials occur can convey information. Higher frequencies can signal stronger stimuli or more intense sensory input.
"Action potentials occur in several types of animal cells, called excitable cells, which include neurons, muscle cells, and in some plant cells."
"In neurons, action potentials play a central role in cell-cell communication by providing for the propagation of signals along the neuron's axon toward synaptic boutons situated at the ends of an axon."
"In muscle cells, for example, an action potential is the first step in the chain of events leading to contraction."
"In beta cells of the pancreas, they provoke release of insulin."
"Action potentials in neurons are also known as 'nerve impulses' or 'spikes'."
"Action potentials are generated by special types of voltage-gated ion channels embedded in a cell's plasma membrane."
"These channels are shut when the membrane potential is near the resting potential of the cell, but they rapidly begin to open if the membrane potential increases to a precisely defined threshold voltage."
"When the channels open, they allow an inward flow of sodium ions, which changes the electrochemical gradient, producing a further rise in the membrane potential towards zero."
"This then causes more channels to open, producing a greater electric current across the cell membrane and so on."
"The rapid influx of sodium ions causes the polarity of the plasma membrane to reverse."
"Potassium channels are then activated, and there is an outward current of potassium ions, returning the electrochemical gradient to the resting state."
"After an action potential has occurred, there is a transient negative shift, called the afterhyperpolarization."
"Sodium-based action potentials usually last for under one millisecond."
"Calcium-based action potentials may last for 100 milliseconds or longer."
"In some types of neurons, slow calcium spikes provide the driving force for a long burst of rapidly emitted sodium spikes."
"In cardiac muscle cells, on the other hand, an initial fast sodium spike provides a 'primer' to provoke the rapid onset of a calcium spike, which then produces muscle contraction."
"The specific types of cells mentioned that can generate action potentials are neurons, muscle cells, some plant cells, pancreatic beta cells, and certain cells of the anterior pituitary gland."
"Action potentials play a central role in providing for the propagation of signals along the neuron's axon toward synaptic boutons situated at the ends of an axon."
"A neuron that emits an action potential, or nerve impulse, is often said to 'fire'."