action potential
The formation of an action potential can be divided into five steps.
(1) A stimulus from a sensory cell or another neuron causes the target cell to depolarize toward the threshold potential.
(2) If the threshold of excitation is reached, all Na+ channels open and the membrane depolarizes.
(3) At the peak action potential, K+ channels open and K+ begins to leave the cell. At the same time, Na+ channels close.
(4) The membrane becomes hyperpolarized as K+ ions continue to leave the cell. The hyperpolarized membrane is in a refractory period and cannot fire.
(5) The K+ channels close and the Na+/K+ transporter restores the resting potential.
Action potentials are formed when a stimulus causes the cell membrane to depolarize past the threshold of excitation, causing all sodium ion channels to open.
When the potassium ion channels are opened and sodium ion channels are closed, the cell membrane becomes hyperpolarized as potassium ions leave the cell; the cell cannot fire during this refractory period.
The action potential travels down the axon as the membrane of the axon depolarizes and repolarizes.
Myelin insulates the axon to prevent leakage of the current as it travels down the axon.
Nodes of Ranvier are gaps in the myelin along the axons; they contain sodium and potassium ion channels, allowing the action potential to travel quickly down the axon by jumping from one node to the next.
Action Potential
A neuron can receive input from other neurons via a chemical called a neurotransmitter. If this input is strong enough, the neuron will pass the signal to downstream neurons. Transmission of a signal within a neuron (in one direction only, from dendrite to axon terminal) is carried out by the opening and closing of voltage-gated ion channels, which cause a brief reversal of the resting membrane potential to create an action potential (Figure 1). As an action potential travels down the axon, the polarity changes across the membrane. Once the signal
(1) A stimulus from a sensory cell or another neuron causes the target cell to depolarize toward the threshold potential.
(2) If the threshold of excitation is reached, all Na+ channels open and the membrane depolarizes.
(3) At the peak action potential, K+ channels open and K+ begins to leave the cell. At the same time, Na+ channels close.
(4) The membrane becomes hyperpolarized as K+ ions continue to leave the cell. The hyperpolarized membrane is in a refractory period and cannot fire.
(5) The K+ channels close and the Na+/K+ transporter restores the resting potential.
Action potentials are formed when a stimulus causes the cell membrane to depolarize past the threshold of excitation, causing all sodium ion channels to open.
When the potassium ion channels are opened and sodium ion channels are closed, the cell membrane becomes hyperpolarized as potassium ions leave the cell; the cell cannot fire during this refractory period.
The action potential travels down the axon as the membrane of the axon depolarizes and repolarizes.
Myelin insulates the axon to prevent leakage of the current as it travels down the axon.
Nodes of Ranvier are gaps in the myelin along the axons; they contain sodium and potassium ion channels, allowing the action potential to travel quickly down the axon by jumping from one node to the next.
Action Potential
A neuron can receive input from other neurons via a chemical called a neurotransmitter. If this input is strong enough, the neuron will pass the signal to downstream neurons. Transmission of a signal within a neuron (in one direction only, from dendrite to axon terminal) is carried out by the opening and closing of voltage-gated ion channels, which cause a brief reversal of the resting membrane potential to create an action potential (Figure 1). As an action potential travels down the axon, the polarity changes across the membrane. Once the signal