Neuron action potential

Summary

This video explains the process of how neurons transmit electrical signals. It details the structure of neurons, including dendrites, soma, and axon, and how neurotransmitters trigger chemical signals that convert into electrical impulses. The action potential is explained as a rapid movement of sodium and potassium ions across the neuron’s membrane. The video also covers the roles of myelin and the nodes of Ranvier in speeding up signal transmission through saltatory conduction. It concludes with a graphical recap of the entire process, from the resting potential to the action potential reaching the axon terminals.

Takeaways

• 😀 Neurons are made up of three main parts: dendrites, soma (cell body), and axon.
• 😀 Dendrites receive signals from other neurons via neurotransmitters, converting chemical signals into electrical ones.
• 😀 If the combined signals from dendrites reach a specific threshold, it triggers an action potential, an electrical signal that travels down the axon.
• 😀 Neurons use neurotransmitters to communicate with each other but rely on action potentials to propagate the signal within the cell.
• 😀 The neuron’s resting membrane potential is negative, around -65 millivolts, due to different ion concentrations inside and outside the cell.
• 😀 When neurotransmitters bind to receptors on dendrites, ion channels open, changing the electrical charge inside the cell, a process called depolarization.
• 😀 EPSPs (excitatory postsynaptic potentials) and IPSPs (inhibitory postsynaptic potentials) are small changes in membrane potential that can lead to a larger signal if they reach the threshold.
• 😀 Voltage-gated sodium channels open when the threshold is reached, allowing sodium to rush into the cell, leading to depolarization and the action potential.
• 😀 After depolarization, potassium ions flow out of the cell, repolarizing the membrane and returning the cell to a more negative state.
• 😀 Myelin, produced by glial cells, speeds up the transmission of action potentials by allowing the signal to jump from node to node in a process called saltatory conduction.

Q & A

What are the three main parts of a neuron?

The three main parts of a neuron are the dendrites, the soma (cell body), and the axon.

How do dendrites receive signals from other neurons?

Dendrites receive signals through neurotransmitters, which bind to receptors on the dendrites and act as a chemical signal.

What happens when neurotransmitters bind to receptors on the dendrite?

When neurotransmitters bind to receptors on the dendrite, they open ion channels that allow charged ions to flow in and out of the cell, converting the chemical signal into an electrical signal.

What triggers an action potential in a neuron?

An action potential is triggered when the combined effect of multiple dendrites changes the overall charge of the cell enough to reach a threshold, typically around -55 millivolts.

What is the role of myelin in neurons?

Myelin, which is a fatty coating around the axon, speeds up the electrical signal transmission by allowing the signal to jump between gaps called nodes of Ranvier, a process known as saltatory conduction.

What causes depolarization in a neuron?

Depolarization occurs when a neurotransmitter opens a ligand-gated ion channel, allowing sodium (Na+) ions to flow into the cell, making the cell less negative and less polarized.

What is the difference between EPSP and IPSP?

An EPSP (excitatory postsynaptic potential) occurs when there is a net influx of positive ions into the cell, making it less negative, while an IPSP (inhibitory postsynaptic potential) occurs when chloride (Cl-) ions flow into the cell, making it more negative.

What happens during the absolute refractory period?

During the absolute refractory period, the sodium channels are inactivated and cannot respond to any stimuli, preventing action potentials from occurring too close together in time.

What causes the repolarization phase of an action potential?

Repolarization happens when potassium (K+) ions flow out of the neuron, removing positive charge and returning the membrane potential to a negative state. The sodium-potassium pump also helps in this process.

What is the function of the sodium-potassium pump during an action potential?

The sodium-potassium pump moves three sodium ions out of the cell and two potassium ions into the cell, helping to restore the resting membrane potential after an action potential.