Neuron Resting Potential

greatpacificmedia

24 Oct 200903:57

Summary

TLDRThe video explains how neurons maintain a resting potential, an electrical difference across their cell membranes, usually between -40 to -90 millivolts. It describes how potassium ions diffuse out of the neuron, leaving the inside more negative, creating this resting state. When a neuron is stimulated and the negative potential becomes less negative, an action potential is triggered, making the inside of the neuron briefly positive. These action potentials, rather than resting potentials, are what transmit information throughout the nervous system.

Takeaways

🧠 Unstimulated neurons maintain a constant electrical difference, known as resting potential, across their cell membranes.
⚡ The resting potential is always negative inside the cell, typically ranging from -40 to -90 millivolts.
🔋 When a neuron is stimulated, the internal potential can become more or less negative, depending on the stimulus.
🚀 If the potential becomes less negative and reaches a certain level, called the threshold, an action potential is triggered.
🔄 During an action potential, the neuron briefly becomes positive inside, reaching between 20 to 50 millivolts.
⏳ Action potentials last only a few milliseconds before the neuron restores its negative resting potential.
🧬 The neuron's cell membrane contains channel proteins that control ion movement, crucial for maintaining potentials.
🧪 Potassium ions mainly reside inside the cell, while sodium ions are found in the extracellular fluid outside the cell.
🛑 In an unstimulated neuron, only potassium channels are open, allowing potassium ions to diffuse out of the cell.
⚖️ The resting potential is achieved when the diffusion of potassium ions out of the neuron is balanced by an opposing electrical force.

Q & A

What is the resting potential of an unstimulated neuron?
-The resting potential of an unstimulated neuron is a constant electrical difference across the cell membrane, which is always negative inside the cell and ranges from -40 to -90 millivolts.
What happens when a neuron is stimulated?
-When a neuron is stimulated, the negative potential inside the neuron can become either more or less negative. If it becomes sufficiently less negative and reaches a level called the threshold, an action potential is triggered.
What is an action potential, and how long does it last?
-An action potential is a rapid change in the neuron's electrical potential, where the inside of the neuron becomes positive, ranging from +20 to +50 millivolts. It lasts for a few milliseconds before the cell restores its negative resting potential.
What ions are found inside and outside the neuron?
-Inside the neuron, there are mainly positively charged potassium ions and large negatively charged organic molecules, such as proteins. Outside the neuron, in the extracellular fluid, there are mostly positively charged sodium ions and negatively charged chloride ions.
How do ions travel across the neuron's cell membrane?
-Ions travel through channel proteins that extend across the neuron's cell membrane because charged particles cannot pass through the lipid bilayer of the membrane on their own.
Which ion channels are open in an unstimulated neuron?
-In an unstimulated neuron, only potassium channels are open, allowing potassium ions to cross the membrane. Sodium channels remain closed in this state.
Why does the inside of the neuron become negative during resting potential?
-The inside of the neuron becomes negative because potassium ions diffuse out of the cell, leaving behind large negatively charged organic ions. As more potassium ions leave, the inside becomes increasingly negative.
What causes potassium ions to be pulled back into the neuron during resting potential?
-As potassium ions diffuse out, an electrical force develops due to the attraction of opposite charges. This electrical force tends to pull potassium ions back into the neuron.
What is the significance of the balance between potassium ion diffusion and electrical attraction?
-The balance between potassium ion diffusion out of the cell (due to concentration differences) and the electrical attraction pulling them back inside creates the resting potential of the neuron.
How many potassium ions need to leave the neuron to create a resting potential of -60 millivolts?
-Only about 1/10,000 of the potassium ions initially inside the neuron need to leave in order to create a resting potential of -60 millivolts.
What is the primary difference between resting potential and action potential in terms of information transmission?
-While resting potential helps maintain the neuron's stable electrical state, it is the action potentials that carry information through the nervous system.

Outlines

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⚡ Resting Potential in Neurons

Unstimulated neurons maintain a stable electrical difference, known as resting potential, across their cell membranes. This potential is always negative inside the cell, ranging from -40 to -90 millivolts. When a neuron is stimulated, this negative potential can be altered depending on the type of stimulus. If it becomes less negative and reaches a threshold, an action potential is triggered, making the inside of the neuron positive for a brief period before returning to its resting state.

🧪 Ions Inside and Outside the Neuron

The neuron's cell membrane encloses cytoplasm filled with various ions. Potassium ions (positively charged) and large organic molecules (negatively charged) are predominant inside the neuron. The surrounding extracellular fluid contains mostly sodium ions (positively charged) and chloride ions (negatively charged). These ions cannot directly pass through the cell membrane's lipid layers and must travel through specialized channel proteins.

🚪 Ion Channels and Resting Potential

In an unstimulated neuron, only potassium ions can cross the membrane via potassium channels. Although sodium channels exist, they remain closed in this state. The movement of potassium ions out of the cell, driven by concentration differences, leaves behind negatively charged organic ions, making the inside of the cell more negative. However, the buildup of this electrical charge begins to pull potassium ions back inside until equilibrium is reached, establishing the resting potential.

⚖️ Equilibrium and Resting Potential

The resting potential is achieved when the diffusion of potassium ions out of the neuron is balanced by the electrical force pulling them back in. This balance is reached with only a small fraction of potassium ions needing to leave the cell. The typical resting potential of a neuron is around -60 millivolts. Importantly, this process is not the one that transmits information in the nervous system; that role belongs to action potentials.

Mindmap

Keywords

💡Resting potential

Resting potential refers to the constant electrical difference maintained by unstimulated neurons across their cell membranes. It is always negative inside the cell, typically ranging from -40 to -90 millivolts. This potential is crucial for neuron function, as it prepares the cell for action potential. In the script, the resting potential is the baseline state that neurons maintain when not stimulated.

💡Action potential

Action potential is the rapid change in electrical charge that occurs when a neuron is sufficiently stimulated. The negative internal charge becomes positive, reaching between +20 and +50 millivolts. This process lasts a few milliseconds and is essential for transmitting information in the nervous system. The video explains how action potentials are triggered once the threshold is reached and carry signals through neurons.

💡Threshold

Threshold refers to the critical level of depolarization that must be reached for an action potential to be triggered. When the neuron's internal potential becomes sufficiently less negative, the cell reaches this point, initiating the action potential. The concept is key in understanding how neurons transition from resting to active states in response to stimuli.

💡Potassium ions (K+)

Potassium ions are positively charged particles that play a central role in maintaining the resting potential of neurons. Inside neurons, potassium ions are more concentrated, and they diffuse out through potassium channels. This movement of K+ ions, combined with the attraction of the negatively charged organic molecules inside the neuron, helps maintain the electrical difference across the membrane.

💡Sodium ions (Na+)

Sodium ions are positively charged particles that are more concentrated in the extracellular fluid outside the neuron. While sodium channels exist, they are closed in an unstimulated neuron. During action potential, these channels open, allowing sodium ions to rush in, which causes the rapid depolarization needed for signal transmission.

💡Extracellular fluid

The extracellular fluid is the salt solution that surrounds neurons and contains ions like sodium (Na+) and chloride (Cl-). It forms the environment in which neurons operate, contributing to the balance of ions that enable electrical signals. The video highlights how the difference in ion concentrations between the cytoplasm and extracellular fluid is fundamental to neuron function.

💡Potassium channels

Potassium channels are specialized proteins embedded in the neuron membrane that allow potassium ions to pass through. In an unstimulated neuron, these channels are open, enabling K+ ions to diffuse out of the cell, which contributes to the negative resting potential. These channels are essential for maintaining the balance of electrical charges across the neuron's membrane.

💡Sodium channels

Sodium channels are proteins in the neuron membrane that allow sodium ions to enter the cell. In an unstimulated neuron, these channels remain closed, preventing Na+ from entering. However, during an action potential, they open, allowing the influx of sodium ions, which causes the neuron to become positively charged, essential for the propagation of nerve signals.

💡Depolarization

Depolarization occurs when the inside of a neuron becomes less negative compared to its resting potential. This happens when sodium channels open, allowing Na+ ions to flow into the neuron. If depolarization reaches the threshold, an action potential is triggered, making depolarization a key step in neuron activation and signal transmission.

💡Cytoplasm

Cytoplasm refers to the gel-like substance within the neuron where various ions, such as potassium and large negatively charged organic molecules, are dissolved. It is the internal environment of the neuron, distinct from the extracellular fluid, and plays a crucial role in maintaining the electrical balance that supports resting potential and action potential.

Highlights

Unstimulated neurons maintain a constant electrical difference called resting potential across their cell membranes.

The resting potential is always negative inside the cell and ranges from -40 to -90 millivolts.

If a neuron is stimulated, the negative potential can be made either more or less negative, depending on the stimulus.

When the potential becomes sufficiently less negative and reaches a level called threshold, an action potential is triggered.

During the action potential, the neuron becomes 20 to 50 millivolts positive inside.

Action potentials last a few milliseconds before the cell restores its negative resting potential.

The cell membrane of a neuron encloses cytoplasm with various dissolved ions, and the neuron is immersed in an extracellular salt solution.

Inside the cell, the cytoplasm mainly contains positively charged potassium ions and large negatively charged organic molecules such as proteins.

The extracellular fluid contains mostly positively charged sodium ions and negatively charged chloride ions.

Charged particles cannot pass through the lipid bilayer of cell membranes, so they travel through channel proteins.

In unstimulated neurons, only potassium ions can cross the membrane via potassium channels.

Sodium channels are present but remain closed in unstimulated neurons.

As potassium ions diffuse out, the inside of the cell becomes increasingly negative, creating an electrical force that pulls them back inside.

At resting potential, the diffusion of potassium out of the cell is balanced by the electrical attraction pulling them back in.

Action potentials, not resting potentials, carry information through the nervous system.