Establishing a RESTING POTENTIAL in a neurone- Do you know what the resting potential is?

Summary

In this informative video, Miss Esther explores the concept of resting potential in neurons, focusing on the structure of myelinated motor neurons and their function. She explains how the resting potential of -70 millivolts is maintained through the action of the sodium-potassium pump and the selective permeability of the cell membrane to potassium ions. The video is an excellent primer for understanding the electrical properties of neurons before delving into action potentials.

Takeaways

• 🧠 The video discusses the structure and function of a myelinated motor neuron, focusing on the cell body, dendrites, axon, and myelin sheath.
• 🔬 The cell body contains organelles necessary for protein and neurotransmitter synthesis, such as the nucleus, mitochondria, and ribosomes.
• 🌿 Dendrites are responsible for carrying action potentials to surrounding cells, playing a key role in neuronal communication.
• 🚀 The axon is a long conductive fiber that carries nerve impulses and is the site of multiple action potentials.
• 🛡️ The myelin sheath, made of lipid layers, acts as an insulator, allowing for faster and more efficient signal transmission along the neuron.
• 🔌 Nodes of Ranvier are gaps in the myelin sheath where action potentials can be generated, facilitating signal propagation.
• 🔋 The resting potential of a neuron, at -70 millivolts, represents the electrical charge difference between the inside and outside of the neuron when it's not conducting an impulse.
• 💡 The resting potential is maintained by the sodium-potassium pump, which actively transports ions across the membrane, creating an electrochemical gradient.
• ⚗️ The sodium-potassium pump moves three sodium ions out and two potassium ions into the axon, contributing to the resting potential.
• 🚫 The cell membrane is more permeable to potassium ions due to a higher number of potassium ion channels compared to sodium ion channels.
• 🔄 Passive diffusion of ions occurs due to the concentration gradient, with potassium ions moving out and sodium ions moving into the axon.
• 📚 The video offers additional resources for learning, including questions on miss Esther's website, and encourages viewers to subscribe for more content.

Q & A

What is the primary function of the myelin sheath in a myelinated motor neuron?

The myelin sheath acts as an insulator, made up of lipid layers that prevent the passage of charged ions, thus facilitating the efficient transmission of electrical impulses along the neuron.

What are the gaps in the myelin sheath called, and where are action potentials generated?

The gaps in the myelin sheath are called the nodes of Ranvier, and these are the locations where action potentials can be generated.

What is the resting potential of a neuron, and what does it measure?

The resting potential of a neuron is the difference in electrical charge between the inside and outside of the neuron when it is not conducting an impulse. It measures the voltage, which is typically at minus 70 millivolts.

Why is the resting potential maintained at minus 70 millivolts?

The resting potential is maintained at minus 70 millivolts due to the presence of more positive ions outside the cell compared to the inside, which is achieved by the sodium-potassium pump and the selective permeability of the cell membrane.

What role does the sodium-potassium pump play in maintaining the resting potential?

The sodium-potassium pump actively transports three sodium ions out of the axon and two potassium ions into the axon, creating an electrochemical gradient that contributes to the resting potential of minus 70 millivolts.

How does the sodium-potassium pump create an electrochemical gradient?

The pump creates an electrochemical gradient by actively moving more sodium ions out of the cell and more potassium ions into the cell, resulting in a higher concentration of sodium ions outside and potassium ions inside the axon.

What is the reason for the unequal distribution of sodium and potassium ions across the neuron's membrane?

The unequal distribution is due to the cell membrane being more permeable to potassium ions, with more potassium ion channels than sodium ion channels, and the selective opening of these channels based on voltage levels.

What is the significance of the dendrites in a neuron?

Dendrites are important for carrying action potentials to surrounding cells, playing a crucial role in the communication between neurons.

What is the function of the axon in a neuron?

The axon is a long conductive fiber that carries the nerve impulse and is the site of multiple action potentials, essential for transmitting signals over long distances within the neuron.

Why are the nodes of Ranvier important for the transmission of action potentials?

The nodes of Ranvier are important because they are the points where the myelin sheath is interrupted, allowing for the regeneration of the action potential as it travels along the neuron.

What is meant by 'sodium ion channels' and 'potassium ion channels' in the context of the neuron's membrane?

Sodium and potassium ion channels are specific protein channels in the neuron's membrane that selectively allow the passage of sodium and potassium ions, respectively, playing a key role in the generation and maintenance of the neuron's resting potential and action potentials.

Outlines

00:00

🧠 Neuron Structure and Resting Potential Basics

In this paragraph, the video introduces the structure of a myelinated motor neuron, explaining the function of its parts: the cell body, dendrites, axon, and myelin sheath. The cell body contains organelles for protein and neurotransmitter production. Dendrites carry action potentials to other cells, while the axon conducts nerve impulses. The myelin sheath, made of lipid layers, acts as an insulator with gaps called nodes of Ranvier where action potentials are generated. The concept of resting potential is introduced as the electrical charge difference when the neuron is not conducting impulses, typically at -70 millivolts due to the uneven distribution of positive ions across the cell membrane.

05:01

🔋 Maintaining the Resting Potential Through Ion Pumps

This paragraph delves into how the resting potential of -70 millivolts is maintained. It highlights the role of the sodium-potassium pump, which actively transports three sodium ions out and two potassium ions into the axon, creating an electrochemical gradient. The axon's membrane is more permeable to potassium ions due to a higher number of potassium channels being open most of the time, compared to sodium channels which open at specific voltages. This permeability and the diffusion of ions contribute to the resting potential, ensuring it remains stable in the absence of stimuli. The paragraph concludes with an invitation for viewers to engage with questions on the website and a prompt to subscribe for more content.

Keywords

💡Neuron

A neuron is a nerve cell that is essential for transmitting nerve impulses throughout the body. In the video, the structure and function of a myelinated motor neuron are discussed, highlighting its components such as the cell body, dendrites, axon, and myelin sheath.

💡Resting Potential

Resting potential is the difference in electrical charge across the neuronal membrane when the neuron is not transmitting an impulse. It is approximately -70 millivolts, maintained by ion distribution and the activity of the sodium-potassium pump, as described in the video.

💡Myelinated Motor Neuron

A myelinated motor neuron is a type of nerve cell with a myelin sheath, which insulates the axon and facilitates rapid transmission of nerve impulses. The video explains its structure and components, including the cell body, dendrites, axon, and myelin sheath.

💡Cell Body

The cell body, or soma, of a neuron contains the nucleus and organelles necessary for cellular functions, such as producing proteins and neurotransmitters. In the video, it is highlighted as the part of the neuron where typical animal cell organelles are found.

💡Dendrites

Dendrites are branched extensions of the neuron that receive signals from other neurons and conduct them towards the cell body. The video mentions dendrites as important for carrying action potentials to surrounding cells.

💡Axon

An axon is a long, slender projection of a neuron that conducts electrical impulses away from the cell body. The video describes the axon as the site of multiple action potentials and essential for transmitting nerve impulses.

💡Myelin Sheath

The myelin sheath is a lipid-rich layer that surrounds the axon, providing insulation and increasing the speed of nerve impulse transmission. In the video, the myelin sheath, formed by Schwann cells, is discussed for its role in efficient nerve conduction.

💡Nodes of Ranvier

Nodes of Ranvier are gaps in the myelin sheath along the axon where action potentials are generated. The video highlights these gaps as crucial sites for the regeneration of action potentials, facilitating rapid signal transmission.

💡Sodium-Potassium Pump

The sodium-potassium pump is a membrane protein that actively transports sodium ions out of the cell and potassium ions into the cell, maintaining the resting potential. The video explains its role in creating an electrochemical gradient and maintaining the -70 millivolts resting potential.

💡Electrochemical Gradient

An electrochemical gradient is the difference in ion concentration and electric charge across a membrane. The video describes how the sodium-potassium pump creates this gradient, essential for the resting potential and the movement of ions through channels.

💡Facilitated Diffusion

Facilitated diffusion is the process by which ions or molecules move across a cell membrane through protein channels, down their concentration gradient. In the video, facilitated diffusion is mentioned in the context of ion movement through sodium and potassium channels.

Highlights

Introduction to the structure of a myelinated motor neuron, including its cell body, dendrites, axon, and myelin sheath.

The cell body contains organelles such as the nucleus, mitochondria, and ribosomes for protein and neurotransmitter synthesis.

Dendrites' role in carrying action potentials to surrounding cells.

The axon's function as a conductive fiber that carries nerve impulses and is a site for multiple action potentials.

Description of the myelin sheath, made up of lipid layers that act as insulators for the axon.

Explanation of nodes of Ranvier as gaps in the myelin sheath where action potentials can be generated.

Focus on resting potential, the electrical charge difference between the inside and outside of a neuron when not conducting an impulse.

Resting potential is measured at minus 70 millivolts due to more positive ions outside the cell.

The role of carrier proteins in maintaining the resting potential, particularly the sodium-potassium pump.

Mechanism of the sodium-potassium pump, actively transporting three sodium ions out and two potassium ions into the axon.

Creation of an electrochemical gradient due to the active transport of ions.

Diffusion of potassium ions out of the axon and sodium ions into the axon due to concentration gradients.

The cell membrane's higher permeability to potassium ions due to more potassium ion channels.

Potassium ion channels are mainly open, unlike sodium ion channels that open only at higher voltages.

How the resting potential of minus 70 millivolts is maintained in the absence of stimulus.

Invitation to practice with questions on miss Esther's website and an encouragement to subscribe for more content.

Transcripts

hi everyone and welcome to learn a level

biology for free with miss Esther ich in

this video I'm going to go through

neurons and resting potential so first

of all the myelinated motor neuron you

need to know the structure of it to be

able to recognize the features label

them but also what the parts do so the

cell body which we have here this is

where all the organelles that you

typically find in an animal cell are say

for example the nucleus mitochondria the

ribosomes and that's so that proteins

and neurotransmitter chemicals can be

made the dendrites which you can see

here branching out of the cell body

those are there to carry action

potentials to surrounding cells the axon

is this long conductive fiber running

all the way through the cell and it

carries the nerve impulse and it's a

site of multiple action potentials and

then lastly we've got the myelin sheath

or the Schwann cells that wrap around

the axon now the strong cell is made up

of lots and lots of layers of myelin

sheath and that is a type of lipid and

because it's a lipid it acts as an

insulator so it means that charged ions

can pass through at that point there are

gaps though which we can see here and we

call those gaps the nodes of ranvier and

that is where the action potentials can

be generated our action potentials are

something that we're going to be doing

in a later video today with just

focusing on the resting potential so

we've looked at the motor neuron

structure and when that motor neuron is

not conducting an impulse or an action

potential there is still a difference in

the electrical charge between the inside

and the outside of the neuron and we

call that the resting potential the

reason why we use the word potential is

it's to do with the measurement the

voltage and voltage is the potential

difference so we're looking at their

potential difference between the inside

and the outside of the neuron so the

resting potential

is minus 70 millivolts the reason for

that is comparatively there are more

positive ions on the outside of the cell

compared to the inside and we can see

that here this graph is actually showing

the generation of an action potential

which is coming up in a later video but

we can see that this section here the

stimulus isn't there until about at 1.2

milliseconds so at that point we are at

minus 70 millivolts our resting

potential because there is no stimulus

so how that minus 70 is maintained then

is all to do with these carrier proteins

inside of the membrane in the axon so

the main protein which is maintaining

this minus 70 millivolts is the sodium

potassium pump so this is an example of

co-transport also an example of the

importance of ions and active transport

because it's actively transporting ions

either side of the membrane so the way

this pump works is it's able to actively

transport three sodium ions out of the

axon and two potassium ions into the

axon now that is going to create an

electrochemical gradient and by that we

mean we have a buildup of sodium ions on

the outside and we have excess potassium

ions on the inside of the axon now

within the membrane of the axon there

are also sodium ion channels and

potassium ion channels so now we have an

electrochemical gradient on those two

sites the silat ated diffusion is able

to occur so that results in the

potassium ions moving from the inside

where there's a high concentration to

the outside where there's a lower

concentration and the opposite for the

sodium ions so they move from the

outside of the axon where there's a high

concentration to the inside of the axon

where there's a lower concentration now

the reason it doesn't balance

meaning you don't have an equal number

of sodium ions inside and potassium ions

outside is because this cell membrane is

more permeable to potassium ions two

different reasons for that number one

which you can't see in this diagram is

as far more potassium ion protein

channels then there are sodium ion

channels and if there's more channels

more potassium ions can diffuse out also

some of the time these channels are

closed but the potassium ion channels

are mainly open whereas some of the

sodium ion channels only open when you

reach a high enough voltage so that is

how we maintain minus 70 millivolts and

that is the resting potential which will

be the voltage of the axon when there is

no stimulus in your neuron so that's it

if you want to have a go at some

questions head over to miss Esther calm

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