Establishing a RESTING POTENTIAL in a neurone- Do you know what the resting potential is?
Summary
TLDRIn 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
🧠 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.
🔋 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.
Mindmap
Keywords
💡Neuron
💡Resting Potential
💡Myelinated Motor Neuron
💡Cell Body
💡Dendrites
💡Axon
💡Myelin Sheath
💡Nodes of Ranvier
💡Sodium-Potassium Pump
💡Electrochemical Gradient
💡Facilitated Diffusion
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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