Neuron Resting Potential
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
⚡ 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
💡Action potential
💡Threshold
💡Potassium ions (K+)
💡Sodium ions (Na+)
💡Extracellular fluid
💡Potassium channels
💡Sodium channels
💡Depolarization
💡Cytoplasm
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.
Transcripts
unstimulated neurons maintain a constant
electrical difference or potential
across their cell membranes this
potential called resting potential is
always negative inside the cell and
ranges from negative 40 to negative 90
millivolts
if a neuron is stimulated the negative
potential inside the neuron can be made
either more or less negative depending
on the stimulus if potential is made
sufficiently less negative it reaches a
level called threshold and an action
potential is triggered
during the action potential the neuron
suddenly 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 ions dissolved in
it the neuron itself is immersed in a
salt solution the extracellular fluid
the ions of the cytoplasm consist mainly
of positively charged potassium ions and
large negatively charged organic
molecules such as proteins
outside the cell the extracellular fluid
contains mostly positively charged
sodium ions and negatively charged
chloride ions
since charged particles cannot pass
through the lipids that make up cell
membranes they must travel through
channel proteins that extend through the
membrane
in an unstimulated neuron only potassium
ions can cross the membrane traveling
through specific proteins called
potassium channels although sodium
channels are also present in
unstimulated neurons they remain closed
since only potassium ions can cross the
membrane and potassium ions are more
concentrated inside the cell they
diffuse out of the cell leaving the
large negatively charged organic ions
behind
as more and more positively charged
potassium ions leave the inside of the
cell becomes increasingly negative
but since opposite charges attract as
potassium ions diffuse out an electrical
force develops that tends to pull them
back inside
at some point the diffusion of potassium
ions out of the neuron due to
concentration differences is balanced by
the electrical attraction tending to
pull them back inside
this is the point at which neurons reach
resting potential
reaching resting potential in this way
does not require significant changes in
the potassium concentration inside or
outside the cell only about 1 10 000 of
the potassium ions initially inside a
neuron must leave to create a resting
potential of negative 60 millivolts
but it is action potentials not resting
potentials that carry information
through a nervous system
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