Every cell in our body has onecell membranewhich separates it from the external environment of the tissue. The concentration of different ions across the cell membrane is different.
This establishes polarity on both sides of the membrane. This is called the membrane potential.
Most cells have more negative ions inside.
membrane side. Therefore, most cells have a negative membrane potential.
DepolarisationIt is a process by which cells experience a change in membrane potential. It is a process of electrical charge change that results in less negative charge inside the cell.
In this article we will discuss the physiology of
Depolarization, ion channels involved in this process and how different
depolarize cells. We will also discuss some medications that may change
the depolarization process.
Physiology of depolarization
The depolarization process is highly dependent on the intrinsic electrical nature of the cells. to understanddepolarization process, we need to understand the concept of the resting membrane potential.
When a cell is at rest, the potential across its cell
membrane is called the resting membrane potential. For most cells, this is
the resting membrane potential is negative relative to the outside of the cell.
The process of creating the resting membrane.
The potential includes passive ion channels, ion pumps and voltage-gated ions.
Channels Cells use these machines to maintain a high concentration of negative ions.
inside the cells. As a result, the negative membrane potential is maintained.
Factors contributing to the resting membrane potential
Includes the following:
Usually cells have moreabundant organic anionswithin cells, such as oxalate ions, etc. The negative charge of these negative anions contributes to the resting potential of the membrane.
Most cells in the body are abundantk+channelson their membranes. In the normal environment, there are ten times more potassium ions in the cell than in the extracellular space.
Thispotassium ionsthey have a diffusion gradient directed towards the extracellular space. Hence, they continue to propagate through the open K.+channels and exit cells. This loss of positively charged ions further contributes to the negative resting membrane potential within the cell.
Potassium and sodium pump
Sodium and potassium pumpcontributes strongly to the resting membrane potential. Outside the cell, the concentration of sodium ions is higher than inside. On the other hand, the concentration of potassium ions inside the cell is higher than outside.
Thus, the sodium diffusion gradient is directed towards the interior of the cell and that of potassium towards the exterior of the cell.
The sodium-potassium pump is an energy-driven pump that uses ATP to pump sodium and potassium ions up their concentration gradient. For every two potassium ions pumped into the cell, three sodium ions are pumped.
This results in a net loss of positive ions from the cell.
All of the above factors contribute to this
Establishment and maintenance of a negative membrane potential within the cell.
Once you understand the concept of a resting membrane
Potential, now let's analyze the process of depolarization.
A cell has the ability to undergo depolarization after establishing a resting potential. Depolarization causes the membrane potential to rapidly change from a negative to a positive state.
Ödepolarization processStart with a stimulus. This stimulus can be a simple touch, a light, a foreign object or even an electrical stimulus. This stimulus causes a voltage change in the cell.
This initial voltage change causes the opening of
voltage-gated sodium and calcium channels within the cell membrane. EITHER
Positively charged ions flow through these channels. This will make the interior of
The cell becomes more positive. The membrane potential changes from negative to
Depolarization in different cells.
The basic principle of depolarization is the same as described inPhysiology degree. However, different cells in the body respond to different stimuli and use different ion channels to undergo the depolarization process. All of this is consistent with the function of this cell.
We will discuss the process of depolarization in
relation to neurons, endothelial cells and cardiac cells.
NeuronsIt can respond to a variety of stimuli, such as B. heat, chemical, light, electrical or physical stimuli, are subject to depolarization. These stimuli create a positive potential within the neurons.
When the positive potential becomes greater than the threshold potential, the sodium channels open. Sodium ions flow into the neuron and cause the membrane potential to change from negative to positive.
The depolarization of a small part of the neuron is created
a strong nerve impulse. The nerve impulse travels the entire length of the
neuron to the synaptic terminal.
Once the nerve impulse reaches the synaptic terminal, it causesrelease of neurotransmitters.These neurotransmitters diffuse across the synaptic cleft. They act as a chemical stimulus for the postsynaptic neuron. These neurotransmitters, in turn, cause depolarization of postsynaptic neurons.
vascular endothelial cellsThey line the inner surface of blood vessels. These cells have the structural ability to resist cardiovascular forces. They also play an important role in maintaining the proper functioning of the cardiovascular system.
These cells use the process of depolarization to change their structural strength. When endothelial cells are in a depolarized state, they show a marked decrease in strength and structural rigidity. Indepolarized stateendothelial cells also cause a sharp decrease in the vascular tone of blood vessels.
Depolarization of heart muscle cellsit causes the cells to contract and thus the heart to contract.
Depolarization begins first in the SA node, also known as the pacemaker. The SA node has automatic. The resting membrane potential of the SA node is less negative than that of other cardiac cells. This opens the sodium channels. Sodium ions continue to diffuse into the cells of the SA node.
When the membrane potential becomes greater than the threshold potential, the membrane opensCalifornia+2channelsCalcium ions precipitate and cause depolarization.
Depolarization propagates from the SA node
to the atria and through the AV node giving rise to an AV bundle to the Purkinje fibers
Depolarization and contraction of the ventricles.
Öexcitation of skeletal musclesby motor neurons causes voltage-gated sodium channels to open. The opening of sodium channels causes depolarization of skeletal muscle.
The motor neuron action potential also travels down the T-tubules, causing the release of Ca2+Ions from the sarcoplasmic reticulum. Thus, skeletal muscle contraction occurs. This entire process is also called excitation-contraction coupling.
Drugs that block the depolarization process
There are certain medications that can block the depolarization process. They cause the sustained opening of ion channels. The positively charged ions diffuse further into the cells.
As a result, the cells cannot recover from the initial period of depolarization. They remain in a sustained state of depolarization and are unresponsive to stimuli.
These drugs include nicotine agonists such as
suxamethonium and decamethonium.
Depolarization is a process that causesrapid change in membrane potentialfrom the negative to the positive state.
When a specific stimulus is applied to a cell, the cell becomes
causes an initial voltage change in the cell.
When the threshold potential is reached, it causes the
opening of ion channels. This changes the membrane potential
negative to positive state.
In order to undergo depolarization, cells must
Establishing and maintaining a negative resting membrane potential. factors that play
An important role in determining the resting membrane potential are:
- organic anions
- Sodium and potassium pump
The depolarization process is different
Consequences in different body cells.
In neurons, the transmission of nerve impulse occurs through
the depolarization process.
In vascular endothelial cells, the process is the
Depolarization helps regulate structural rigidity and vascular tone.
In the heart muscle, the depolarization causes a contraction.
the heart muscles.
Skeletal muscle also responds to depolarization
Nicotine agonists can cause prolonged depolarization
cell state. They prevent repolarization of the cells. like one
As a result, the cells do not react to new stimuli.
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What is the process of depolarization? ›
In the process of depolarization, the negative internal charge of the cell temporarily becomes more positive (less negative). This shift from a negative to a more positive membrane potential occurs during several processes, including an action potential.What is the importance of depolarization? ›
Depolarization of cardiac myocytes causes contraction of the cells and thus heart contraction occurs. Depolarization first begins in the SA node, which is also called the cardiac pacemaker.What is needed for depolarization? ›
In neurons, the rapid rise in potential, depolarization, is an all-or-nothing event that is initiated by the opening of sodium ion channels within the plasma membrane. The subsequent return to resting potential, repolarization, is mediated by the opening of potassium ion channels.What does depolarization depend on? ›
Neuronal depolarization depends on the opening of ion channels in the neuronal membrane and the subsequent influx of sodium ions (Na+) and efflux of potassium ions (K+). The response of a neuron to ion channel receptor activation by either the natural ligand/neurotransmitter or a drug is rapid and brief.What is an example of depolarization? ›
The opening of channels that let positive ions flow into the cell can cause depolarization. Example: Opening of channels that let Na+start text, N, a, end text, start superscript, plus, end superscript into the cell.What phase is depolarization? ›
Phase zero is the phase of depolarization. This phase starts when the membrane potential reaches -40 mV, the threshold potential for pacemaker cells. There is the opening of voltage-gated Ca2+ channels on reaching the threshold, causing the influx of Ca2+ ions.