Nernst equation
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Objective of the study:-Introduction, Resting Membrane Potential, concept of selective Permeability of membrane, Nernst Equation, Example, Goldman-Hodgkin-Katz equation and its significance
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Nernst Equation
This document discusses the Nernst equation and its role in determining the membrane potential of cells. It introduces concepts like the resting membrane potential, selective permeability of cell membranes to different ions, and the Gibbs-Donnan equilibrium. It then explains the Nernst equation, which calculates the equilibrium potential for each ion based on its concentration gradient across the cell membrane. Finally, it discusses the Goldman-Hodgkin-Katz equation, which integrates the effects of multiple ions, and the role of the sodium-potassium pump in maintaining ion concentration gradients.
Na k pump
The document discusses cell membranes and transport across membranes. It notes that plasma membranes are composed of lipids, proteins, and carbohydrates arranged in a fluid mosaic structure. Transport across membranes can occur through passive diffusion, facilitated diffusion, or active transport. Active transport uses carrier proteins and ATP hydrolysis to move substances against their concentration gradient. A key example is the sodium-potassium pump, which transports 3 sodium ions out of the cell in exchange for 2 potassium ions into the cell, contributing to the cell's membrane potential.
Action potential
This document summarizes the action potential in neurons. It describes how an action potential is initiated by voltage-gated sodium channels opening during depolarization. This allows sodium ions to rush into the neuron, further depolarizing the membrane. Then, the sodium channels quickly inactivate while voltage-gated potassium channels open, allowing potassium ions to leave the neuron and repolarize the membrane back to its resting potential. The precise opening and closing of sodium and potassium channels underlies the generation and propagation of action potentials along neuronal membranes.
Membrane Potentials
- Excitable tissues like neurons and muscle cells have more negative resting membrane potentials (-70 to -90 mV) compared to non-excitable tissues like red blood cells (-40 mV) due to ion distributions and the sodium-potassium pump.
- When excitable cells are stimulated above a threshold, voltage-gated sodium channels open, causing rapid sodium influx and depolarization. Then, voltage-gated potassium channels open, causing repolarization.
- This generates an action potential that propagates along the cell membrane via local current flows, allowing nerve and muscle impulses to be transmitted. The sodium-potassium pump then restores ion gradients for the next action potential.
Transport across cell membrane
Transport across the cell membrane is necessary to maintain cellular function. There are three main types of transport: passive transport which includes diffusion, facilitated diffusion, and osmosis and does not require energy; active transport which uses energy and transports molecules against their concentration gradient, including primary active transport using ATP and secondary active transport utilizing ion gradients; and vesicular transport which transports larger molecules through vesicles via endocytosis, exocytosis, and transcytosis. Specialized proteins are involved in each of these transport mechanisms to regulate the passage of substances into and out of cells.
Sodium potassium pump
The sodium-potassium pump, also known as the Na+-K+ ATPase pump, transports sodium and potassium ions across cell membranes. It pumps 3 sodium ions out of the cell in exchange for 2 potassium ions into the cell, maintaining ion gradients crucial for nerve and muscle function. First discovered in 1957, it is critical for establishing the resting membrane potential and driving secondary active transport of nutrients into cells.
Active transport
Active transport uses energy to move molecules across membranes against their concentration gradients. There are two types: primary active transport directly uses ATP, while secondary active transport relies on gradients set up by primary transport. Examples of primary transport include sodium-potassium and calcium pumps, which directly hydrolyze ATP to pump ions against their gradients. Secondary transport couples this gradient to co-transport other molecules, like sodium-glucose transporters importing glucose along with sodium ions. Membrane proteins mediate transport through symport, antiport or uniport of single molecules.
Action potential and resting potential
The document discusses resting membrane potential and action potential in cells. At resting potential, the intracellular fluid is negatively charged compared to extracellular fluid due to higher potassium ion and chloride ion concentrations inside cells. This creates a potential difference of -60mV to -100mV across the cell membrane. During an action potential, the membrane becomes permeable to sodium ions, depolarizing the intracellular space until it reaches +20mV. Then, the membrane repolarizes back to its resting potential.
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Nernst Equation
This document discusses the Nernst equation and its role in determining the membrane potential of cells. It introduces concepts like the resting membrane potential, selective permeability of cell membranes to different ions, and the Gibbs-Donnan equilibrium. It then explains the Nernst equation, which calculates the equilibrium potential for each ion based on its concentration gradient across the cell membrane. Finally, it discusses the Goldman-Hodgkin-Katz equation, which integrates the effects of multiple ions, and the role of the sodium-potassium pump in maintaining ion concentration gradients.
Na k pump
The document discusses cell membranes and transport across membranes. It notes that plasma membranes are composed of lipids, proteins, and carbohydrates arranged in a fluid mosaic structure. Transport across membranes can occur through passive diffusion, facilitated diffusion, or active transport. Active transport uses carrier proteins and ATP hydrolysis to move substances against their concentration gradient. A key example is the sodium-potassium pump, which transports 3 sodium ions out of the cell in exchange for 2 potassium ions into the cell, contributing to the cell's membrane potential.
Action potential
This document summarizes the action potential in neurons. It describes how an action potential is initiated by voltage-gated sodium channels opening during depolarization. This allows sodium ions to rush into the neuron, further depolarizing the membrane. Then, the sodium channels quickly inactivate while voltage-gated potassium channels open, allowing potassium ions to leave the neuron and repolarize the membrane back to its resting potential. The precise opening and closing of sodium and potassium channels underlies the generation and propagation of action potentials along neuronal membranes.
Membrane Potentials
- Excitable tissues like neurons and muscle cells have more negative resting membrane potentials (-70 to -90 mV) compared to non-excitable tissues like red blood cells (-40 mV) due to ion distributions and the sodium-potassium pump.
- When excitable cells are stimulated above a threshold, voltage-gated sodium channels open, causing rapid sodium influx and depolarization. Then, voltage-gated potassium channels open, causing repolarization.
- This generates an action potential that propagates along the cell membrane via local current flows, allowing nerve and muscle impulses to be transmitted. The sodium-potassium pump then restores ion gradients for the next action potential.
Transport across cell membrane
Transport across the cell membrane is necessary to maintain cellular function. There are three main types of transport: passive transport which includes diffusion, facilitated diffusion, and osmosis and does not require energy; active transport which uses energy and transports molecules against their concentration gradient, including primary active transport using ATP and secondary active transport utilizing ion gradients; and vesicular transport which transports larger molecules through vesicles via endocytosis, exocytosis, and transcytosis. Specialized proteins are involved in each of these transport mechanisms to regulate the passage of substances into and out of cells.
Sodium potassium pump
The sodium-potassium pump, also known as the Na+-K+ ATPase pump, transports sodium and potassium ions across cell membranes. It pumps 3 sodium ions out of the cell in exchange for 2 potassium ions into the cell, maintaining ion gradients crucial for nerve and muscle function. First discovered in 1957, it is critical for establishing the resting membrane potential and driving secondary active transport of nutrients into cells.
Active transport
Active transport uses energy to move molecules across membranes against their concentration gradients. There are two types: primary active transport directly uses ATP, while secondary active transport relies on gradients set up by primary transport. Examples of primary transport include sodium-potassium and calcium pumps, which directly hydrolyze ATP to pump ions against their gradients. Secondary transport couples this gradient to co-transport other molecules, like sodium-glucose transporters importing glucose along with sodium ions. Membrane proteins mediate transport through symport, antiport or uniport of single molecules.
Action potential and resting potential
The document discusses resting membrane potential and action potential in cells. At resting potential, the intracellular fluid is negatively charged compared to extracellular fluid due to higher potassium ion and chloride ion concentrations inside cells. This creates a potential difference of -60mV to -100mV across the cell membrane. During an action potential, the membrane becomes permeable to sodium ions, depolarizing the intracellular space until it reaches +20mV. Then, the membrane repolarizes back to its resting potential.
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Action potential
This document provides a summary of the action potential in excitable tissues like nerves and muscles. It explains that excitable cells maintain a resting membrane potential with a negative charge inside and positive outside due to potassium ion leakage and intracellular proteins. An action potential is triggered by stimuli and causes rapid depolarization as sodium ions enter the cell, repolarization as potassium ions exit, returning the membrane to its resting potential. Precise ion channel openings and closings enable impulse transmission and functions like muscle contraction. Sodium-potassium pumps then restore ion gradients using ATP.
Active Transport New
Active transport requires cells to use energy in the form of ATP to move substances against their concentration gradient, such as the sodium-potassium pump transporting sodium and potassium ions across nerve cell membranes. The sodium-potassium pump uses ATP to pump 3 sodium ions out and 2 potassium ions into the cell against their gradients. Transport proteins also use active transport for molecules too large to pass through the membrane on their own, such as during endocytosis and exocytosis.
High energy compounds
High energy compounds, also known as energy rich compounds, contain high energy bonds that release free energy of -7.3 kcal/mol or greater during hydrolysis. ATP is the most important high energy compound, containing two high energy phosphoanhydride bonds. The hydrolysis of ATP releases -7.3 kcal/mol of free energy and is coupled to endergonic reactions in cells, functioning to link catabolic and anabolic processes through the transfer of its phosphoryl groups. ATP serves as the universal energy currency in living organisms, driving many biological reactions and processes.
Ion channels
Ion channels are membrane proteins that allow ions to pass through their pore, regulating ion flow and electrical signals. There are two main types of gated ion channels: ligand-gated channels, which open when neurotransmitters bind, and voltage-gated channels, which open in response to changes in membrane potential. Ligand-gated channels allow sodium influx upon acetylcholine binding, depolarizing the membrane and triggering action potentials. Voltage-gated channels maintain the resting potential and enable action potential propagation along axons by selectively transporting sodium, potassium, calcium, and chloride ions in response to changes in voltage.
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The document summarizes membrane potentials and action potentials in nerve cells. It discusses:
1) The concentration gradients that give rise to resting membrane potentials via the Nernst equation and Goldman equation. Key ions like sodium, potassium and chloride contribute to a resting potential of around -90mV.
2) How action potentials are initiated when the membrane reaches a threshold potential, causing voltage-gated sodium channels to open and depolarize the membrane. Potassium channels then open to repolarize the membrane.
3) The roles of other ions like calcium and various ion pumps and channels in maintaining resting potentials and propagating action potentials down nerve fibers via saltatory conduction. Action potentials rely on precise ion concentration gradients maintained
Membrane transport
Membrane transport involves selective transport of solutes across membranes via transport proteins. There are three main types of transport: passive transport via diffusion, facilitated transport via carrier proteins, and active transport via pumps which move solutes against concentration gradients using ATP. Key transport proteins include carrier proteins that selectively transport particular solutes, ion channels that selectively transport ions, and the sodium-potassium pump which actively transports sodium and potassium ions out and into cells respectively to maintain electrochemical gradients.
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Membrane transport
This document discusses various mechanisms of membrane transport including passive diffusion, facilitated diffusion, active transport, filtration, and endocytosis. It describes passive diffusion as a bidirectional process that moves molecules down a concentration gradient without requiring energy. Facilitated diffusion and active transport are described as carrier-mediated processes, with active transport moving molecules against a concentration gradient by utilizing energy. Factors affecting drug absorption like solubility, pH, surface area, and vascularity are also summarized. Specific transporters like P-glycoprotein and classes of transporters like ABC and SLC families are briefly mentioned.
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Ion Transport Through cell Membrane
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classification of nerve fibers
about nerve fibers
It is the structural and the functional unit of nervous system.
The human nervous system contains approximate 1012 neurons.
A nerve fiber is a thread like extension of a nerve cell and consists of an axon and myelin sheath (if present) in the nervous system.
In peripheral nervous system it is formed by
schwann’s cell. While in case of central nervous system it is formed by oligodendroglia.
The places ,where myelin sheath is absent are called node of ranvier(2-3µm) and these are present once about 1-3 mm distance along the myelin sheath.
IT PREVENTS LEAKAGE OF IONS BY 5000 FOLDS.
IT INCREASES VELOCITY OF CONDUCTION BY 5-50 FOLDS DUE TO
SALTATORY CONDUCTION i.e. ABOUT 100 m/s IN CASE OF
MYELINATED NERVE FIBERS WHILE IN NONMYELINATED
IT IS ABOUT 0.25 m/s.
SALTATORY CONDUCTION CONSERVES ENERGY BECAUSE ONLY NODES OF RANVIER GET DEPOLARISED.
These are α type motor nerve fibers.
The neurotransmitter released at the neuron endings is acetylcholine(Ach).
It always leads to muscles excitation . Inhibition takes place centrally due to participation of interneurons.
they innervate smooth muscles , cardiac muscles and glands.
Their main work is to maintain homeostasis with the help of autonomic nervous system.
they can lead to either excitation or inhibition of effector organs
Erlanger and Grasser studied the action potential of mixed nerve trunk by means of cathode ray oscilloscope and they obtained the compounded spike. So they divided nerve fibers into 3 groups. They observed that the main cause of difference in nerve fibers is diameter
AS Diameter increases
Velocity of conduction increases.
Magnitude of electrical response increases.
Threshold of excitation decreases.
Duration of response decreases.
Refractory period decreases.
Bioenergetics
Bioenergetics is the study of energy changes in biochemical reactions and biological systems. The laws of thermodynamics govern energy changes. ATP is the primary energy currency in cells. It is produced through oxidative phosphorylation where the energy released from redox reactions is used to pump protons across the mitochondrial inner membrane, creating a proton gradient. ATP synthase uses this proton gradient to phosphorylate ADP, producing ATP. Diseases can result from defects in the electron transport chain or oxidative phosphorylation.
Osmotic pressure
This presentation discusses osmotic pressure and its related concepts. Osmosis is the passage of solvent through a semipermeable membrane from a less concentrated to a more concentrated solution. Osmotic pressure is the minimum pressure required to prevent osmosis, or the flow of water across the membrane. It further defines isotonic, hypertonic, and hypotonic solutions and outlines methods to determine osmotic pressure. Van't Hoff's law relates osmotic pressure to concentration and temperature. Osmotic pressure has important applications including desalination and maintaining fluid balance in the body.
Resting membrane potential
The resting membrane potential (RMP) refers to the stable voltage difference between the inside and outside of a cell membrane when the cell is not actively transmitting signals. The RMP results from selective permeability of ions like potassium and sodium across the membrane. At rest, the neuron's RMP is approximately -70mV due to higher intracellular potassium concentration creating a diffusion potential of -94mV, and lower intracellular sodium contributing +61mV. Additional contribution from the sodium-potassium pump, which actively transports ions against their gradients, results in the overall RMP of -90mV in neurons.
Conduction of action potential
Conduction of action potential through neurons which is a basic phenomena of transmission of information through the neurons within the human brain.
Nerve & Action potential
This document discusses the generation and propagation of action potentials in neurons. It notes that neurons respond to stimuli by producing either local, non-propagated potentials or propagated action potentials. Action potentials are generated when voltage-gated sodium channels open in response to depolarization, allowing sodium ions to rush in and briefly reverse the membrane potential. This wave of depolarization then propagates down the axon by electrotonic conduction. The document outlines the changes in membrane permeability and potential during an action potential and describes how action potentials conduct in either direction along the axon.
Myoglobin
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Membrane potentials
Diffusion potential. Large Nerve. Na -K ATPase. Guyton and Hall. Medical Physiology. Dr. Nusrat Tariq. Professor Of Physiology. M.I.M.D.C. GOLDMAN HODGKIN KATZ EQUATION
1 03-F Potencial de membranayybb.pdf.pdf
The resting membrane potential of neurons is approximately -70 mV, with the intracellular side being negatively charged relative to the extracellular fluid. This potential is generated by three main factors: 1) Differences in ion concentrations between intracellular and extracellular fluids, maintained by the sodium-potassium pump, with higher potassium and negatively charged proteins intracellularly and lower sodium intracellularly. 2) Differential permeability of the membrane, being much more permeable to potassium than sodium. 3) This generates a net outward diffusion of potassium ions, leaving the intracellular space negatively charged and establishing the resting potential.
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Action potential
This document provides a summary of the action potential in excitable tissues like nerves and muscles. It explains that excitable cells maintain a resting membrane potential with a negative charge inside and positive outside due to potassium ion leakage and intracellular proteins. An action potential is triggered by stimuli and causes rapid depolarization as sodium ions enter the cell, repolarization as potassium ions exit, returning the membrane to its resting potential. Precise ion channel openings and closings enable impulse transmission and functions like muscle contraction. Sodium-potassium pumps then restore ion gradients using ATP.
Active Transport New
Active transport requires cells to use energy in the form of ATP to move substances against their concentration gradient, such as the sodium-potassium pump transporting sodium and potassium ions across nerve cell membranes. The sodium-potassium pump uses ATP to pump 3 sodium ions out and 2 potassium ions into the cell against their gradients. Transport proteins also use active transport for molecules too large to pass through the membrane on their own, such as during endocytosis and exocytosis.
High energy compounds
High energy compounds, also known as energy rich compounds, contain high energy bonds that release free energy of -7.3 kcal/mol or greater during hydrolysis. ATP is the most important high energy compound, containing two high energy phosphoanhydride bonds. The hydrolysis of ATP releases -7.3 kcal/mol of free energy and is coupled to endergonic reactions in cells, functioning to link catabolic and anabolic processes through the transfer of its phosphoryl groups. ATP serves as the universal energy currency in living organisms, driving many biological reactions and processes.
Ion channels
Ion channels are membrane proteins that allow ions to pass through their pore, regulating ion flow and electrical signals. There are two main types of gated ion channels: ligand-gated channels, which open when neurotransmitters bind, and voltage-gated channels, which open in response to changes in membrane potential. Ligand-gated channels allow sodium influx upon acetylcholine binding, depolarizing the membrane and triggering action potentials. Voltage-gated channels maintain the resting potential and enable action potential propagation along axons by selectively transporting sodium, potassium, calcium, and chloride ions in response to changes in voltage.
Synaptic transmission
this ppt shares what synapses are and how information of one neuron is transmitted to other through the synapses. it also includes the properties and plasticity of synaptic transmission
General Physiology - Action potential
The document summarizes membrane potentials and action potentials in nerve cells. It discusses:
1) The concentration gradients that give rise to resting membrane potentials via the Nernst equation and Goldman equation. Key ions like sodium, potassium and chloride contribute to a resting potential of around -90mV.
2) How action potentials are initiated when the membrane reaches a threshold potential, causing voltage-gated sodium channels to open and depolarize the membrane. Potassium channels then open to repolarize the membrane.
3) The roles of other ions like calcium and various ion pumps and channels in maintaining resting potentials and propagating action potentials down nerve fibers via saltatory conduction. Action potentials rely on precise ion concentration gradients maintained
Membrane transport
Membrane transport involves selective transport of solutes across membranes via transport proteins. There are three main types of transport: passive transport via diffusion, facilitated transport via carrier proteins, and active transport via pumps which move solutes against concentration gradients using ATP. Key transport proteins include carrier proteins that selectively transport particular solutes, ion channels that selectively transport ions, and the sodium-potassium pump which actively transports sodium and potassium ions out and into cells respectively to maintain electrochemical gradients.
Calcium atpase pumps
The document summarizes different calcium and proton pumps in the cell. It describes the calcium ATPase pump that actively transports calcium out of cells using ATP. Calcium is an important secondary messenger but must be tightly regulated as too much can cause apoptosis. It also discusses the sodium calcium exchanger that removes calcium from cells using the sodium gradient, and proton pumps like the lysosomal ATPase and vacuolar ATPase that acidify organelles by transporting protons across membranes using ATP. All of these pumps help maintain calcium and pH gradients crucial for cellular signaling and function.
Membrane transport
This document discusses various mechanisms of membrane transport including passive diffusion, facilitated diffusion, active transport, filtration, and endocytosis. It describes passive diffusion as a bidirectional process that moves molecules down a concentration gradient without requiring energy. Facilitated diffusion and active transport are described as carrier-mediated processes, with active transport moving molecules against a concentration gradient by utilizing energy. Factors affecting drug absorption like solubility, pH, surface area, and vascularity are also summarized. Specific transporters like P-glycoprotein and classes of transporters like ABC and SLC families are briefly mentioned.
Electron Transport Chain ETC
The electron transport chain (ETC) is a series of protein complexes and carriers in the inner mitochondrial membrane that transport electrons from electron donors like NADH to final acceptors like oxygen. This transports protons from the mitochondrial matrix to the intermembrane space, building up a proton gradient. ATP synthase uses this proton gradient to phosphorylate ADP, producing approximately 34 ATP per glucose. The ETC is crucial for aerobic respiration as it extracts much more energy than glycolysis and the Krebs cycle alone.
Ion Transport Through cell Membrane
Ion transport through cell membranes occurs through passive and active transport mechanisms. Passive transport includes simple diffusion, facilitated diffusion, and osmosis. Simple diffusion allows small, nonpolar molecules to freely pass through the phospholipid bilayer. Facilitated diffusion uses channel and carrier proteins to transport ions and larger molecules down their concentration gradients without expending energy. Osmosis allows for the diffusion of water through semipermeable membranes. Active transport moves solutes against their concentration gradients and requires energy in the form of ATP hydrolysis. Primary active transport uses ATP and carrier proteins like Na+/K+ ATPase to pump ions. Secondary active transport couples the uphill transport of one solute to the downhill flow of another.
classification of nerve fibers
about nerve fibers
It is the structural and the functional unit of nervous system.
The human nervous system contains approximate 1012 neurons.
A nerve fiber is a thread like extension of a nerve cell and consists of an axon and myelin sheath (if present) in the nervous system.
In peripheral nervous system it is formed by
schwann’s cell. While in case of central nervous system it is formed by oligodendroglia.
The places ,where myelin sheath is absent are called node of ranvier(2-3µm) and these are present once about 1-3 mm distance along the myelin sheath.
IT PREVENTS LEAKAGE OF IONS BY 5000 FOLDS.
IT INCREASES VELOCITY OF CONDUCTION BY 5-50 FOLDS DUE TO
SALTATORY CONDUCTION i.e. ABOUT 100 m/s IN CASE OF
MYELINATED NERVE FIBERS WHILE IN NONMYELINATED
IT IS ABOUT 0.25 m/s.
SALTATORY CONDUCTION CONSERVES ENERGY BECAUSE ONLY NODES OF RANVIER GET DEPOLARISED.
These are α type motor nerve fibers.
The neurotransmitter released at the neuron endings is acetylcholine(Ach).
It always leads to muscles excitation . Inhibition takes place centrally due to participation of interneurons.
they innervate smooth muscles , cardiac muscles and glands.
Their main work is to maintain homeostasis with the help of autonomic nervous system.
they can lead to either excitation or inhibition of effector organs
Erlanger and Grasser studied the action potential of mixed nerve trunk by means of cathode ray oscilloscope and they obtained the compounded spike. So they divided nerve fibers into 3 groups. They observed that the main cause of difference in nerve fibers is diameter
AS Diameter increases
Velocity of conduction increases.
Magnitude of electrical response increases.
Threshold of excitation decreases.
Duration of response decreases.
Refractory period decreases.
Bioenergetics
Bioenergetics is the study of energy changes in biochemical reactions and biological systems. The laws of thermodynamics govern energy changes. ATP is the primary energy currency in cells. It is produced through oxidative phosphorylation where the energy released from redox reactions is used to pump protons across the mitochondrial inner membrane, creating a proton gradient. ATP synthase uses this proton gradient to phosphorylate ADP, producing ATP. Diseases can result from defects in the electron transport chain or oxidative phosphorylation.
Osmotic pressure
This presentation discusses osmotic pressure and its related concepts. Osmosis is the passage of solvent through a semipermeable membrane from a less concentrated to a more concentrated solution. Osmotic pressure is the minimum pressure required to prevent osmosis, or the flow of water across the membrane. It further defines isotonic, hypertonic, and hypotonic solutions and outlines methods to determine osmotic pressure. Van't Hoff's law relates osmotic pressure to concentration and temperature. Osmotic pressure has important applications including desalination and maintaining fluid balance in the body.
Resting membrane potential
The resting membrane potential (RMP) refers to the stable voltage difference between the inside and outside of a cell membrane when the cell is not actively transmitting signals. The RMP results from selective permeability of ions like potassium and sodium across the membrane. At rest, the neuron's RMP is approximately -70mV due to higher intracellular potassium concentration creating a diffusion potential of -94mV, and lower intracellular sodium contributing +61mV. Additional contribution from the sodium-potassium pump, which actively transports ions against their gradients, results in the overall RMP of -90mV in neurons.
Conduction of action potential
Conduction of action potential through neurons which is a basic phenomena of transmission of information through the neurons within the human brain.
Nerve & Action potential
This document discusses the generation and propagation of action potentials in neurons. It notes that neurons respond to stimuli by producing either local, non-propagated potentials or propagated action potentials. Action potentials are generated when voltage-gated sodium channels open in response to depolarization, allowing sodium ions to rush in and briefly reverse the membrane potential. This wave of depolarization then propagates down the axon by electrotonic conduction. The document outlines the changes in membrane permeability and potential during an action potential and describes how action potentials conduct in either direction along the axon.
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Presentation on Electrical Properties of Cell Membrane
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Similar to Nernst equation
Membrane potentials
Diffusion potential. Large Nerve. Na -K ATPase. Guyton and Hall. Medical Physiology. Dr. Nusrat Tariq. Professor Of Physiology. M.I.M.D.C. GOLDMAN HODGKIN KATZ EQUATION
1 03-F Potencial de membranayybb.pdf.pdf
The resting membrane potential of neurons is approximately -70 mV, with the intracellular side being negatively charged relative to the extracellular fluid. This potential is generated by three main factors: 1) Differences in ion concentrations between intracellular and extracellular fluids, maintained by the sodium-potassium pump, with higher potassium and negatively charged proteins intracellularly and lower sodium intracellularly. 2) Differential permeability of the membrane, being much more permeable to potassium than sodium. 3) This generates a net outward diffusion of potassium ions, leaving the intracellular space negatively charged and establishing the resting potential.
Lecture4
1. The document discusses facilitated diffusion, which is the transport of substances across a membrane with the aid of carrier proteins. It involves substances moving uphill against a concentration gradient, with the carrier protein having a fixed affinity for the substance and ATP being used to flip the orientation or change the affinity of the binding site.
2. It then covers the resting membrane potential, how cells create charge separation across the membrane by establishing ion concentration gradients and allowing diffusion through leak channels, and how this results in a membrane potential. Key ions involved are sodium, potassium, and macromolecular anions.
3. It defines graded potentials as local changes in membrane potential caused by transient opening of non-voltage gated ion channels that
Nerve physiology
The document discusses the resting membrane potential and action potential in nerve cells. It explains that the resting membrane potential of -70 mV is established primarily due to the concentration gradients of potassium and sodium ions across the plasma membrane. Potassium ions diffuse out of the cell, while sodium ions diffuse into the cell. This creates an equilibrium potential close to the potassium equilibrium potential of -94 mV. When an excitatory stimulus is strong enough to depolarize the membrane past its threshold, voltage-gated sodium channels open, allowing rapid sodium influx and further depolarization. The membrane potential then reaches about +30 mV before sodium channels inactivate and voltage-gated potassium channels open, causing repolarization back to the resting potential.
Membrane potential + action potential
The membrane potential arises from separation of charges across the plasma membrane due to unequal distribution of ions such as sodium, potassium, and chloride between the intracellular and extracellular fluids. Nerve and muscle cells have the greatest membrane potential due to their ability to generate rapid changes in potential when stimulated. The resting membrane potential results from small passive leak of potassium out of the cell, generating a potential of around -70 mV. An action potential is initiated when the membrane potential surpasses the threshold, causing voltage-gated sodium channels to open and allow sodium to rush in, rapidly depolarizing the membrane before voltage-gated potassium channels open to repolarize it.
Membrane potential + action potential
The membrane potential arises from separation of charges across the plasma membrane due to unequal distribution of ions such as sodium, potassium, and chloride between the intracellular and extracellular fluids. Nerve and muscle cells have the greatest membrane potential due to their ability to generate rapid changes in potential when stimulated. The resting membrane potential results from small passive leak of potassium out of the cell, generating a potential of around -70 mV. An action potential is initiated when the membrane potential surpasses the threshold, causing voltage-gated sodium channels to open and allow sodium to rush in, rapidly depolarizing the membrane before voltage-gated potassium channels open to repolarize it.
RESTING MEMBRANE POTENTIAL BY DR QAZI IMTIAZ RASOOL
The document discusses electrical properties of cell membranes, including diffusion potentials and equilibrium potentials. It defines diffusion potential as the potential generated across a membrane when an ion diffuses down its concentration gradient. Equilibrium potential is the diffusion potential that exactly balances the tendency for diffusion. The Nernst equation is introduced for calculating the theoretical equilibrium potential for a given ion. The Goldman equation accounts for membranes that are permeable to multiple ions by taking a weighted average of the individual ion equilibrium potentials.
Action potential
1. The document discusses the basics of nerve structure, electrical current, capacitance, resistance, and action potentials.
2. It defines key concepts like resting potential, depolarization, repolarization, and hyperpolarization that characterize the phases of an action potential.
3. The action potential results from changes in sodium and potassium permeability that cause the membrane potential to rapidly shift from its resting potential of -70mV to a peak of +30mV before returning to the resting potential.
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D05092229
The document studies the window effect of rectangular electrical pulses on the membrane potential of an osteoblast cell modeled as a dielectric. It presents an equivalent circuit model of the cell subjected to time domain electric fields such as rectangular pulses. The model includes separate charging time constants and relaxation times for the inner and outer cell membranes. Simulation results show that shorter pulse durations selectively affect the inner membrane more than the outer membrane, while longer pulses can fully charge both membranes. The window effect provides insight into bioelectric phenomena like electroporation and nanopore formation, with applications to cancer treatment.
MEMBRANE POTENTIAL.pptx
- The membrane potential is caused by a difference in electrical potential across cell membranes, with the inside being negative relative to the outside. This is due to selective permeability of ions like Na+, K+, and Cl- across the membrane.
- The Nernst equation and Goldman-Hodgkin-Katz equation can be used to calculate membrane potentials based on ion concentration gradients and permeabilities. Key ions involved are Na+, K+, and Cl-.
- The sodium-potassium pump helps maintain the resting potential by actively transporting more Na+ out and K+ in, making the intracellular side more negative.
Cellular electrophysiology
this presentation on cellular electrophysiology carry the information of electrical properties of biophysiology in cellular level. i hope it help you all.
2. BIOPHYSICS – Membrane Potentials and Action Potential.pptx
step by step description of membrane potential, action potential and other electrophysiological variables
2b. Membrane Potentials n Excitable Tissues - PPT.pptx
Excitable tissues include nerves and muscles that can generate action potentials in response to stimuli. Nerve cells transmit nerve impulses along their axons via action potentials initiated by the opening of sodium and potassium ion channels. Muscle cells similarly generate action potentials that trigger contraction. The membrane potential of excitable cells is maintained by ion concentration gradients and can be altered to produce local or propagating signals.
EFFECTS OF ELECTRICITY ON CELL BIOLOGY, PHYSIOLOGY AND ON THIS BASIS INVESTIG...
EFFECTS OF ELECTRICITY ON CELL BIOLOGY, PHYSIOLOGY AND ON THIS BASIS INVESTIGATION OF THE PATHOPHYSIOLOGICAL RELATIONSHIP OF DISEASES
Mossbauer spectroscopy
Mossbauer spectroscopy involves the resonant absorption and emission of gamma rays between atomic nuclei bound in a solid material. It can provide information about the chemical and electronic environment of atomic nuclei. The document discusses the basic principles, instrumentation, and analysis of Mossbauer spectroscopy. Key applications include determining chemical shifts, quadrupole splitting, magnetic properties, and using these parameters to study chemical bonding, structure, and biochemical systems.
Zeta potential
This document provides an overview of zeta potential, including:
- Zeta potential is the electric potential at the boundary between the double layer and bulk solution surrounding charged particles suspended in a colloidal system.
- Factors that affect zeta potential include pH, thickness of the double layer, and concentration of formulation components.
- Zeta potential is important for predicting particle interactions and stability in colloidal systems based on DLVO theory of electrostatic repulsion and van der Waals attraction.
- Measurement techniques include electrophoresis and electroacoustic methods to determine particle mobility from which zeta potential is calculated.
zeta potential
This document provides an overview of zeta potential, including:
- Zeta potential is the electric potential at the boundary between the double layer and bulk solution surrounding charged particles suspended in a colloid.
- Factors that affect zeta potential include pH, thickness of the double layer, and concentration of formulation components.
- Zeta potential is important for predicting particle interactions and stability in colloidal systems based on DLVO theory of electrostatic repulsion and van der Waals attraction.
- Measurement techniques include electrophoresis and electroacoustic methods to determine particle mobility from which zeta potential is calculated.
4 ghe membrane_electricalmodel (3)
This document defines key concepts in electrophysiology including the Goldman equation, membrane models, ion conductances, equilibrium potentials, and the relationship between these factors and the membrane potential. It provides examples of how changing conductance ratios affect the membrane potential. It also describes the electrical properties of neurons including voltage sources, current sources, resistances, and capacitance. The membrane acts as a capacitor and neuronal geometry influences capacitance. Patch clamp techniques are used to study single ion channels and their opening/closing kinetics.
Similar to Nernst equation (20)
RESTING MEMBRANE POTENTIAL BY DR QAZI IMTIAZ RASOOL
RESTING MEMBRANE POTENTIAL BY DR QAZI IMTIAZ RASOOL
Welcome to International Journal of Engineering Research and Development (IJERD)
Welcome to International Journal of Engineering Research and Development (IJERD)
2. BIOPHYSICS – Membrane Potentials and Action Potential.pptx
2. BIOPHYSICS – Membrane Potentials and Action Potential.pptx
2b. Membrane Potentials n Excitable Tissues - PPT.pptx
2b. Membrane Potentials n Excitable Tissues - PPT.pptx
EFFECTS OF ELECTRICITY ON CELL BIOLOGY, PHYSIOLOGY AND ON THIS BASIS INVESTIG...
EFFECTS OF ELECTRICITY ON CELL BIOLOGY, PHYSIOLOGY AND ON THIS BASIS INVESTIG...
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SDSS1335+0728: The awakening of a ∼ 106M⊙ black hole⋆
Context. The early-type galaxy SDSS J133519.91+072807.4 (hereafter SDSS1335+0728), which had exhibited no prior optical variations during the preceding two decades, began showing significant nuclear variability in the Zwicky Transient Facility (ZTF) alert stream from December 2019 (as ZTF19acnskyy). This variability behaviour, coupled with the host-galaxy properties, suggests that SDSS1335+0728 hosts a ∼ 106M⊙ black hole (BH) that is currently in the process of ‘turning on’. Aims. We present a multi-wavelength photometric analysis and spectroscopic follow-up performed with the aim of better understanding the origin of the nuclear variations detected in SDSS1335+0728. Methods. We used archival photometry (from WISE, 2MASS, SDSS, GALEX, eROSITA) and spectroscopic data (from SDSS and LAMOST) to study the state of SDSS1335+0728 prior to December 2019, and new observations from Swift, SOAR/Goodman, VLT/X-shooter, and Keck/LRIS taken after its turn-on to characterise its current state. We analysed the variability of SDSS1335+0728 in the X-ray/UV/optical/mid-infrared range, modelled its spectral energy distribution prior to and after December 2019, and studied the evolution of its UV/optical spectra. Results. From our multi-wavelength photometric analysis, we find that: (a) since 2021, the UV flux (from Swift/UVOT observations) is four times brighter than the flux reported by GALEX in 2004; (b) since June 2022, the mid-infrared flux has risen more than two times, and the W1−W2 WISE colour has become redder; and (c) since February 2024, the source has begun showing X-ray emission. From our spectroscopic follow-up, we see that (i) the narrow emission line ratios are now consistent with a more energetic ionising continuum; (ii) broad emission lines are not detected; and (iii) the [OIII] line increased its flux ∼ 3.6 years after the first ZTF alert, which implies a relatively compact narrow-line-emitting region. Conclusions. We conclude that the variations observed in SDSS1335+0728 could be either explained by a ∼ 106M⊙ AGN that is just turning on or by an exotic tidal disruption event (TDE). If the former is true, SDSS1335+0728 is one of the strongest cases of an AGNobserved in the process of activating. If the latter were found to be the case, it would correspond to the longest and faintest TDE ever observed (or another class of still unknown nuclear transient). Future observations of SDSS1335+0728 are crucial to further understand its behaviour. Key words. galaxies: active– accretion, accretion discs– galaxies: individual: SDSS J133519.91+072807.4
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Nernst equation
- 1. NERNST EQUATION Sem-5,Paper-2, Unit-4 Abhijeet Bhattacharya KSD’s Model College Dombivali
- 2. INTRODUCTION ➢Electric potential difference existing across the cell membrane of all living cells is called membrane potential. ➢ The inside of the cell being negative in relation to the outside. ➢The magnitude of membrane potential varies from cell to cell and in a particular cell according to its functional status. ➢For example, a nerve cell has a membrane potential of -70 mv at rest, but when it gets exited the membrane potential becomes about +30mv.
- 3. Resting Membrane Potential The membrane potential at rest is called Resting Membrane Potential (RMP) RMP in nerve cell -70mv, in smooth muscle -50mv RMP is due to :- ➢Unequal distribution of ions across the cell membrane because of its selective permeability. ➢Due to combined effect of forces acting on ions.
- 4. SELECTIVE PERMEABILITY OF CELL MEMBRANE ➢The cell membrane is selectively permeable that is, it is freely permeable to K+ and Cl¯ , moderately to Na+ , and impermeable to proteins & organic phosphate which are negatively charged ions. ➢Major intracellular cation is K+ and major intracellular anions are proteins and organic phosphate. Major extracellular cation is Na+ and anion is Cl¯ . ➢Presence of gated protein channels in the cell membrane is responsible for variable permeability of ions.
- 6. NERNST EQUATION ➢Walther H Nernst was a German physical chemist, received noble prize in chemistry 1920, in recognition of his work in thermo chemistry. ➢His contribution to chemical thermodynamics led to the well known Nernst equation correlating chemical energy and electric potential. ➢The forces acting on the ions across the cell membrane produces variations in the membrane potential. The magnitude of forces acting across the cell membrane on each ion can be analyzed by Nernst equation.
- 7. Concentration gradient :- ➢The asymmetrical distribution of diffusible ions across the cell membrane in the form of excess diffusible cation inside due to Donnan’s effect results in concentration gradient. ➢The Donnan's effect is a name for the behavior of charged particles near a semi-permeable membrane that sometimes fail to distribute evenly across the two sides of the membrane.
- 8. Electrical gradient ➢As a result of concentration gradient cation K + , will try to diffuse back into ECF from ICF. ➢But it is counter acted by electrical gradient which will be created due to presence of non diffusible anions (proteins) inside the cell. ➢The membrane potential at which the electrical force is equal in magnitude but opposite in direction to the concentration force is called equilibrium potential for that ion. The magnitude of equilibrium potential is determined by Nernst equation.
- 9. Formula for Nernst Equation Ex= RT/ZF × In × (C out/C in) V • Ex= Equilbrium Potential • R= Gas Constant(8.31 J mol¯¹ K¯¹) • T= Temperature(Kelvin) • F=Faraday Constant(96500 C mol¯¹) • Z= Ion Valence (Na+=+1, Cl¯=-1) • In= Natural log substituting for the constants (R, T & F) converting Volts into millivolts and to common logarithm. T=37°C=310.2°K We get, Ex=61.5/Z ×log10 ×(C out/C in) mV
- 10. Example to illustrate the Nernst Equation. Ex=61.5/Z ×log10×(C out/C in) mV For Na+ ions C out =5mM C in= 100mM Na+= Valence +1 ENa=61.5 log 0.05mV =61.5(-1.3)mV =-80mV
- 11. Equilibrium potential (E) for important ions in a neuron. Ecl¯ -70mV Ek+ -90mV ENa+ +60mV ECa2+ +130mV
- 13. GOLDMANN-HODGKIN-KATZ (GHK) EQUATION The Nernst equation helps in calculating the equilibrium potential for each ion individually. However, the magnitude of membrane potential at any given time depends on distribution and permeability of Na+ , K+ and Cl ions. The integrated role of different ions in the generation of membrane potential can be described accurately by the GHK equation. V=RT/F ln Pĸ [K+ ] out + Pŋa[Na+ ] out +PCl[Cl- ]in ------------------------------------------------------ PK [K+ ]in + Pŋa[Na+ ]in +PCl[Cl- ] out
- 14. Inferences of Goldmann constant field equation 1. Most important ions for development of membrane potentials in nerve and muscle fibers are sodium, potassium and chloride. The voltage of membrane potential is determined by the concentration gradient of each of these ions. 2. Degree of each of the ions in determining the voltage depends upon the membrane permeability of the individual ion. 3. Positive ion concentration from inside the membrane to outside is responsible for electro negativity inside the membrane. 4. Signal transmission in the nerves is primarily due to change in the sodium and potassium permeability because their channels undergo rapid change during conduction of the nerve impulse and not much change is seen in chloride channels.