Membrane potentials of a nerve impulse
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The document describes ion concentrations inside and outside neuronal cells under polarized conditions. Potassium ion concentration is higher inside the cell while sodium and chloride ion concentrations are higher outside. An action potential is a brief reversal of the resting potential as the neuronal membrane becomes depolarized, allowing a wave of electrical activity to pass along the neuron. It involves sodium ions entering the cell through open voltage-gated sodium channels, causing further depolarization, followed by potassium ions leaving through open voltage-gated potassium channels to repolarize the membrane potential.
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It is over 60 years since Hodgkin and
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potential. Using an electrode placed inside a
squid giant axon they were able to measure a
transmembrane potential of around 260 mV
inside relative to outside, under resting
conditions (this is called the resting membrane
potential). The action potential is a
transient (,1 millisecond) reversal in the
polarity of this transmembrane potential
which then moves from its point of initiation,
down the axon, to the axon terminals. In a
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Katz, discovered that the action potential
results from transient changes in the permeability
of the axon membrane to sodium (Na+)
and potassium (K+) ions. Importantly, Na+ and
K+ cross the membrane through independent
pathways that open in response to a change
in membrane potential.
As testimony to their pioneering work, the
fundamental mechanisms described by
Hodgkin, Huxley and Katz remain applicable
to all excitable cells today. Indeed, the
predictions they made about the molecular
mechanisms that might underlie the changes
in membrane permeability showed remarkable
foresight. The molecular basis of the action
potential lies in the presence of proteins
called ion channels that form the permeation
pathways across the neuronal membrane.
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recordings from individual ion channels were
not made until the mid 1970s,2 Hodgkin and
Huxley predicted many of the properties now
known to be key components of their
function: ion selectivity, the electrical basis
of voltage-sensitivity and, importantly, a
mechanism for quickly closing down the
permeability pathways to ensure that the
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Huxley1 made the first direct recording of
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membrane that mediate the action
potential. Using an electrode placed inside a
squid giant axon they were able to measure a
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inside relative to outside, under resting
conditions (this is called the resting membrane
potential). The action potential is a
transient (,1 millisecond) reversal in the
polarity of this transmembrane potential
which then moves from its point of initiation,
down the axon, to the axon terminals. In a
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Katz, discovered that the action potential
results from transient changes in the permeability
of the axon membrane to sodium (Na+)
and potassium (K+) ions. Importantly, Na+ and
K+ cross the membrane through independent
pathways that open in response to a change
in membrane potential.
As testimony to their pioneering work, the
fundamental mechanisms described by
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to all excitable cells today. Indeed, the
predictions they made about the molecular
mechanisms that might underlie the changes
in membrane permeability showed remarkable
foresight. The molecular basis of the action
potential lies in the presence of proteins
called ion channels that form the permeation
pathways across the neuronal membrane.
Although the first electrophysiological
recordings from individual ion channels were
not made until the mid 1970s,2 Hodgkin and
Huxley predicted many of the properties now
known to be key components of their
function: ion selectivity, the electrical basis
of voltage-sensitivity and, importantly, a
mechanism for quickly closing down the
permeability pathways to ensure that the
action potential only moves along the axon in
one direction.
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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
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The document summarizes key concepts about neuromuscular transmission:
1. It describes the generation of action potentials in neurons, including the resting and depolarized states and the roles of sodium, potassium, and calcium ions.
2. It explains the formation, storage, and release of acetylcholine at the neuromuscular junction, as well as the roles of calcium and SNARE proteins in the release process.
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Resting membranepotential
1) The resting membrane potential of a mammalian nerve cell is -90mV, maintained by the sodium-potassium pump that pumps 3Na+ ions out of the cell for every 2K+ ions into the cell.
2) An action potential occurs when the membrane potential rapidly changes from negative to positive and back again. It is triggered when voltage-gated sodium channels open and allow sodium ions to rush into the cell, reversing the potential.
3) Voltage-gated potassium channels then open, allowing potassium ions to efflux and repolarize the membrane back to its resting potential. The sodium-potassium pump then restores the ion gradients across the membrane.
Membrane potentials
Nerve cells transmit electrical signals through action potentials. Action potentials are brief changes in the electrical potential across the cell membrane that are triggered when the membrane potential reaches a threshold. They are generated by the rapid influx of sodium ions through voltage-gated sodium channels, which causes further opening of these channels in a positive feedback loop. After peaking, the membrane repolarizes as sodium channels inactivate and potassium channels open, restoring the ion gradients. Action potentials propagate along axons without loss of strength through the active opening of sodium channels just beyond the leading edge of depolarization.
Nerve Action Potential (1).pptx
1. An action potential is a brief change in the membrane potential of a muscle or nerve cell triggered by the stimulation of voltage-gated ion channels.
2. During an action potential, sodium channels open allowing sodium ions to enter the cell, causing rapid depolarization. Then, potassium channels open and sodium channels close, repolarizing the membrane back to its resting potential.
3. The stages of an action potential are resting, depolarization, and repolarization. After an action potential occurs, the cell enters an absolute refractory period where it cannot generate another action potential, followed by a relative refractory period.
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1. The document describes the process of muscle contraction, which begins when a motor neuron releases acetylcholine (ACh) at the neuromuscular junction, triggering an electrical signal called an action potential.
2. The action potential spreads across the muscle cell membrane and into invaginations called T-tubules, signaling the release of calcium ions from the sarcoplasmic reticulum.
3. Calcium ions bind to troponin, exposing binding sites on actin filaments for myosin heads to attach in cross bridges, pulling the filaments together and causing muscle contraction.
Nerve impulses
1) The sodium-potassium ion pump creates concentration gradients across the cell membrane which maintains the resting potential of -70mV.
2) Changes in the voltage across the membrane cause voltage-gated sodium and potassium channels to open, allowing ions to flow and trigger an action potential.
3) An action potential is caused by an initial rapid influx of sodium ions through open sodium channels, followed by the opening of potassium channels which pump ions out to return the membrane potential to its resting state.
RestingMembranePotential
The resting membrane potential of cells is normally more negative inside the cell compared to outside, ranging from -9mV to -100mV. This polarization is due to the concentration gradients of sodium ions outside the cell and potassium ions inside the cell. When a stimulus causes voltage-gated sodium channels to open, sodium ions rush into the cell, depolarizing the membrane and initiating an action potential. Then, voltage-gated potassium channels open, allowing potassium ions to efflux and repolarize the membrane. Sodium-potassium pumps then restore the membrane back to its resting potential.
Physiology com3-week2
The document discusses membrane potential and action potentials. It begins by defining action potentials as signals that trigger communication between cells through electrical and chemical signaling. It then discusses:
- Excitable cells like neurons, muscle and endocrine cells that are able to generate and conduct action potentials.
- The resting membrane potential of -70mV that exists due to ion concentration gradients established by the sodium-potassium pump and selective permeability of the membrane.
- How action potentials are initiated when the membrane potential rapidly depolarizes past a threshold due to opening of voltage-gated sodium channels, then repolarizes due to opening of voltage-gated potassium channels.
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inside relative to outside, under resting
conditions (this is called the resting membrane
potential). The action potential is a
transient (,1 millisecond) reversal in the
polarity of this transmembrane potential
which then moves from its point of initiation,
down the axon, to the axon terminals. In a
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potential. Using an electrode placed inside a
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inside relative to outside, under resting
conditions (this is called the resting membrane
potential). The action potential is a
transient (,1 millisecond) reversal in the
polarity of this transmembrane potential
which then moves from its point of initiation,
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As testimony to their pioneering work, the
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predictions they made about the molecular
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potential lies in the presence of proteins
called ion channels that form the permeation
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Although the first electrophysiological
recordings from individual ion channels were
not made until the mid 1970s,2 Hodgkin and
Huxley predicted many of the properties now
known to be key components of their
function: ion selectivity, the electrical basis
of voltage-sensitivity and, importantly, a
mechanism for quickly closing down the
permeability pathways to ensure that the
action potential only moves along the axon in
one direction.
Earthing
Lightning is an abrupt electrostatic discharge that occurs between clouds or from clouds to the earth. It is accompanied by a flash. Charges build up in clouds during storms and separate, with negative charges near the ground and positive charges higher up. When enough charge builds up, electrons move toward the positive charges, ionizing the air and allowing discharge along a path of least resistance in a zigzag pattern. Upward and downward leaders form until they meet, causing a stroke and releasing a large amount of heat and producing the flash and thunder. Lightning arrestors safely guide the current from a strike to ground to dissipate the energy.
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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
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Similar to Membrane potentials of a nerve impulse
Action potential
An action potential is a brief change in the voltage of a neuron's membrane caused by the flow of ions into and out of the neuron. It occurs when a neuron fires, transmitting an electrical signal down its axon away from the cell body. During an action potential, sodium ions enter the neuron and potassium ions exit, causing the inside of the membrane to rapidly become more positive. This process then resets as the sodium channels close and potassium channels open to repolarize the membrane.
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The document discusses the generation and propagation of action potentials in neurons. It begins by explaining the resting membrane potential, which arises from ion concentration gradients maintained by the sodium-potassium pump and potassium leakage channels. It then describes how an action potential is triggered when the membrane potential reaches a threshold, causing voltage-gated sodium channels to open and sodium ions to rush in, rapidly depolarizing the membrane. This wave of depolarization then propagates along the neuron as adjacent areas are triggered to reach threshold. The action potential involves sequential phases of depolarization, repolarization, and hyperpolarization.
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2. It explains the formation, storage, and release of acetylcholine at the neuromuscular junction, as well as the roles of calcium and SNARE proteins in the release process.
3. It outlines the binding of acetylcholine to postsynaptic nicotinic receptors, the resulting endplate depolarization, and the conformational changes in sodium channels that underlie muscle fiber excitation.
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Resting membranepotential
1) The resting membrane potential of a mammalian nerve cell is -90mV, maintained by the sodium-potassium pump that pumps 3Na+ ions out of the cell for every 2K+ ions into the cell.
2) An action potential occurs when the membrane potential rapidly changes from negative to positive and back again. It is triggered when voltage-gated sodium channels open and allow sodium ions to rush into the cell, reversing the potential.
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Nerve cells transmit electrical signals through action potentials. Action potentials are brief changes in the electrical potential across the cell membrane that are triggered when the membrane potential reaches a threshold. They are generated by the rapid influx of sodium ions through voltage-gated sodium channels, which causes further opening of these channels in a positive feedback loop. After peaking, the membrane repolarizes as sodium channels inactivate and potassium channels open, restoring the ion gradients. Action potentials propagate along axons without loss of strength through the active opening of sodium channels just beyond the leading edge of depolarization.
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1. An action potential is a brief change in the membrane potential of a muscle or nerve cell triggered by the stimulation of voltage-gated ion channels.
2. During an action potential, sodium channels open allowing sodium ions to enter the cell, causing rapid depolarization. Then, potassium channels open and sodium channels close, repolarizing the membrane back to its resting potential.
3. The stages of an action potential are resting, depolarization, and repolarization. After an action potential occurs, the cell enters an absolute refractory period where it cannot generate another action potential, followed by a relative refractory period.
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1. The document describes the process of muscle contraction, which begins when a motor neuron releases acetylcholine (ACh) at the neuromuscular junction, triggering an electrical signal called an action potential.
2. The action potential spreads across the muscle cell membrane and into invaginations called T-tubules, signaling the release of calcium ions from the sarcoplasmic reticulum.
3. Calcium ions bind to troponin, exposing binding sites on actin filaments for myosin heads to attach in cross bridges, pulling the filaments together and causing muscle contraction.
Nerve impulses
1) The sodium-potassium ion pump creates concentration gradients across the cell membrane which maintains the resting potential of -70mV.
2) Changes in the voltage across the membrane cause voltage-gated sodium and potassium channels to open, allowing ions to flow and trigger an action potential.
3) An action potential is caused by an initial rapid influx of sodium ions through open sodium channels, followed by the opening of potassium channels which pump ions out to return the membrane potential to its resting state.
RestingMembranePotential
The resting membrane potential of cells is normally more negative inside the cell compared to outside, ranging from -9mV to -100mV. This polarization is due to the concentration gradients of sodium ions outside the cell and potassium ions inside the cell. When a stimulus causes voltage-gated sodium channels to open, sodium ions rush into the cell, depolarizing the membrane and initiating an action potential. Then, voltage-gated potassium channels open, allowing potassium ions to efflux and repolarize the membrane. Sodium-potassium pumps then restore the membrane back to its resting potential.
Physiology com3-week2
The document discusses membrane potential and action potentials. It begins by defining action potentials as signals that trigger communication between cells through electrical and chemical signaling. It then discusses:
- Excitable cells like neurons, muscle and endocrine cells that are able to generate and conduct action potentials.
- The resting membrane potential of -70mV that exists due to ion concentration gradients established by the sodium-potassium pump and selective permeability of the membrane.
- How action potentials are initiated when the membrane potential rapidly depolarizes past a threshold due to opening of voltage-gated sodium channels, then repolarizes due to opening of voltage-gated potassium channels.
Mechanism of Generation and Propagation of Nerve Impulse.docx
This document is a project write-up submitted by Abhinav Baranwal on the topic of the mechanism of generation and propagation of nerve impulses. It begins with an introduction discussing neurons and nerve impulses. It then explains that neurons maintain a resting membrane potential due to ion gradients established by ion pumps and channels. When stimulated, voltage-gated sodium channels open, causing rapid sodium influx and depolarization. This initiated action potential travels as a wave of depolarization along the axon. Myelination and nodes of Ranvier allow saltatory conduction to increase speed. The write-up provides detailed explanations and diagrams of these concepts in 13 pages.
BSC Lecture Action potential.pptx
1) Action potentials are electrical signals that propagate along excitable cell membranes and are initiated by stimuli. They involve the movement of ions through voltage-gated ion channels.
2) In neurons, an action potential is a brief reversal of the membrane potential followed by repolarization. This allows communication over long distances.
3) Cardiac action potentials have a depolarizing phase, plateau phase, and repolarizing phase due to calcium ion involvement. This allows for sustained contraction of heart muscle.
Biopotential generation
This document discusses biopotentials and how they are generated in the human body. Biopotentials result from the electrochemical activity of excitable cells like neurons and muscles. The resting membrane potential of these cells ranges from -70 to -80 mV due to ion gradients maintaining a separation of charges inside and outside the cell. When a stimulus causes ion channels to open, allowing ions to rush in and out, the membrane potential reverses and an action potential of around 110 mV is generated as the impulse travels along the cell. This precise sequence of depolarization and repolarization allows electrical signals to be transmitted through the nervous system.
cardiac ion channels and channelopathies
The document discusses ion channels and their role in generating cardiac action potentials. It begins by defining ion channels as pore-forming proteins that gate the flow of ions across cell membranes. It then describes the key properties of ion channels including selectivity, gating, and their role in establishing membrane potentials. The remainder of the document details the specific ion channels involved in each phase of the cardiac action potential, including the fast sodium current underlying the upstroke in Phase 0, the potassium and chloride currents producing Phase 1 repolarization, the calcium and potassium currents maintaining the Phase 2 plateau, and the currents responsible for Phase 3 repolarization. Pacemaker cell action potentials are also discussed, noting their unique pacemaker potential in Phase 4 and lack of Phase
BSC Lecture Action potential.pdf
1) All cells possess electrical excitability, the ability to generate an action potential in response to a stimulus.
2) An action potential is an electrical signal that propagates along the neuronal membrane due to the movement of sodium and potassium ions through ion channels.
3) The resting membrane potential is maintained by the uneven distribution of ions across the membrane and the sodium-potassium pump, which works to keep the intracellular concentration of sodium ions low and potassium ions high.
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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Membrane potentials of a nerve impulse
- 1. ©HannahRTweddle 26/02/2013
- 2. Ion Concentration in cell – Concentration outside mmoldm-3 cell -mmoldm-3 K+ 150.0 2.5 Na+ 15.0 145.0 Cl- 9.0 101.0 In this condition the condition of the axon is said to be polarised. Sodium ions are transported out of the axon and Potassium ions are actively transported into the axon both by the sodium-potassium pump. An equilibrium is established in which the chemical and electrical gradients are balanced and henceforth there is no net movement of ions. Resting potential is usually at -70mV inside the axon. ©HannahRTweddle 26/02/2013
- 3. An abrupt but short-lived reversal of the resting potential of a neurone. It occurs at a specific point and passes along a neurone as a wave. It is when the neurone sends an explosion of electrical activity. The membrane is said to have become depolarised at this point. ©HannahRTweddle 26/02/2013
- 4. When stimulisation happens depolarisation happens. Stimulus causes the membrane at one part of the neurone to increase in permeability to Na+ Na+ voltage gated channels open and Na+ enter the axon down the electrochemical gradient by diffusion. This causes resting potential to move to 0mV. When depolarisation reaches -30mV (or the threshold limit) more Na+ channels open which causes Na+ to rush in by diffusion the cell becomes more positive. ©HannahRTweddle 26/02/2013
- 5. Once the action potential of around 40mV has been established the voltage gates on the Na+ close this causes K+ to begin to open. ©HannahRTweddle 26/02/2013
- 6. With the K+ voltage channels now open the electrochemical gradient that was preventing the further movement of potassium is reversed. K+ rushes out making the inside of the cell more negative Since this restores the original polarity within the axon it is called repolarisation ©HannahRTweddle 26/02/2013
- 7. The outward diffusion of the K+ ions causes a temporary overshoot of the electrical gradient. Inside the axon becomes more negative (relative to the outside) . This is hyperpolarisation. The gates on the K+ ions now close and the activities of the sodium potassium pumps once again cause sodium ions to be pumped out and potassium ions to be pumped in. ©HannahRTweddle 26/02/2013
- 8. The term “action and resting potential” can be quite misleading The diffusion of the ions in “active potential” is primarily down to diffusion – which is a passive process. The diffusion of the ions in “resting potential” is down to active transport – which is a passive process. In this case the term “action potential” simply means the nerve is transmitting a nerve impulse, where as in “resting potential” it no longer is transmitting a nerve impulse. ©HannahRTweddle 26/02/2013