Action Potential
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Action potential is an abrupt change in membrane potential lasting 1-2 milliseconds. It involves a reversal of the membrane potential where the inside becomes positive and outside negative. Key properties include: being all-or-none, self-propagating, and not decreasing in amplitude with distance. It has distinct phases of depolarization, repolarization, and hyperpolarization before returning to resting potential. The mechanism involves voltage-gated sodium and potassium channels, and the sodium-potassium pump, which regulate ion movements and concentrations to generate the pulse.
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Action potential (the guyton and hall physiology)
ACTION POTENTIAL
Action potential is abrupt pulse like change in the membrane potential lasting for a fraction of second
During action potential there is reversal of membrane potential i.e. inside becomes positive and outside becomes Negative.
We can see the action potential on cathode ray oscilloscope
Abrupt or sudden in onset
2. Have limited magnitude or amplitude i.e. Inside, the potential will go to + 35 or + 45 mV and not beyond that.
3. It is of short duration. Duration is in milli seconds. Duration of spike potential Is 1 -2 milli second. Action potential with plateau has longer duration i.e. may be up to 300 m sec
4. It obeys All or None law i.e. if stimulus is sub threshold it is not produced and when the stimulus is threshold or supra threshold it will be produced with maximum amplitude.
5. It is self propagated i.e. once produced in a membrane it is automatically propagated in both directions.
6. It is not decremented with distance i.e. it will travel with same amplitude through all the distance.
7. It has refractory period. The period during which the tissue will not respond to second stimulus after the application of first stimulus. It could be Absolute and Refractory.
Absolute no response of tissue what so ever may be the strength of stimulus example closure of inactivation gate of sodium channels.
Relative response with higher stimulus than threshold stimulus
DEPOLARIZATION: Sudden loss of Negativity inside the membrane is depolarization.
REPOLARIZATION: return of negativity inside the membrane is Repolarization.
HYPERPOLARIZATION: More Negativity inside
Resting Membrane Potential
Understanding of
Channels Involved
Voltage gated Sodium Channels
Voltage gated Potassium Channels
Sodium Potassium ATPase Pump
Movements of ions
Concentrations of Sodium and Potassium in ECF and ICF
Direction of movement
Plateau is known as Sustained depolarization.
In some instances, the excited membrane does not repolarize immediately after depolarization.
Duration of depolarization of cardiac muscle is 300 milli sec.
Plateau phase has got advantages:
1. It prolongs the duration of depolarization, AP and Contraction. It prolongs the refractory period. Cardiac muscle cannot be tetanized because of this.
2. There is influx of calcium into the sarcoplasm from the ECF which is used for muscle contraction.
Action potential and Resting membrane potential, Excitability, Action potenti...
This document discusses excitability and action potentials in nerve and muscle tissues. It defines excitability as the physiological response of a tissue to a stimulus. The key types of stimuli that can excite tissues are mechanical, electrical, thermal, and chemical stimuli. An action potential occurs when the membrane potential of a nerve or muscle cell rapidly changes from its resting potential to a more positive peak, then back again. This document outlines the stages of an action potential, including depolarization, repolarization, and the afterpotential phases. It also describes how action potentials are propagated as nerve impulses through both myelinated and unmyelinated nerve fibers.
Action potential
It is over 60 years since Hodgkin and
Huxley1 made the first direct recording of
the electrical changes across the neuronal
membrane that mediate the action
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
subsequent series of elegant experiments
Hodgkin and Huxley, along with Bernard
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.
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.
Initiation or generation of a nerve impulse
The document summarizes how a nerve impulse is initiated and transmitted. At rest, sodium and potassium gates are closed, maintaining a -70mV potential. When stimulated, sodium gates open, allowing sodium to enter and depolarize the membrane to +30mV. Then potassium gates open, repolarizing the membrane back to -70mV. This rapid depolarization and repolarization generates an action potential that is transmitted along the axon to the synaptic knob. At the synapse, neurotransmitters are released into the cleft and can trigger a new action potential in the receiving neuron.
Propagation of action potential
The document discusses the structure and function of neurons. It describes how neurons transmit signals through dendrites, the cell body and axon. An action potential is generated when the membrane potential reaches threshold. This involves the opening of voltage-gated sodium and potassium channels. Action potentials propagate along axons through continuous conduction in unmyelinated axons or saltatory conduction in myelinated axons between nodes of Ranvier. Factors like myelination, axon diameter and temperature can influence conduction velocity.
Action potential by Hamidul Kowsar
An action potential is a rapid change in the electrical potential of a nerve or muscle cell membrane in response to stimulation. It allows electrical impulses to travel across the cell membrane. There are six stages of an action potential: 1) Resting stage with a large negative potential, 2) Depolarization from sodium ion influx, 3) Repolarization by potassium ion efflux, 4) A spike potential from the sharp depolarization and repolarization waves, 5) A negative after potential where the potential does not fully return to resting, and 6) Sometimes hyperpolarization where the potential becomes more negative than resting due to excess potassium permeability.
Action Potential
The document discusses action potentials and their propagation in excitable tissues. It begins by stating the objectives of understanding the mechanisms of action potential production and propagation. It then lists the main contents that will be covered, including the definition of action potential, its typical stages in large myelinated nerve fibers, the ion channels involved, propagation, and different types of action potentials. The document provides detailed explanations and diagrams of these topics. It emphasizes that action potentials are rapid changes in membrane potential that transmit signals through tissues via the coordinated opening and closing of sodium and potassium ion channels.
IB BIOLOGY 6.5.5 Explain how a nerve impulse passes along a non-myelinated ne...
In a non-myelinated neuron, an action potential is triggered when a stimulus opens voltage-gated sodium channels, causing sodium ions to diffuse into the neuron and depolarize the membrane. This depolarization then triggers adjacent areas of the neuron to open their sodium channels, creating a domino effect that propagates the action potential along the axon. After transmission, potassium channels open, allowing potassium ions to flow out and repolarize the membrane, restoring the resting potential between activations.
Recommended
Action potential (the guyton and hall physiology)
ACTION POTENTIAL
Action potential is abrupt pulse like change in the membrane potential lasting for a fraction of second
During action potential there is reversal of membrane potential i.e. inside becomes positive and outside becomes Negative.
We can see the action potential on cathode ray oscilloscope
Abrupt or sudden in onset
2. Have limited magnitude or amplitude i.e. Inside, the potential will go to + 35 or + 45 mV and not beyond that.
3. It is of short duration. Duration is in milli seconds. Duration of spike potential Is 1 -2 milli second. Action potential with plateau has longer duration i.e. may be up to 300 m sec
4. It obeys All or None law i.e. if stimulus is sub threshold it is not produced and when the stimulus is threshold or supra threshold it will be produced with maximum amplitude.
5. It is self propagated i.e. once produced in a membrane it is automatically propagated in both directions.
6. It is not decremented with distance i.e. it will travel with same amplitude through all the distance.
7. It has refractory period. The period during which the tissue will not respond to second stimulus after the application of first stimulus. It could be Absolute and Refractory.
Absolute no response of tissue what so ever may be the strength of stimulus example closure of inactivation gate of sodium channels.
Relative response with higher stimulus than threshold stimulus
DEPOLARIZATION: Sudden loss of Negativity inside the membrane is depolarization.
REPOLARIZATION: return of negativity inside the membrane is Repolarization.
HYPERPOLARIZATION: More Negativity inside
Resting Membrane Potential
Understanding of
Channels Involved
Voltage gated Sodium Channels
Voltage gated Potassium Channels
Sodium Potassium ATPase Pump
Movements of ions
Concentrations of Sodium and Potassium in ECF and ICF
Direction of movement
Plateau is known as Sustained depolarization.
In some instances, the excited membrane does not repolarize immediately after depolarization.
Duration of depolarization of cardiac muscle is 300 milli sec.
Plateau phase has got advantages:
1. It prolongs the duration of depolarization, AP and Contraction. It prolongs the refractory period. Cardiac muscle cannot be tetanized because of this.
2. There is influx of calcium into the sarcoplasm from the ECF which is used for muscle contraction.
Action potential and Resting membrane potential, Excitability, Action potenti...
This document discusses excitability and action potentials in nerve and muscle tissues. It defines excitability as the physiological response of a tissue to a stimulus. The key types of stimuli that can excite tissues are mechanical, electrical, thermal, and chemical stimuli. An action potential occurs when the membrane potential of a nerve or muscle cell rapidly changes from its resting potential to a more positive peak, then back again. This document outlines the stages of an action potential, including depolarization, repolarization, and the afterpotential phases. It also describes how action potentials are propagated as nerve impulses through both myelinated and unmyelinated nerve fibers.
Action potential
It is over 60 years since Hodgkin and
Huxley1 made the first direct recording of
the electrical changes across the neuronal
membrane that mediate the action
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
subsequent series of elegant experiments
Hodgkin and Huxley, along with Bernard
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.
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.
Initiation or generation of a nerve impulse
The document summarizes how a nerve impulse is initiated and transmitted. At rest, sodium and potassium gates are closed, maintaining a -70mV potential. When stimulated, sodium gates open, allowing sodium to enter and depolarize the membrane to +30mV. Then potassium gates open, repolarizing the membrane back to -70mV. This rapid depolarization and repolarization generates an action potential that is transmitted along the axon to the synaptic knob. At the synapse, neurotransmitters are released into the cleft and can trigger a new action potential in the receiving neuron.
Propagation of action potential
The document discusses the structure and function of neurons. It describes how neurons transmit signals through dendrites, the cell body and axon. An action potential is generated when the membrane potential reaches threshold. This involves the opening of voltage-gated sodium and potassium channels. Action potentials propagate along axons through continuous conduction in unmyelinated axons or saltatory conduction in myelinated axons between nodes of Ranvier. Factors like myelination, axon diameter and temperature can influence conduction velocity.
Action potential by Hamidul Kowsar
An action potential is a rapid change in the electrical potential of a nerve or muscle cell membrane in response to stimulation. It allows electrical impulses to travel across the cell membrane. There are six stages of an action potential: 1) Resting stage with a large negative potential, 2) Depolarization from sodium ion influx, 3) Repolarization by potassium ion efflux, 4) A spike potential from the sharp depolarization and repolarization waves, 5) A negative after potential where the potential does not fully return to resting, and 6) Sometimes hyperpolarization where the potential becomes more negative than resting due to excess potassium permeability.
Action Potential
The document discusses action potentials and their propagation in excitable tissues. It begins by stating the objectives of understanding the mechanisms of action potential production and propagation. It then lists the main contents that will be covered, including the definition of action potential, its typical stages in large myelinated nerve fibers, the ion channels involved, propagation, and different types of action potentials. The document provides detailed explanations and diagrams of these topics. It emphasizes that action potentials are rapid changes in membrane potential that transmit signals through tissues via the coordinated opening and closing of sodium and potassium ion channels.
IB BIOLOGY 6.5.5 Explain how a nerve impulse passes along a non-myelinated ne...
In a non-myelinated neuron, an action potential is triggered when a stimulus opens voltage-gated sodium channels, causing sodium ions to diffuse into the neuron and depolarize the membrane. This depolarization then triggers adjacent areas of the neuron to open their sodium channels, creating a domino effect that propagates the action potential along the axon. After transmission, potassium channels open, allowing potassium ions to flow out and repolarize the membrane, restoring the resting potential between activations.
Action potential
It is over 60 years since Hodgkin and
Huxley1 made the first direct recording of
the electrical changes across the neuronal
membrane that mediate the action
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
subsequent series of elegant experiments
Hodgkin and Huxley, along with Bernard
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.
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.
The Nerve Impulse Part 2
An action potential is generated when an impulse reaches a point on an axon. This causes local currents that excite the next part of the axon, allowing the action potential to progress along the length of the axon. The passage of an action potential is followed by a refractory period where the axon membrane is unable to generate another action potential to allow impulses to travel in one direction. Myelination of axons speeds up impulse transmission by allowing action potentials to "jump" between nodes of Ranvier.
The nerve impulse
The document summarizes how nerve impulses are conducted along neurons. It explains that neurons maintain a resting potential through sodium-potassium pumps that pump sodium ions out and potassium ions in. When a neuron is stimulated, sodium channels open, allowing sodium to rush in and depolarize the neuron. This triggers an action potential. The neuron then repolarizes as sodium channels close and potassium channels open, restoring the resting potential. The action potential then propagates along the neuron as each segment is depolarized by the previous one, allowing nerve impulses to be transmitted rapidly.
Nerve impulse conduction
Nerve impulse conduction involves the generation and propagation of action potentials along neurons. At rest, neurons maintain a negative resting potential due to an unequal distribution of ions across the cell membrane. When stimulated, the opening of voltage-gated sodium channels causes rapid depolarization and the generation of an action potential. This potential then propagates along the axon as adjacent regions are depolarized, triggering their own action potentials. At synapses, the action potential is converted to a chemical signal via neurotransmitter release, which can then trigger a new action potential in the post-synaptic cell. Myelination and large axon diameters increase conduction velocity.
section 4, chapter 10: action potentials
This document summarizes key concepts about graded and action potentials from chapter 10, section 4 of an anatomy textbook. It describes how graded potentials are localized changes in membrane potential that summate to reach threshold and trigger an action potential. An action potential has 3 phases: depolarization due to sodium influx, repolarization due to potassium efflux, and hyperpolarization. It propagates along the axon via adjacent regions reaching threshold. The all-or-none property and refractory period are also summarized. Diagrams illustrate these concepts.
Action potential
The document discusses membrane potential and action potentials in neurons. It provides details on:
- The resting membrane potential is established by ion gradients maintained by the sodium-potassium pump. There is a net negative charge inside and positive outside the membrane.
- An action potential is initiated when the membrane reaches its threshold potential due to sodium influx. It involves stages of depolarization, repolarization and refractory periods.
- The all-or-none principle states that an action potential will only be generated if the threshold is reached. Speed and propagation depends on myelination.
- Different cell types like cardiac and smooth muscles exhibit variations in their action potential waveforms.
Action potential
this presentation explains what is action potential, how it is initiated.
it deals with short notes and brief description on the various processes that undergoes in the action potential
this presentation will help you out to summarize and conclude important points.
Nerve Impulse
1) Nerve impulses propagate along axons via the movement of sodium and potassium ions across the axon membrane.
2) At rest, the axon maintains a negative charge due to higher concentrations of potassium and organic ions inside the axon and higher concentrations of sodium and chloride ions outside.
3) When an impulse is generated, the permeability of the axon membrane to sodium briefly increases, allowing sodium to flow inside and depolarize the membrane. This creates an electrical signal called an action potential.
Nerve impulses
This document discusses the transmission of nerve impulses along axons. It begins by explaining that nerve impulses are transmitted as electrical signals along the axon membrane. During resting state, the inside of the axon membrane is negatively charged compared to the outside due to differences in sodium and potassium ion concentrations maintained by the sodium-potassium pump. When an axon is stimulated, sodium channels open allowing sodium ions to rush in, depolarizing the membrane and generating an action potential. Then, potassium channels open and potassium ions diffuse out, beginning to repolarize the membrane back to the resting potential. The sodium-potassium pump then restores ion concentrations to complete repolarization.
Action potential By Dr. Mrs. Padmaja R Desai
To study the Concept of Action Potential and describe the stages of action potential.
Ionic basis of Action Potential & its Propogation.
Properties of Action Potential.
Types action Potential
Action potential
This document provides an overview of the nervous system, including classifications of neurons, their properties, and how nerve impulses are transmitted. Neurons are classified as myelinated or unmyelinated. Their key properties include excitability, conduction, transmission, integration and plasticity. The resting membrane potential is established by ion gradients maintaining different electrical charges on either side of the neuronal membrane. An action potential is initiated by the movement of ions across the membrane when it is stimulated. Neurotransmitters are released at synapses to transmit signals between neurons and elicit excitatory or inhibitory postsynaptic potentials.
Propagation of nerve impulses
This document summarizes the key aspects of nerve impulse propagation. It begins by describing the structure of a typical neuron, including the cell body, dendrites, axon, and axon endings. It then discusses the resting potential of neurons and how ion concentration gradients across the neuronal membrane contribute to a negative resting potential. Next, it explains how an action potential is generated when the membrane potential reaches threshold, driven by the opening of voltage-gated sodium and potassium channels. It describes how action potentials propagate along axons via adjacent regions reaching threshold. Finally, it summarizes how action potentials are converted to chemical signals at synapses and how neurotransmitters trigger new action potentials in receiving neurons.
Graded potential
There are four main types of gated ion channels that open or close in response to different stimuli: voltage-gated, chemically-gated, mechanically-gated, and thermally-gated channels. Graded potentials are local changes in membrane potential that vary in strength and duration depending on the stimulus. They can be excitatory or inhibitory and occur through temporal or spatial summation of incremental stimuli at the dendrite or soma. Graded potentials spread passively within the cell and may cause a secondary action potential if they reach the axon hillock threshold.
Nerve impulses
1. Nerve cells transmit signals via changes in their membrane potential. At rest, the inside of the cell membrane is negatively charged due to high potassium and low sodium concentrations inside the cell.
2. When stimulated, the membrane becomes permeable to sodium, causing sodium to rush inside and depolarize the membrane.
3. The rapid sodium influx reverses the membrane potential briefly before sodium channels close and potassium channels open, allowing potassium to leave and repolarize the membrane.
Action potential
An action potential occurs when a neuron fires, sending an electrical signal down its axon. It is triggered when the membrane potential reaches a threshold of around -55 mV due to sodium ions rushing into the cell. This depolarizes the neuron to 0 mV. Then, potassium ions exit the cell, repolarizing it back below the resting potential of -70 mV. The influx and efflux of ions is due to the specific opening and closing of sodium and potassium channels. This process results in a consistent action potential amplitude regardless of the strength of the stimulus, following the all-or-none principle.
Nerve Impulse
An action potential occurs when a neuron reaches its membrane threshold. This causes sodium channels to open, allowing sodium ions to enter the neuron and depolarize the membrane. Then, potassium channels open, allowing potassium ions to exit the neuron and repolarize the membrane back to its resting potential. This process of depolarization and repolarization propagates as a self-sustaining wave along the neuron, conducting the nerve impulse. Myelinated neurons enhance conduction velocity through salutatory conduction, where the action potential jumps between nodes of Ranvier.
Action potential
An action potential is a rapid change in the electrical potential of a neuron's membrane. When a stimulus reaches the threshold level, voltage-gated sodium channels open, allowing sodium ions to rush into the neuron. This reversal of the membrane potential propagates along the axon as it triggers adjacent sodium channels. Once the peak is reached, voltage-gated potassium channels open to return the membrane potential to its resting state. The sodium-potassium pump then restores the ion concentrations, and the neuron enters a refractory period where it cannot fire again. Myelin sheaths allow the action potential to propagate rapidly along the axon.
Rmp
1. The document discusses the electrical changes that occur in muscles during contraction, known as the resting membrane potential and action potential.
2. The resting membrane potential is the voltage difference across the cell membrane at rest, around -70mV for nerves and -80mV to -90mV for muscles. It results from ion gradients established by the sodium-potassium pump and diffusion of sodium and potassium ions.
3. When a muscle is stimulated, an action potential occurs through depolarization and repolarization phases, resulting in a rapid change in membrane potential. The action potential propagates the signal along the membrane.
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.
Lecture 5 (membrane potential and action potential)
This document discusses membrane potentials and action potentials in excitable cells like neurons and muscles. It covers:
1. The resting membrane potential of -70mV that is maintained by selective permeability of potassium ions and active transport by the sodium-potassium pump.
2. How an action potential is generated when the membrane reaches its threshold voltage due to an influx of sodium ions, causing rapid depolarization. It then repolarizes as potassium ions efflux.
3. The propagation of action potentials along neurons or muscle fibers to transmit electrical signals and cause effects like muscle contraction or neurotransmitter release.
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.
Action Potential.ppt
The document defines key terms related to action potentials and summarizes their properties. It describes:
1) Phases of an action potential - depolarization, repolarization, and hyperpolarization.
2) Ionic basis - sodium influx causes depolarization, potassium efflux causes repolarization, and leakage of excess potassium causes hyperpolarization.
3) Propagation through myelinated and unmyelinated nerve fibers. In myelinated fibers, saltatory conduction jumps from node to node, while unmyelinated fibers conduct point-to-point.
4) Properties including the all-or-none law, refractory periods which prevent summation, and factors that determine excitation thresholds like the strength-duration curve
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Action potential
It is over 60 years since Hodgkin and
Huxley1 made the first direct recording of
the electrical changes across the neuronal
membrane that mediate the action
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
subsequent series of elegant experiments
Hodgkin and Huxley, along with Bernard
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.
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.
The Nerve Impulse Part 2
An action potential is generated when an impulse reaches a point on an axon. This causes local currents that excite the next part of the axon, allowing the action potential to progress along the length of the axon. The passage of an action potential is followed by a refractory period where the axon membrane is unable to generate another action potential to allow impulses to travel in one direction. Myelination of axons speeds up impulse transmission by allowing action potentials to "jump" between nodes of Ranvier.
The nerve impulse
The document summarizes how nerve impulses are conducted along neurons. It explains that neurons maintain a resting potential through sodium-potassium pumps that pump sodium ions out and potassium ions in. When a neuron is stimulated, sodium channels open, allowing sodium to rush in and depolarize the neuron. This triggers an action potential. The neuron then repolarizes as sodium channels close and potassium channels open, restoring the resting potential. The action potential then propagates along the neuron as each segment is depolarized by the previous one, allowing nerve impulses to be transmitted rapidly.
Nerve impulse conduction
Nerve impulse conduction involves the generation and propagation of action potentials along neurons. At rest, neurons maintain a negative resting potential due to an unequal distribution of ions across the cell membrane. When stimulated, the opening of voltage-gated sodium channels causes rapid depolarization and the generation of an action potential. This potential then propagates along the axon as adjacent regions are depolarized, triggering their own action potentials. At synapses, the action potential is converted to a chemical signal via neurotransmitter release, which can then trigger a new action potential in the post-synaptic cell. Myelination and large axon diameters increase conduction velocity.
section 4, chapter 10: action potentials
This document summarizes key concepts about graded and action potentials from chapter 10, section 4 of an anatomy textbook. It describes how graded potentials are localized changes in membrane potential that summate to reach threshold and trigger an action potential. An action potential has 3 phases: depolarization due to sodium influx, repolarization due to potassium efflux, and hyperpolarization. It propagates along the axon via adjacent regions reaching threshold. The all-or-none property and refractory period are also summarized. Diagrams illustrate these concepts.
Action potential
The document discusses membrane potential and action potentials in neurons. It provides details on:
- The resting membrane potential is established by ion gradients maintained by the sodium-potassium pump. There is a net negative charge inside and positive outside the membrane.
- An action potential is initiated when the membrane reaches its threshold potential due to sodium influx. It involves stages of depolarization, repolarization and refractory periods.
- The all-or-none principle states that an action potential will only be generated if the threshold is reached. Speed and propagation depends on myelination.
- Different cell types like cardiac and smooth muscles exhibit variations in their action potential waveforms.
Action potential
this presentation explains what is action potential, how it is initiated.
it deals with short notes and brief description on the various processes that undergoes in the action potential
this presentation will help you out to summarize and conclude important points.
Nerve Impulse
1) Nerve impulses propagate along axons via the movement of sodium and potassium ions across the axon membrane.
2) At rest, the axon maintains a negative charge due to higher concentrations of potassium and organic ions inside the axon and higher concentrations of sodium and chloride ions outside.
3) When an impulse is generated, the permeability of the axon membrane to sodium briefly increases, allowing sodium to flow inside and depolarize the membrane. This creates an electrical signal called an action potential.
Nerve impulses
This document discusses the transmission of nerve impulses along axons. It begins by explaining that nerve impulses are transmitted as electrical signals along the axon membrane. During resting state, the inside of the axon membrane is negatively charged compared to the outside due to differences in sodium and potassium ion concentrations maintained by the sodium-potassium pump. When an axon is stimulated, sodium channels open allowing sodium ions to rush in, depolarizing the membrane and generating an action potential. Then, potassium channels open and potassium ions diffuse out, beginning to repolarize the membrane back to the resting potential. The sodium-potassium pump then restores ion concentrations to complete repolarization.
Action potential By Dr. Mrs. Padmaja R Desai
To study the Concept of Action Potential and describe the stages of action potential.
Ionic basis of Action Potential & its Propogation.
Properties of Action Potential.
Types action Potential
Action potential
This document provides an overview of the nervous system, including classifications of neurons, their properties, and how nerve impulses are transmitted. Neurons are classified as myelinated or unmyelinated. Their key properties include excitability, conduction, transmission, integration and plasticity. The resting membrane potential is established by ion gradients maintaining different electrical charges on either side of the neuronal membrane. An action potential is initiated by the movement of ions across the membrane when it is stimulated. Neurotransmitters are released at synapses to transmit signals between neurons and elicit excitatory or inhibitory postsynaptic potentials.
Propagation of nerve impulses
This document summarizes the key aspects of nerve impulse propagation. It begins by describing the structure of a typical neuron, including the cell body, dendrites, axon, and axon endings. It then discusses the resting potential of neurons and how ion concentration gradients across the neuronal membrane contribute to a negative resting potential. Next, it explains how an action potential is generated when the membrane potential reaches threshold, driven by the opening of voltage-gated sodium and potassium channels. It describes how action potentials propagate along axons via adjacent regions reaching threshold. Finally, it summarizes how action potentials are converted to chemical signals at synapses and how neurotransmitters trigger new action potentials in receiving neurons.
Graded potential
There are four main types of gated ion channels that open or close in response to different stimuli: voltage-gated, chemically-gated, mechanically-gated, and thermally-gated channels. Graded potentials are local changes in membrane potential that vary in strength and duration depending on the stimulus. They can be excitatory or inhibitory and occur through temporal or spatial summation of incremental stimuli at the dendrite or soma. Graded potentials spread passively within the cell and may cause a secondary action potential if they reach the axon hillock threshold.
Nerve impulses
1. Nerve cells transmit signals via changes in their membrane potential. At rest, the inside of the cell membrane is negatively charged due to high potassium and low sodium concentrations inside the cell.
2. When stimulated, the membrane becomes permeable to sodium, causing sodium to rush inside and depolarize the membrane.
3. The rapid sodium influx reverses the membrane potential briefly before sodium channels close and potassium channels open, allowing potassium to leave and repolarize the membrane.
Action potential
An action potential occurs when a neuron fires, sending an electrical signal down its axon. It is triggered when the membrane potential reaches a threshold of around -55 mV due to sodium ions rushing into the cell. This depolarizes the neuron to 0 mV. Then, potassium ions exit the cell, repolarizing it back below the resting potential of -70 mV. The influx and efflux of ions is due to the specific opening and closing of sodium and potassium channels. This process results in a consistent action potential amplitude regardless of the strength of the stimulus, following the all-or-none principle.
Nerve Impulse
An action potential occurs when a neuron reaches its membrane threshold. This causes sodium channels to open, allowing sodium ions to enter the neuron and depolarize the membrane. Then, potassium channels open, allowing potassium ions to exit the neuron and repolarize the membrane back to its resting potential. This process of depolarization and repolarization propagates as a self-sustaining wave along the neuron, conducting the nerve impulse. Myelinated neurons enhance conduction velocity through salutatory conduction, where the action potential jumps between nodes of Ranvier.
Action potential
An action potential is a rapid change in the electrical potential of a neuron's membrane. When a stimulus reaches the threshold level, voltage-gated sodium channels open, allowing sodium ions to rush into the neuron. This reversal of the membrane potential propagates along the axon as it triggers adjacent sodium channels. Once the peak is reached, voltage-gated potassium channels open to return the membrane potential to its resting state. The sodium-potassium pump then restores the ion concentrations, and the neuron enters a refractory period where it cannot fire again. Myelin sheaths allow the action potential to propagate rapidly along the axon.
Rmp
1. The document discusses the electrical changes that occur in muscles during contraction, known as the resting membrane potential and action potential.
2. The resting membrane potential is the voltage difference across the cell membrane at rest, around -70mV for nerves and -80mV to -90mV for muscles. It results from ion gradients established by the sodium-potassium pump and diffusion of sodium and potassium ions.
3. When a muscle is stimulated, an action potential occurs through depolarization and repolarization phases, resulting in a rapid change in membrane potential. The action potential propagates the signal along the membrane.
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.
Lecture 5 (membrane potential and action potential)
This document discusses membrane potentials and action potentials in excitable cells like neurons and muscles. It covers:
1. The resting membrane potential of -70mV that is maintained by selective permeability of potassium ions and active transport by the sodium-potassium pump.
2. How an action potential is generated when the membrane reaches its threshold voltage due to an influx of sodium ions, causing rapid depolarization. It then repolarizes as potassium ions efflux.
3. The propagation of action potentials along neurons or muscle fibers to transmit electrical signals and cause effects like muscle contraction or neurotransmitter release.
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Lecture 5 (membrane potential and action potential)
Lecture 5 (membrane potential and action potential)
Similar to Action Potential
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.
Action Potential.ppt
The document defines key terms related to action potentials and summarizes their properties. It describes:
1) Phases of an action potential - depolarization, repolarization, and hyperpolarization.
2) Ionic basis - sodium influx causes depolarization, potassium efflux causes repolarization, and leakage of excess potassium causes hyperpolarization.
3) Propagation through myelinated and unmyelinated nerve fibers. In myelinated fibers, saltatory conduction jumps from node to node, while unmyelinated fibers conduct point-to-point.
4) Properties including the all-or-none law, refractory periods which prevent summation, and factors that determine excitation thresholds like the strength-duration curve
PPt action potential.pptx
- An action potential is a brief change in the membrane potential of an excitable cell, such as a neuron, that occurs when the membrane potential rapidly rises and falls.
- The phases of an action potential include the resting stage, depolarization, repolarization, and hyperpolarization. Depolarization is caused by an influx of sodium ions, repolarization by an efflux of potassium ions.
- For an action potential to occur, the membrane potential must reach the threshold potential, around -55 mV. Once initiated, the action potential propagates along the cell membrane via voltage-gated ion channels.
Excitable t is issues.pptx
- Nerve and muscle cells are excitable tissues that respond to stimuli through generation of electrical impulses.
- Nerve cells called neurons transmit signals through electrical impulses called action potentials. Action potentials are generated when the membrane potential rapidly changes from resting potential to threshold potential.
- At chemical synapses, an action potential causes release of neurotransmitters which may excite or inhibit the next neuron. Summation of multiple synaptic signals can trigger action potentials in post-synaptic neurons.
Nerve Potentials
This explains in detail about the different nerve potentials like Resting Membrane Potential and Action Potential.
https://www.youtube.com/channel/UC1QhJfPiWnmk2WpKVH1fzrQ
Subscribe and share for more topics of Neurophysiology.
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provides a basic picture of excitable cells and the relative concentration of key electrolytes inside versus outside the cell.
Cell membrane potential.pdf
The document discusses cell membrane potential and action potentials. It explains that cell membranes maintain a voltage gradient called the membrane potential due to different ion concentrations inside and outside the cell. Ion channels, including passive, chemically-gated, and voltage-gated channels, control the flow of ions across the membrane and influence the membrane potential. An action potential occurs when the membrane potential rapidly changes from its normal resting potential of -70mV to +30mV before repolarizing back. This wave of depolarization propagates along the membrane via opening and closing of sodium and potassium ion channels.
Neuronal conduction.pptx
Neural signals are transmitted through both electrical and chemical means. An electrical signal travels down a neuron's dendrites to its cell body. If the signal reaches the axon hillock's threshold, the axon is activated and fires, transmitting an electrical signal down the axon. At the axon terminals, neurotransmitters are released across the synaptic cleft to the next cell. The membrane potential, maintained by ion concentration gradients and sodium-potassium pumps, underlies the neuron's resting potential. When neurotransmitters bind to receptors on the post-synaptic cell, they generate graded excitatory or inhibitory post-synaptic potentials that are integrated and can trigger an all-or-none action potential for signal transmission along the ax
TOPIC 6 : HUMAN HEALTH AND PHYSIOLOGY
The document discusses the resting potential, graded potential, and action potential in neurons. It provides details on:
1) The resting potential of neurons is normally between -60 to -80 mV due to concentrations of potassium and sodium ions inside and outside the cell. The sodium-potassium pump helps maintain this gradient.
2) A graded potential is an intermediate voltage change before an action potential. It involves the opening of voltage-gated potassium and sodium ion channels, making the intracellular voltage more negative or less negative.
3) An action potential is a brief, all-or-nothing increase in voltage caused by the rapid influx of sodium ions through opened voltage-gated channels, followed by the efflux
Action potential
1. An action potential occurs when there is a rapid change in the membrane potential of a neuron from a negative resting potential to a positive potential and then back to a negative potential. This is driven by the movement of ions across the cell membrane through voltage-gated ion channels.
2. For an action potential to be initiated, the membrane potential must be depolarized beyond the threshold potential of around -65mV. This opens voltage-gated sodium channels, allowing sodium ions to enter the cell.
3. The influx of sodium ions causes further depolarization, followed by the opening of voltage-gated potassium channels which causes repolarization back to the resting potential and then hyperpolarization below the resting potential.
Action Potential.ppt
1. When an axon is depolarized past its threshold, voltage-gated sodium channels open, allowing sodium ions to enter and further depolarize the membrane in a positive feedback loop.
2. As the membrane depolarizes further, voltage-gated potassium channels open, allowing potassium ions to exit and repolarize the membrane.
3. After an action potential occurs, sodium-potassium pumps actively transport ions to restore the resting membrane potential, before the axon can initiate another action potential.
NERVE PHYSIOLOGY
DESCRIBES THE ACTION POTENTIAL OCCURING IN THE NERVE. IT ALSO TACKLES ON THE NUERON AND ITS 3 BASIC PARTS NAMELY 1)DENDRITES 2) BODY 3) AXON
A and P Polarization
The action potential is an electrochemical signal carried by neurons. It is initiated by a stimulus that opens sodium channels, allowing sodium ions to enter the neuron and depolarize it. Repolarization occurs as potassium channels open and sodium-potassium pumps restore ion concentrations. The action potential then propagates down the axon through continued depolarization of adjacent areas. At synapses, neurotransmitters trigger action potentials in the next neuron. Different arrangements of neurons allow signals to converge, diverge, or oscillate in circuits.
Nerve physiology
This presentation contains the basic information about nerve cells and action potential. This work is done for academic purpose only so if you are using give proper reference.
Biology- Control and Coordination.pdf
This document discusses the nervous system and how it coordinates the activities of sensory receptors, decision making in the central nervous system, and effectors like muscles and glands. It describes the three types of neurons - sensory, intermediate, and motor neurons. It explains how motor neurons transmit impulses from the CNS to effectors and discusses their structure. The document also covers myelin sheaths, nodes of Ranvier, reflex arcs, impulse transmission through action potentials, and synaptic transmission between neurons.
Nerve and muscle physiology
This document discusses nerve and muscle physiology, including:
1. It describes the different types of ion channels in the plasma membrane, including leak channels, chemically-gated channels, mechanically-gated channels, and voltage-gated channels.
2. It explains the concepts of resting membrane potential, graded potentials, and action potentials in excitable cells like nerves and muscles. Key factors that determine resting membrane potential are the concentration gradients and permeability of ions like sodium and potassium.
3. It provides details on the initiation and propagation of action potentials, which involve the opening and closing of voltage-gated sodium and potassium channels in response to changes in membrane potential.
Resting membrane potential and action potential
The document discusses the resting membrane potential and action potential in neurons. It explains that:
1) The resting membrane potential is around -70mV, created by different ion concentrations inside and outside the neuron.
2) Graded potentials are local, short-lived changes in membrane potential caused by ion channels opening briefly in response to stimuli.
3) Action potentials are brief, large changes in potential from -70mV to +30mV caused by voltage-gated sodium and potassium channels. The influx of sodium ions depolarizes the membrane before potassium channels repolarize it.
4) Action potentials propagate along the axon as one area repolarizes and depolarizes the next, allowing nerve
RMP .pptx
Electrical changes occur both during resting and active conditions of muscles. The resting membrane potential (RMP) is the electrical potential difference across the cell membrane under resting conditions, ranging from -70mV in neurons to -12mV in erythrocytes. The RMP is maintained by the sodium-potassium pump and selective permeability of the cell membrane. The action membrane potential is a series of electrical changes that occurs when a muscle or nerve is stimulated, consisting of depolarization, where the inside becomes positive, and repolarization, where the muscle returns to its resting potential.
Electrodiagnosis.pptx
This document summarizes the generation and propagation of action potentials in neurons. It discusses:
- The resting membrane potential is maintained by selective permeability to potassium ions.
- Action potentials are initiated by the opening of voltage-gated sodium channels, causing rapid depolarization. If the threshold is reached, an action potential fires.
- After firing, potassium channels open to repolarize the membrane back to the resting potential. Some axons are myelinated to promote faster signal conduction via saltatory propagation between nodes of Ranvier.
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Action Potential
- 2. • Action potential is abrupt pulse like change in the membrane potential lasting for a fraction of second • During action potential there is reversal of membrane potential i.e. inside becomes positive and outside becomes Negative. • We can see the action potential on cathode ray oscilloscope
- 3. Properties of Action Potential • Abrupt or sudden in onset • Have limited magnitude or amplitude i.e. Inside, the potential will go to + 35 or + 45 mV and not beyond that. • It is of short duration. Duration is in milli seconds. Duration of spike potential Is 1 -2 milli second. Action potential with plateau has longer duration i.e. may be upto 300 msec
- 4. Properties of Action Potential • It obeys All or None law i.e. if stimulus is sub threshold it is not produced and when the stimulus is threshold or supra threshold it will be produced with maximum amplitude. • It is self propagated i.e. once produced in a membrane it is automatically propagated in both directions. Inside the body because of presence of synapses it is transmitted in one direction i.e. from pre synaptic to post synaptic. • It is not decremented with distance i.e. it will travel with same amplitude through all the distance.
- 5. Properties of Action Potential • It has refractory period. The period during which the tissue will not respond to second stimulus after the application of first stimulus. It could be Absolute and Refractory. ▫ Absolute no response of tissue what so ever may be the strength of stimulus ▫ Relative response with higher stimulus than threshold stimulus
- 6. Phases of Action Potential • DEPOLARIZATION: Sudden loss of Negativity inside the membrane is depolarization. • REPOLARIZATION: return of negativity inside the membrane is Repolarization. ▫ After Depolarization • HYPERPOLARIZATION: More Negativity inside • RESTING MEMBRANE POTENTIAL
- 9. Mechanism of Action Potential • Understanding of ▫ Channels Involved Voltage gated Sodium Channels Voltage gated Potassium Channels Sodium Potassium ATPase Pump ▫ Movements of ions Concentrations of Sodium and Potassium in ECF and ICF Direction of movement
- 10. Voltage Gated Sodium Channels • Two gates: outer side activation gate, inner side inactivation gate • In resting state activation gate is closed and inactivation gate is open
- 11. Voltage Gated Potassium Channels • Voltage Gated Potassium Channel: Have one gate on inner side • Remains closed at rest
- 12. Sodium Potassium ATPase Pump
- 16. Roles of Other Ions During the Action Potential • Impermeant Negatively Charged Ions (Anions) Inside the Nerve Axon. • Calcium Ions