Examples of action potential in the following topics:
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- Voltage pulses along a cell membrane, called action potentials, allow us to sense the world, control parts of our body, and think.
- This sequence of events results in a voltage pulse, called the action potential and is shown in .
- The action potential is a voltage pulse at one location on a cell membrane.
- Voltage channels are critical in the generation of an action potential
- Top: view of an idealized action potential shows its various phases as the action potential passes a point on a cell membrane.
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- Although all of the heart's cells have the ability to generate the electrical impulses (or action potentials) that trigger cardiac contraction, the sinoatrial node normally initiates it, simply because it generates impulses slightly faster than the other areas with pacemaker potential .
- Cells in the SA node, located in the upper right corner of the heart, will typically discharge (create action potentials) at about 60-100 beats/minute.
- The reason Purkinje cells do not normally control the heart rate is that they generate action potentials at a lower frequency than the AV or SA nodes.
- These fibers consist of specialized cardiomyocytes that are able to conduct cardiac action potentials more quickly and efficiently than any other cells in the heart.
- In short, they generate action potentials, but at a slower rate than sinoatrial node and other atrial ectopic pacemakers.
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- Electric potential and field are related in that potential is a property of the field that describes the field's action.
- The relationship between electric potential and field is similar to that between gravitational potential and field in that the potential is a property of the field describing the action of the field upon an object (see ).
- The electric potential at a point is the quotient of the potential energy of any charged particle at that location divided by the charge of that particle.
- Thus, the electric potential is a measure of energy per unit charge.
- In terms of units, electric potential and charge are closely related.
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- The action of stretching the spring or lifting the mass of an object is performed by an external force that works against the force field of the potential.
- This work is stored in the force field as potential energy.
- More specifically, every conservative force gives rise to potential energy.
- For example, the work of an elastic force is called elastic potential energy ; work done by the gravitational force is called gravitational potential energy; and work done by the Coulomb force is called electric potential energy.
- In the case of a bow and arrow, the energy is converted from the potential energy in the archer's arm to the potential energy in the bent limbs of the bow when the string is drawn back.
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- Work is the energy associated with the action of a force.
- Thus a force does work when there is movement under the action of the force.
- The work of forces generated by a potential function is known as potential energy and the forces are said to be conservative.
- Therefore work on an object moving in a conservative force field is equal to minus the change of potential energy of the object:
- Work is the energy associated with the action of a force.
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- Electric potentials are commonly found in the body, across cell membranes and in the firing of neurons.
- Electric potentials are not limited in function to inorganic processes.
- Thus, a potential, called the resting potential, is created on either side of the membrane.
- Potentials can change as ions move across the cell membrane.
- When the brain decides on an action, it sends an impulse that cascades to the extremity where a muscle contracts.
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- If a force results in only deformation, with no thermal, sound, or kinetic energy, the work done is stored as elastic potential energy.
- A mouse trap stores elastic potential energy by twisting a piece of metal; this energy is released when the mouse steps into it.
- Elastic energy is the potential mechanical energy stored in the configuration of a material or physical system when work is performed to distort its volume or shape.
- For example, the potential energy PEel stored in a spring is
- The applied force is exactly opposite to the restoring force (action-reaction), and so $F_{app}=kx$.
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- Equipotential lines depict one-dimensional regions in which the electric potential created by one or more nearby charges is constant.
- Equipotential lines depict one-dimensional regions in which the electric potential created by one or more nearby charges has a constant value.
- For a single, isolated point charge, the formula for potential (V) is functionally dependent upon charge (Q) and inversely dependent upon radial distance from the charge (r):
- The radial dependence means that at any point a certain distance from the point charge, potential will be the same.
- This is because the continuity of charges results in a continuity of action upon any point a certain distance from either plate.
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- The potential energy due to elevated positions is called gravitational potential energy, evidenced, for example, by water held in an elevated reservoir or behind a dam (as an example, shows Hoover Dam).
- (The surface will be the zero point of the potential energy. ) We can express the potential energy (gravitational potential energy) as:
- For this choice, the potential at infinity is defined as 0.
- Hoover dam uses the stored gravitational potential energy to generate electricity.
- Generate an equation that can be used to express the gravitational potential energy near the earth
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- A potential energy curve plots potential energy as a function of position; equipotential lines trace lines of equal potential energy.
- A potential energy curve plots the potential energy of an object as a function of that object's position.
- The utility of a potential energy curve is that we can quickly determine the potential energy of the object in question at a given position.
- Equipotential lines trace lines of equal potential energy.
- Work (W) is a measure of the change in potential energy (ΔPE): W = -ΔPE.