Membrane Potential & Action Potential ppt/pdf Flashcards
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RESTING MEMBRANE POTENTIAL
Net result intracellular Na+ is maintained in?
CONSTANT AT A LOW LEVEL
Na+ and K+ enters the cell by?
PASSIVE TRANSPORT
Net result intracellular K+ is maintained in constant at a?
HIGH LEVEL
Can cross the membranes of every living cell and each contribute to the RPM
Potassium, sodium and chloride
Cell membrane of most living cells are much more permeable to __ than to any other ions
potassium ions
It Describes the 💡Relation of Diffusion Potential to the Ion Concentration Difference Across a Membrane
NERNST EQUATION
The 💡diffusion potential level across a membrane that exactly opposes the net diffusion of a particular ion through the membrane is called?
Nernst potential
The most important 💡ions involved in the 💡development of membrane potentials in nerve and muscle fibers, as well as in the neuronal cells in the nervous system
SODIUM
POTASSIUM
CHLORIDE
The quantitative importance of each of the ions in determining the voltage is ___ to the membrane permeability for that particular ion.
Proportional
A (1)__ concentration gradient from inside the membrane to the outside causes (2)__ inside the membrane
(1) POSITIVE ION
(2) ELECTRONEGATIVITY
The permeability of the (1)__ channels undergoes rapid changes during transmission of a nerve impulse, whereas the permeability of the (2)__ channels does not change greatly during this process
(1) SODIUM & POTASSIUM
(2) CHLORIDE
The resting membrane potential of large nerve fibers when they are 💡not transmitting nerve signals is about __.
-90 millivolts
If 💡potassium ions were the only factor causing the resting potential, the resting potential inside the fiber would be equal to
−94 millivolts
Three conditions in the establishment of resting membrane potentials in nerve fibers:
💡💡
K
Na K
Na K Pump
- When the membrane potential is caused entirely by potassium diffusion alone
- When the membrane potential is caused by diffusion of both sodium and potassium ions
- When the membrane potential is caused by diffusion of both sodium and potassium ions plus pumping of both these ions by the Na+-K+ pump.
The diffusion potentials alone caused by potassium and sodium diffusion would give a membrane potential of about (1)\_\_, with almost all of this being determined by potassium diffusion. An additional (2)\_\_ is then contributed to the membrane potential by the continuously acting electrogenic Na+-K+ pump, giving a net membrane potential of (3)\_\_.
(1) −86 millivolts
(2) −4 millivolts
(3) −90 millivolts
When a membrane is permeable to several different ions, the diffusion potential that develops depends on three factors:
💡💡
Polarity
Permeability
Concentration
(1) The polarity of the electrical charge of each ion
(2) The permeability of the membrane (P) to each ion
(3) The concentrations (C) of the respective ions on the inside (i) and outside (o) of the membrane.
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STEADY STATE
It is the 💡basis of ion movement across the plasma membrane
ELECTROCHEMICAL POTENTIAL
The successive stages of the action potential are:
- RESTING STAGE
- DEPOLARIZATION STAGE
- REPOLARIZATION STAGE
It is the 💡value of membrane potential when all the permeable are all accounted
Represents the concentration inside and outside of the membrane
Used to calculate the 💡diffusion potential when the membrane is 💡permeable to different ions
Gives the 💡calculated membrane potential on the inside of the membrane when two univalent 💡positive ions, sodium (Na+) and potassium (K+), and one univalent 💡negative ion, chloride (Cl−), are involved.
GOLDMAN-HODGKIN KATZ EQUATION
It is an ionotrophic channel which is necessary actor in 💡causing both depolarization and repolarization of the nerve membrane during the action potential
Voltage-gated sodium channel
It is an ionotrophic cannel that plays an important role in 💡increasing the rapidity of repolarization of the membrane.
Voltage-gated potassium channel
It is generated by ion gradients not directly by ion pumps
MEMBRANE POTENTIAL
💡Transient change in the membrane potential characterized by a gradual 💡depolarization to threshold, a 💡rapid rising phase, an 💡overshoot, and a 💡repolarization followed by after 💡hyperpolarization (undershoot) before the membrane potential reaches resting level.
Nerve signals are transmitted by __, which are 💡rapid changes in the membrane potential that spread rapidly along the nerve fiber membrane.
It begins with a 💡sudden change from the normal resting negative membrane potential to a positive potential and ends with an almost equally rapid change back to the negative potential.
ACTION POTENTIAL
If the duration of the stimulus is short, the intensity must be high
If the duration is long, a lower-intensity stimulus can trigger an action potential
STRENGTH DURATION CURVE
A 💡second response is 💡not possible regardless of strength or duration of the stimulus
Time from the opening of the Na+ channels until the resetting of the channel
Ensures that each 💡AP is in all or none event
Enforces 💡one-way transmission of nerve impulses
ABSOLUTE REFRACTORY PERIODS
Most Na+ channels have returned to their resting state.
Some K+ channels are still open
Repolarization is occurring
Threshold for AP generation is elevated
Exceptionally strong stimulus may generate an AP
RELATIVE REFRACTORY PERIOD
It is the resting membrane potential 💡before the action potential begins
The membrane is said to be 💡“polarized” during this stage because of the 💡 −90 millivolts negative membrane potential that is present.
RESTING STAGE
The membrane suddenly becomes 💡permeable to sodium ions, allowing tremendous numbers of positively charged sodium ions to diffuse to the interior of the axon.
DEPOLARIZATION
After the membrane becomes highly permeable to sodium ions, the sodium channels begin to close and the 💡potassium channels open to a greater degree than normal.
Then, rapid diffusion of potassium ions to the exterior re-establishes the normal negative resting membrane potential.
REPOLARIZATION
Na+ channel opens and is activated
THRESHOLD
Undershoot
HYPERPOLARIZATION
Amplitude:
Small Large
Intensity of stimulus:
Subthreshold Threshold/maximal
Summation:
Intensity dependent Intensity independent
All or none law:
None Present
Type of propagation:
Passive/non-propagated Active propagated
LOCAL POTENTIAL vs.
ACTION POTENTIAL
