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Questions and Answers
What is the resting membrane potential (RMP) of large nerve fibers when not transmitting signals?
What is the resting membrane potential (RMP) of large nerve fibers when not transmitting signals?
What term describes the state of a membrane when it has a potential difference between its two sides?
What term describes the state of a membrane when it has a potential difference between its two sides?
Which two factors primarily determine the magnitude of the resting membrane potential?
Which two factors primarily determine the magnitude of the resting membrane potential?
If the potential inside a nerve fiber becomes more positive, what is this change called?
If the potential inside a nerve fiber becomes more positive, what is this change called?
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What measurement technique is used to assess the membrane potential of a nerve fiber?
What measurement technique is used to assess the membrane potential of a nerve fiber?
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What occurs during the depolarization phase of an action potential?
What occurs during the depolarization phase of an action potential?
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What is the firing level in the context of an action potential?
What is the firing level in the context of an action potential?
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Which phase occurs immediately after the peak of an action potential?
Which phase occurs immediately after the peak of an action potential?
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What is the role of voltage-gated potassium channels during an action potential?
What is the role of voltage-gated potassium channels during an action potential?
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What is indicated by after hyperpolarization in the action potential sequence?
What is indicated by after hyperpolarization in the action potential sequence?
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What primarily establishes the resting membrane potential in neurons?
What primarily establishes the resting membrane potential in neurons?
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What function does the sodium-potassium pump serve in the cell membrane?
What function does the sodium-potassium pump serve in the cell membrane?
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Which of the following best describes selective permeability in the context of the cell membrane?
Which of the following best describes selective permeability in the context of the cell membrane?
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What is the role of large negatively charged proteins inside the cell?
What is the role of large negatively charged proteins inside the cell?
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How does the sodium-potassium pump contribute to the overall charge difference across the cell membrane?
How does the sodium-potassium pump contribute to the overall charge difference across the cell membrane?
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Study Notes
General Physiology: Membrane Potential
- Electrical potentials exist across cell membranes in virtually all cells.
- Some cells, like nerve and muscle cells, generate electrochemical impulses at their membranes.
- These impulses transmit signals.
Measuring Membrane Potential
- Nerve fiber membrane potential measured using microelectrodes.
- Two electrodes are used: one inside the nerve fiber and the other on the outside of the nerve membrane.
Resting Membrane Potential
- The potential inside a nerve fiber is 90 millivolts more negative than the potential in the extracellular fluid.
- RMP (resting membrane potential) is the voltage difference across the cell membrane under resting conditions.
- Also called membrane potential, transmembrane potential, transmembrane potential difference, or transmembrane potential gradient.
Factors Affecting Resting Membrane Potential
- Differences in ion concentrations (intracellular vs. extracellular).
- Differences in membrane permeability to different ions (reflect number of open channels).
Magnitude of Resting Membrane Potential
- Large nerve fibers: approximately –90 mV.
- Small neurons: approximately –70 mV.
Membrane Polarization
- A polarized membrane has a potential difference between its two sides.
- Depolarization: Inside becomes more positive.
- Hyperpolarization: Inside becomes more negative.
Physiological Ionic Basis of RMP
- Unequal distribution of ions.
- Selective permeability of the cell membrane.
- Na+/K+ pump actively transports ions, maintaining concentration gradients.
- More positive ions pumped outside than inside leads to negativity inside and positivity outside the cell.
- Potassium channels are significantly more permeable than sodium channels.
Action Potential
- A sudden change in the membrane potential.
- Obeys the all-or-none law.
- Propagated, not graded.
- Series of electrical changes when a muscle or nerve is stimulated that is propagated along the nerve fiber membrane.
Properties of Action Potential
- Propagated.
- Obeys all-or-none law.
- Not graded.
Action Potential Curve
- Latent Period: Time immediately after a stimulus.
- Depolarization: Membrane potential rapidly changes from negative to positive.
- Overshoot: Membrane potential exceeds zero mV (positive).
- Repolarization: Membrane potential returns to negative.
- After hyperpolarization: Membrane potential briefly dips more negative than the resting potential.
Ionic Basis of Action Potential
- Voltage-gated Na+ channels open rapidly upon depolarization. This causes more Na+ to flow into the cell.
- Na+ channels become inactivated, halting the inflow.
- Voltage-gated K+ channels open slowly, allowing K+ to flow out of the cell. This repolarizes the membrane.
- K+ channels close slowly causing a temporary hyperpolarization of the cell before returning to resting potential.
- The Na+/K+ pump restores the original ion concentration gradients.
Types of Changes in Membrane Potential
- Polarization: Membrane potential is not zero.
- Depolarization: Inside becomes less negative relative to outside.
- Repolarization: Membrane returns to resting potential after depolarization.
- Hyperpolarization: Inside becomes more negative than resting potential.
Graded Potential
- Local, short-distance signals.
- Non-propagated.
- Magnitude varies with stimulus intensity.
- Do not obey the all-or-none law.
- Occur in varying amplitudes and grades.
- Example include synaptic potential, neuromuscular junction potential and receptor potential.
Conductivity of the Nerve
- The ability of nerve fibers to transmit impulses along areas.
- Action potential transmitted as nerve impulse.
- Usually in one direction.
- Conducted by contiguous or saltatory conduction.
Contiguous Conduction
- Action potential spreads along every patch of membrane.
- Occurs in unmyelinated nerve fibers.
Saltatory Conduction
- Impulse jumps from node to node of Ranvier.
- Faster than contiguous conduction.
- Occurs in myelinated nerve fibers.
Action Potential Propagation
- Diagrams demonstrate action potential propagation in both myelinated and unmyelinated neurons
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Description
Explore the concept of membrane potential in general physiology, focusing on the electrical potentials across cell membranes. This quiz examines measuring techniques, resting membrane potential, and the factors affecting it. Ideal for students of physiology and biology.
