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D) If during the generation of an action potential in the skeletal muscle cell the membrane potential approaches +65 mV, membrane permeability for which ion likely plays a major role in membrane depolarization? Explain your choice.

D) If during the generation of an action potential in the skeletal muscle cell the membrane potential approaches +65 mV, membrane permeability for which ion likely plays a major role in membrane depolarization? Explain your choice.

Human Anatomy & Physiology (11th Edition)
Human Anatomy & Physiology (11th Edition)
11th Edition
ISBN:9780134580999
Author:Elaine N. Marieb, Katja N. Hoehn
Publisher:Elaine N. Marieb, Katja N. Hoehn
Chapter1: The Human Body: An Orientation
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### Ion Concentration and Nernst Potential in Skeletal Muscle Cells | Ion | Intracellular Concentration (mM) | Extracellular Concentration (mM) | Nernst (equilibrium) Potential (mV) | |-----|---------------------------------|---------------------------------|------------------------------------| | K⁺ | 155 | 4 | -6.101 | | Na⁺ | 12 | 145 | 0.07 | | Ca²⁺| 10⁻⁴ | 1.5 | 0.125 | | Cl⁻ | 4 | 120 | 0.094 | In the table above, the intracellular and extracellular concentrations of different ions (potassium, sodium, calcium, and chloride) are listed along with their corresponding Nernst (equilibrium) potentials. #### Question D: **Question:** If during the generation of an action potential in the skeletal muscle cell the membrane potential approaches +65 mV, membrane permeability for which ion likely plays a major role in membrane depolarization? Explain your choice. **Answer:** When the membrane potential approaches +65 mV during the generation of an action potential in the skeletal muscle cell, increased permeability to Na⁺ (sodium ions) likely plays a major role in membrane depolarization. This is because the observed membrane potential (+65 mV) is more similar to the Nernst potential of Na⁺, which is 0.07 mV, compared to the Nernst potentials of the other ions. Specifically, during depolarization, sodium channels open, allowing Na⁺ to flow into the cell due to the significant concentration gradient, leading to a rapid rise in the membrane potential. The positive charge carried by Na⁺ ions moving into the cell results in a shift of the membrane potential towards the positive direction, aligning closely with the equilibrium potential of Na⁺, thereby indicating the dominant role of Na⁺ in the depolarization phase of the action potential.
Transcribed Image Text:### Ion Concentration and Nernst Potential in Skeletal Muscle Cells | Ion | Intracellular Concentration (mM) | Extracellular Concentration (mM) | Nernst (equilibrium) Potential (mV) | |-----|---------------------------------|---------------------------------|------------------------------------| | K⁺ | 155 | 4 | -6.101 | | Na⁺ | 12 | 145 | 0.07 | | Ca²⁺| 10⁻⁴ | 1.5 | 0.125 | | Cl⁻ | 4 | 120 | 0.094 | In the table above, the intracellular and extracellular concentrations of different ions (potassium, sodium, calcium, and chloride) are listed along with their corresponding Nernst (equilibrium) potentials. #### Question D: **Question:** If during the generation of an action potential in the skeletal muscle cell the membrane potential approaches +65 mV, membrane permeability for which ion likely plays a major role in membrane depolarization? Explain your choice. **Answer:** When the membrane potential approaches +65 mV during the generation of an action potential in the skeletal muscle cell, increased permeability to Na⁺ (sodium ions) likely plays a major role in membrane depolarization. This is because the observed membrane potential (+65 mV) is more similar to the Nernst potential of Na⁺, which is 0.07 mV, compared to the Nernst potentials of the other ions. Specifically, during depolarization, sodium channels open, allowing Na⁺ to flow into the cell due to the significant concentration gradient, leading to a rapid rise in the membrane potential. The positive charge carried by Na⁺ ions moving into the cell results in a shift of the membrane potential towards the positive direction, aligning closely with the equilibrium potential of Na⁺, thereby indicating the dominant role of Na⁺ in the depolarization phase of the action potential.
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