Which of the following statements is correct about a resting neuron?a)...
- The membrane is permeable to K+ at rest because many channels are open.
- In a normal cell, Na+ permeability is about 5% of the K+ permeability or even less.
- This implies that the permeability of the plasma membrane for K+ ions is greater than its permeability for Na+ ions.
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Which of the following statements is correct about a resting neuron?a)...
Permeability of the plasma membrane for K ions is greater than its permeability for Na ions.
Explanation:
The resting membrane potential of a neuron refers to its electrical charge when it is not transmitting any signals or impulses. During this resting state, the concentration of ions inside and outside the neuron is maintained by the sodium-potassium pump, which actively transports sodium (Na+) ions out of the cell and potassium (K+) ions into the cell.
Differential Permeability:
The plasma membrane of a neuron is differentially permeable, meaning that it allows certain ions to pass through more easily than others. This permeability is determined by the presence of ion channels, which are proteins embedded in the membrane that allow specific ions to move across.
Resting Neuron:
In a resting neuron, the permeability of the plasma membrane for K ions is greater than its permeability for Na ions. This means that potassium ions are more likely to move across the membrane compared to sodium ions.
Reasoning:
1. The sodium-potassium pump actively transports three sodium ions out of the cell for every two potassium ions it transports into the cell. This process helps maintain the concentration gradient of these ions.
2. Due to the differential permeability of the membrane, potassium ions can move more freely across the membrane compared to sodium ions.
3. As potassium ions move out of the cell, they establish a negative charge inside the neuron, creating a potential difference across the membrane.
4. This potential difference is known as the resting membrane potential and is typically around -70 millivolts in neurons.
5. The higher permeability of the membrane to potassium ions compared to sodium ions contributes to the establishment and maintenance of the resting membrane potential.
Conclusion:
In summary, the correct statement is that the permeability of the plasma membrane for K ions is greater than its permeability for Na ions in a resting neuron. This differential permeability allows potassium ions to move more freely across the membrane, contributing to the establishment of the resting membrane potential.
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