A resting axonal membrane is comparatively more permeable to....... and nealy impermeable to.

Options

A. `Na^(+)` ions and `K^(+)` ions
B. `K^(+)` ions and `Na^(+)` ions
C. `Ca^(+)` ions and `Na^(+)` ions
D. `K^(+)` ions and `Ca^(+)` ions

Answer

To answer the question, "A resting axonal membrane is comparatively more permeable to....... and nearly impermeable to...", we need to analyze the permeability characteristics of the axonal membrane concerning different ions.

### Step-by-Step Solution:

1. **Understanding Membrane Permeability**:
- The axonal membrane has selective permeability, meaning it allows certain ions to pass through more easily than others.

2. **Identify Key Ions**:
- The key ions to consider in this context are sodium ions (Na+), potassium ions (K+), and calcium ions (Ca2+).

3. **Resting Membrane Potential**:
- At rest, the axonal membrane maintains a resting membrane potential (RMP) of approximately -70 mV. This potential is largely influenced by the distribution of ions across the membrane.

4. **Permeability to Potassium Ions**:
- The resting axonal membrane is highly permeable to potassium ions (K+). This means that K+ can move freely across the membrane, contributing significantly to the resting membrane potential.

5. **Impermeability to Sodium Ions**:
- In contrast, the resting axonal membrane is nearly impermeable to sodium ions (Na+). While some Na+ can enter the cell, the flow is restricted, and the concentration of Na+ inside the cell is kept low compared to the outside.

6. **Conclusion**:
- Therefore, we conclude that a resting axonal membrane is comparatively more permeable to potassium ions (K+) and nearly impermeable to sodium ions (Na+).

### Final Answer:
A resting axonal membrane is comparatively more permeable to **potassium ions (K+)** and nearly impermeable to **sodium ions (Na+)**.

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