Pick out the incorrect statement?

Options

A. Myelinated nerve fibres are found in spinal and cranial nerve.
B. Unmyelinated nerve fibre is enclosed by a schwann cell.
C. In resting stage the axcnal membrane is comparatively more permeable to potassium ion and nearly impermeable to sodium ions.
D. Axolemma is more permeable to negatively charged protein present in the axoplasm

Answer

To solve the question "Pick out the incorrect statement," we will analyze each of the provided statements regarding nerve fibers and their properties:

1. **Statement 1**: "Myelinated nerve fibers are found in the spinal and the cranial nerve."
- This statement is **correct**. Myelinated nerve fibers are indeed present in both spinal and cranial nerves. The myelin sheath around these fibers increases the speed of nerve impulse conduction.

2. **Statement 2**: "Unmyelinated nerve fiber is enclosed by the Schwann cells."
- This statement is also **correct**. Unmyelinated fibers are indeed associated with Schwann cells, which provide support and protection, even though they do not form a myelin sheath around these fibers.

3. **Statement 3**: "In resting stage, the axonal membrane is comparatively more permeable to potassium ions and nearly impermeable to sodium ions."
- This statement is **correct**. During the resting potential, the axonal membrane is more permeable to potassium ions (K+) than to sodium ions (Na+), which is essential for maintaining the resting membrane potential.

4. **Statement 4**: "Exolema is more permeable to negatively charged proteins present in the exoplasm."
- This statement is **incorrect**. The exolema (the outer membrane of the axon) is not more permeable to negatively charged proteins. In fact, the membrane is generally impermeable to large charged molecules, including negatively charged proteins.

**Conclusion**: The incorrect statement is the fourth one: "Exolema is more permeable to negatively charged proteins present in the exoplasm."

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