Question

Which of the following statements are correct and incorrect?
1. Synaptic cleft of neurons secrete adrenaline.
2. Myelinated nerve fibres are enveloped with Schwann cells, that form a myelin sheath around the axon.
3. Non-myelinated nerve fibre is enclosed by a Schwann cell that does not form a myelin sheath.
4. Spinal cord and cranial nerves are made of non-myelinated nerve fibres.

Out of the four statements.

• A. 1, 2 are correct but 3 and 4 are incorrect.
• B. 1, 2 and 3 are correct but 4 is incorrect.
• C. 3 and 4 are correct but 1 and 2 are incorrect.
• D. 1 and 4 are correct, while 2 and 3 are incorrect.
• E. 2 and 3 are correct, while 1 and 4 are incorrect.

Answer 1

The correct option is E 2 and 3 are correct, while 1 and 4 are incorrect.

• Synaptic vesicles of the synaptic knob secrete the neurotransmitter (e.g., adrenaline).
  
• Myelinated nerve fibres are enveloped with Schwann cells, which form a myelin sheath around the axon.
• Non-myelinated nerve fibres are also enclosed by a Schwann cell but that does not form a myelin sheath.
• Spinal cord and cranial nerves are made of myelinated nerve fibres.

So, the correct option is option E.