Which statements are wrong?
I. Synaptic cleft of neurons secrete adrenaline.
II. Myelinated nerve fibres are enveloped with Schwann cells, which form a myelin sheath around the axon.
III. Non-myelinated nerve fibre is enclosed by a Schwann cell that does not form myelin sheath.
IV. Spinal cord and cranial nerves are made of non-myelinated nerve fibres.
Of the four statements, select the correct answer using the codes given below.
1
I, II are correct but III and IV are incorrect
2
I, II and III are correct but IV is incorrect.
3
III and IV are correct but I and II are incorrect.
4
II and III are correct but I and IV are incorrect.