What is the primary function of the myelin sheath that surrounds axons in the mammalian nervous system?

Answer and explanation

Correct answer: A. To increase the velocity of nerve impulse conduction via saltatory conduction

  1. Step 1: Examine neuroanatomy: Myelin is an insulating lipid-rich sheath produced by Schwann cells in the PNS and oligodendrocytes in the CNS.
  2. Step 2: Gaps between myelin segments are called Nodes of Ranvier.
  3. Step 3: Action potentials jump rapidly from node to node, a mechanism known as saltatory conduction, greatly increasing signal speed while conserving energy.
Answer
To increase the velocity of nerve impulse conduction via saltatory conduction.
Why not the others: 'To synthesize neurotransmitters stored in synaptic vesicles' is carried out in the neuron cell body and axon terminal; 'To generate resting membrane potential through active ion transport' is performed by sodium-potassium ATPase pumps across the axolemma; 'To connect motor neuron dendrites directly to skeletal muscle myofibrils' misidentifies neuromuscular junctions located at axon terminals.

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