Final answer:
Myelin is a lipid-rich insulating substance that surrounds the axons of many neurons, produced by glial cells. Its role in nervous physiology is to speed up the transmission of electrical signals through a process called saltatory conduction, which is essential for the efficient function of the nervous system. The correct option is A.
Step-by-step explanation:
The molecule known as myelin is a lipid-rich insulating substance that surrounds the axons of many neurons. Myelin is essential in nervous physiology because it serves as an insulating sheath for the axon, which greatly speeds up the transmission of electrical signals.
The myelin sheath is produced by oligodendrocytes in the central nervous system (CNS) and Schwann cells in the peripheral nervous system (PNS), and it works by reducing the capacitance of the axonal membrane and increasing the electrical resistance across the membrane.
Nerve impulses are thus allowed to jump from one node to the next (the Nodes of Ranvier), via a process known as saltatory conduction, which dramatically increases the speed of signal transmission along the axon.
Various medical conditions are related to myelin impairment, such as multiple sclerosis, where the myelin sheath is damaged, leading to disruptions in signal transmission, which results in a variety of neurological symptoms. Proper myelination is thus critical for the efficient function of the nervous system.