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Why is mature mammalian nerve tissue rich in cholesterol?
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Steroid
Many important physiological functions of vertebrates are controlled by steroid hormones.
Mature mammalian nerve tissue is exceptionally rich in cholesterol because it is a primary component of the myelin sheath.1
The myelin sheath, which insulates the axons of neurons to facilitate rapid nerve conduction, is formed by multiple layers of neighboring cell membranes. Because free sterols serve to stabilize the structures of these cellular membranes, the high density of membrane layers in nerve tissue necessitates a high concentration of cholesterol.21
Furthermore, cholesterol provides essential structural integrity to these membranes. Its rigid, fused-ring steroid nucleus inserts itself between phospholipid molecules, adding necessary rigidity to the bilayer and strengthening the membrane against mechanical rupture.3