Question

Nerve fibres are surrounded by an insulating fatty layer called:
A. Adipose sheath
B. Myelin sheath
C. Hyaline sheath
D. Peritoneum

Answer 1

Hint:
A nerve fibre also referred to as an axon, is a long and slender projection of nerve cells (or neurons) that transmit electrical impulses far from the nerve cell body. A neuron typically has a single nerve fibre that emanates from its cell body that transmits impulses to other neurons, glands, or muscles.

Complete answer:
Myelin is an insulating layer or sheath that forms around nerves, including those in the spinal cord and brain. It consists of fatty substances and protein. This myelin sheath permits electrical impulses to transmit rapidly and effectively along the nerve cells. If myelin is harmed, these impulses slow down. Once the myelin sheath is damaged, nerves do not conduct electrical impulses generally. Sometimes the nerve fibres are also harmed. If the sheath can repair and regenerate itself, normal nerve function may return. Though, if the sheath is severely damaged, the underlying nerve fibre can die. Myelin is an electrically insulating material, which forms a layer, the myelin sheath, around only the axon of a neuron. Myelin aids to insulate the axons from electrically charged molecules and atoms. Cholesterol is a major component of myelin. There are two kinds of myelin sheath: PNS myelin and CNS myelin. CNS myelin is generated by specialised cells known as oligodendrocytes. Although PNS myelin is generated by Schwann cells. Both kinds of myelin are chemically diverse but perform a similar function i.e., to facilitate the effective transmission of a nerve impulse along the axon.

Option ‘B’ is correct

Note:
Multiple sclerosis (MS) is the most prevalent demyelinating disease of the central nervous system. In this condition, the immune system attacks the myelin sheath or cells that make and sustain it.