Myelinated neurons are a type of nerve cells that have a protective covering called myelin sheath. This sheath is made up of a fatty substance called myelin, which acts as an insulator and helps in the fast and efficient conduction of nerve impulses. These neurons are found in various parts of the body, but primarily in the central and peripheral nervous system.

a) In Spinal cord and cranial nerves:
Myelinated neurons are found in the spinal cord and cranial nerves. The spinal cord is a long, cylindrical bundle of nerve fibers that is enclosed within the vertebral column. It acts as a pathway for nerve impulses to travel between the brain and the rest of the body. The cranial nerves are a set of twelve pairs of nerves that originate from the brain and primarily innervate the head and neck region. Both the spinal cord and cranial nerves contain myelinated neurons that help in the transmission of sensory and motor information.

c) In peripheral nerves:
Myelinated neurons are also found in the peripheral nerves. The peripheral nervous system consists of all the nerves that are outside the brain and spinal cord. These nerves connect the central nervous system to the muscles, organs, and other tissues of the body. The peripheral nerves contain both myelinated and unmyelinated neurons. Myelinated neurons in the peripheral nerves play a crucial role in the rapid transmission of signals to and from the central nervous system.

d) In motor neurons:
Motor neurons are a type of nerve cells that transmit signals from the central nervous system to muscles or glands, resulting in movement or secretion. Myelinated neurons are found in motor neurons, which are responsible for the voluntary movement of skeletal muscles. The myelin sheath surrounding the axons of motor neurons helps in the rapid and efficient transmission of motor signals.

In conclusion, myelinated neurons are found in the spinal cord, cranial nerves, peripheral nerves, and motor neurons. These neurons are essential for the fast and efficient conduction of nerve impulses, allowing for the proper functioning of the nervous system.