<P> The term "nucleus" is in some cases used rather loosely, to mean simply an identifiably distinct group of neurons, even if they are spread over an extended area . The reticular nucleus of the thalamus, for example, is a thin layer of inhibitory neurons that surrounds the thalamus . </P> <P> Some of the major anatomical components of the brain are organized as clusters of interconnected nuclei . Notable among these are the thalamus and hypothalamus, each of which contains several dozen distinguishable substructures . The medulla and pons also contain numerous small nuclei with a wide variety of sensory, motor, and regulatory functions . </P> <P> In the peripheral nervous system (PNS), a cluster of cell bodies of neurons (homologous to a CNS nucleus) is called a ganglion . The fascicles of nerve fibers in the PNS (homologous to CNS tracts) are called nerves . </P> <Ul> <Li> Brainstem: red nucleus, vestibular nucleus, inferior olive </Li> <Li> Cerebellum: dentate nucleus, emboliform nucleus, globose nucleus, fastigial nucleus </Li> <Li> Basal ganglia: striatum (caudate and putamen), pallidum (globus pallidus, medial and lateral), substantia nigra, subthalamic nucleus </Li> <Li> Cranial nerve nuclei </Li> <Li> Ventromedial nucleus of the hypothalamus: "The ventromedial hypothalamus (VMH) is a distinct morphological nucleus involved in feeding, fear, thermoregulation, and sexual activity ." </Li> </Ul>

How does a nucleus in the brain differ from a nucleus within a neuron