What is the difference between nuclei and tracts

Nuclei make the grey matter while tracts make the white matter in the central nervous system. Brian is a large collection of nuclei, where processing of information occur. Tracts that interconnect the groups of nuclei transfer the nerve impulse to their end points. Some of the major parts of the brain such as thalamus and hypothalamus are identified with the help of interconnected groups of nuclei.

Even though the term ganglia is associated with peripheral nervous system, there are special multiple subcortical nuclei called basal ganglia in the brain. Basal ganglia are interconnected with cerebral cortex , thalamus, and brainstem of the brain and are linked with certain functions of the brain including motor control, emotions, cognition , and learning.

Yashoda Ramyajith Somarathna holds a B. Figure 2: Cranial and Autonomic Ganglia. The cranial and the autonomic ganglia are shown in figure 2. The term nuclei refer to the clusters of cell bodies in the central nervous system CNS. They are located deep in the cerebral hemispheres and the brainstem. Nuclei are found in the gray matter of the brain. They are interconnected to each other by tracts. Tracts are bundles of axons, which extend from nuclei. Generally, the brain consists of hundreds of distinguishable nuclei.

Inside the nucleus, multiple subnuclei can be identified, which are arranged as clumps. Both thalamus and hypothalamus are organized clusters of nuclei in the brain. Basal nuclei are a group of interconnected nuclei of the cerebral cortex, thalamus, and the brainstem. Basal nuclei are sometimes called basal ganglia. The basal nuclei are composed of caudate, putamen, pallidum, substantia nigra, and subthalamic nuclei.

The brain stem contains three nuclei called red nucleus, vestibular nucleus, and inferior olive. The cerebellum contains dentate nucleus, emboliform nucleus, globose nucleus, and fastigial nucleus. The basal nuclei of the front section of the brain are shown in figure 3. Ganglia: Ganglia refer to the structures that contain a number of cell bodies of the peripheral nervous system.

SGCs have a variety of roles, including control over the microenvironment of sympathetic ganglia. They are thought to have a similar role to astrocytes in the central nervous system CNS.

They supply nutrients to the surrounding neurons and also have some structural function. Satellite cells also act as protective, cushioning cells. Additionally, they express a variety of receptors that allow for a range of interactions with neuroactive chemicals. A bundle of axons is called a nerve in the peripheral nervous system and a tract in the central nervous system.

Neurons feature many long, slender projections termed axons, along which electrochemical nerve impulses are transmitted. In the central nervous system CNS bundles of these axons are called tracts, whereas in the peripheral nervous system PNS they are called nerves. Each nerve is covered externally by a dense sheath of connective tissue, the epineurium. Underlying this layer of flat cells, the perineurium, forms a complete sleeve around a bundle of axons called fascicles.

Surrounding each axon is the endoneurium. The endoneurium consists of an inner sleeve of material called the glycocalyx and an outer delicate meshwork of collagen fibers. Within the endoneurium, the individual nerve axons are surrounded by a protein liquid called endoneurial fluid. The endoneurium has properties analogous to the blood-brain barrier, in that it prevents certain molecules from crossing from the blood into the endoneurial fluid.

The longest axons in the human body are those of the sciatic nerve, which run from the base of the spinal cord to the big toe of each foot. Axons in the central nervous system typically show complex trees with many branch points allowing for the simultaneous transmission of messages to a large number of target neurons. Axons are described as either un-myelinated or myelinated.

Myelin is a layer of a fatty insulating substance, which is formed by two types of glial cells: Schwann cells en-sheathing peripheral neurons and oligodendrocytes insulating those of the central nervous system. Myelination enables an especially rapid mode of electrical impulse propagation called saltatory conduction.

De-myelination of axons causes the multitude of neurological symptoms found in the disease multiple sclerosis. Nerves in the PNS are typically divided into cranial and spinal nerves. There are twelve pairs of cranial nerves and thirty one pair of spinal nerves.

Cranial nerves innervate parts of the head and connect directly to the brain especially to the brainstem. They are typically assigned Roman numerals from 1 to 12, although cranial nerve zero is sometimes included. In addition, cranial nerves have descriptive names. Spinal nerves innervate much of the body, and connect through the spinal column to the spinal cord. They are given letter-number designations according to the vertebra through which they connect to the spinal column.