The position of the central nervous system

(CNS)
Brain, encephalon (A1)
The spinal cord (SC)
Medulla Spinalis (A2)
Vertebrae (intervertebral foramina) (A3) -> PNS(the peripheral nervous system)
The brachial plexus (A4)
lumbosacral plexus (A5)-> the fibers of the spinal nerves intermingle here
ganglia (A6)
* the CNS is protected from all sides by bony walls and
the cushioning effect of a fluid (fluid cushion EX the cerebrospinal fluid fills the cranial cavity, and the cavity between the vertebral canal and the spinal cord).

- Color Atlas and Textbook of Human Anatomy.

A nerve plexus is a network of intersecting nerves. They combine sets of spinal nerves that serve the same area of the body into one large grouped nerve. There are several in the body, including:

Cervical plexus - serves the head, neck and shoulders
Brachial plexus - serves the chest, shoulders, arms and hands
Lumbar plexus - serves the back, abdomen, groin, thighs, knees, and calves
Sacral plexus - serves the pelvis, buttocks, genitals, thighs, calves, and feet
Solar plexus - serves internal organs
Coccygeal plexus - Same as Solar Plexus




In neurological contexts, ganglia are composed mainly of somata and dendritic structures which are bundled or connected together. Ganglia often interconnect with other ganglia to form a complex system of ganglia known as a plexus. Ganglia provide relay points and intermediary connections between different neurological structures in the body, such as the peripheral and central nervous systems.

There are two major groups of ganglia:

Dorsal root ganglia (also known as the spinal ganglia) contain the cell bodies of sensory (afferent) nerves.
Autonomic ganglia contain the cell bodies of autonomic nerves.
In the autonomic nervous system, fibers from the central nervous system to the ganglia are known as preganglionic fibers, while those from the ganglia to the effector organ are called postganglionic fibers.