Peripheral nervous system

The peripheral nervous system encompasses all neural structures located outside the central nervous system (CNS). It includes cranial nerves, spinal nerves, peripheral ganglia, and plexuses, along with their associated sensory and motor components. Functionally, the peripheral nervous system acts as the conduit through which the central nervous system communicates with the body’s tissues and organs, facilitating both voluntary and involuntary responses.

The peripheral nervous system is structurally divided into the somatic nervous system, which controls skeletal muscle and mediates conscious perception, and the autonomic nervous system, which regulates visceral functions and homeostasis. The somatic component includes sensory (afferent) fibers that transmit information from the skin, muscles, joints, and special sense organs to the CNS, as well as motor (efferent) fibers that carry impulses from the CNS to skeletal muscles. In contrast, the autonomic component operates largely involuntarily and is further divided into sympathetic and parasympathetic part.

The peripheral nervous system gives rise to the :

• Cranial nerves arise from the brain and innervate the head and some thoracic and abdominal structures;

• Spinal nerves emerge segmentally from the spinal cord, each composed of dorsal (sensory) and ventral (motor) roots. These nerves give rise to dorsal and ventral branches, forming complex networks such as the brachial and lumbosacral plexus, which distribute innervation to the limbs and trunk.

The peripheral nervous system also contains numerous ganglia—collections of neuronal cell bodies—including sensory ganglia (such as the dorsal root ganglia) and autonomic ganglia, which serve as relay stations in the sympathetic and parasympathetic pathways. These elements are embedded within connective tissue and closely associated with vascular and lymphatic structures, ensuring integrated responses to internal and external stimuli.