Our body’s nervous system is classified into the Central Nervous System (CNS) and the Peripheral Nervous System (PNS). The Central Nervous System comprises the brain and the spinal cord. The Peripheral Nervous System comprises any other system of nerves in our body other than the central nervous system. The body’s nervous systems can further be classified into voluntary and involuntary nervous systems.
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The autonomic nerves are responsible for controlling vital organs such as the heartbeat and breathing–also known as involuntary actions. Individual nerves within this classification include the vagus nerve, which slows down the heart. Together with the endocrine system, the autonomic nervous system also helps prepare our body for acute stress responses such as fight and flight.
Our somatic nervous system controls voluntary (conscious) action–movement. Muscle contraction and relaxation when someone wants to start walking, running, stretching the arm, or jumping is controlled by the somatic nerves, which fall under our peripheral nervous system.
Nerves of the peripheral nervous system collect stimuli from the external environment and relay them to the brain (part of the CNS) through neurons for integration and appropriate response initiation. Signals for the voluntary control of our muscles also arise from the brain through an efferent system.
Cranial nerves such as the vestibular nerve arise from the brain segments such as the medulla oblongata and the pons. Most somatic nerves that control locomotion arise from the spinal segments in a systematic arrangement.
Nerves of the Peripheral Nervous System are generally more exposed to Injury than the central nervous system, which is shielded by the cranium (skull). The cervical and vertebral column protect the spinal cord. Peripheral nerve injuries can occur due to physical trauma, burn, or diseases.
Some of the diseases associated with the peripheral nervous system include peripheral neuropathies, myasthenia gravis, Charcot-Marie-Tooth disorder, and neurofibromatosis, among others. Myasthenia gravis is caused by a breakdown in communication between muscles and nerves. CMT is a hereditary disorder caused by faulty genes. Peripheral neuropathies can be brought about due to many underlying factors such as diabetes, autoimmune diseases, and infections. Neurofibromatosis is also a hereditary disorder passed on by the parent or occurs spontaneously at conception.
People tend to think that nerves are tiny and microscopic. Some nerves are, but as they travel from the adjacent CNS column, they are visible to the naked eye. The sciatic nerve, for example, is relatively big, which makes doctors take caution when administering injections. They do it on the upper outer quadrant of the gluteal region to avoid injuring the sciatic nerve. The sciatic nerve size varies in individuals but is a few millimeters wide. Injury to the sciatic nerve leads to paralysis of the affected foot. Other peripheral nerves that can be seen without a microscope include; the ulnar nerve and median nerves, both located on the forearm.