Peripheral Nerve System
What is the peripheral nerve?
“Peripheral nerve” is a term used synonymously to describe the peripheral nervous system. The peripheral nervous system is a network of 43 pairs of motor and sensory nerves that connect the brain and spinal cord (the central nervous system) to the entire human body. These nerves control the functions of sensation, movement and motor coordination.
Which nerves are peripheral nerves?
The peripheral nervous system includes the following nerves:
- Brachial plexus nerve – This nerve is actually a network of nerves that consists of the last 4 cervical nerve roots (vertebrae C5-C8) and the first thoracic (vertebrae T1) nerve root, and ensures motion and feeling in the upper limbs.
- Common peroneal nerve – This nerve is a branch of the sciatic nerve and is made up of the deep and superficial peroneal branches. They provide sensation to the anterior (front) and lateral (side) parts of the legs and top of the feet. They innervate muscles in the legs that pull the ankle and toes up (dorsi flexion).
- Femoral nerve – This nerve is a part of the lumbar plexus. The femoral nerve provides sensation to the anterior (front) aspect of the thigh. It innervates muscles in the anterior thigh which allow the knee to extend.
- Lateral femoral cutaneous nerve – This nerve is part of the lumbar plexus nerve network. The lateral femoral cutaneous nerve provides sensation to the anterior and lateral sides of the thigh.
- Median nerve – This nerve is a branch of the medial and lateral cords of the brachial plexus. The median nerve provides sensation to the thumb, 1st, 2nd, 3rd and half of the 4th finger. It innervates muscles in the forearm and hand that allow pincher grasp (the ability to grasp an object between the thumb and forefinger).
- Radial nerve – This nerve branches from the posterior (back) cord of the brachial plexus. The radial nerve provides sensation to a portion of the skin on the back of the hand. It innervates muscles in the arm that extend the elbow and muscles in the forearm, which enables the wrist and fingers to straighten or extend.
- Sciatic nerve – The sciatic nerve is the largest single nerve in the body, extending from the back of the pelvis down the back of the thigh. It is the primary nerve of the leg and is responsible for innervating the muscles in the hip and lower limbs (including the tibial nerve and common fibular nerve).
- Spinal accessory nerve – This nerve is part of the cranial nerve network. It is located on the side of the neck and innervates the trapezius and sternomastoid muscle, which control specific shoulder movements, such as shrugging and adduction of the scapula.
- Tibial nerve – This nerve is a branch of the sciatic nerve and provides sensation to the bottom of the foot. It innervates the calf muscles which allow the foot and toes to flex (plantar flexion).
- Ulnar nerve – This nerve is a branch of the medial cord of the brachial plexus. The ulnar nerve provides sensation to half of the 4th and the entire 5th finger. It innervates muscles in the forearm and hand that allow the wrist and finger to flex (flexion) and fine finger control.