The nervous system

The nervous system


The nervous system consists of the brain, spinal cord, sensory organs, and all of the nerves that connect these organs with the rest of the body. Together, these organs are responsible for the control of the body and communication among its parts. The brain and spinal cord form the control center known as the central nervous system (CNS), where information is evaluated and decisions made. The sensory nerves and sense organs of the peripheral nervous system (PNS) monitor conditions inside and outside of the body and send this information to the CNS. Efferent nerves in the PNS carry signals from the control center to the muscles, glands, and organs to regulate their functions.

The sciatic nerve



The sciatic nerve is the largest and longest spinal nerve in the human body. Extending from the lumbar and sacral plexuses in the lower back, the sciatic nerve runs through the buttocks and into the thighs. It delivers nerve signals to and from the muscles and skin of the thighs, lower legs and feet.

The sciatic nerve forms from the merger of the fourth and fifth lumbar nerves with the first, second, and third sacral nerves. From the lower back, the sciatic nerve runs inferiorly into the gluteal region and into the posterior of the femoral region of the leg. Smaller individual nerves branch off from the sciatic nerve to innervate our thigh muscles and skin. At the inferior end of the femoral region, the sciatic nerve branches off into the tibial and common fibular nerves, which continue carrying nerve signals into the lower legs and feet.

The femoral nerve



The femoral nerve is the major nerve that serves the tissues of the thigh and leg, including the muscles and skin. While the much larger sciatic nerve also passes through the thigh on its way to the lower leg and foot, only the femoral nerve innervates the tissues of the thigh. Nerve signals carried by the femoral nerve are crucial to the function of the legs, including standing, walking, and running.

The femoral nerve begins as the largest nerve to extend from the lumbar plexus in the lower back as a combination of fibers from the L2, L3, and L4 spinal nerves. From the lumbar plexus it extends with the fibers of the psoas major muscle inferiorly through the abdomen along the anterior surface of the hip bone. As it passes through the abdomen, a branch of the femoral nerve extends to provide nervous connections to the iliacus muscle, a flexor of the thigh. From the abdomen the femoral nerve next passes deep to the inguinal ligament in the groin and crosses the hip joint to enter the femoral region. In the femoral region, the femoral nerve separates into two nerve trunks - the anterior and posterior divisions - before further dividing into many smaller branches throughout the anterior and medial thigh.

The nerves of the leg and foot



The nerves of the leg and foot serve to propel the body through the actions of the legs, feet, and toes while maintaining balance, both while the body is moving and when it is at rest. Sensory nerves are of course present throughout the lower extremities; however, with the exception of the bottom of the foot, they play a lesser role here than in the upper extremities. Primarily, this section of the peripheral nervous system sends and receives signals regarding locomotion and balance of the body.

The nerves of the arm and hand



The nerves of the arm and hand perform a substantial two-fold role: commanding the intricate movements of the arms all the way down to the dexterous fingers, while also receiving the vast sensory information supplied by the sensory nerves of the hands and fingers. The movements of the arms must be fast, precise, and strong to complete the diverse activities the body engages in throughout the day. Even the tiny hand muscles, which perform very delicate and precise movements, are driven by about 200,000 neurons. Rapid conduction of sensory nerve signals from the hands provides critical information to the brain and feedback during precise activities.

The nervous system of the abdomen, lower back, and pelvis

The nervous system of the abdomen, lower back, and pelvis


The nervous system of the abdomen, lower back, and pelvis contains many important nerve conduits that service this region of the body as well as the lower limbs. This section of the nervous system features the most inferior portion of the spinal cord along with many major nerves, plexuses, and ganglia that serve the vital organs of the abdominopelvic cavity.

The spinal cord



The spinal cord is a major component of the central nervous system (CNS) that forms the vital link between the brain and most of the body. Its 31 spinal segments connect the CNS to the organs and tissues of the neck, torso, and limbs. The spinal cord also performs important processing functions to maintain balance and respond quickly to stimuli.

Nerves of the chest and upper back

Nerves of the chest and upper back


The nervous system of the thorax is a vital part of the nervous system as a whole, as it includes the spinal cord, peripheral nerves, and autonomic ganglia that communicate with and control many vital organs. Sensory information from the body and critical signals traveling to and from the limbs, trunk and vital organs all pass through this region on their way to and from the brain.

The taste buds

The taste buds


The taste buds are sensory taste receptors found on the tongue, throat, and palate that help form the perception of taste. Taste buds detect chemicals dissolved in saliva from food in the mouth and throat. Then, these taste buds send their sensory information through neurons to the gustatory center of the brain. The average person has around 10,000 taste buds in their mouth and throat, although the number of taste buds peaks in early childhood and declines throughout our lives.

The facial nerve



The facial nerve is one of the twelve pairs of cranial nerves in the peripheral nervous system. It is the seventh cranial nerve, and so is often referred to as cranial nerve VII or simply CN VII. Nerve signals from the cranial nerve play important roles in sensing taste as well as controlling the muscles of the face, salivary glands, and lacrimal glands.