Cranial vs Spinal Nerves
Nervous system of human and other vertebrates are more or less the same and can be categorized into three main categories; Central nervous system, Peripheral nervous system and Autonomic nervous system. Nervous system is basically made up of neurons and nerve fibers, which collectively control and regulate body activities by conducting nerve impulse throughout the body. Basically brain and spinal cord make up the central nervous system, while their branches make up the peripheral nervous system. Depending on the originating place (either brain or spinal cord), peripheral nervous system can be classified into two categories; namely, cranial nerves and spinal nerves. Along these two types of nerves that arise from brain and spinal cord, central nerve system communicates with the rest of the body.
Cranial nerves are mainly associated with head and neck (with the exception of vagus nerve) and are involved in transmission of both sensory and motor information to and from the brain. There are 12 pairs of cranial nerves, and these pairs are designated by number and name where the name may associate with its function. For example, the olfactory nerve is named as cranial nerve I and is responsible for vision. The optic spinal nerve, which is cranial nerve II, is responsible for vision / eyesight. Except olfactory, optic, and vestibulocochlear nerves, all other cranial nerves are mixed nerves, where they carry both sensory and motor fibers. Olfactory, optic, and vestibulocochlear nerves consist only a sensory fiber; hence they pick only the stimuli.
Nerves that are originating from the spinal cord are known as spinal nerves. There are 31 pairs of spinal nerves that are named in relation to their location on the spinal cord. All of these nerves are mixed nerves, so that each nerve consists of both ventral (motor) and dorsal root (sensory) components. These nerves mainly carry nerve impulse to and from the spinal cord and brain, and to all parts of the body. Spinal nerves either go directly to a particular body segment or form a network with adjacent spinal nerves and veins called a plexus. There are four main spinal nerve plexus are present in the body, namely; cervical plexus, brachial plexus, lumber plexus, and sacral plexus.
What is the difference between cranial and spinal nerves?
• Nerves connected to the brain are called cranial nerves, whereas nerves connected with spinal cord are called spinal nerves.
• The functions of cranial nerves are concerned mainly with the activities associated with head and neck (except vagus nerve), while the functions of spinal nerves are associated with all the body parts, below the neck.
• In mammals, there are 12 pairs of cranial nerves while 31 pairs of spinal nerves exist.
• Spinal cords are named according to their location on the spinal cord, whereas cranial nerves are designated by serial numbers and names.
• Most of the cranial nerves are mixed nerves with the exception of olfactory, optic, and vestibulocochlear nerves, whereas all the spinal nerves are mixed nerves.