We all know that the nerve cell or Neuron is the structural and functional unit of the nervous system and our nervous system consists of around about 10 billion of them, which communicate each other in a specific manner. Nerves are connected to the brain and spinal cord. The brain is situated in the bony box-like structure called Cranium and the nerves arising from here are called Cranial Nerves and the nerves connecting the spinal cord are called as Spinal Nerves.
The Cranial Nerves originate from the different parts of the brain and mainly related to the head and neck position of the person.
⦿ There are 12 pairs of Cranial Nerves in the human body.
⦿ Some of the cranial nerves are sensory, some are motor nerves and very few are mixed nerves.
⦿ Branches of these nerves connect to the retina, ear, nose, tongue, eye, muscles, neck, face and pharynx.
⦿ Of the total 12 pairs of cranial nerves in the human body, Vagus (the 10th Cranial Nerve) is more important.
⦿ 10th Cranial Nerve, Vagus controls the rate of heartbeat and secretions of the pancreas.
⦿ Vagus Nerve is a mixed nerve in the human body.
1. Cranial Nerve-II or Optic Nerve
This is a sensory nerve running from the retina to the brain
2. Cranial Nerve-III or Oculomotor Nerve
This is the motor nerve running from the brain to eye muscles.
Spinal Nerves are the nerves which originate from the spinal cors of the human being. The spinal nerves play the major role in reflex actions and the spinal cord saves us from the dangerous stimuli through its reflex actions.
⦿ There are 31 pairs of Spinal Nerves in the human body.
⦿ All the spinal nerves are mixed nerves because they have both sensory and motor fibres.
⦿ The sensory nerves originate from the Dorsal Horn of the spinal cord and they carry information from organs to the spinal cord.
⦿ The motor fibres originate from the Ventral Horns of the spinal cord and supply information required for the movement of the muscles.
The Cranial Nerves and Spinal Nerves are the parts of the peripheral nervous system. It consists of the nerves arising from brain and spinal cord.