The cranial nerves connect to the brain. In humans, they are made up of 12 pairs that start from the brain and connect it to the sense organs and muscles.
Meanwhile, the spinal or spinal nerves connect the spinal cord to sensory cells and various muscles throughout the body. These are made up of 31 pairs.
Cranial nerves perform sensory and motor functions. The function is determined according to the structures innervated by each pair. The 12 pairs of cranial nerves are numbered, in Roman numerals, in craniocaudal sequence.
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Cranial nerves and their respective functions
I- Olfactory nerves
They originate in the olfactory region of each nasal fossa, cross the ethmoid bone and end in the olfactory bulb.
They have an exclusively sensitive function, being responsible for conducting olfactory impulses.
II- Optical nerves
They are composed of a thick bundle of nerve fibers originating in the retinal region that penetrate the skull through the optic channel.
They have a strictly sensitive function.
III- Oculomotor nerve
It is a motor nerve, responsible for eye movement.
IV- Trochlear nerve
It is a nerve with a sensory and motor part, also related to eye movement and vision.
V - Trigeminal nerve
It has a motor and a sensory portion.
The motor portion acts on muscles related to chewing.
The sensitive portion has three branches: ophthalmic, maxillary and mandibular. It is responsible for the innervation of the face, part of the scalp and inner regions of the skull.
VI - Abducens nerve
It is responsible for the innervation of the lateral rectus muscle of the eye.
VII- Facial nerve
It is a mixed nerve, presenting a motor and a sensory portion. The motor portion is represented by the facial nerve itself, related to facial expressions, saliva secretion and tear production.
The facial nerve provides motor innervation to all cutaneous muscles of the head and neck.
The sensory portion is called the intermediate nerve and acts on muscle and gustatory sensitivity.
VIII- Vestibulocochlear nerve
It is an exclusively sensitive nerve. In reference to its name, it has the vestibular and cochlear parts.
The vestibular part is related to balance. The cochlear part is related to hearing.
IX- Glossopharyngeal nerve
It is a nerve with sensory and motor function. It is responsible for the sensitivity of part of the tongue, pharynx and eustachian tube. The motor part is related to the pharyngeal muscles.
X- Vague nerve
It is a nerve with motor and sensory function. Innervates almost all organs below the neck, with parasympathetic innervation. It is responsible for maintaining vital functions such as regulating heart rate.
XI- Accessory nerve
It is essentially a motor nerve, acting in functions related to swallowing and head and neck movements.
XII - Hypoglossal nerve
It is an exclusively motor nerve. It emerges from the skull through the hypoglossal canal and goes to the intrinsic and extrinsic muscles of the tongue. Relating to the movement of the tongue.
To gain more knowledge, see also:
- Nerves of the Human Body
- Nervous system
- Exercises on the Nervous System
