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[[Image:brainstemcranialnervespyramids.jpg|thumb|right|150px|The brainstem, cranial nerves and pyramids. © BioMed Archive.]]

[[Image:brainstemcranialnervespyramids.jpg|thumb|right|150px|The brainstem, cranial nerves and pyramids. © BioMed Archive.]]

==Introduction==

==Introduction==

Cranial nerves are those nerves which arise from the brain and brain stem rather than the spinal cord. Nerves arising from the spinal cord are the [[PNS Structure - Anatomy & Physiology|peripheral nerves]]. There are 12 pairs of cranial nerves and these pairs of nerves passage through foramina in the skull, either individually or in groups. Cranial nerves are traditionally referred to by Roman numerals and these numerals begin cranially and run caudally.

Cranial nerves are those nerves which arise from the brain and [[Hindbrain_-_Anatomy_%26_Physiology|brain stem]] rather than the spinal cord. Nerves arising from the spinal cord are the [[PNS Structure - Anatomy & Physiology|peripheral nerves]]. There are 12 pairs of cranial nerves and these pairs of nerves passage through [[Skull_and_Facial_Muscles_-_Anatomy_%26_Physiology|foramina in the skull]], either individually or in groups. Cranial nerves are traditionally referred to by Roman numerals and these numerals begin cranially and run caudally.

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The most cranial nerve is the '''Olfactory nerve (I)''' which runs from the nasal cavity through to the olfactory bulb. The next most cranial is the '''Optic nerve (II)''' which runs from the eyes to the thalamus. Cranial nerves III to XII all exit from the brain stem and innervate the head, neck and organs in the thorax and abdomen. In order of most cranial to caudal, these include the '''Oculomotor nerve (III)''', the '''Trochlear nerve (IV)''', the '''Trigeminal nerve (V)''', the '''Abducens nerve (VI)''', the '''Facial nerve (VII)''', the '''Vestibulocochlear nerve (VIII)''', the '''Glossopharyngeal nerve (IX)''', the '''Vagus nerve (X)''', the '''Accessory nerve (XI)''' and the '''Hypoglossal nerve (XII)'''.   

The most cranial nerve is the '''Olfactory nerve (I)''' which runs from the nasal cavity through to the olfactory bulb. The next most cranial is the '''Optic nerve (II)''' which runs from the eyes to the [[Forebrain_-_Anatomy_%26_Physiology#Thalamus|thalamus]]. Cranial nerves III to XII all exit from the brain stem and innervate the head, neck and organs in the thorax and abdomen. In order of most cranial to caudal, these include the '''Oculomotor nerve (III)''', the '''Trochlear nerve (IV)''', the '''Trigeminal nerve (V)''', the '''Abducens nerve (VI)''', the '''Facial nerve (VII)''', the '''Vestibulocochlear nerve (VIII)''', the '''Glossopharyngeal nerve (IX)''', the '''Vagus nerve (X)''', the '''Accessory nerve (XI)''' and the '''Hypoglossal nerve (XII)'''.   

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Many of the cranial nerves with nuclei within the brain stem contain sensory and motor neurone components. The sensory fibre components have their cell bodies located in ganglia outside the central nervous system and the motor fibre element have their cell bodies within the central nervous system.

Many of the cranial nerves with nuclei within the brain stem contain sensory and motor neurone components. The sensory fibre components have their cell bodies located in ganglia outside the central nervous system and the motor fibre element have their cell bodies within the central nervous system.

==Cranial Nerve Fibre Types==

==Cranial Nerve Fibre Types==

Prior to a full explanation of each cranial nerve function, physiology, anatomy and particularly composition, the numerous types of nerve fibre found in cranial nerves must be explained to ensure that the following page can be better understood. Nerve fibres can undertake numerous roles within the body and their function is dictated by what type of fibre the nerve is composed of. A classification scheme is used to describe the type of fibres found within the cranial nerves and therefore provide a better understanding of the function and composition of that particular nerve. Below is a brief outline of this nerve fibre classification.

Prior to a full explanation of each cranial nerve function, physiology, anatomy and particularly composition, the numerous types of nerve fibre found in cranial nerves must be explained to ensure that the following page can be better understood. Nerve fibres can undertake numerous roles within the body and their function is dictated by what type of fibre the nerve is composed of. A classification scheme is used to describe the type of fibres found within the cranial nerves and therefore provide a better understanding of the function and composition of that particular nerve. Below is a brief outline of this nerve fibre classification.