Cranial nerve, cranial nerves, optic nerve, olfactory nerve, oculomotor nerve, trochlear nerve, trigeminal nerve, facial nerve, abducens nerve, vestibulocochlear nerve, glossopharyngeal nerve, vagus nerve
The generic term cranial nerves (Nervi craniales) denotes 12 specific nerves of outstanding importance on each half of the body. For practical reasons, these are usually abbreviated with Roman numerals, i.e. from I (1) to XII (12). All but one (the 11th cranial nerve, accessory nerve) have the common feature that they either arise from the brain and leave it or flow directly into it.
By definition, cranial nerves are actually so-called "peripheral nerves", e.g. comparable to annoythat from the Spinal cord emerge and take care of our arms (body nerves). Ultimately, however, there are also deviations from this (e.g. with the 2nd cranial nerve, optic nerve), which are mainly due to the fact that the meninges are grouped differently around the actual nerve fibers of the nerve. Incidentally, behind the medical term of a normal peripheral nerve (e.g. a cranial nerve) there is always a large number of nerve fibers including special connective tissue and not the extension (axon) of a single nerve cell (Neuron). The finished nerves and their nerve branches then pass partially in the skull or on the outside of the skull, in certain connective tissue spaces, or also on the neck a very characteristic course, which is described in more detail for the individual nerves. The attending physician must of course not only observe this process during surgical interventions, the cranial nerves are systematically checked as part of a typical neurological examination.
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In the following, the cranial nerves are referred to in the text with the Roman numerals I-XII.
The order 1-12 of the cranial nerves reflects the height of the position of their core areas (nuclei) in the majority of the cranial nerves Brain stem again (due to certain peculiarities this assignment does not apply to the 1st, 2nd and 11th cranial nerves, see there). That's how they lie Neuronswhich in their entirety make up the core area of the 4th cranial nerve, for example further up (cranial) in the brain stem than the nerve cells that bundle to form the 12th cranial nerve.
Each cranial nerve is formally assigned to 1-4 core areas in the brain, smaller nerves such as the 4th cranial nerve originate / flow out of / into only one core area, larger nerves such as the 5th cranial nerve from / into 4 cores!
It is also possible that a single core shares fibers with several cranial nerves: The core responsible for our sensitivity in the head area (nucleus spinalis trigeminalis) contains inflows from three cranial nerves, namely V, IX and X.
What exactly do the cranial nerves do, what do we need them for?
$config[ads_text3] not foundIn short: They guide the sensations of our sense organs, i.e. what we do see (II), hear (VIII), taste (VII, IX, X), smell (I), in the area of the Head feel (V), information of ours Sense of balance (VIII), information about the Blood pressure in large cervical arteries (IX and X from the carotid body) etc. directly into our brain for further processing. In addition, they transmit commands from the brain to a large number of muscles, including the Eye muscles (III, IV, VI), the masticatory muscles (V), the mimic muscles of the face (VII), the muscles of the throat (IX, X), the muscles of the larynx (X), some neck muscles (XI) and the tongue muscles ( IX, XII). In addition to muscles, glands are also controlled, e.g. lacrimal gland and Salivary glands as well as numerous reflexes such as the swallowing reflex or the eyelid closing reflex (corneal reflex). Only the Xth cranial nerve, Vagus nerve, supplies areas to us that far exceed the head- / neck area, such as all organs of the chest and abdomen. This shortened list already shows how important our 12 cranial nerves actually are.
Cranial nerve I: Olfactory nerve (also olfactory nerve)
Cranial nerve II: Optic nerve (also optic nerve)
Cranial nerve III: Oculomotor nerve
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Cranial nerve IV: Trochlear nerve
Cranial nerve V: trigeminal nerve (also triple nerve)
Cranial nerve VI: Abducens nerve
Cranial nerve VII: Facial nerve
Cranial Nerve VIII: Vestibulocochlear nerve (also auditory and equilibrium nerves)
Cranial nerve IX: Glossopharyngeal nerve
Cranial nerve X: Vagus nerve
Cranial nerve XI: Accessory nerve
Cranial nerve XII: Hypoglossal nerve
In view of the diverse functions of our cranial nerves, there are theoretically typical failure symptoms or diseases for each of them (see table). Often, however, certain combinations of deficits occur, such as damage to IX, X and XI, because they are close to each other at the base of the skull and run through a common hole (foramen jugular).
So-called double vision occurs with disorders (lesions) of III, IV and VI whenever the visual axes of both eyes no longer coincide. This is the case when the eyeballs (bulbi) are aligned differently in the eye socket (orbit).