Abducens nucleus
Encyclopedia
The abducens nucleus is the originating nucleus from which the abducens nerve (VI) emerges - a cranial nerve nucleus
. This nucleus is located beneath the fourth ventricle
in the caudal
portion of the pons
, medial
to the sulcus limitans
.
The abducens nucleus along with the internal genu of the facial nerve
make up the facial colliculus
, a hump at the caudal end of the medial eminence
on the dorsal aspect of the pons.
: specifically, loss of the ability to move the ipsilateral eye outward (abduction). This is also seen in damage of the abducens nerve.
In contrast, damage to the area of the nucleus can also result in lateral gaze paralysis
: loss of the ability to move either eye in the direction of the side with the lesion. This is due to damage to both the motoneurons and interneuron
s projecting through the medial longitudinal fasciculus
to the contralateral medial rectus neuron
s.
Cranial nerve nucleus
A cranial nerve nucleus is a collection of neurons in the brain stem that is associated with one or more cranial nerves. Axons carrying information to and from the cranial nerves form a synapse first at these nuclei. Lesions occurring at these nuclei can lead to effects resembling those seen by...
. This nucleus is located beneath the fourth ventricle
Fourth ventricle
The fourth ventricle is one of the four connected fluid-filled cavities within the human brain. These cavities, known collectively as the ventricular system, consist of the left and right lateral ventricles, the third ventricle, and the fourth ventricle...
in the caudal
Anatomical terms of location
Standard anatomical terms of location are designations employed in science that deal with the anatomy of animals to avoid ambiguities that might otherwise arise. They are not language-specific, and thus require no translation...
portion of the pons
Pons
The pons is a structure located on the brain stem, named after the Latin word for "bridge" or the 16th-century Italian anatomist and surgeon Costanzo Varolio . It is superior to the medulla oblongata, inferior to the midbrain, and ventral to the cerebellum. In humans and other bipeds this means it...
, medial
Anatomical terms of location
Standard anatomical terms of location are designations employed in science that deal with the anatomy of animals to avoid ambiguities that might otherwise arise. They are not language-specific, and thus require no translation...
to the sulcus limitans
Sulcus limitans
In the floor of the fourth ventricle, the sulcus limitans separates the cranial nerve motor nuclei from the sensory nuclei . In the superior part of the rhomboid fossa, it corresponds with the lateral limit of the fossa and presents a bluish-gray area, the locus ceruleus In the floor of the fourth...
.
The abducens nucleus along with the internal genu of the facial nerve
Facial nerve
The facial nerve is the seventh of twelve paired cranial nerves. It emerges from the brainstem between the pons and the medulla, and controls the muscles of facial expression, and functions in the conveyance of taste sensations from the anterior two-thirds of the tongue and oral cavity...
make up the facial colliculus
Facial colliculus
The facial colliculus is an elevated area located on the dorsal pons. In the floor of the 4th ventricle It is formed by motor fibers of the facial nerve as they loop over the abducens nucleus...
, a hump at the caudal end of the medial eminence
Medial eminence
In the human brain, the rhomboid fossa is divided into symmetrical halves by a median sulcus which reaches from the upper to the lower angles of the fossa and is deeper below than above...
on the dorsal aspect of the pons.
Clinical significance
Damage to the abducens nucleus causes monocular medial ophthalmoparesisOphthalmoparesis
Ophthalmoparesis or ophthalmoplegia refers to paralysis of one or more extraocular muscles which are responsible for eye movements. It is a physical finding in certain neurologic illnesses.-Classification:...
: specifically, loss of the ability to move the ipsilateral eye outward (abduction). This is also seen in damage of the abducens nerve.
In contrast, damage to the area of the nucleus can also result in lateral gaze paralysis
Ophthalmoparesis
Ophthalmoparesis or ophthalmoplegia refers to paralysis of one or more extraocular muscles which are responsible for eye movements. It is a physical finding in certain neurologic illnesses.-Classification:...
: loss of the ability to move either eye in the direction of the side with the lesion. This is due to damage to both the motoneurons and interneuron
Interneuron
An interneuron is a multipolar neuron which connects afferent neurons and efferent neurons in neural pathways...
s projecting through the medial longitudinal fasciculus
Medial longitudinal fasciculus
The medial longitudinal fasciculus is a pair of crossed fiber tracts , one on each side of the brainstem. These bundles of axons are situated near the midline of the brainstem and are composed of both ascending and descending fibers that arise from a number of sources and terminate in different...
to the contralateral medial rectus neuron
Neuron
A neuron is an electrically excitable cell that processes and transmits information by electrical and chemical signaling. Chemical signaling occurs via synapses, specialized connections with other cells. Neurons connect to each other to form networks. Neurons are the core components of the nervous...
s.
External links
- Template (look for "GSE")
- NIF Search - Abducens Nucleus via the Neuroscience Information FrameworkNeuroscience Information FrameworkThe Neuroscience Information Framework is a repository of global neuroscience web resources, including experimental, clinical, and translational neuroscience databases, knowledge bases, atlases, and genetic/genomic resources.-Description:...