Where is the facial nucleus located?
ponsThe facial motor nucleus is located in the lower third of the pons, beneath the fourth ventricle. The neurons leaving the nucleus pass around the abducens nucleus as they emerge from the brainstem. Involvement of the facial nerve nucleus and VI nerve nucleus are suggestive of a lesion near the fourth ventricle.Jul 21, 2015
Where is the nucleus of facial VII nerve is located?
The facial nerve's motor component begins in the facial nerve nucleus in the pons, and the sensory component begins in the nervus intermedius. The nerve then runs through the facial canal, passes through the parotid gland, and divides into five branches.Aug 13, 2020
What is the nucleus of facial nerve?
The facial nerve is comprised of three nuclei: The main motor nucleus. The parasympathetic nuclei. The sensory nucleus.Jul 31, 2021
Where is the nucleus located in a nerve?
The Nucleus of a neuron is an oval shaped membrane-bound structure found in the soma or body of the neuron. It contains the nucleolus and chromosomes, necessary for the coded production of proteins within the cell.
Where is the 7th and 8th cranial nerve located?
The vestibulocochlear nerve is located in the internal auditory meatus (internal auditory canal). The nerve is responsible for equilibrium and hearing.Feb 26, 2021
What layer is the facial nerve located?
The fifth layer is the facial nerve, which is discussed in detail below.
Do brain cells have a nucleus?
Neurons are similar to other cells in the body because: Neurons are surrounded by a cell membrane. Neurons have a nucleus that contains genes. Neurons contain cytoplasm, mitochondria and other organelles.
Do brain neurons have nucleus?
Most neurons have a cell body, an axon, and dendrites. The cell body contains the nucleus and cytoplasm. The axon extends from the cell body and often gives rise to many smaller branches before ending at nerve terminals.Apr 1, 2012
What does nucleus mean in neurology?
In neuroanatomy, a nucleus (plural form: nuclei) is a cluster of neurons in the central nervous system, located deep within the cerebral hemispheres and brainstem. The neurons in one nucleus usually have roughly similar connections and functions.
Where is the facial motor nucleus located?
The facial motor nucleus lies in the middle of the hindbrain at the level of the 6th rhombomere.
What is the facial nucleus of a mouse?
The anatomy of the facial nucleus in mammals is highly conserved, and the mouse facial motor nucleus is typical of all mammals that have been studied so far; it consists of six major rostrocaudal columns of motoneurons, and a smaller accessory nucleus dorsal to the main group (Fig. 12.6, 12.7) ( Ashwell, 1982; Ashwell and Watson, 1983 ).
Where is the genu located?
The genu lies dorsal to the abducens motoneurons in the fifth rhombomere. From here, the fibers run ventrolaterally in a compact bundle through the fourth rhombomere to exit ventral to the spinal tract of the trigeminal as the facial nerve ( Fig. 12.5 ).
Which muscle is innervated by the facial nerve?
Most of the fibers that remain in the facial nerve at this point provide motor innervation to the muscles of facial expression ( Fig. 14.14 ), the posterior belly of the digastric muscle, and the stylohyoid muscle.
What is the facial motor nucleus?
The facial motor nucleus is the main nucleus of the facial nerve, but it should be noted that the nerve also contains secretomotor fibers (from the superior salivatory nucleus), taste fibers (connected to the solitary complex), and a small group of cutaneous sensory fibers that supply the ear (connected to the trigeminal complex).
Where are the motoneurons located in the mouse?
The motoneurons that supply the superficial muscles of the face are arranged in a topographically organized fashion in the main facial nucleus in the mouse, with the auricular motor neurons medially placed and the nasolabial motor neurons laterally placed ( Ashwell and Watson, 1983; Ashwell, 1984).
How are oro-facial motor nuclei organized?
The oro-facial motor nuclei are organized into subdivisions defined both myotopically and cytoarchitectonically . In the case of 5N and 12N, muscle antagonists are segregated in distinct subdivisions and motor agonists have adjacent representation. Differential projections to motor neuron antagonists are well established for 5N, somewhat less so for 12N. In 7N, a pronounced topography related to peripheral musculature is evident, and myotopic subdivisions are further defined by their distinct afferent input. Pathways specific to eye-blink, vibrissal whisking and pinna movements can all be discerned.
Which neuron is responsible for facial expression?
All lower motor neuron (LMN) groups except the facial nerve nucleus that supplies the muscles of facial expression consist of both alpha LMNs that supply the skeletal muscle fibers (extrafusal fibers) and gamma LMNs that supply the small contractile elements in the muscle spindles (intrafusal fibers). The muscles of facial expression do not have muscle spindles and are not supplied by gamma LMNs. The alpha LMNs regulate contraction of the skeletal muscles to produce movement. The gamma LMNs regulate the sensitivity of the muscle spindles for group Ia and group II afferent modulation of alpha LMN excitability.
What is the function of the alpha LMN?
An alpha LMN supplies motor axons to a variable number of skeletal muscle fibers (extrafusal fibers), ranging from just a few (e.g., extraocular muscles) to several thousand (large muscles such as the quadriceps). The LMN and its innervated skeletal muscle fibers are called a motor unit. Supporting cells (such as Schwann cells) and myocytes produce trophic factors to maintain the nerve-muscle association; when nerve injury occurs, growth factors help to attract motor axonal regrowth to reestablish the prior nerve-muscle association. When motor axons degenerate, the neuromuscular junctions (NMJs) disappear, and the nicotinic cholinergic receptors spread across the membrane of the denervated skeletal muscle fibers. This results in denervation hypersensitivity to nicotinic cholinergic stimulation, noted as random individual muscle fiber twitches (fibrillation), best observed by electromyography. If motor nerves are attracted back to the muscle fibers and NMJs are restored, the nicotinic cholinergic receptors are again restricted to the secondary folds of the NMJ. If the motor axon that was lost cannot regrow, neighboring motor axons of other motor units that supply adjacent skeletal muscle fibers may send sprouts to the denervated muscle fibers and incorporate them into the motor unit; the consequence is a larger motor unit and a greater demand on the LMN cell body that now supplies a greater than normal number of skeletal muscle fibers. This mechanism may account for recovery of physiological function in some LMN diseases such as polio. If the alpha-LMN cell body itself is damaged or is in the process of dying (e.g., in amyotrophic lateral sclerosis), the axon may produce aberrant action potentials (agonal bursts of electrical activity) that result in muscle fiber contraction throughout the motor unit, called a fasciculation, which is visually observable. A denervated muscle fiber must be reinnervated within 1 year or so if it is to restore relatively normal function; a longer period leads to permanent changes that preclude proper reinnervation. Many experimental approaches are seeking to restore innervation or attract a more robust nerve supply to denervated muscle fibers by applying or inducing gene expression of growth factors and trophic factors. Denervated skeletal muscle fibers are flaccidly paralyzed, lack muscle tone, cannot be induced to contract with muscle stretch reflexes, and undergo atrophy; these are classic characteristics of LMN syndrome.
Anatomy
The nucleus is situated in the caudal portion of the ventrolateral pontine tegmentum. Its axons take an anusual course, traveling dorsally and looping around the abducens nucleus, then traveling ventrally to exit the ventral pons medial to the spinal trigeminal nucleus.
Classification
Because it innervates muscles derived from pharyngeal arches, the facial motor nucleus is considered part of the special visceral efferent (SVE) cell column, which also includes the trigeminal motor nucleus, nucleus ambiguus, and (arguably) the spinal accessory nucleus .
Cortical input
The like all lower motor neurons, cells of the facial motor nucleus receive input from the primary motor cortex in the frontal lobe of the brain. Upper motor neurons of the cortex send axons that descend through the internal capsule and synapse on neurons in the facial motor nucleus.
Effects of lesions
As a result of the corticobulbar input to the facial motor nucleus, an upper motor neuron lesion to fibers innervating the facial motor nucleus results in central seven. The syndrome is characterized by flaccid paralysis of the contralateral lower face.
What is the facial motor nucleus?
Anatomical terms of neuroanatomy. The facial motor nucleus is a collection of neurons in the brainstem that belong to the facial nerve ( cranial nerve VII). These lower motor neurons innervate the muscles of facial expression and the stapedius .
Where does the facial motor nucleus receive input?
Cortical input. Like all lower motor neurons, cells of the facial motor nucleus receive cortical input from the primary motor cortex in the frontal lobe of the brain. Upper motor neurons of the cortex send axons that descend through the internal capsule and synapse on neurons in the facial motor nucleus. This pathway from the cortex ...
What is the result of the corticobulbar input to the facial motor nucleus?
As a result of the corticobulbar input to the facial motor nucleus, an upper motor neuron lesion to fibers innervating the facial motor nucleus results in central seven. The syndrome is characterized by spastic paralysis of the contralateral lower face. For example, a left corticobulbar lesion results in paralysis of the muscles that control the lower right quadrant of the face.
Which part of the brain receives input from both sides of the cortex?
This pathway from the cortex to the brainstem is called the corticobulbar tract . The neurons in the dorsal aspect of the facial motor nucleus receive inputs from both sides of the cortex, while those in the ventral aspect mainly receive contralateral inputs (i.e. from the opposite side of the cortex).
Which hemispheres of the brain receive motor input?
This means that the temporal branch of the facial nerve receives motor input from both hemispheres of the cerebral cortex whereas the zygomatic, buccal, mandibular and cervical branches receive information from only contralateral hemispheres.
Which region of the nucleus is the innervating muscle?
The nucleus has a dorsal and ventral region, with neurons in the dorsal region innervating muscles of the upper face and neurons in the ventral region innervating muscles of the lower face.
Where do the lower motor neurons of the facial nerve leave?
In other words, this means lower motor neurons of the facial nerve can leave either from the left anterior, left posterior, right anterior or right posterior facial motor nucleus. The temporal branch travels out from the left and right posterior components. The inferior four branches do so via the left and right anterior components.
Where is the facial nerve located?
It is one of the longest cranial nerves, extending from the brainstem to the terminal (end) branches, which are located throughout the face. Several structures of the facial nerve—described as nuclei, segments, and branches—produce the four components of facial nerve function. 1
What are the branches of the facial nerve?
Most of the branches of the facial nerve are motor branches that stimulate the movement of the facial muscles. These muscles include: 1 the stapedius muscle in the ear, which controls the vibration of a bone in the ear to help moderate hearing 2 the stylohyoid muscle in the neck, which is involved with swallowing 3 the posterior belly of the digastric muscle, which is involved with movements of chewing, swallowing, talking, and breathing 4 the muscles of facial expression are controlled by the facial nerve 5 the frontalis muscle moves the forehead and eyebrows 6 the orbiculus oculi, which controls the muscles of the eyelids 7 the buccinator muscle, which moves the mouth and cheek 8 the orbicularis oris, which controls movements of the mouth and lips 9 the platysma, which is a large muscle in the neck that controls movements of the neck and jaw 10 the occipitalis muscle, which is located in the back of the head and moves the scalp skin posteriorly.
How many sections does the facial nerve have?
The facial nerve has: six major sections (described as segments) along the pathway from the brainstem to the terminal branches in the face. divisions and subdivisions (also called branches), which are small nerves in and around the face that merge along the segments into the main facial nerve.
How to recover from facial nerve damage?
If you have had any type of facial nerve disease or injury, recovery includes physical therapy , which can help your face and mouth muscles regain at least some of their strength. 10 The extent of recovery depends on the type and severity of the damage, how much of the nerve was involved, and the type of disease.
Why does the forehead move?
The fascinating thing about this redundancy is that if the facial nerve can’t function properly due to a problem in the brain, the muscles of the forehead can still move. When the area of the brain that controls the face becomes damaged, only the lower two-thirds of the face becomes weak.
What neurotransmitter is released by the facial nerve?
The motor branches of the facial nerve activate muscles to move by releasing acetylcholine, a neurotransmitter that binds to the surface of muscle cells. Activated muscles respond by contracting (becoming shorter in length), pulling or twisting nearby joints and bones, and ultimately producing movement of the face.
What nerves regulate the mouth and face?
Associated Conditions. Rehabilitation. The facial nerve and its branches regulate a number of functions of the mouth and face. Most of its divisions stimulate muscles that allow eyelids to open and close, as well as facial movements.
Where do facial nerve roots fuse?
The facial nerve roots then enter the facial canal in petrous part of temporal bone, where the small sensory and large motor roots fuse, forming the facial nerve. This united nerve enlarges at the geniculate ganglion, which contains cell bodies for sensory neurons.
What is the facial nerve?
The facial nerve is one of a group of nerves called the cranial nerves (CN), twelve pairs of nerves that , with the exception of the spinal accessory nerve (CN XI), originate in the brain and contribute to the peripheral nervous system (PNS).
What happens if the facial nerve is damaged?
If the facial nerve itself is damaged prior to dividing into the temporal, zygomatic, buccal, marginal mandibular, and cervical branches, the muscles of facial expression in the entire side of the face supplied by the damaged nerve may be weakened or paralyzed.
Which glands do facial nerves enter?
The nerve then enters the parotid gland, from whence it gives off five terminal branches–the temporal, zygomatic, buccal, marginal mandibular, and cervical branches–which emerge from around the parotid gland and innervate structures across the entire face. Notice how the facial nerve penetrates the parotid gland.
What is the vascular damage of the facial nerve?
Vascular damage to the facial nerve usually occurs at the supranuclear, pontine, and (rarely) cerebellopontine angle. Upper motor neuron (UMN) lesions occur in strokes and can easily be differentiated with lower motor neuron (LMN) lesions by their presentation. A LMN lesion causes paralysis of the whole side of face, ...
What are the components of the facial nerve?
The facial nerve contains many different types of fibers, including general sensory (afferent) fibers, special sensory fibers, visceral/autonomic motor (efferent) fibers, and somatic motor fibers. General sensory fibers in the facial nerve are responsible for transmitting signals to the brain from ...
What is the function of the facial nerve?
While it is indeed responsible for innervating the muscles of facial expression, the facial nerve is a complex structure containing many fiber types with a variety of functions, including motor, sensory, and autonomic. The following article will discuss the importance and versatility facial nerve.
