Cranial nerve VII

The parasympathetic nervous system. Here the postganglionic fibres are always short. The preganglionic fibres are long and pus almost up to the muscle or gland to be innervated. The preganglionic fibres arise from the brain stem (cranial nerves VII, IX and X), from the tectal region (cranial nerve III which supplies the eye, p. 38), and from the sacral region. 

Figure 14-3 Classification of dry eye. (cnVII = cranial nerve VII HIV = human immunodeficiency virus.) (Adapted from Lemp MA. Report of the National Eye Institute Industry Workshop on Clinical Trials in Dry Eyes. CLAO J 1995 21 221-232.)...

The seventh cranial nerve is responsible for eyelid closure during the blink reflex. Partial or complete disturbance of cranial nerve VII can interrupt these impulses, resulting in incomplete lid closure. Loss of muscular tone can also lead to ectropion, disruption of the lacrimal pump, and ultimately impaired tear drainage. 

Evaporative loss can also occnr from abnormal ocular surfece exposure, due to incomplete blink, nocturnal lagophthalmos, exophthalmos, proptosis, cranial nerve VII palsy, lid retraction, or other eyelid position and apposition disorders. Contact lenses may also contribute to an increased tear evaporation rate. 

A 73-year-old woman was given a Nadbath Rehman block behind the left pinna to provide motor blockade of cranial nerve VII, before retrobulbar block for cataract surgery. Several minutes later she complained of a metallic taste in her mouth. After surgery she had altered taste sensation on the anterior left side of the tongue, with recovery a day later. 

The author postulated this to be due to block of the chorda tympani, which runs with cranial nerve VII close to the site of the Nadbath Rehman block. 

Taste receptors reside within taste buds on the tongue, the larynx, and the palate. There are four primary taste sensations sour, sweet, bitter, and salty. By mixing these primary taste sensations, the brain can identify many specific tastes (analogous to primary color mixing). Impulses from the taste buds are carried through the facial, glossopharyngeal, and vagus nerves (cranial nerves VII, IX, and X, respectively) to the brain. Taste is modified by the presence of odor, and in the absence of olfactory ability, taste is virtually eliminated. 

Cranial nerve VII - palsy Dizziness (vertigo, true)... 

Schematic diagram of the gustatory pathway in rodents. Taste receptor cells are innervated by one of three cranial nerves (VII, IX, or X), which project topographically into the rostral portion of nucleus of the solitary tract (NST). Cells within the NST send projections into the reticular formation (RF), through which connections are made to oral motor nuclei V, VII, and XII and the nucleus ambiguous (NA). Ascending fibers connect to the parabrachial nuclei (PbN) of the pons, from which two parallel pathways emerge. One pathway carries taste information to the insular cortex (IC) via the ventral posterior medial nucleus, parvicellularis (VPMpc), of the thalamus. The other pathway projects into areas of the limbic forebrain involved in food and water regulation, reinforcement, reward, and stress, including the lateral hypothalamus (LH), the central nucleus ofthe amygdala (CeA), and the bed nucleus of the stria terminalis (BST). These areas and the IC are interconnected and send descending projections back to both the PbN and NST...

Neural connections project information from taste receptors in the taste buds of the mouth, via cranial nerves VII and IX, and from nutrient sensors in the gastrointestinal (Gl) tract, via cranial nerve X. The nutrient sensors of the Gl tract may be activated by cholecystokinin (CCK) or serotonin (5-HT). The afferent fibers end at the nucleus of the solitary tract in the brainstem. From there, after integration with other signals, projections to the forebrain carry the sensory information to higher structures... 

Acute exposure to trichloroethylene and its decomposition products (e.g., dichloroacetylene) has also led to residual neuropathy, characterized by nerve damage. This neuropathy is characterized by facial numbness, jaw weakness, and facial discomfort (indicating damage to cranial nerves V and VII) which can persist for several months (Buxton and Hayward 1967 Feldman 1970). Chronic exposure in the workplace has also been associated with damage to the cranial nerves in several cases (Bardodej and Vyskocil 1956 Barret et al. 1987 Cavanagh and Buxton 1989). Persons who have died from overexposure have shown degeneration of cranial nuclei in the brain stem (Buxton and Hayward 1967). Some of these effects may be attributed to... 

Originates in brainstem (cranial nerves III, VII, IX, and X) and sacral region of spinal cord (S2-S4)... 

Diabetes mellitus is the most common cause of peripheral neuropathy in the United States. Approximately half of all diabetics demonstrate evidences of neuropathy. The usual clinical pattern is that of a slowly progressive, mixed sensorimotor and autonomic polyneuropathy. More acute, asymmetrical motor neuropathies are also seen, usually affecting the lumbosacral plexus, particularly in older persons with type 2 (non-insulin-dependent) diabetes mellitus. Patients with diabetes mellitus are also prone to develop isolated palsies of cranial nerve III or VII, and there is a high incidence of asymptomatic focal demyelin-ation in the distal median nerve. 

COX-1 Constitutive form of cyclooxygenase enzyme. COX-2 Inducible form of cyclooxygenase enzyme, cranial nerve Any of 12 pairs of nerves that arise directly from the brain I (olfactory) II (optic) III (oculomotor) IV (trochlear) V (trigeminal) VI (abducens) VII (facial) VIII (vestibulocochlear) IX (glossopharyngeal) X (vagus) XI (accessory) XII (hypoglossal). They comprise part of the peripheral nervous stem. 

Neurologic pathways in the sympathetic nervous system originate from the thoracic (T1 to T12) and the upper lumbar segments (LI and L2) of the spinal cord. Neurologic pathways in the parasympathetic nervous system originate from cranial nerves III, VII, IX, and X, from the brainstem, and the sacral segments S2, S3, and S4 from the spinal cord. This is why the parasympathetic nervous system is also known as the craniosacral division of the autonomic nervous system. 

Fish taste buds, with morphological variations depending on the species (Northcutt 2004), can be observed in trunk, face, lip, oral, and pharyngeal (gill) epithelia, where sensory components of cranial nerves, facial (VII), glossopharyngeal (IX), and... 

Before studies of effects of TCE on many brain functions came the measurement of blink reflex latency in 22 people exposed at home to solvents rich in TCE at Woburn, MA. They showed significant delay of blink but no other functions were measured. In France about this time workers exposed to TCE had similar delays of blink. Earlier experimental exposure of 12 subjects to TCE at 1,000 parts per million (ppm) for 2 homs in a chamber had produced rapid flickering eye movements when following figures on a rotating drum (optokinetic nystagmus), a lowered fusion limit. Thus TCE induced dysfunction of several cranial nerves VI (with III, IV) and V and VII. Nystagmus normalized after a washout and recovery time. Blink is the easier and quicker measurement. ... 

At postmortem examination there were no gross abnormalities, except for mild atrophy of the brainstem, and microscopy showed only mild gliosis in the medial reticular formation of the medulla oblongata. There was slight myelin pallor in the cerebral hemispheres and brainstem. There was bilateral focal necrosis and calcification in the brain stem nuclei. The distribution of the lesions extended into the tegmentum of the pons and medulla oblongata, with involvement of the nuclei of cranial nerves VI, VII, X, and XII, where there was moderate to severe neuronal loss and free... 

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