| posterior longitudinal bundle | A longitudinal bundle of fibres extending from the upper border of the mesencephalon into the cervical segments of the spinal cord, located close to the midline and ventral to the central gray matter; it is composed largely of fibres from the vestibular nuclei ascending to the motor neurons innervating the external eye muscles (abducens, trochlear, and oculomotor nuclei), and descending to spinal cord segments innervating the musculature of the neck. Synonym: fasciculus longitudinalis medialis, Collier's tract, medial longitudinal bundle, posterior longitudinal bundle. (05 Mar 2000) |
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| precommissural bundle | See: olfactory bundle. (05 Mar 2000) |
| predorsal bundle | A bundle of thick, heavily myelinated fibres originating in the deep layers of the superior colliculus, crossing to the opposite side in the dorsal tegmental decussation, descending along the median plane, between the medial longitudinal fasciculus dorsally, the medial lemniscus ventrally, into the anterior funiculus of the spinal cord. The tract ends in the medial region of the anterior horn of the cervical spinal cord, and appears to be involved in head movements during visual and auditory tracking. Throughout its course in the brainstem it is accompanied by fibres of the tectobulbar tract. Synonym: tractus tectospinalis, Held's bundle, Loewenthal's bundle, Loewenthal's tract, Marchi's tract, predorsal bundle. (05 Mar 2000) |
| Held's bundle | A bundle of thick, heavily myelinated fibres originating in the deep layers of the superior colliculus, crossing to the opposite side in the dorsal tegmental decussation, descending along the median plane, between the medial longitudinal fasciculus dorsally, the medial lemniscus ventrally, into the anterior funiculus of the spinal cord. The tract ends in the medial region of the anterior horn of the cervical spinal cord, and appears to be involved in head movements during visual and auditory tracking. Throughout its course in the brainstem it is accompanied by fibres of the tectobulbar tract. Synonym: tractus tectospinalis, Held's bundle, Loewenthal's bundle, Loewenthal's tract, Marchi's tract, predorsal bundle. (05 Mar 2000) |
| Helie's bundle | A vertically arched bundle of fibres in the superficial layer of the myometrium. (05 Mar 2000) |
| Helweg's bundle | A slender bundle of nerve fibres in the peripheral zone of the lateral funiculus of the spinal cord, composed of spino-olivary fibres more likely than olivospinal fibres. Synonym: Helweg's bundle. (05 Mar 2000) |
| Schutz' bundle | A bundle of thin, poorly myelinated nerve fibres reciprocally connecting the periventricular zone of the hypothalamus with ventral parts of the central gray substance of the midbrain. Synonym: fasciculus longitudinalis dorsalis, Schutz' bundle, tract of Schutz. (05 Mar 2000) |
| His bundle electrogram | An electrogram recorded from the His bundle, either in the experimental animal or in man during cardiac catheterization. (05 Mar 2000) |
| his bundle electrography | <investigation> This test studies the electrical activity of the bundle of HIS. The bundle of HIS is a group of electrical fibres in the heart that are responsible for transmitting the electrical impulses which generate a normal cardiac contraction. This test may be performed in cases of cardiac arrhythmias, to locate a specific area responsible for a conduction defect and to determine the need for cardiac pacemaker placement. The test involves the passage of a an electrode tipped catheter into the heart. This catheter is usually threaded through a neck, arm or chest vein. Measurements of the HIS bundle can then be performed while standard ECG leads are placed on the arms and legs. This test carries a small risk of bleeding, arrhythmias, embolism, heart attack and stroke. It is performed by a specially trained cardiologist. (27 Sep 1997) |
| his bundle studies | <cardiology> This test studies the electrical activity of the bundle of HIS. The bundle of HIS is a group of electrical fibres in the heart that are responsible for transmitting the electrical impulses which generate a normal cardiac contraction. This test may be performed in cases of cardiac arrhythmias, to locate a specific area responsible for a conduction defect and to determine the need for cardiac pacemaker placement. The test involves the passage of a an electrode tipped catheter into the heart. This catheter is usually threaded through a neck, arm or chest vein. Measurements of the HIS bundle can then be performed while standard ECG leads are placed on the arms and legs. This test carries a small risk of bleeding, arrhythmias, embolism, heart attack and stroke. It is performed by a specially trained cardiologist. (27 Sep 1997) |
| Hoche's bundle | A compact bundle composed of descending branches of posterior root fibres located near the border between the fasciculi gracilis and cuneatus of the cervical and thoracic spinal cord; it corresponds to the septomarginal fasciculus, Hoche's tract, or oval area of Flechsig in the lumbar, and to the triangle of Philippe-Gombault in the sacral spinal segments; like these, it can be demonstrated only in cases of demyelination resulting from dorsal root lesions. Synonym: fasciculus semilunaris, fasciculus interfascicularis, comma bundle of Schultze, comma tract of Schultze, interfascicular fasciculus. (05 Mar 2000) |
| hooked bundle of Russell | Fastigial efferent fibres that cross with the cerebellum and descend over the lateral surface of the superior cerebellar peduncle; these fibres largely terminate in the vestibular nuclei and the reticular formation of the pons and medulla. Synonym: hooked bundle of Russell, uncinate fasciculus of Russell. (05 Mar 2000) |
| solitary bundle | A slender, compact fibre bundle extending longitudinally through the dorsolateral region of the medullary tegmentum, surrounded by the nucleus of the solitary tract, below the obex decussating over the central canal, and descending over some distance into the upper cervical segments of the spinal cord. It is composed of primary sensory fibres that enter with the vagus, glossopharyngeal, and facial nerves, and in part convey information from stretch receptors and chemoreceptors in the walls of the cardiovascular, respiratory, and intestinal tracts; in rostral parts of the tract impulses are generated by the receptor cells of the taste buds in the mucosa of the tongue. Its fibres are distributed to the nucleus of the solitary tract. Synonym: tractus solitarius, fasciculus rotundus, fasciculus solitarius, funiculus solitarius, Gierke's respiratory bundle, Krause's respiratory bundle, round fasciculus, solitary bundle, solitary fasciculus. (05 Mar 2000) |
| oblique bundle of pons | A bundle of fibres in the ventral surface of the pons running from the anterior mesial portion outward and backward. Synonym: fasciculus obliquus pontis, oblique bundle of pons. (05 Mar 2000) |
| olfactory bundle | A fibre system, described by E. Zuckerkandl as "Reichbundel," descending from the transparent septum in front of the anterior commissure toward the base of the forebrain; it contains precommissural fibres of the fornix, fibres from the septum to the hypothalamus and innominate substance, as well as fibres ascending to the septum and hippocampus from the hypothalamus and midbrain; it bears no special relation to the sense of smell. (05 Mar 2000) |