Medulla Oblongata


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Related to Medulla Oblongata: cerebellum, pons, hypothalamus, midbrain, spinal cord

medulla oblongata

[mə′dəl·ə ‚äb‚lȯŋ′gäd·ə]
(neuroscience)
The somewhat pyramidal, caudal portion of the vertebrate brain which extends from the pons to the spinal cord. Also known as medulla.

Medulla Oblongata

 

the most posterior (inferior) part of the brain, extending from the spinal cord below to the pons varolii above (toward the front). The posterior surface of the medulla oblongata forms the lower part of the floor of the fourth ventricle.

The medulla oblongata transmits (often after modification) signals from the spinal cord to the brain by centripetal conduction paths and from the brain to the spinal cord by centrifugal paths. The neurons of the medulla oblongata (the nuclei of the reticular formation and craniocerebral nerves) help regulate blood circulation, respiration, digestion, and the functioning of the higher portions of the brain and of the segmental apparatus of the spinal cord, including sleep. Motor impulses are transmitted at the level of the medulla oblongata to spinal cord neurons through the pyramidal system of conduction paths (the corticospinal tract), which forms a chiasma, and through the extrapyramidal system.

The medial portions of the reticular formation of the medulla oblongata contain accumulations of nerve cells that form the descending reticular spinal system, which inhibits the motor apparatus of the spinal cord and mediates the coordinating influences from the cerebral cortex, subcortical nuclei, cerebellum, and other portions of the brain that control movement and position. The raphe nuclei contain neurons that have processes in almost all the higher-situated portions of the brain and synchronize the electrical activity of the cerebral cortex with the onset of the slow sleep phase. The mediator exciting these neurons is serotonin. Destruction of the neurons in experimental animals causes persistent insomnia and behavioral disturbances; pharmacological block of the neuron’s development and release of serotinin has the same effect. On the floor of the fourth ventricle in the medulla oblongata are neurons (the region of the blue spot), which together with the mediator norepinephrine influence other cells of the reticular formation and cause inclusion of the inhibitory reticular spinal system in the rapid sleep phase and inhibition of muscle tone and cerebrospinal reflexes. Thus, the medulla oblongata, the phylogeneti-cally oldest portion of the brain, plays an important role in sleep.

Nerve pathways in the posterosuperior portions of the medulla oblongata transmit from the spinal cord sensory signals from receptors of the skin, muscles and joints, and internal organs. Some of these pathways are intercepted in the medulla oblongata’s nuclei, where second neurons of the sensory pathway are situated; the nerve pathways also proceed to the opposite side, forming a chiasma. The medulla oblongata’s neuronal mechanisms automatically regulate respiration, cardiac rhythm, blood pressure, the secretion of saliva, the secretion and peristalsis of the stomach and small intestine, chewing, swallowing, vomiting, and sneezing; these neuronal mechanisms also issue commands to the speech apparatus (the tongue and the muscles of the soft palate and larynx). This regulation occurs by means of signals proceeding through the sensory fibers of the somatic and autonomic craniocerebral nerves (from the skin, mucous membranes, and muscles of the head, taste receptors, heart, major blood vessels, respiratory tract, lungs, and alimentary canal) and by commands sent through the efferent nerve fibers to the muscular and glandular portions of these organs and to the corresponding skeletal muscles. Impairment of the above-mentioned functions as a result of bilateral injury to the medulla oblongata causes the severe syndrome called bulbar paralysis.

L. P. LATASH

References in periodicals archive ?
Prenatal and perinatal acrylamide disrupts the development of cerebrum and medulla oblongata in rat: biochemical and morphological studies," African Journal of Biotechnology, vol.
9 Different neuronal centers in medulla oblongata may be affected by gag reflex afferents or other trigger inputs from higher centers.
A third MRI scanning was performed 12 days later, which demonstrated hyperintense lesions on T2W, T1W, FLAIR and diffusion weighted images spreading over the basal ganglia, pons, cerebellum, medulla oblongata and middle cerebellar peduncle (Figure 2).
When the neurons die, their content is expelled into the extraneural space in the medulla oblongata.
While I was plenty accurate to get the job done had I been targeting the bad guy's medulla oblongata, I was unable to achieve quarter-MOA groups as others have.
medulla oblongata in general and the root entry zones [REZ] of cranial nerves 9 and 10 as well as the nucleus tract solitarius [NTS] in particular) as will be reviewed in a following section on surgical interventions for the treatment of medullary neurovascular compression.
The centre in medulla oblongata is very close to the vomiting, salivating and cardiac centre, explaining why gagging may be accompanied by additional reflex activity (Ex.
According to the press blurb Dirtbox aims to 'Happy slap your frontal lobes and squirt originality into your medulla oblongata from a hose pipe of absurdity.
The surgeons found arterial compression of the left lateral medulla oblongata in 51 of 53 hypertensive patients but not in patients with normal blood pressure.
2] level is adjusted for by the breathing centre in the brain (the medulla oblongata and pons) and breathing further adjusts to cope with these lower C[O.
Abnormalities of serotonin in regions of the medulla oblongata involved in this control have been reported in infants who have died from SIDS.
Perhaps there are neurons and synapses, dendrites and axons that spark from hippocampus to amygdala and thalamus and neo-cortex and that depend on the medulla oblongata to send breath to galvanize the body into speaking action.