Medulla oblongata
From Wikipedia, the free encyclopedia
| Brain: Medulla oblongata | ||
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| Beginning of medulla oblongata in the human brain | ||
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| Section of the medulla oblongata at about the middle of the olive. | ||
| Latin | medulla oblongata | |
| Gray's | subject #187 767 | |
| NeuroNames | hier-695 | |
| MeSH | A08.186.211.132.810.406 | |
| Dorlands/Elsevier | m_06/12519731 | |
The medulla oblongata is the lower portion of the brainstem. By anatomical terms of location, it is rostral to the spinal cord and caudal to the pons, which is in turn ventral to the cerebellum. For a human or other bipedal species, this means it is above the spinal cord, below the pons, and anterior to the cerebellum. It controls autonomic functions and relays nerve signals between the brain and spinal cord.
The medulla is often thought of as being in two parts, an open part (close to the pons), and a closed part (further down towards the spinal cord). The 'opening' referred to is on the dorsal side of the medulla, and forms part of the fourth ventricle of the brain.
Running down the ventral aspect of the medulla are the pyramids which contain corticospinal fibres. On the open medulla, there is a slight bulge just behind the pyramids called the olive or olivary nuclei. Cranial nerve XII (the hypoglossal nerve) emerges between these two structures. Cranial nerves IX and X (glossopharyngeal and vagus nerves) also emerge from the medulla.
The base of the medulla is defined by the commissural fibres, crossing over from the ipsilateral side in the spinal cord to the contralateral side in the brain stem - below this is the spinal cord.
The Medulla oblongata is responsible for controlling several major autonomic functions of the body, including respiration, blood pressure, heart rate, and reflex arcs.
Contents |
[edit] Blood supply
Blood to the medulla is supplied by a number of arteries.
- Direct branches of the vertebral artery
- Posterior inferior cerebellar artery (PICA)
- Anterior spinal artery
The anterior spinal artery supplies the whole medial part of the medulla oblongata. A blockage (such as in a stroke) will injure the pyramidal tract, medial lemniscus and the hypoglossal nucleus. This causes a syndrome called medial medullary syndrome.
The posterior inferior cerebellar artery, a major branch of the vertebral artery, supplies the posterolateral part of the medulla, where the main sensory tracts run and synapse. (As the name implies, it also supplies some of the cerebellum.)
The vertebral artery supplies an area between the other two main butt cheeks, including the nucleus solitarius and other sensory nuclei and fibres. Lateral medullary syndrome can be caused by occlusion of either the PICA or the vertebral arteries.
* Relays Nerve Signals Between the Brain and Spinal Cord
[edit] Effects on the Body
Some specialised Special Forces units, notably the anti-terrorist divisions who specialise in close-quarter combat and hostage rescue situations (i.e. S.A.S.) are trained to shoot through the target's head just below the nose and eviscerate the medulla oblongata. This will cause the subject's motor-functions to immediately cease working so that their trigger finger will not clench or spasm causing their weapon to fire uncontrollably. This is not the only technique used to reduce the chance of a target's muscles spasming when they are shot, but is one of the most simple and reliable techniques known.
[edit] Additional images
 Lobes |
 Pituitary and pineal glands |
 Anteroinferior view of the medulla oblongata and pons. |
