Brainstem

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The brainstem (or brainstem ) is the posterior part of the brain, side by side and structurally continuous with the spinal cord. In the human brain the brain stem includes the midbrain, the pons, and the medulla oblongata. Sometimes diencephalon, the tail of the forebrain, is included.

The brain stem provides the main motor and sensory innervation to the face and neck through the cranial nerve. Of the twelve pairs of cranial nerves, ten pairs are from the brainstem. Although small, this is a very important part of the brain as the motor neuron connections and the sensory system from the main part of the brain to the entire body through the brain stem. These include the corticospinal (motor) tract, the medial dorsal lemniscus path (fine touch, vibration sensation, and proprioception), and the spinothalamic tract (pain, temperature, itching, and harsh touch).

The brainstem also plays an important role in the regulation of cardiac and respiratory function. It also regulates the central nervous system, and is essential in maintaining awareness and regulating the sleep cycle. The brain stem has many basic functions including heart rate, breathing, sleeping, and eating.

Video Brainstem

Structure

Middle Brain

The midbrain is divided into three parts: the tectum, the tegmentum, and the ventral tegmentum. The texts (Latin: roof), which form the ceiling. The tektum consists of a paired structure of the superior and inferior colliculi and is the dorsal cover of the cerebral aqueduct. The inferior colliculus, is the central central brain nucleus of the auditory pathway and receives input from some peripheral brain stem nuclei, as well as input from the auditory cortex. The inferior brachium (arms-like process) reaches to the medial geniculate nucleus of the diencephalon. Superior to the inferior colliculus, the superior colliculus marks the midbrain of the rostral. He is involved in special vision and sends his superior brachium to the geniculate lateral diencephalon. The tegmentum that forms the floor of the midbrain, and ventral to the cerebral ducts. Some of the nuclei, tracts, and reticular formations are here. The ventral tegmentum consists of coupled cerebral gaguncas. This sends the upper motor neuron axons.

The middle brain consists of:

• Periaqueductal gray: A gray matter area around the cerebral aqueduct, which contains various neurons involved in the pain desensitization pathway. Synapse neurons here and, when stimulated, cause activation of neurons in the core of raphe magnus, which then project downward to the posterior gray column of the spinal cord and prevent transmission of pain sensation.
• The oculomotor nerve nucleus: This is the third cranial nerve nucleus.
• Trochlear nerve nerve: This is the fourth cranial nerve.
• Red nucleus: This is the motor nucleus that sends the descending tract to the lower motor neurons.
• Substantia nigra pars compacta: This is the concentration of neurons in the ventral part of the midbrain that use dopamine as a neurotransmitter and is involved in motor and emotional function. This dysfunction is involved in Parkinson's disease.
• Reticular formation: This is a large area of ​​the midbrain involved in important functions of the midbrain. In particular, it contains lower motor neurons, is involved in pain desensitization pathways, is involved in the awareness and awareness system, and contains the coeruleus locus, which is involved in intensive alert modulation and autonomous reflexes.
• Central tegmental tract: Directly anterior to the fourth ventricle floor, this is the pathway through which many tracts point to the cortex and to the spinal cord.
• Ventral tegmental area: Dopaminergic nuclei located near the midline on the floor of the midbrain.
• Genomial tegmental nucleus: GABAergic nucleus located adjacent to the ventral tegmental area.

Pons

The punch is between the medulla oblongata and the midbrain. It contains a channel that carries signals from the cerebrum to the medulla and to the cerebellum as well as the channel carrying the sensory signal to the thalamus. Pons are connected to the cerebellum by cerebellar peduncle. Pons home the respiratory center of the pneumothorax and apneustic center that make up the pontine respiratory group in the respiratory center. Pons coordinates cerebellar cleavage activities.

Medulla oblongata

Medulla oblongata often just referred to as the medulla, is the underside of the brainstem continuously with the spinal cord. The top is continuous with the puncher. The medulla contains the heart, respiratory, vomiting and vasomotor centers associated with heart rate, breathing, and blood pressure.

Ventral view of medulla and pons

In the medial part of the medulla is the anterior median fissure. The lateral moves on each side are medullary pyramids. The pyramid contains fibers from the corticospinal tract (also called the pyramid tract), or the upper motor neuron axle when their head is inferior to the synapse in the lower nerve cell underneath the motor in the anterior gray column of the spinal cord.

Anterolateral sulcus is on the lateral pyramid. Emerging from the anterolateral sulci is the root of CN XII (hypoglossal nerve). Lateral for this root and anterolateral sulci are olives. Olive is a swelling in the medulla that contains the underlying nuclei of the inferior nucleus (containing various nuclei and afferent fibers). Lateral (and dorsal) to olive is the root for CN IX (glossopharyngeal), CN X (vagus) and CN XI (accessory nerve). The pyramid ends at the intersection of the medulla pontine, noted most clearly by large basaltons. From this junction, CN VI (nerve abducens), CN VII (facial nerve) and CN VIII (vestibulocochlear nerve) appear. At the mid-level, CN V (trigeminal nerve) appears. The cranial nerve III (oculomotor nerve) appears ventrally from the midbrain, while CN IV (the troklear nerve) appears out of the dorsal aspect of the midbrain.

Between the two pyramids can be seen a decrease in fiber that marks the transition from the medulla to the spinal cord. The medulla is above the decussation and spinal cord below.

Dorsal view of medulla and pons

The medulla's most medullary part is the posterior sulcus median. The lateral moves on each side are fasciculus gracilis, and lateral which is cuneatus fasciculus. Superior to each, and directly inferior to the obex, are gracile and cuneate tubercle, respectively. Underlying this is the core of each. Obex marks the end of the fourth ventricle and the beginning of the central canal. The posterior intermediate syringe separates the fasciculus gracilis from the fasciculus cuneatus. Lateral in the fasciculus cuneatus is lateral funiculus.

Superior to obex is the fourth ventricle floor. On the fourth floor of the ventricle, various nuclei can be visualized by the small protrusions they make in the upper tissues. In the midline and directly superior to the obeks is the vagal and trigon higher than that hypoglossal trigonic. The underlying one is the motor nucleus for each cranial nerve. Superior to this trigon is a fiber that runs in both directions laterally. These fibers are known collectively as medullares striae. Continuing in the rostral direction, a large bump is called colliculi face. Each facial colliculus, contrary to their name, does not contain the facial nerve nuclei. Instead, they have a facial nerve axis that crosses the superficial to the underlying nucleus abducens (CN VI). Lateral for all the lumps discussed earlier is the indentation line, or the sulcus that runs rostral, and is known as the pyramid sulcus. It separates the medial motor neurons from the lateral sensory neurons. Lateral on the pyramid sulcus is the area of ​​the vestibular system, which is involved in special sensations. Moving rostrally, inferior, inferior, and superior serebellar pedunkle is found to link the midbrain to the cerebellum. Directly rostral to superior cerebral gag, there is superior medullary velum and then two troklear nerves. This marks the end of the punch as the inferior colliculus directly rostral and marks the midbrain of the tail. Middle cerebellar peduncle lies inferior and lateral to the superior peduncellar peduncle, connecting the pons to the cerebellum. Similarly, the inferior pedunkle pedunkle is found linking the medulla oblongata to the cerebellum.

Maps Brainstem

Development

The adult human brain stem arises from two of the three major vesicles formed from the neural tube. Mesencephalon is the second of three major vesicles, and no further differentiates into secondary vesicles. It will be the midbrain. The third primary vesicle, rhombencephalon (rear brain) will further differentiate into two secondary vesicles, metencephalon and myelencephalon. Metencephalon will be the cerebellum and the pons. The more caudal Myelencephalon will become the medulla.

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Blood supply

The main supply of blood to the brain stem is provided by the basilar artery and the vertebral artery.

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Cranial nerves

Ten of the twelve pairs of cranial nerves either target or are sourced from the brainstem. The oculomotor (III) and trolear (IV) nerve nuclei are located in the midbrain. The trigeminal nerve nucleus (V), nerve abducens (VI), facial nerve (VII) and vestibulocochlear nerve (VIII) are located in the pons. The core of the glossopharyngeal nerve (IX), vagus nerve (X), accessory nerve (XI) and hypoglossal nerve (XII) lies in the medulla. These cranial nerve fibers come out of the brain stem of this nuclei.

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Function

There are three main functions of the brainstem:

1. The brainstem plays a role in conduction. That is, all information is delivered from the body to the cerebrum and cerebellum and vice versa should cross the brainstem. The ascending pathways that pass from the body to the brain are the sensory pathways and include the spinotalamic tract for pain and temperature sensation and the medial dorsal-leminal dorsal path (DCML) including the fasciculus gracile and fasciculus cuneate for touch, proprioception, and pressure. sensation. Facial sensations have similar pathways, and will move in the spinothalamic and DCML tracts. The Descending Tract is a top motor neuron akson that is destined to synapse in the lower motor neurons in the ventral horn and the posterior horn. In addition, there are top motor neurons derived from the vestibular nuclei, red, tektal, and reticular brain stem, which are also down and synced in the spinal cord.
2. The III-XII cranial nerve arises from the brain stem. This cranial nerve supplies the face, head, and innards. (Two pairs of first cranial nerves arise from the cerebrum).
3. The brain stem has integrative functions involved in controlling the cardiovascular system, control of breathing, controlling pain sensitivity, alertness, awareness, and awareness. Thus, brainstem damage is a very serious and often life-threatening problem.

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Clinical significance

Brainstem disease can lead to cranial nerve abnormalities that may cause visual impairment, pupal abnormalities, sensation changes, muscle weakness, hearing problems, vertigo, swallowing and speech impairment, voice changes, and coordination problems. The localization of neurological lesions in the brain stem may be very precise, although it depends on a clear understanding of the functioning of the brainstem anatomy structure and how it is tested.

Brainstem stroke syndrome can cause a variety of disorders including locked syndrome.

Duret bleeding is the area of ​​bleeding in the midbrain and upper pons due to traumatic displacement under the brainstem.

Cysts known as syrinxes can affect the brainstem, in a condition called syringobulbia. Cavities are filled in this fluid can be congenital, acquired or the result of a tumor.

The criteria for claiming brain stem deaths in the UK have been developed to make decisions when to stop ventilation of someone who can not sustain life. These determinants are that the patient can not regain consciousness and is unable to breathe without help. All other possible causes should be set aside which may indicate temporary conditions. The state of irreversible brain damage must be firm. There is a brainstem reflex examined by two senior physicians so imaging technology is not required. The absence of cough and gag reflexes, from corneal reflexes and vestibulo-ocular reflexes needs to be established; pupils must be repaired and dilated; there must be a lack of motor response to stimulation and absence of breathing characterized by the concentration of carbon dioxide in arterial blood. All of these tests should be repeated after a certain time before death can be stated.

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Additional images

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See also

• Tritilian brain brain

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References

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External links

• Comparative Neuroscience at Wikiversity
• http://www.meddean.luc.edu/lumen/Meded/Neuro/frames/nlBSsL/nl40fr.htm
• http://biology.about.com/library/organs/brain/blbrainstem.htm
• http://www.waiting.com/brainanatomy.html
• http://braininjuryhelp.com/video-tutorial/brain-injury-help-video-tutorial/
• http://www.martindalecenter.com/MedicalAnatomy_3_SAD.html
• NIF Search - Brainstem via the Neuroscience Information Framework

Source of the article : Wikipedia