Sunday, May 15, 2022

What Are Pons In The Brain

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Internal Anatomy Of The Pons

Pons, simplified sections of internal structure

The pons is recognized as having two major divisions: the ventral pons and the tegmentum The ventral pons is home to the pontine nuclei, structures that are responsible for the coordination of movement. These nuclei travel from the pons across the midline and form the middle cerebellar peduncles as they make their way to the cerebellum.

The tegmentum of the pons is considered to be the older region of the pons evolutionarily .

The tegmentum forms a part of the reticular formation, a network of nerves that extend from the medulla oblongata and connect to the spinal cord and thalamus.

Pontine Nuclei

These nuclei are a part of the pons that is concerned with motor activity. They are among the largest nuclei informing the cerebellum and provide some of the most important neuronal transmissions. The pontine nuclei are informed primarily by the cerebral cortex and project to the cerebellar hemispheres.

Reticular Formation

The reticular formation is a complex collection of nerve fibers and cell bodies that are comprised of both ascending and descending nerve tracts. Nuclei within the reticular formation are involved with the production of neurotransmitters, and associated with several cranial nerves, controlling both sensory and motor functions with the descending tracts and arousal and consciousness with the ascending tracts.

Causes Of Pons Stroke

An ischemic stroke occurs when a blood clot blocks blood flow through an artery to a certain region in the brain.

A hemorrhagic stroke occurs when a blood vessel breaks, reducing or halting the flow of blood to a region in the brain.

Ischemic and hemorrhagic strokes have the same basic result. Once the blood supply to part of the brain is interrupted, brain cells begin to die. This causes brain damage.

A hemorrhage can also cause damage to nearby brain structures. This is because the bleeding can cause pressure and irritation.

The blood vessels that supply blood to the pons and the rest of the brainstem are located in the back of the neck.

In rare cases, these may become injured as a result of neck injury, sudden pressure, or sudden movement of the head or neck. When this happens, a pons stroke may occur.

A stroke affects the physical and cognitive function of the part of the brain where it occurs. Cognitive functions include memory and thought. The extent of the damage depends on the location and size of the stroke.

Structure Of The Medulla Oblongata

The region between the anterior median and anterolateral sulci is occupied by an elevation on either side known as the pyramid of medulla oblongata. This elevation is caused by the corticospinal tract. In the lower part of the medulla, some of these fibers cross each other, thus obliterating the anterior median fissure. This is known as the decussation of the pyramids. Other fibers that originate from the anterior median fissure above the decussation of the pyramids and run laterally across the surface of the pons are known as the external arcuate fibers.

The region between the anterolateral and posterolateral sulcus in the upper part of the medulla is marked by a swelling known as the olivary body, caused by a large mass of gray matter known as the inferior olivary nucleus.

The posterior part of the medulla between the posterior median and posterolateral sulci contains tracts that enter it from the posterior funiculus of the spinal cord. These are the fasciculus gracilis, lying medially next to the midline, and the fasciculus cuneatus, lying laterally.

The lower part of the medulla, immediately lateral to the fasciculus cuneatus, is marked by another longitudinal elevation known as the tuberculum cinereum. It is caused by an underlying collection of gray matter known as the spinal nucleus of the trigeminal nerve. The gray matter of this nucleus is covered by a layer of nerve fibers that form the spinal tract of the trigeminal nerve.

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Injuries To The Pons Can Disrupt Any Or All Of Its Functions

Strokes that affect the pons, called pontine strokes, are the most common way injuries occur that affect the pons. Other ways a person can suffer injuries to this area include:

  • Brain tumors

No matter how they occur, injuries to the pons can be either complete or incomplete. An incomplete injury can cause impairments related to:

  • Motor function

Function Of The Medulla Oblongata

Midbrain and Pons

The medulla oblongata controls autonomic functions and connects the higher levels of the brain to the spinal cord. It is also responsible for regulating several basic functions of the autonomic nervous system, including:

  • Respiration: chemoreceptors
  • Reflex centers of vomiting, coughing, sneezing, and swallowing

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Side Effects Of Pontine Stroke

Once the pontine stroke has been treated and blood flow has been restored in the brain, the medical team will assess the side effects of the stroke.

When the pons becomes damaged by stroke, it can cause the following side effects:

  • Impaired breathing
  • Loss of consciousness
  • Weakness in the limbs
  • Swallowing and speech difficulty

The larger the stroke was, the more severe the side effects will be. For example, locked-in syndrome is a chronic condition that involves paralysis everywhere except for the eyes.

If a person sustains a massive pontine stroke, the chances are higher for experiencing chronic side effects like this.

Fortunately, some of these side effects can be restored through stroke rehabilitation.

Blood Supply And Lymphatics

Three groups of arteries from posterior circulation provide blood supply to the pons: anteromedial, lateral, and dorsal. The anteromedial group of arteries originates from the terminal branches of the vertebral artery and the basilar artery that nourish the paramedian ventral pons , bilateral medial longitudinal fasciculus , medial lemniscus, and abducens nucleus.

The lateral group of arteries derives mainly from the superior cerebellar artery, anterior inferior cerebellar artery, and long pontine arteries. Perforating branches of lateral group arteries nourish the superior cerebellar peduncle, motor and main sensory trigeminal nuclei, central tegmental tract, superior olivary nucleus, pontine reticular nucleus, abducens nerve nucleus, facial nerve nucleus, and locus ceruleus. Terminal superior cerebellar arteries provide the arterial supply of the dorsal pons that perfuse the superior cerebellar peduncle, the mesencephalic nucleus of the CN V, and the locus ceruleus.

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What Is The Pons And What Does It Do

Instead of attempting to identify one overall function for the pons, it is better to think of the structure as a collection of various tracts and nuclei, all with their own functions. Although describing the pons in this way may make it sound like the pons is involved with a confusing hodgepodge of activities, it is a more accurate approach than attempting to summarize the functions of the pons in just a few actions.

The most prominent feature of the pons is the bridge-like portion of it from where its name is derived. Despite appearing like a bridge, however, the basal pons is not a direct connection between the two cerebellar hemispheres. Instead, fibers that travel down from the cortex synapse on a variety of nuclei here called pontine nuclei. Then, groups of fibers project from the pontine nuclei on one side of the pons, cross to the other side of the pons, and come together to form the middle cerebellar peduncles. The middle cerebellar peduncles are large bundles of fibers that connect the pons to the cerebellum, which thus make up the connecting portions of the “bridge.” They represent one of the major pathways for information to travel from the brain and brainstem to the cerebellum.

Comparison With Areas Near The Lpt

Neurology | Pons Anatomy & Function

Although the vlPAG and PPT are in close proximity to the LPT, the connectivity of these GABAergic neurons is different from that of the LPT. Whereas vlPAG GABAergic neurons primarily receive inputs from the ventral medulla, the SLD, and the LHA , the LPT is mainly innervated by the SC and SNr. In contrast to LPT GABAergic neurons, the vlPAG has major projections to the RMg and nearby areas, commonly known as the rostral ventral medulla . Moreover, PPT GABAergic neurons are rarely innervated by the SNr , while LPT GABAergic neurons are strongly innervated by this area.

There are also clear differences in the physiological and pathological functions of the LPT, vlPAG, and PPT. GABAergic neurons in the vlPAG are important for the sleep-wake cycle, micturition, and nociception. In addition, optogenetic studies revealed that vlPAG GABAergic neurons regulated non-REM and REM sleep . Other studies based on genetically engineered systems showed that activation of vlPAG GABAergic neurons delayed detrusor contraction and inhibited voiding . In contrast, PPT GABAergic neurons are mostly involved in gait and balance regulation, a function that is not identified in LPT GABAergic neurons. For example, loss of rostral PPT GABAergic neurons was reported in Parkinson√Ęs disease patients with gait and balance disorders . In spite of the close proximity of the vlPAG, PPT, and LPT GABAergic neurons, it is likely that these areas have distinguishing physiological and pathological roles.

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The Pons Controls Some Aspects Of Sleep/wake Cycles

Some aspects of regulating sleep/wake cycles occur in the pons, particularly deep sleep. Deep sleep is when dreaming is most likely to happen and is essential for getting the rest you need to function at optimum levels. Some people with injuries to the pons may require medication to regulate their sleep/wake cycles.

Nerve Tracts That Pass Through The Pons

There are four major nerve tracts that pass through the pons to control the sensory, autonomic, and voluntary functions of the body.

Corticospinal Tract

The corticospinal tract , also known as the pyramidal tract, comprises part of the descending nerve tracts that emerge from the pons into the spinal cord and into the peripheral nervous system. There are about 1 million nerve fibers that make up the CST, each of the transmitting neuronal information at speeds of 60m/s!

The CST travels through the corona radiata and posterior limb of the internal capsule to terminate in the brainstem. Once it reaches the brainstem, one of the structures it passes through, of course, is the pons. The CST controls many motor functions including spinal reflexes, and the most notable of the voluntary movements are the voluntary distal movements.

Corticobulbar Tract

This is a descending neuronal pathway responsible for innervating several of the cranial nerves, controlling the muscles in the face, tongue, jaw, and pharynx.

The cranial nerves that are supplied by the corticobulbar tract include the trigeminal nerve , facial nerve , accessory nerve , and the hypoglossal nerve .

Medial Lemniscus Tract

The nerve tract is part of a greater pathway called the dorsal column-medial lemniscal pathway, which is responsible for the transmission of sensory information related to fine tactile sensation, detection of vibrations, and proprioception .

Spinothalamic Tract

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Increase Pixel Dimensions Of Mri Of Brain

Another potential advancement which is not getting much attention is to increase the pixel size of the scan to 1024 by 768, from what is typically something more equivalent to 360 pixels by 240 This type of resolution is now common when scanning for tumors. Why not brain injury? The failure to ask for a higher resolution images if partially because of priorities. Tumors are thought to be more dangerous than hemosiderin. But the fundamental reason a more focused and higher resolution scan isnt asked for is that few neurologists or neuroradiologists have thought about the advantages to aiming a telescopic image. Shouldnt such higher processing power be directed at the frontal lobes? Wouldnt those particularly vulnerable undersides of the frontal lobes and get a closer look? What about the lower brain structures and at the brain stem, areas that are difficult to image conventionally?

With all tailored protocols, there is always a cost benefit analysis. A tailored MRI protocol costs more. A tailored MRI protocol costs requires more attention from the neuroradiologist. A tailored MRI protocol also extends the amount of time that the patient must stay in the scanner. Time in a scanner can be unpleasant and exceedingly boring. Faster scanning times are eliminating some of that disadvantage. The ultimate answer as to why these more tailored protocols arent done is that no one is demanding it.

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Stroke And The Pons Region Of The Brain

The Bridge Of The Brain: What Is The Pons?

The pons is a small region of the brain located in the brainstem. It is a relatively small part of the lower brain. It is sometimes also called the hindbrain.

The cerebral cortex is the outer layer of the brain. The medulla oblongata is the part of the brain that sends messages to the spinal cord. The pons connects these two structures.

This article discusses stroke and its impact on the pons. It also looks at the symptoms, causes and risk factors of stroke, as well as diagnosis and treatment.

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Pontine Stroke Recovery Time

As you can see, stroke rehabilitation revolves around rewiring the brain, and massed practice is very powerful for healing.

Its impossible to estimate your stroke recovery timeline because every stroke is different and therefore each person will take different amounts of time to heal.

There are some general patterns that can help give you an idea of what to expect after a stroke, though.

Typically, if the stroke was small, you can recover within about 6 months. If the stroke was massive, then recovery can take years.

Again, every stroke is different so its possible to have a very fast recovery from a massive pontine stroke just as its possible to recover slowly from a minor stroke.

Instead of focusing on how long things will take, focus on the steps you can take to maximize recovery, such as massed practice.

What Does The Pons Regulate

In addition to all these functions, the pons also plays a regulatory role in two vital processes.

One of those processes is deep sleep. As already mentioned, it is the most refreshing sleep that helps your brain process, consolidate, and store information. Sleep also frees up space in your brain, thus making room for even more useful information.

While youre sleeping, the pons sends signals to groups of muscles that are responsible for limb movements and body posture to rest along with the rest of your body. This, in turn, prevents you from acting out on your dreams, which can happen if your pons stop functioning properly.

The pons is also home to the pneumotaxic center, which allows it to regulate the breathing process.

This center is made up of a large number of nerve cells that monitor your oxygen levels throughout the day. At any given moment, the pneumotaxic center measures your breathing rate to determine how much air your body needs and how often you need to breathe in.

If the pneumotaxic center detects an increased need for oxygen, your breathing rate will increase. This most often happens while youre performing physically demanding tasks like running or exercising. Conversely, your breathing rate will decrease while youre resting as your body needs less oxygen then.

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Symptoms Of Pontine Stroke

When a stroke occurs, it results in the following symptoms that the American Stroke Association summarized in the acronym FAST:

  • Facial dropping
  • Slurred speech
  • Time is brain!

Pontine stroke may also have other unique symptoms such as dizziness and vertigo, likely because the pons controls your sense of equilibrium.

A pontine stroke can also result in weakness on both sides of the body, not just one side like most strokes. This can make pontine strokes difficult to diagnose without an MRI scan.

If you ever suspect that someone is having a stroke without typical symptoms, insist that your doctor take an MRI scan. Do not settle for anything less!

S Of The Brain And The Function Of Pons

Brain Stem Pons

The brain is comprised of 3 major sections the forebrain, the midbrain, and the hindbrain. The forebrain is comprised of: the thalamus, the cerebrum, and the hypothalamus. The midbrain houses the tegmentum and the tectum. Finally, the hindbrain consists of the cerebellum, medulla, and the pons . There are also 4 lobes: the occipital lobe, temporal lobe, frontal lobe, and finally the parietal lobe. Lets cover what each portion of the brain does:

  • Temporal lobe: associated with hearing, speech, memory, and it also has a part of emotions
  • Occipital lobe: responsible for vision
  • Frontal lobe: involved with emotion, reasoning, movement, judgment, and planning
  • Parietal lobe: involved with movement, recognition, sense of touch, language, and even temperature
  • Thalamus: receives sensory information that it then sends to the cerebral cortex. Think of it as a relay station
  • Cerebrum: comprised of different parts, is responsible for learning, memory, language, sensory processing, smell, and movement
  • Hypothalamus: controls body temperature, hunger, thirst, emotion, and sleep
  • Tegmentum: involved in motor function and controls movement
  • Tectum: involved in auditory and visual functions
  • Cerebellum: responsible for movement and coordination
  • Medulla oblongata: besides being responsible for why alligators are so cranky, controls breathing, digestion, sneezing, swallowing, and heart function

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What Does The Left Side Of The Brain Control

The left side of the brain is generally dominant for language and other logical tasks. This side of the brain is also used for math or various calculations, according to the University of Washington. The left side of the brain also controls muscles on the right side of the body. Sensory information from the bodys right side crosses over to the left side of the brain.

The ability to form words primarily lies in the left hemisphere, states the National Institute of Neurological Disorders and Stroke. Both hemispheres are divided into sections, or lobes, which specialize in different functions. The Brocas area, which is found on the left frontal lobe, enables thoughts to be transformed into words.

The left hemisphere of around 95 percent of right-handed individuals and 60 to 70 percent of left-handed persons is dominant for language, explains the University of Washington. The two specific areas of the brain that are important for language are named the Brocas area and Wernickes area.

As most of the signals from the brain to the body and vice versa cross over when reaching the brain, both left and right hemispheres control the opposite side of the body, notes the NINDS. Thus, when the left hemisphere is damaged, the right part of the body is affected. For instance, a stroke in the left hemisphere usually leaves the right arm and leg paralyzed.

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