Thursday, June 16, 2022

What Part Of The Brain Controls Swallowing

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The Natural Swallowing Process From Mouth To Stomach

Swallowing Reflex, Phases and Overview of Neural Control, Animation.

Here we will look at all the phases of swallowing and how the signals flow from mouth to brain to pharynx, esophagus, diaphragm and stomach. During a day a normal person swallows approximately 600 times: 350 of these are during the day, 200 when eating, and 50 times when asleep .

Simply described, the swallowing process starts when we transfer food from the plate to our mouths .

After this we close our lips, chew, reduce the food to manageable pieces and mix it with saliva. And then immediately before the swallowing reflex is triggered we press our lips together creating a low pressure in our mouths , this activity takes up to 10 seconds.

The chewing is carried out with the tongues upwards and backwards movements towards the pharynx. At the same time the floor of the mouth is raised. The decrease in pressure in the mouth eases the transport of the food mixture from the mouth to the pharynx.

Right Brain Left Brain

The cerebrum is divided into two halves: the right and left hemispheres They are joined by a bundle of fibers called the corpus callosum that transmits messages from one side to the other. Each hemisphere controls the opposite side of the body. If a stroke occurs on the right side of the brain, your left arm or leg may be weak or paralyzed.

Not all functions of the hemispheres are shared. In general, the left hemisphere controls speech, comprehension, arithmetic, and writing. The right hemisphere controls creativity, spatial ability, artistic, and musical skills. The left hemisphere is dominant in hand use and language in about 92% of people.

B Rhythmic Swallowing Movements

Rhythmic swallowing behavior can occur during physiological activities such as drinking, which involves a train of closely spaced swallows. It has been reported that depending on the amount of liquid being drunk, several successive swallows occur, numbering up to 100 in horses . Under experimental conditions, the best way of inducing rhythmic swallowing is to apply long-lasting repetitive stimulation to the SLN . Under repetitive stimulation of the SLN, at 20â30 Hz, swallowing rates of 1â2/s can be readily induced in species such as rats and sheep during short periods of time . Even during very long-lasting stimulation, the rhythmic pattern can continue, although obviously with a lower frequency. Under urethane anesthesia for example, a dog can swallow repetitively for 1 h at a rate of 0.4 Hz . In fact, as long as there is a bolus to swallow, or at least saliva, it is possible to observe sustained swallowing at a rapid rate with only slight signs of fatigue.

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B Supramedullary Influences On Swallowing

Experimental data have shown that the basic swallowing pattern can be induced without any supramedullary structures being involved. Under physiological conditions, however, the swallowing network receives inputs from higher centers, and several cortical and subcortical structures also influence swallowing . The fact that an individual can swallow voluntarily without the existence of any need to ingest food or to protect the upper airways shows that the medullary swallowing network can be activated at least by inputs from the cerebral cortex. In addition, several clinical reports have indicated that cortical dysfunction of the kind resulting from cerebrovascular accidents, cerebral palsy, or neurological diseases such as Parkinsonism, may result in dysphagia or swallowing impairments or may affect esophageal peristalsis . These observations point to the involvement of supramedullary influences, although the peripheral afferent pathway and the CPG, which is localized in the caudal brain stem, seem to remain unaltered in these patients.

The Function Of The Three Swallowing Centres

Neurophysiology and Neuroplasticity Studies  Purdue I

The NTS in the brain stem, which gathers all incoming signals from the oral cavity and the pharynx, sends a part of this information directly to the first of the three swallowing centres in the brain stem, whilst the remainder of the information continues upwards to the cortex to be processed before being switched back to the first swallowing centre.

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Animal Studies Of Brain Stem Control For Swallowing

Extensive work has been conducted in mammals on the brain stem pathways involved in swallowing . The pharyngeal phase of swallowing has been studied extensively in the rat and two regions found involving central patterning for swallowing one in the dorsal medulla activated by inputs to nucleus tractus solitarius referred to as the dorsal swallowing group and the other involving more ventral regions with inputs to the nucleus ambiguus, hypoglossal and other cranial muscle nuclei .

Brain Injury And Speech

What happens if one or more of these parts is injured, damaged, or abnormal?

If you have a problem speaking or understanding speech, its a condition called aphasia. If you have trouble putting together the correct muscle movements necessary to produce speech, its a condition called .

Both aphasia and apraxia are most often caused by a stroke or trauma to the brain, usually when the left side of the brain is affected. Other less common causes are brain tumors and infections.

Symptoms of aphasia or apraxia depend on where the damage occurs in the brain and the severity of the damage. These symptoms include:

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S Of The Brain Involved In Speech

In recent decades, there has been an explosion of research into language processing in the brain. Its now generally accepted that the control of speech is part of a complex network in the brain.

The formation of speech requires many different processes, from putting thoughts into words, forming a comprehensible sentence, and then actually making the mouth move to make the correct sounds.

There are several areas of the brain known to play a role in speech:

Anatomy Of The Autonomic Nervous System

What are the different parts of the brain and what do they do? | Cancer Research UK

The autonomic nervous system Autonomic nervous system The peripheral nervous system consists of more than 100 billion nerve cells that run throughout the body like strings, making connections with the brain, other parts of the body, and⦠read more is the part of the nervous system that supplies the internal organs, including the blood vessels, stomach, intestine, liver, kidneys, bladder, genitals, lungs, pupils, heart, and sweat, salivary, and digestive glands.

The autonomic nervous system has two main divisions:

  • Sympathetic

  • Parasympathetic

After the autonomic nervous system receives information about the body and external environment, it responds by stimulating body processes, usually through the sympathetic division, or inhibiting them, usually through the parasympathetic division.

An autonomic nerve pathway involves two nerve cells. One cell is located in the brain stem Brain stem The brains functions are both mysterious and remarkable, relying on billions of nerve cells and the internal communication between them. All thoughts, beliefs, memories, behaviors, and moods⦠read more or spinal cord. It is connected by nerve fibers to the other cell, which is located in a cluster of nerve cells . Nerve fibers from these ganglia connect with internal organs. Most of the ganglia for the sympathetic division are located just outside the spinal cord on both sides of it. The ganglia for the parasympathetic division are located near or in the organs they connect with.

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What Part Of The Brain Controls Speech

Your brain is responsible for nearly all functions of your body and for interpreting sensory information from the world around you.

Your brain has many parts but speech is primarily controlled by the largest part of the brain, the cerebrum.

The cerebrum can be divided into two parts, called hemispheres, which are joined by a band of nerve fibers called the corpus callosum.

Your speech is typically governed by the left side of your cerebrum. In about a third of people who are left-handed, however, speech may actually be controlled by the right side.

Connections Between The Various Neuronal Groups

The latency of the synaptic response is shorter among the neurons of the DSG than those of the VSG. In the case of SLN stimulation, the latency is 1â4 ms in the DSG and 7â12 ms in the VSG . A synaptic response can also be initiated in swallowing neurons by stimulating a specific cortical area, which induces swallowing . Here again, the latency of the response is shorter in the NTS swallowing neurons than in the neurons in the ventrolateral medulla . These results suggest that the neurons of the VSG are probably activated via neurons of the DSG. Indeed, regardless of which afferent pathway is stimulated, the initial response of the VSG neurons is abolished after lesion of the DSG . Although no direct evidence is available at the single cell level that a connection of this kind exists between the DSG and VSG, connections between the NTS region and the ventrolateral reticular formation surrounding the nucleus ambiguus, where swallowing neurons are located, have been found to exist in several anatomical experiments . Other anatomical results have shown that the ventrolateral medulla also projects to the NTS region . However, whether or not these possible reciprocal connections are involved in swallowing still remains to be established.

Esophageal DSG neuronsE

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Study Types And Characteristics

Of the 22 articles included in the review, one was a case study , and 21 included multiple participants and were observational, i.e., there was no intervention assessed . The most frequent observational study design employed was retrospective cohort , followed by three case control studies, and one prospective cohort study. Six studies did not neatly fit into one of the main observational study categories . Four of these were closest to a prospective cohort design . However, instead of examining whether an outcome of interest would develop over time, these four studies included only participants who had already failed a dysphagia screening or were diagnosed with dysphagia. One study identified a convenience sample with a common diagnosis and used observational methods to determine dysphagia status , and one study recruited healthy individuals to look at both a risk factor and changes in swallowing . Because these six studies did not fit into a specific pre-defined study type, but all involved carefully defined groups of subjects, we identified them broadly as âcohort design.â

Table 2. Demographics and participant characteristics across studies.

The Cerebellum And Neurostimulation


As stated previously, pyramidal neurones in the cerebellar cortex connect to and communicate with deep nuclei within the cerebellum . These in turn communicate with cerebral motor cortical areas . The most well studied cerebello-cortical pathway involves the dentate motor nuclei located in both cerebellar hemispheres . When stimulated, these communicate with the thalamus before crossing over to terminate in the contralateral motor cortical hemisphere .

Fig. 1

Some functional imaging studies have highlighted greater swallowing related activation of the left cerebellar hemisphere compared to the right . The significance of this finding is currently unknown but if investigated and confirmed, future studies may indicate the existence of cerebellar swallowing area hemispheric asymmetry in a manner reminiscent of the known phenomenon of cortical hemispheric pharyngeal area asymmetry .

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Signals Down To The Muscles And Glands Via Motor Neurons

The nerves can be thought of as cables that contain various fibres, motor neurons, that conduct signals to the muscles and glands. In the brain stem there are three different kinds of motor neurons that are important in the act of swallowing:

  • General Somatic Efferent The GSE transmits signals onwards to the tongues and the eyes voluntary musculature, .
  • Special Visceral Efferent The SVE transmits signals to the voluntary musculature in the mouth, chewing muscles, facial musculature, pharynx, larynx, esophagus and diaphragm. Note however that the neurological connection to the diaphragm is somewhat more complex.
  • General Visceral Efferent The GVE transmits signals to the glands, blood vessels and smooth muscles in the pharynx, stomach and rectum.
  • The signal pathways from the above-named motor neurons are:

    • CN Trigeminus signals via the SVE
    • CN Facialis signals via the SVE and the GVE
    • CN Glossopharyngeus signals via the SVE and the GVE
    • CN Vagus signals via the SVE
    • CN Hypoglossus signals via the GSE

    The sum of all the above signals to the brain stem set off a pre-programmed cooperation between all 148 muscles that are involved in the transport of each food bite from the mouth down to the stomach.

    Function Of The Medulla Oblongata

    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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    Can You Recover From A Brainstem Injury

    A brainstem injury can have severe effects because the brainstem controls so many of your bodys most basic functions. But people do recover from some types of brainstem injuries.

    Its important to get care right away if you suspect a brainstem injury. The sooner you get care, the more likely your healthcare providers can reduce the damage. You may need rehabilitation and other special care after a brainstem injury.

    Role Of Sensory Stimulation For Modulating Human Swallowing

    Brain fog, breathing and swallowing difficulty, dizziness, tinnitus – treated with Prolotherapy

    Evidence that changes in sensory stimulation can alter the frequency of swallowing is available and studies have shown that different types of stimuli can enhance cortical activation in the same regions that are active for swallowing . Brain stem studies cited earlier have shown that sensory stimulation can invoke fictive swallowing in anesthetized animals however, the degree to which sensory stimulation also modulated cortical activity and central control of swallowing has both theoretical and practical importance. A study in dysphagia early post stroke demonstrated that recovery of swallowing was enhanced by electrical stimulation in the pharynx providing enhanced sensation from that region . The role of sensory function in executing swallowing was also demonstrated by the disruption of swallowing in healthy volunteers due to a bilateral dysruption of sensory input from the superior laryngeal nerve .

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    Cranial Nerves And Muscles Involved In Swallowing

    Swallowing occurs in three sequential phases, all requiring the careful coordination of muscles in the mouth, pharynx , larynx , and esophagus . These muscles are all under the control of a group of nerves called your cranial nerves.

    The cranial nerves are 12 pairs of nerves that emerge from the brainstem, located at the base of your brain. Your cranial nerves control functions such as smelling, tasting, swallowing, seeing, moving your face and eyes, and shrugging your shoulders. Several of the cranial nerves are involved with controlling the coordination and movements involved in chewing and swallowing.

    The following cranial nerves are involved in swallowing:

    • Trigeminal
    • Vagus
    • Hypoglossal nerve

    In turn, cranial nerves are controlled by processing centers in the brain where information related to swallowing is processed. These centers include areas located in the cerebral cortex, the medulla oblongata, and the cranial nerve nuclei.

    Data Extraction And Qualitative Synthesis

    After completion of the bias assessment, the two first authors independently extracted data from all articles. Information extracted from each paper included study type and population characteristics, white matter techniques and information, swallowing evaluation methods, outcome measurements, and main findings from each study.

    Extracted data on study type and population characteristics included: study design , number of patients, number of participants in control group , underlying diagnosis/disease of patient group or subgroups, severity/state of disease, age, sex, race, and ethnicity. Data extracted on white matter measurement included: scan type, scanner model and strength, head coil type, b-values, and number of directions , scan settings, analysis type, and analysis method.

    We also extracted details on how the primary outcome variable was assessed in order to compare clinical findings across studies. Data extracted included swallowing measurement method and analysis of swallowing components , temporal measures, binary clinical ratings, etc.). Finally, information was extracted on the studies’ main findings, which included implicated white matter areas and their suggested role in swallowing , and limitations of each study.

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    Central Nervous System Control Of The Laryngeal Musculature In The Brain Stem

    Innervation of the laryngeal muscles is essential for both voice and swallowing. For voice, both vocal folds must be moved to the midline so they can be set into vibration by airflow from the lungs. The relationship between cricothyroid and thyroarytenoid determines the tension and rate of vibration or fundamental frequency . This is precisely controlled by auditory feedback during voice production . For swallowing, vocal fold and ventricular or false fold closure prevent the aspiration of food or liquid into the trachea and lungs. Thus bilateral vocal fold function is essential to both systems.

    Cortical control of the laryngeal musculature is bilateral within each hemisphere in non-human primates electrical stimulation of the laryngeal muscle area in the primary motor cortex in either hemisphere will induce bilateral vocal fold closure in anesthetized animals . Infarcts affecting the cortical primary motor on one side can induce paralysis in the contralateral limb, brain injury affecting the cortical primary motor area for the laryngeal muscles on one side do not produce vocal fold paralysis likely due to bilateral cortical control of the laryngeal musculature in each hemisphere. In fact vocal fold paralysis due to central nervous system lesions only occur in Wallenberg syndrome with infarction of the vertebral artery or the posterior inferior cerebellar artery on one side in the medial and lateral medulla .

    How Swallowing Is Affected By Stroke

    physiology of deglutition by ROOHIA

    As you can see, there are multiple areas of the central nervous system which, if affected by a stroke or another neurological condition like multiple sclerosis, Parkinson’s disease, or dementia, could disrupt the ability to swallow.

    Even more so, the medulla is a relatively small area of the brainstem that contains multiple structures that are critical in carrying out the swallowing reflexso strokes that involve the medulla are especially likely to cause swallowing problems. In fact, people with medullary strokes may require temporary or permanent feeding tube placement to prevent choking and aspiration pneumonia.

    Guidelines published in 2019 by the American Heart Association for treatment of patients with stroke recommend early screening for dysphagia to prevent potential aspiration and avoid related illness. The AHA also recommends feeding tubes for patients with dysphagia for at least the few days immediately following a stroke as doctors continue to check for problems with swallowing.

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