Vasomotor center

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Vasomotor center
Details
Part of Medulla
Identifiers
Acronym(s)VMC
MeSH D014666
Anatomical terminology

The vasomotor center (VMC) is a portion of the medulla oblongata. Together with the cardiovascular center and respiratory center, it regulates blood pressure. [1] It also has a more minor role in other homeostatic processes.[ citation needed ] Upon increase in carbon dioxide level at central chemoreceptors, it stimulates the sympathetic system to constrict vessels. This is opposite to carbon dioxide in tissues causing vasodilatation, especially in the brain. [2] Cranial nerves IX (glossopharyngeal nerve) and X (vagus nerve) both feed into the vasomotor centre and are themselves involved in the regulation of blood pressure.

Contents

Structure

The vasomotor center is a collection of integrating neurons in the medulla oblongata of the middle brain stem. The term "vasomotor center" is not truly accurate, since this function relies not on a single brain structure ("center") but rather represents a network of interacting neurons. [3]

Afferent fibres

The vasomotor center integrates nerve impulses from many places via the solitary nucleus: [4]

Efferent fibres

The vasomotor center gives off sympathetic fibres through the spinal cord and sympathetic ganglia, which reach vascular smooth muscle. [6]

Function

The vasomotor center changes vascular smooth muscle tone. [1] [5] This changes local and systemic blood pressure. [1]

A drop in blood pressure leads to increased sympathetic tone from the vasomotor center. [7] This acts to raise blood pressure. [7]

Clinical significance

Methyldopa acts on the vasomotor center, leading to selective stimulation of α2-adrenergic receptor. [8] Guanfacine also causes the same stimulation. [9] This reduces sympathetic tone to vascular smooth muscle. [9] This reduces heart rate and vascular resistance. [9]

Digoxin increases vagal tone from the vasomotor centre, which decreases pulse. [7]

G-series nerve agents have their most potent effect in the vasomotor center. [10] Unlike other parts of the body, where continued stimulation of acetylcholine receptors leads to recoverable paralysis, overstimulation of the vasomotor center is often causes a fatal rise in blood pressure. [11]

History

The localization of vasomotor center was determined by Filipp Ovsyannikov in 1871. [10]

See also

Related Research Articles

<span class="mw-page-title-main">Autonomic nervous system</span> Division of the nervous system supplying internal organs, smooth muscle and glands

The autonomic nervous system (ANS), formerly referred to as the vegetative nervous system, is a division of the nervous system that operates internal organs, smooth muscle and glands. The autonomic nervous system is a control system that acts largely unconsciously and regulates bodily functions, such as the heart rate, its force of contraction, digestion, respiratory rate, pupillary response, urination, and sexual arousal. This system is the primary mechanism in control of the fight-or-flight response.

<span class="mw-page-title-main">Medulla oblongata</span> Structure of the brain stem

The medulla oblongata or simply medulla is a long stem-like structure which makes up the lower part of the brainstem. It is anterior and partially inferior to the cerebellum. It is a cone-shaped neuronal mass responsible for autonomic (involuntary) functions, ranging from vomiting to sneezing. The medulla contains the cardiac, respiratory, vomiting and vasomotor centers, and therefore deals with the autonomic functions of breathing, heart rate and blood pressure as well as the sleep–wake cycle.

Baroreceptors are sensors located in the carotid sinus and in the aortic arch. They sense the blood pressure and relay the information to the brain, so that a proper blood pressure can be maintained.

<span class="mw-page-title-main">Glossopharyngeal nerve</span> Cranial nerve IX, for the tongue and pharynx

The glossopharyngeal nerve, also known as the ninth cranial nerve, cranial nerve IX, or simply CN IX, is a cranial nerve that exits the brainstem from the sides of the upper medulla, just anterior to the vagus nerve. Being a mixed nerve (sensorimotor), it carries afferent sensory and efferent motor information. The motor division of the glossopharyngeal nerve is derived from the basal plate of the embryonic medulla oblongata, whereas the sensory division originates from the cranial neural crest.

<span class="mw-page-title-main">Subclavian artery</span> Major arteries of the upper thorax, below the clavicle

In human anatomy, the subclavian arteries are paired major arteries of the upper thorax, below the clavicle. They receive blood from the aortic arch. The left subclavian artery supplies blood to the left arm and the right subclavian artery supplies blood to the right arm, with some branches supplying the head and thorax. On the left side of the body, the subclavian comes directly off the aortic arch, while on the right side it arises from the relatively short brachiocephalic artery when it bifurcates into the subclavian and the right common carotid artery.

<span class="mw-page-title-main">Adrenal medulla</span> Central part of the adrenal gland

The adrenal medulla is the inner part of the adrenal gland. It is located at the center of the gland, being surrounded by the adrenal cortex. It is the innermost part of the adrenal gland, consisting of chromaffin cells that secrete catecholamines, including epinephrine (adrenaline), norepinephrine (noradrenaline), and a small amount of dopamine, in response to stimulation by sympathetic preganglionic neurons.

A chemoreceptor, also known as chemosensor, is a specialized sensory receptor which transduces a chemical substance to generate a biological signal. This signal may be in the form of an action potential, if the chemoreceptor is a neuron, or in the form of a neurotransmitter that can activate a nerve fiber if the chemoreceptor is a specialized cell, such as taste receptors, or an internal peripheral chemoreceptor, such as the carotid bodies. In physiology, a chemoreceptor detects changes in the normal environment, such as an increase in blood levels of carbon dioxide (hypercapnia) or a decrease in blood levels of oxygen (hypoxia), and transmits that information to the central nervous system which engages body responses to restore homeostasis.

The control of ventilation is the physiological mechanisms involved in the control of breathing, which is the movement of air into and out of the lungs. Ventilation facilitates respiration. Respiration refers to the utilization of oxygen and balancing of carbon dioxide by the body as a whole, or by individual cells in cellular respiration.

<span class="mw-page-title-main">Carotid body</span>

The carotid body is a small cluster of chemoreceptor cells and supporting sustentacular cells situated at bifurcation of each common carotid artery in its adventitia.

<span class="mw-page-title-main">Solitary nucleus</span> Sensory nuclei in medulla oblongata

The solitary nucleus is a series of sensory nuclei forming a vertical column of grey matter in the medulla oblongata of the brainstem. It receives general visceral and/or special visceral inputs from the facial nerve, glossopharyngeal nerve and vagus nerve ; it receives and relays stimuli related to taste and visceral sensation. It sends outputs to various parts of the brain. Neuron cell bodies of the SN are roughly somatotopically arranged along its length according to function.

The cardiovascular centre is a part of the human brain which regulates heart rate through the nervous and endocrine systems. It is considered one of the vital centres of the medulla oblongata.

<span class="mw-page-title-main">Baroreflex</span> Homeostatic mechanism in the body

The baroreflex or baroreceptor reflex is one of the body's homeostatic mechanisms that helps to maintain blood pressure at nearly constant levels. The baroreflex provides a rapid negative feedback loop in which an elevated blood pressure causes the heart rate to decrease. Decreased blood pressure decreases baroreflex activation and causes heart rate to increase and to restore blood pressure levels. Their function is to sense pressure changes by responding to change in the tension of the arterial wall The baroreflex can begin to act in less than the duration of a cardiac cycle and thus baroreflex adjustments are key factors in dealing with postural hypotension, the tendency for blood pressure to decrease on standing due to gravity.

<span class="mw-page-title-main">Carotid sinus</span> Dilated area near internal carotid artery above bifurcation

In human anatomy, the carotid sinus is a dilated area at the base of the internal carotid artery just superior to the bifurcation of the internal carotid and external carotid at the level of the superior border of thyroid cartilage. The carotid sinus extends from the bifurcation to the "true" internal carotid artery. The carotid sinus is sensitive to pressure changes in the arterial blood at this level. It is the major baroreception site in humans and most mammals.

<span class="mw-page-title-main">Aortic body</span>

The aortic bodies are one of several small clusters of peripheral chemoreceptors located along the aortic arch. They are important in measuring partial pressures of oxygen and carbon dioxide in the blood, and blood pH.

<span class="mw-page-title-main">Tympanic nerve</span>

The tympanic nerve is a branch of the glossopharyngeal nerve found near the ear. It gives sensation to the middle ear, the Eustachian tube, the parotid gland, and mastoid air cells. It gives parasympathetic to supply to the parotid gland via the otic ganglion and the auriculotemporal nerve.

<span class="mw-page-title-main">Thoracic splanchnic nerves</span>

Thoracic splanchnic nerves are splanchnic nerves that arise from the sympathetic trunk in the thorax and travel inferiorly to provide sympathetic supply to the abdomen. The nerves contain preganglionic sympathetic fibers and general visceral afferent fibers.

<span class="mw-page-title-main">Carotid sinus nerve</span>

The carotid branch of the glossopharyngeal nerve is a small branch of the glossopharyngeal nerve that innervates the carotid sinus, and carotid body.

Central chemoreceptors of the central nervous system, located on the ventrolateral medullary surface in the vicinity of the exit of the 9th and 10th cranial nerves, are sensitive to the pH of their environment.

Bulbar palsy refers to a range of different signs and symptoms linked to impairment of function of the glossopharyngeal nerve, the vagus nerve, the accessory nerve, and the hypoglossal nerve. It is caused by a lower motor neuron lesion in the medulla oblongata, or from lesions to these nerves outside the brainstem, and also botulism. This may be caused by any of a number of genetic, vascular, degenerative, inflammatory, and other underlying conditions. It can be differentiated from pseudobulbar palsy. When there is airway obstruction, intubation is used.

The aortic nerve, also known as the aortic depressor nerve, is a branch of the vagus nerve. It supplies autonomic afferent nerve fibers to the peripheral baroreceptors and chemoreceptors found in the aortic arch.

References

  1. 1 2 3 Sear, John W. (January 1, 2019), Hemmings, Hugh C.; Egan, Talmage D. (eds.), "26 - Antihypertensive Drugs and Vasodilators", Pharmacology and Physiology for Anesthesia (Second Edition), Philadelphia: Elsevier, pp. 535–555, doi:10.1016/b978-0-323-48110-6.00026-0, ISBN   978-0-323-48110-6, S2CID   220688413 , retrieved November 29, 2020
  2. ↑ "Bionic blood pressure device being developed at Vanderbilt" . Retrieved October 6, 2008.
  3. ↑ Guyenet, Patrice G. (May 2006). "The sympathetic control of blood pressure". Nature Reviews. Neuroscience. 7 (5): 335–346. doi:10.1038/nrn1902. ISSN   1471-003X. PMID   16760914. S2CID   8752032.
  4. ↑ Northcott, Carrie A.; Haywood, Joseph R. (January 1, 2007), Lip, Gregory Y. H.; Hall, John E. (eds.), "Chapter 25 - Central Nervous System Control of Blood Pressure", Comprehensive Hypertension, Philadelphia: Mosby, pp. 281–290, doi: 10.1016/b978-0-323-03961-1.50028-3 , ISBN   978-0-323-03961-1
  5. 1 2 Schwarzwald, Colin C.; Bonagura, John D.; Muir, William W. (January 1, 2009), Muir, William W.; Hubbell, John A. E. (eds.), "Chapter 3 - The Cardiovascular System", Equine Anesthesia (Second Edition), Saint Louis: W.B. Saunders, pp. 37–100, doi:10.1016/b978-1-4160-2326-5.00003-1, ISBN   978-1-4160-2326-5 , retrieved November 29, 2020
  6. ↑ Touyz, Rhian M. (January 1, 2014), Willis, Monte S.; Homeister, Jonathon W.; Stone, James R. (eds.), "Chapter 14 - Blood Pressure Regulation and Pathology", Cellular and Molecular Pathobiology of Cardiovascular Disease, San Diego: Academic Press, pp. 257–275, doi:10.1016/b978-0-12-405206-2.00014-4, ISBN   978-0-12-405206-2 , retrieved November 29, 2020
  7. 1 2 3 Waller, Derek G.; Sampson, Anthony P. (January 1, 2018), Waller, Derek G.; Sampson, Anthony P. (eds.), "7 - Heart failure", Medical Pharmacology and Therapeutics (Fifth Edition), Elsevier, pp. 131–142, doi:10.1016/b978-0-7020-7167-6.00007-5, ISBN   978-0-7020-7167-6 , retrieved November 29, 2020
  8. ↑ O'Shaughnessy, Kevin M. (January 1, 2012), Bennett, Peter N.; Brown, Morris J.; Sharma, Pankaj (eds.), "Chapter 24 - Arterial hypertension, angina pectoris, myocardial infarction and heart failure", Clinical Pharmacology (Eleventh Edition), Oxford: Churchill Livingstone, pp. 393–427, doi:10.1016/b978-0-7020-4084-9.00063-x, ISBN   978-0-7020-4084-9 , retrieved November 29, 2020
  9. 1 2 3 Rizzo, Renata; Gulisano, Mariangela (January 1, 2013), Martino, Davide; Cavanna, Andrea E. (eds.), "Chapter Fourteen - Clinical Pharmacology of Comorbid Attention Deficit Hyperactivity Disorder in Tourette Syndrome", International Review of Neurobiology, Advances in the Neurochemistry and Neuropharmacology of Tourette Syndrome, Academic Press, 112: 415–444, doi:10.1016/b978-0-12-411546-0.00014-7, PMID   24295629 , retrieved November 29, 2020
  10. 1 2 Owsjannikow, PH. Die tonischen und reflektorischen Centren der Gefäßnerven. / Berichte ueber die Verhandlungen der Königlich Sächsischen Gesellschaft der Wissenschaften zu Leipzig (1871) 23.
  11. ↑ Abdollahi, M.; Mostafalou, S. (January 1, 2014), "G-Series Nerve Agents", in Wexler, Philip (ed.), Encyclopedia of Toxicology (Third Edition), Oxford: Academic Press, pp. 800–805, ISBN   978-0-12-386455-0 , retrieved November 29, 2020
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