The vasomotor center (VMC) is a portion of the

medulla oblongata 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 (involun ...

. Together with the cardiovascular center and

respiratory center The respiratory center is located in the medulla oblongata and pons, in the brainstem. The respiratory center is made up of three major respiratory groups of neurons, two in the medulla and one in the pons. In the medulla they are the dorsal res ...

, it regulates

blood pressure Blood pressure (BP) is the pressure of circulating blood against the walls of blood vessels. Most of this pressure results from the heart pumping blood through the circulatory system. When used without qualification, the term "blood pressure" r ...

. It also has a more minor role in other

homeostatic In biology, homeostasis (British also homoeostasis) (/hɒmɪə(ʊ)ˈsteɪsɪs/) is the state of steady internal, physical, and chemical conditions maintained by living systems. This is the condition of optimal functioning for the organism and i ...

processes. Upon increase in

carbon dioxide Carbon dioxide (chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is transpar ...

level at

central chemoreceptors 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. These act to detect the changes in ...

, it stimulates the sympathetic system to constrict vessels. This is opposite to carbon dioxide in tissues causing vasodilatation, especially in the brain. Cranial nerves IX (

glossopharyngeal nerve 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 oblongata, medulla, just anterior (closer to the nose) to t ...

) and X (

vagus nerve The vagus nerve, also known as the tenth cranial nerve, cranial nerve X, or simply CN X, is a cranial nerve that interfaces with the parasympathetic control of the heart, lungs, and digestive tract. It comprises two nerves—the left and right ...

) both feed into the vasomotor centre and are themselves involved in the regulation of blood pressure.vasomotor center has other actions also

Structure

The vasomotor center is a collection of integrating

neurons A neuron, neurone, or nerve cell is an electrically excitable cell that communicates with other cells via specialized connections called synapses. The neuron is the main component of nervous tissue in all animals except sponges and placozoa. N ...

in the

of the middle

brain stem The brainstem (or brain stem) is the posterior stalk-like part of the brain that connects the cerebrum with the spinal cord. In the human brain the brainstem is composed of the midbrain, the pons, and the medulla oblongata. The midbrain is conti ...

. 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.

Afferent fibres

The vasomotor center integrates nerve impulses from many places via the

solitary nucleus In the human brainstem, the solitary nucleus, also called nucleus of the solitary tract, nucleus solitarius, and nucleus tractus solitarii, (SN or NTS) is a series of purely sensory nuclei (clusters of nerve cell bodies) forming a vertical column ...

: *

aortic body 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. Structure The aortic bodies ...

chemoreceptors A chemoreceptor, also known as chemosensor, is a specialized sensory receptor which transduces a chemical substance (endogenous or induced) to generate a biological signal. This signal may be in the form of an action potential, if the chemorecept ...

, which send impulses via the vagus nerves *

carotid body The carotid body is a small cluster of chemoreceptor cells, and supporting sustentacular cells. The carotid body is located in the adventitia, in the bifurcation (fork) of the common carotid artery, which runs along both sides of the neck. The ca ...

chemoreceptors, which send impulses via the

glossopharyngeal nerves 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 (closer to the nose) to the vagus nerve. B ...

aortic sinus An aortic sinus, also known as a sinus of Valsalva, is one of the anatomic dilations of the ascending aorta, which occurs just above the aortic valve. These widenings are between the wall of the aorta and each of the three cusps of the aortic val ...

high-pressure

baroreceptors Baroreceptors (or archaically, pressoreceptors) are sensors located in the carotid sinus (at the bifurcation of external and internal carotids) and in the aortic arch. They sense the blood pressure and relay the information to the brain, so that a ...

, which send impulses via the vagus nerves *

carotid sinus 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 ...

high-pressure baroreceptors, which send impulses via the glossopharyngeal nerves

Efferent fibres

The vasomotor center gives off sympathetic fibres through the

spinal cord The spinal cord is a long, thin, tubular structure made up of nervous tissue, which extends from the medulla oblongata in the brainstem to the lumbar region of the vertebral column (backbone). The backbone encloses the central canal of the spi ...

and

sympathetic ganglia The sympathetic ganglia, or paravertebral ganglia are autonomic ganglia, of the sympathetic nervous system. Ganglia are 20,000 to 30,000 afferent and efferent nerve cell bodies that run along on either side of the spinal cord. Afferent nerve c ...

, which reach vascular smooth muscle.

Function

The vasomotor center changes

vascular smooth muscle Vascular smooth muscle is the type of smooth muscle that makes up most of the walls of blood vessels. Structure Vascular smooth muscle refers to the particular type of smooth muscle found within, and composing the majority of the wall of blood ...

tone. This changes local and systemic

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

Clinical significance

Methyldopa Methyldopa, sold under the brand name Aldomet among others, is a medication used for high blood pressure. It is one of the preferred treatments for high blood pressure in pregnancy. For other types of high blood pressure including hypertensive e ...

acts on the vasomotor center, leading to selective stimulation of α₂-adrenergic receptor.

Guanfacine Guanfacine, sold under the brand name Tenex among others, is an oral medication used to treat attention deficit hyperactivity disorder (ADHD) and high blood pressure. Guanfacine is FDA-approved for monotherapy treatment of ADHD as well as being ...

also causes the same stimulation. This reduces

sympathetic tone The sympathetic nervous system (SNS) is one of the three divisions of the autonomic nervous system, the others being the parasympathetic nervous system and the enteric nervous system. The enteric nervous system is sometimes considered part of t ...

to vascular smooth muscle. This reduces

heart rate Heart rate (or pulse rate) is the frequency of the heartbeat measured by the number of contractions (beats) of the heart per minute (bpm). The heart rate can vary according to the body's physical needs, including the need to absorb oxygen and excr ...

and

vascular resistance Vascular resistance is the resistance that must be overcome to push blood through the circulatory system and create flow. The resistance offered by the systemic circulation is known as the systemic vascular resistance (SVR) or may sometimes be ca ...

Digoxin Digoxin (better known as Digitalis), sold under the brand name Lanoxin among others, is a medication used to treat various heart conditions. Most frequently it is used for atrial fibrillation, atrial flutter, and heart failure. Digoxin is on ...

increases

vagal tone Vagal tone is activity of the vagus nerve, the 10th cranial nerve and a fundamental component of the parasympathetic branch of the autonomic nervous system. This branch of the nervous system is not under conscious control and is largely responsible ...

from the vasomotor centre, which decreases

pulse In medicine, a pulse represents the tactile arterial palpation of the cardiac cycle (heartbeat) by trained fingertips. The pulse may be palpated in any place that allows an artery to be compressed near the surface of the body, such as at the nec ...

. G-series

nerve agents Nerve agents, sometimes also called nerve gases, are a class of organic chemicals that disrupt the mechanisms by which nerves transfer messages to organs. The disruption is caused by the blocking of acetylcholinesterase (AChE), an enzyme that ...

have their most potent effect in the vasomotor center. Unlike other parts of the body, where continued stimulation of

acetylcholine receptors An acetylcholine receptor (abbreviated AChR) is an integral membrane protein that responds to the binding of acetylcholine, a neurotransmitter. Classification Like other transmembrane receptors, acetylcholine receptors are classified according ...

leads to recoverable

paralysis Paralysis (also known as plegia) is a loss of motor function in one or more muscles. Paralysis can also be accompanied by a loss of feeling (sensory loss) in the affected area if there is sensory damage. In the United States, roughly 1 in 50 ...

, overstimulation of the vasomotor center is often causes a fatal rise in blood pressure.

History

The localization of vasomotor center was determined by Filipp Ovsyannikov in 1871.Owsjannikow, PH. Die tonischen und reflektorischen Centren der Gefäßnerven. / Berichte ueber die Verhandlungen der Königlich Sächsischen Gesellschaft der Wissenschaften zu Leipzig (1871) 23.

References

{{Medulla and pons of rhombencephalon Brainstem