Vasomotor function includes all movement processes in the arteries and arterioles. These movements correspond to either contraction and relaxation of the vascular musculature and cause lumenal changes in the vessels. Patients with Raynaud’s syndrome suffer from vasomotor spastic disorders.
What is vasomotor spasm?
Active movement processes take place in the vessels to transport blood. These movement processes are called vasomotor activity and regulate blood volume. Arteries and arterioles carry blood to individual organs. The blood contains hemoglobin-bound oxygen, which is released depending on factors such as pH. Thus, the arteries and arterioles are responsible for the vital transport of oxygen to individual organs and tissues. Active movement processes take place in the vessels to transport blood. These movement processes are referred to as vasomotor activity and regulate the volume of blood. Vasomotor activity includes vasoconstriction. This is the contraction of the muscles in the vessels. The vessel lumen becomes narrow and blood flow decreases. The opposite process is vasodilation, in which the vascular musculature relaxes. The vascular lumens widen and blood flow increases. These processes are subject to control by the autonomic nervous system. In addition to baroreceptors in the common carotid artery and the internal or external carotid artery for determining the stretch of the vessel wall, the vessels contain chemoreceptors for determining the partial pressure of oxygen and carbon dioxide. Afferent innervation of these receptors leads to the sympathetic nervous system, which initiates vasomotor processes and responds with a constriction of norepinephrine in response to increased vasomotor activity.
Function and task
Vasomotor function includes all movements of blood vessels. These movement processes are based partly on spontaneous activity and partly on humoral and nervous influences. Mediators such as histamine and norepinephrine play a role. The control of vasomotor activity is subject to the autonomic nervous system, especially the sympathetic nervous system. It has a vasoconstrictive and tonic effect on the blood vessels. In active vasodilation and vasoconstriction, the nerves and muscles of the vessels play together. Active vasodilation corresponds to a relaxation of the muscles. Active constriction is a contraction of the vascular muscles. Passive forms of vasomotor activity depend on blood volume. An increased blood volume leads to passive vasodilation. In contrast, a low volume leads to passive vasoconstriction. Vasomotor activity plays an increased role in arterial blood pressure. The basic requirement for pressure control in the arteries and arterioles is the endogenous ability to measure pressure in the vessels. In the aorta as well as the carotid arteries and other arteries in the chest and neck, pressure is measured by pressure-sensitive mechanoreceptors. These sensory cells of the skin sense are the baroreceptors, which register elongation of the vessel walls and transmit elongation changes to the autonomic nervous system. Similarly, the oxygen content in the blood is measured by the chemoreceptors in the vessel walls. This measured information plays a role in the regulation of respiration. For example, one mechnanism for short-term arterial pressure regulation is the baroreceptor reflex. The sympathetic nervous system has a vasoconstrictive effect. That is, it provides basal tone to the vessels. When high pressure is measured by increased volume in the arterial wall, the baroreceptors reflexively send an inhibitory impulse to the sympathetic nervous system. If, on the other hand, the arterial blood pressure is too low, they send hardly any inhibitory impulses. This irritates the sympathetic nervous system so that the ejected blood volume at the heart increases. Apart from this, vasoconstriction of the skin, kidneys and gastrointestinal tract can be induced. Basically, relaxation of vascular smooth muscle triggers vasodilation as induced by visceromotor autonomic nerve fibers. Locally formed mediators such as acetylcholine or endothelin also stimulate endothelial receptors, thus stimulating the formation of nitric oxide and prostacyclin, which contribute to vasodilation. In contrast, messenger substances such as arginine vasopressin, epinephrine, and norepinephrine have a vasoconstrictive effect. Vasomotor activity maintains circulation. The organs and tissues receive sufficient blood and oxygen through the processes.
Diseases and ailments
Disorders of vasomotor function are also known as vasomotor disorders and are observed primarily in association with lesions of the vasomotor autonomic nerves. These lesions may involve both the vasoconstrictor and vasodilator nerves. The disorders are also associated with damage to the brain, medulla oblongata, spinal cord, and peripheral nerves. In some circumstances, neuroses may also be related to vasomotor disorders. In most cases, the vessels undergo pathological changes in vasomotor disorders. Accompanying symptoms may include hot flashes, headaches, sweating, circulatory instability, or cold sensations. Vasomotor headaches correspond to a regulatory disorder that affects the vessels in the head and causes vegetative dystonia. The most common accompanying symptoms of such headaches are dizziness, palpitations and nausea, and cold clammy hands and feet. One of the most common primary causes of vasomotor disturbances is menopause. In some circumstances, the disorders may also be due to Raynaud’s syndrome. This clinical picture causes ischemic states with reduced blood flow due to vasoconstrictions and vascular spasms, which preferentially affect the arteries of the toes and fingers. As the disease progresses, the vessel walls become damaged. The tunica intima thickens or a capillary aneurysm develops. Primary Raynaud’s syndrome is thought to be a genetic predisposition to vasomotor disease. Hormonal factors may be involved. Secondary Raynaud’s syndrome may occur in the setting of collagenoses, rheumatoid arthritis, atherosclerosis, or cryoglobulinemia. The syndrome is only one of several diseases that promote spastic phenomena within the vasomotor system. Other diseases in this group include migraine and angina pectoris, which may also occur in combination with Raynaud’s syndrome if predisposed.
