Maximus Gage
Vascular smooth muscle is the type of smooth muscle that composes the majority of the walls of blood vessels. It is innervated primarily by the sympathetic nervous system through adrenergic receptors. The main function of vascular smooth muscle is to regulate the calibre of the blood vessels in the body by contracting or relaxing to change the volume of blood vessels and local blood pressure. This mechanism is responsible for the redistribution of blood within the body to areas where it is needed. Smooth muscle also plays a role in regulating the function of a variety of hollow organ systems including the vasculature, airways, gastrointestinal tract, uterus and reproductive tract, bladder and urethra.
| Characteristics | Values |
|---|---|
| Definition | Vascular smooth muscle is the type of smooth muscle that makes up most of the walls of blood vessels. |
| Composition | Vascular smooth muscle cells are small, mononucleate, and spindle-shaped, with a large central nucleus surrounded by an array of endoplasmic reticulum and golgi apparatus. |
| Function | Regulating the function of hollow organ systems, including the vasculature, airways, gastrointestinal tract, uterus, reproductive tract, bladder, and urethra. |
| Role | Altering the shape of an organ and withstanding the force of an internal load presented to that organ. |
| Regulation | The sympathetic nervous system through adrenergic receptors (alpha-1, alpha-2, and beta-2). |
| Contraction | Regulated by calcium concentrations and influenced by competing drives, with the degree of contraction determined by the balance of these forces. |
| Blood Flow | Responsible for controlling total peripheral resistance, arterial and venous tone, and the distribution of blood flow throughout the body. |
| Blood Pressure | Vascular smooth muscle contraction (vasoconstriction) increases blood pressure, while relaxation (vasodilation) decreases it. |
| Disease | Excessive vascular smooth muscle cell proliferation contributes to pathological conditions such as vascular inflammation, atherosclerosis, and pulmonary hypertension. |
| Treatment | Drugs like clonidine, which cause vasodilation, can be used to treat high blood pressure by activating alpha-2 receptors. |
Explore related products
What You'll Learn
Vascular smooth muscle cells
VSMCs form the cells of the media and maintain the matrix of the normal vascular wall. They are quiescent in this media but upon injury, they undergo phenotypic transformation to proliferating, secreting, and migrating cells with a capacity to become myofibroblasts and participate in repair. They may also become foam cells through ingestion of lipids. These secretory cells lose most of their muscle markers.
VSMCs play a crucial role in regulating blood flow and pressure by contracting and dilating in response to stimuli, thereby changing the volume of blood vessels and local blood pressure. This mechanism is responsible for the redistribution of blood within the body to areas where it is needed, such as areas with temporarily enhanced oxygen consumption. The main endogenous agonist of the adrenergic receptors in VSMCs is norepinephrine (NE). NE binding to alpha-1 receptors causes vasoconstriction (contraction of the VSMCs, decreasing the diameter of the vessels), while agonism of beta-2 receptors leads to vasodilation and low blood pressure.
VSMCs also play important roles during development, such as driving osteocyte differentiation from undifferentiated precursors during osteogenesis. Excessive proliferation of VSMCs contributes to the progression of pathological conditions, including vascular inflammation, plaque formation, atherosclerosis, restenosis, and pulmonary hypertension.
Relieving Inflamed Muscles: Natural Ways to Heal and Soothe
You may want to see also
Explore related products
Blood vessel walls
Blood vessels are composed of three layers: the adventitia or outer layer, the tunica media or middle layer, and the tunica intima or inner layer. The amount of muscle and collagen fibrils in each layer varies depending on the size and location of the vessel.
The outer layer, or adventitia, provides structural support and shape to the vessel. The middle layer, or tunica media, is composed of elastic and muscular tissue and regulates the internal diameter of the vessel. The internal elastic membrane, which is a thick and distinct layer of elastic fibres, is found at the boundary between the tunica media and the tunica intima. The internal elastic membrane provides structure while allowing the vessel to stretch and contains small openings that allow for the exchange of materials between the tunics.
The inner layer, or tunica intima, consists of an endothelial lining that provides a frictionless pathway for blood movement. The endothelium is a specialized simple squamous epithelium that is continuous throughout the entire vascular system, including the lining of the chambers of the heart. It plays a critical role in regulating capillary exchange and altering blood flow by releasing local chemicals called endothelins that can constrict the smooth muscle within the vessel walls to increase blood pressure.
Vasa vasorum, or "vessels of the vessel," are small blood vessels within the walls of larger arteries and veins that provide nourishment and remove waste from the vessel's cells. The vasa vasorum internae originate from the lumen of a vessel and penetrate the vessel wall to supply oxygen and nutrients, while the vasa vasorum externae originate from a nearby branching vessel and feedback into the larger vessel wall. The location of the vasa vasorum is thought to contribute to the higher prevalence of arterial diseases compared to venous diseases, as they are restricted to the outer layers of arteries due to the high pressure within these vessels.
Vascular smooth muscle cells make up most of the walls of blood vessels and play a crucial role in regulating blood flow and pressure. These cells can contract or relax to change the volume of blood vessels and local blood pressure, redistributing blood within the body to areas with increased oxygen consumption. Excessive vasoconstriction, or contraction of the vascular smooth muscle cells, leads to high blood pressure, while excessive vasodilation can result in shock and low blood pressure. Agonists of alpha-2 receptors in the vascular smooth muscle lead to vasoconstriction, while agonism of beta-2 receptors causes vasodilation and a decrease in blood pressure. SMCs, or smooth muscle cells, are important regulators of vascular remodelling and exhibit phenotype plasticity in response to vascular injury or disease.
HGH's Muscle-Preserving Power: Fact or Fiction?
You may want to see also
Explore related products
Calcium and contractile state
Calcium is essential for muscle movement, controlling both contraction and relaxation. Calcium ions (Ca2+) are the main regulatory and signalling molecule for all muscle fibres. Calcium triggers contraction by reacting with regulatory proteins that, in the absence of calcium, prevent the interaction of actin and myosin.
Calcium-stimulated CaMKII activates and causes the translocation of CaMKIV to the nucleus, where it can activate CREB, which promotes transcription of components of the contractile apparatus and other targets. Calcium also activates calcineurin, which induces genes associated with proliferation and migration.
Calcium is released from the sarcoplasmic reticulum (a storage unit inside muscle cells) when a nerve signal reaches a muscle. The cytosolic Ca2+ level is mainly determined by Ca2+ movements between the cytosol and the sarcoplasmic reticulum. The importance of Ca2+ entry from extracellular spaces to the cytosol has gained significant attention over the past decade. Store-operated Ca2+ entry with a low amplitude and relatively slow kinetics is a main extracellular Ca2+ entryway into skeletal muscle.
Calcium reabsorption occurs when contraction is complete, with calcium pumped back into the sarcoplasmic reticulum. Without calcium, actin and myosin fibres separate, allowing the muscle to relax. Proper calcium levels ensure smooth relaxation and prevent muscle stiffness.
Swimming and Muscle Gain: What's the Real Deal?
You may want to see also
Explore related products
Adrenergic receptors
ARs are the most important receptors in regulating vascular homeostasis. They mediate NO-dependent vasodilation, permeability, and angiogenesis in the endothelium. In vascular smooth muscle cells (VSMCs), ARs regulate contraction, trans-differentiation, proliferation, and vessel wall calcification. These processes are crucial for the development of cardiovascular diseases, including atherosclerosis, hypertension, and type-II diabetes.
There are two main groups of adrenoreceptors, α and β, with 9 subtypes in total. α receptors are subdivided into α1 (a Gq coupled receptor) and α2 (a Gi coupled receptor). β receptors are subdivided into β1, β2, and β3. All 3 are coupled to Gs proteins, but β2 and β3 also couple to Gi. The α1 receptor couples to Gq, increasing intracellular Ca2+ and causing smooth muscle contraction. The α2 receptor couples to Gi, decreasing neurotransmitter release and cAMP activity, resulting in smooth muscle contraction. The β receptor couples to Gs, increasing intracellular cAMP activity, resulting in heart muscle contraction, smooth muscle relaxation, and glycogenolysis.
The β-adrenergic signalling pathway is important for muscle growth, development, and muscle regeneration. Research is needed to understand how this pathway can be manipulated to enhance muscle fibre growth and improve the repair of damaged and regenerating skeletal muscle after injury. β2-adrenergic receptor stimulation using anabolic drugs increases muscle mass by promoting muscle protein synthesis and/or attenuating protein degradation. However, excessive stimulation of β2-adrenergic receptors negates their beneficial effects, and prolonged administration of β2-adrenergic agonists leads to the downregulation of β2-AR density in skeletal muscles.
Relieving a Bulky Trapezius Muscle: Effective Strategies and Techniques
You may want to see also
Explore related products
Atherosclerosis
The progression of atherosclerosis is influenced by high cholesterol levels, high blood pressure, blood clots, smoking, and thickened artery walls. Smoking, in particular, speeds up the growth of fatty deposits. Atherosclerosis may start in childhood and progresses slowly over a person's lifetime, worsening with age.
Vascular smooth muscle cells (VSMCs) are key participants in both early and late-stage atherosclerosis. They are the major component of the vessel wall and are responsible for regulating blood pressure and vascular tone through their contractile properties. In atherosclerosis, the ultrastructure of VSMCs changes, with downregulation of contractile marker gene expression. This plasticity allows VSMCs to exhibit multiple phenotypes and play various roles in atherosclerosis, including plaque formation and stabilisation.
The identification of molecular markers in SMCs has allowed for the study of these cells in disease conditions, including atherosclerosis. SMC plasticity is an important feature in the response of the vascular wall to vascular injury. For example, SMCs may become foam cells through lipid ingestion, which is important in atherosclerosis.
Calorie Deficit: Friend or Foe for Muscle Retention?
You may want to see also
Frequently asked questions
Vascular smooth muscle is the type of smooth muscle that makes up most of the walls of blood vessels. It is innervated primarily by the sympathetic nervous system through adrenergic receptors.
Vascular smooth muscle has two fundamental roles: 1) to alter the shape of an organ and 2) to withstand the force of an internal load presented to that organ. It does this by contracting or relaxing to change both the volume of blood vessels and the local blood pressure, redistributing blood within the body to areas where it is needed.
Vascular smooth muscle is responsible for the control of total peripheral resistance, arterial and venous tone, and the distribution of blood flow throughout the body. It also plays crucial structural and physiological roles in the cardiovascular system.
Vascular smooth muscle cells are small, mononucleate, and spindle-shaped. They are usually arranged in helical or circular layers around large blood vessels and in a single circular layer around arterioles.
