Maximus Gage
Vascular smooth muscle is the type of smooth muscle that makes up most of the walls of blood vessels. It is responsible for the control of total peripheral resistance, arterial and venous tone, and the distribution of blood flow throughout the body. Vascular smooth muscle cells (VSMCs) depend on Ca2+ influx to initiate contraction, and the VSMC intracellular Ca2+ concentration determines the contractile state. The adrenergic receptors exert opposite physiologic effects in the vascular smooth muscle under activation: alpha-1 receptors cause vasoconstriction (contraction of the vascular smooth muscle cells decreasing the diameter of the vessels), while alpha-2 and beta-2 adrenergic receptors cause vasodilation.
| Characteristics | Values |
|---|---|
| Type of muscle | Smooth muscle |
| Composition of blood vessels | Vascular smooth muscle makes up most of the walls of blood vessels |
| Control | 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 |
| Shape of cells | Small, mononucleate, and spindle-shaped |
| Arrangement of cells | Usually arranged in helical or circular layers around large blood vessels and in a single circular layer around arterioles |
| Interaction with other cells | Parts of endothelial cells project into the vascular smooth muscle layer (myoendothelial junctions) at various points along the arterioles |
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What You'll Learn
- 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
- Vascular smooth muscle is innervated primarily by the sympathetic nervous system through adrenergic receptors (adrenoceptors)
- The three types of adrenergic receptors are alpha-1, alpha-2 and beta-2 adrenergic receptors
- The main endogenous agonist of these cell receptors is norepinephrine (NE)
- The adrenergic receptors exert opposite physiologic effects in the vascular smooth muscle under activation: alpha-1 receptors cause vasoconstriction (contraction of the vascular smooth muscle cells decreasing the diameter of the vessels)
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
Vascular smooth muscle is a type of muscle that makes up most of the walls of blood vessels. It is responsible for the control of total peripheral resistance, arterial and venous tone, and the distribution of blood flow throughout the body.
Vascular smooth muscle cells (VSMCs) 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. Parts of endothelial cells project into the vascular smooth muscle layer (myoendothelial junctions) at various points along the arterioles. These projections suggest a functional interaction between the endothelium and adjacent vascular smooth muscle.
The close association between action potentials and contraction observed in skeletal and cardiac muscle cells cannot be demonstrated in vascular smooth muscle. Unlike other muscle cells, vascular smooth muscle is innervated primarily by the sympathetic nervous system through adrenergic receptors (alpha-1, alpha-2, and beta-2). The main endogenous agonist of these cell receptors is norepinephrine (NE). When NE binds to alpha-1 receptors, it causes vasoconstriction (contraction of the vascular smooth muscle cells, decreasing the diameter of the vessels).
Vascular smooth muscle reactivity loss can lead to distributive shock, which is characterised by widespread peripheral vasodilation. This causes hypotension with resulting tissue hypoperfusion.
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Vascular smooth muscle is innervated primarily by the sympathetic nervous system through adrenergic receptors (adrenoceptors)
Vascular smooth muscle is the type of smooth muscle that makes up most of the walls of blood vessels. It is responsible for controlling total peripheral resistance, arterial and venous tone, and the distribution of blood flow throughout the body.
The activation of alpha-1 and alpha-2 adrenergic receptors elicits vasoconstriction. Norepinephrine released from sympathetic nerve terminals binds to these receptors, which are located on vascular smooth muscle cells. This binding increases intracellular Ca2+ levels, which causes contraction of the smooth muscle.
The close association between action potentials and contraction observed in skeletal and cardiac muscle cells is not observed in vascular smooth muscle.
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The three types of adrenergic receptors are alpha-1, alpha-2 and beta-2 adrenergic receptors
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. The smooth muscle cells are small, mononucleate, and spindle-shaped. They are usually arranged in helical or circular layers around the large blood vessels and in a single circular layer around arterioles.
There are three types of adrenergic receptors: alpha-1, alpha-2, and beta-2 adrenergic receptors. Adrenergic receptors are proteins found on the surface of cells that respond to the hormone adrenaline (epinephrine). They are distributed throughout the body and serve as receptors for catecholamines (noradrenaline and epinephrine) secreted from the autonomic sympathetic nervous system and adrenal medulla. Catecholamines are involved in the stimulation of our organs by the sympathetic nervous system; they help to trigger the fight or flight response.
Alpha-1 adrenoceptors mediate smooth muscle contraction and vasoconstriction. They play an important signalling role in all vasculature, including the vasculature of the urinary tract, and mediate vasoconstriction. The alpha-1 receptor is of the Gq type, resulting in activation of phospholipase C, increasing IP3 and DAG, and ultimately increasing the intracellular calcium concentrations leading to smooth muscle contraction and glycogenolysis.
Alpha-2 receptors act as allosteric inhibitors through Gi function, leading to an inhibition of adenylyl cyclase, decreasing the formation of intracellular cAMP. This also leads to a reduced amount of cytoplasmic calcium, which decreases neurotransmitter release and central vasodilation.
Beta-2 receptors mediate vasodilation, smooth muscle relaxation, bronchodilation, and excitatory cardiac function. There are three types of beta-receptors that can be identified: beta-1 receptors located in the heart, beta-2 receptors located in the lungs, and beta-3 receptors located in adipose tissue.
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The main endogenous agonist of these cell receptors is norepinephrine (NE)
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. The smooth muscle cells are small, mononucleate, and spindle-shaped. They are usually arranged in helical or circular layers around the large blood vessels and in a single circular layer around arterioles.
Vascular smooth muscle is innervated primarily by the sympathetic nervous system through adrenergic receptors (adrenoceptors). The three types present are: alpha-1, alpha-2 and beta-2 adrenergic receptors. The main endogenous agonist of these cell receptors is norepinephrine (NE). NE binding to alpha-1 receptors causes vasoconstriction (contraction of the vascular smooth muscle cells decreasing the diameter of the vessels).
In distributive shock, there is widespread peripheral vasodilation caused by vascular smooth muscle reactivity loss. This causes hypotension with resulting tissue hypoperfusion. Patients with septic shock, a type of distributive shock, often have elevated levels of catecholamines. The body releases catecholamines as endogenous vasoconstrictors but cannot elicit an appropriate pressure response in the pathologic shock state. Endothelial cells can also overexpress nitric oxide, contributing to even more pronounced vasodilation. Management of this vasodilatory shock requires fluid resuscitation and the initiation of norepinephrine, a potent vasopressor.
Parts of endothelial cells project into the vascular smooth muscle layer (myoendothelial junctions) at various points along the arterioles. These projections suggest a functional interaction between endothelium and adjacent vascular smooth muscle.
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The adrenergic receptors exert opposite physiologic effects in the vascular smooth muscle under activation: alpha-1 receptors cause vasoconstriction (contraction of the vascular smooth muscle cells decreasing the diameter of the vessels)
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. The smooth muscle cells are small, mononucleate, and spindle-shaped. They are usually arranged in helical or circular layers around the large blood vessels and in a single circular layer around arterioles.
Vascular smooth muscle is innervated primarily by the sympathetic nervous system through adrenergic receptors (adrenoceptors). The three types present are: alpha-1, alpha-2 and beta-2 adrenergic receptors. The main endogenous agonist of these cell receptors is norepinephrine (NE).
The adrenergic receptors exert opposite physiological effects in the vascular smooth muscle under activation. Alpha-1 receptors cause vasoconstriction (contraction of the vascular smooth muscle cells decreasing the diameter of the vessels). This is caused by NE binding to the alpha-1 receptors.
Distributive shock is one of the most common mechanisms that contribute to shock. It demonstrates widespread peripheral vasodilation caused by vascular smooth muscle reactivity loss. The vasodilation causes hypotension with resulting tissue hypoperfusion.
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Frequently asked questions
Vascular smooth muscle is the type of smooth muscle that makes up most of the walls of blood vessels. It is responsible for the control of total peripheral resistance, arterial and venous tone, and the distribution of blood flow throughout the body.
Vascular smooth muscle is innervated primarily by the sympathetic nervous system through adrenergic receptors (adrenoceptors). The three types present are: alpha-1, alpha-2 and beta-2 adrenergic receptors. The main endogenous agonist of these cell receptors is norepinephrine (NE). The adrenergic receptors exert opposite physiologic effects in the vascular smooth muscle under activation: alpha-1 receptors cause vasoconstriction (contraction of the vascular smooth muscle cells decreasing the diameter of the vessels), while alpha-2 and beta-2 receptors cause vasodilation (relaxation of the vascular smooth muscle cells increasing the diameter of the vessels).
Vascular smooth muscle plays a crucial role in controlling the distribution of blood flow throughout the body. It regulates total peripheral resistance and arterial and venous tone, ensuring that blood is distributed appropriately to different tissues and organs.
