Smooth muscle

Within single-unit cells, the whole bundle or sheet contracts as a syncytium.

Unlike skeletal muscle, the contractions of smooth and cardiac muscles are myogenic (meaning that they are initiated by the smooth or heart muscle cells themselves instead of being stimulated by an outside event such as nerve stimulation), although they can be modulated by stimuli from the autonomic nervous system.

It is divided into two subgroups; the single-unit (unitary) and multiunit smooth muscle.

Single-unit smooth muscle, or visceral smooth muscle is a type of smooth muscle found in the uterus, gastro-intestinal tract, and the bladder.

Smooth muscle cells are found in the walls of hollow organs, including the stomach, intestines, urinary bladder and uterus, and in the walls of passageways, such as the arteries and veins of the circulatory system, and the tracts of the respiratory, urinary, and reproductive systems.

The trigone is a smooth-muscle area that forms the floor of the bladder above the urethra.

Smooth muscle cells are found in the walls of hollow organs, including the stomach, intestines, urinary bladder and uterus, and in the walls of passageways, such as the arteries and veins of the circulatory system, and the tracts of the respiratory, urinary, and reproductive systems.

The outer part of the lining of the stomach, the gastric mucosa, consists of an outer layer of column-shaped cells, a lamina propria, and a thin layer of smooth muscle called the muscularis mucosa.

Smooth muscle is fundamentally different from skeletal muscle and cardiac muscle in terms of structure, function, regulation of contraction, and excitation-contraction coupling.

Cardiac muscle (also called heart muscle or myocardium) is one of three types of vertebrate muscles, with the other two being skeletal and smooth muscles.

Smooth muscle is fundamentally different from skeletal muscle and cardiac muscle in terms of structure, function, regulation of contraction, and excitation-contraction coupling.

Skeletal muscle is one of three major muscle types, the others being cardiac muscle and smooth muscle.

Smooth muscle cells are found in the walls of hollow organs, including the stomach, intestines, urinary bladder and uterus, and in the walls of passageways, such as the arteries and veins of the circulatory system, and the tracts of the respiratory, urinary, and reproductive systems.

The myometrium of the uterus mostly consists of smooth muscle.

Smooth muscle cells are found in the walls of hollow organs, including the stomach, intestines, urinary bladder and uterus, and in the walls of passageways, such as the arteries and veins of the circulatory system, and the tracts of the respiratory, urinary, and reproductive systems.

The middle layer of bands of smooth muscle are called tunica media and are, in general, much thinner than those of arteries, as veins do not function primarily in a contractile manner and are not subject to the high pressures of systole, as arteries are.

These cells are also present in the eyes and are able to change the size of the iris and alter the shape of the lens.

The muscle cells of the iris are smooth muscle in mammals and amphibians, but are striated muscle in reptiles (including birds).

A substantial portion of the volume of the cytoplasm of smooth muscle cells are taken up by the molecules myosin and actin, which together have the capability to contract, and, through a chain of tensile structures, make the entire smooth muscle tissue contract with them.

The term was originally used to describe a group of similar ATPases found in the cells of both striated muscle tissue and smooth muscle tissue.

A substantial portion of the volume of the cytoplasm of smooth muscle cells are taken up by the molecules myosin and actin, which together have the capability to contract, and, through a chain of tensile structures, make the entire smooth muscle tissue contract with them.

In fact, this is true only in smooth muscle, and was not supported through experimentation until 2001.

Troponin, or the troponin complex, is a complex of three regulatory proteins (troponin C, troponin I, and troponin T) that is integral to muscle contraction in skeletal muscle and cardiac muscle, but not smooth muscle.

Dense bodies are rich in α-actinin, and also attach intermediate filaments (consisting largely of vimentin and desmin), and thereby appear to serve as anchors from which the thin filaments can exert force.

Desmin is a subunit of intermediate filaments in cardiac muscle, skeletal muscle and smooth muscle tissue.

Smooth muscle is an involuntary non-striated muscle.

These bind to a molecule called calmodulin, and form a calcium-calmodulin complex.

Calmodulin mediates many crucial processes such as inflammation, metabolism, apoptosis, smooth muscle contraction, intracellular movement, short-term and long-term memory, and the immune response.

These invaginations in the sarcoplasm contain a host of receptors (prostacyclin, endothelin, serotonin, muscarinic receptors, adrenergic receptors), second messenger generators (adenylate cyclase, phospholipase C), G proteins (RhoA, G alpha), kinases (rho kinase-ROCK, protein kinase C, protein Kinase A), ion channels (L type calcium channels, ATP sensitive potassium channels, calcium sensitive potassium channels) in close proximity.

Endothelins are 21-amino acid vasoconstricting peptides produced primarily in the endothelium having a key role in vascular homeostasis.

The sarcolemma also contains caveolae, which are microdomains of lipid rafts specialized to cell signaling events and ion channels.

In addition, ion channels are key components in a wide variety of biological processes that involve rapid changes in cells, such as cardiac, skeletal, and smooth muscle contraction, epithelial transport of nutrients and ions, T-cell activation and pancreatic beta-cell insulin release.

Phosphorylation of calponin by a protein kinase, which is dependent upon calcium binding to calmodulin, releases the calponin's inhibition of the smooth muscle ATPase.

Recent research indicates that sphingosine-1-phosphate (S1P) signaling is an important regulator of vascular smooth muscle contraction.

Vascular smooth muscle refers to the particular type of smooth muscle found within, and composing the majority of the wall of blood vessels.

For example, the great arteries are viscolelastic vessels that act like a Windkessel, propagating ventricular contraction and smoothing out the pulsatile flow, and the smooth muscle within the tunica media contributes to this property.

Tunica media is made up of smooth muscle cells, elastic tissue and collagen.

Smooth muscle may contract spontaneously (via ionic channel dynamics) or as in the gut special pacemakers cells interstitial cells of Cajal produce rhythmic contractions.

Myenteric Interstitial cells of Cajal (ICC-MY) serve as a pacemaker which creates the bioelectrical slow wave potential that leads to contraction of the smooth muscle.

For instance, blood vessels in skin, gastrointestinal system, kidney and brain respond to norepinephrine and epinephrine (from sympathetic stimulation or the adrenal medulla) by producing vasoconstriction (this response is mediated through alpha-1 adrenergic receptors).

α1-receptors primarily mediate smooth muscle contraction, but have important functions elsewhere as well.

These invaginations in the sarcoplasm contain a host of receptors (prostacyclin, endothelin, serotonin, muscarinic receptors, adrenergic receptors), second messenger generators (adenylate cyclase, phospholipase C), G proteins (RhoA, G alpha), kinases (rho kinase-ROCK, protein kinase C, protein Kinase A), ion channels (L type calcium channels, ATP sensitive potassium channels, calcium sensitive potassium channels) in close proximity.

These invaginations in the sarcoplasm contain a host of receptors (prostacyclin, endothelin, serotonin, muscarinic receptors, adrenergic receptors), second messenger generators (adenylate cyclase, phospholipase C), G proteins (RhoA, G alpha), kinases (rho kinase-ROCK, protein kinase C, protein Kinase A), ion channels (L type calcium channels, ATP sensitive potassium channels, calcium sensitive potassium channels) in close proximity.

These invaginations in the sarcoplasm contain a host of receptors (prostacyclin, endothelin, serotonin, muscarinic receptors, adrenergic receptors), second messenger generators (adenylate cyclase, phospholipase C), G proteins (RhoA, G alpha), kinases (rho kinase-ROCK, protein kinase C, protein Kinase A), ion channels (L type calcium channels, ATP sensitive potassium channels, calcium sensitive potassium channels) in close proximity.