A report on Smooth muscle, Cardiac muscle and Actin

Ribbon diagram of G-actin. ADP bound to actin's active site (multi color sticks near center of figure) as well as a complexed calcium dication (green sphere) are highlighted.

Smooth muscle tissue, highlighting the inner circular layer (nuclei then rest of cells in pink), outer longitudinal layer (nuclei then rest of cells), then the serous membrane facing the lumen of the peritoneal cavity

3D rendering showing thick myocardium within the heart wall.

Fluorescence micrograph showing F-actin (in green) in rat fibroblasts

The dense bodies and intermediate filaments are networked through the sarcoplasm, which cause the muscle fiber to contract.

The swirling musculature of the heart ensures effective pumping of blood.

A merged stack of confocal images showing actin filaments within a cell. The image has been colour coded in the z axis to show in a 2D image which heights filaments can be found at within cells.

A series of axon-like swellings, called varicosities from autonomic neurons, loosely form motor units through the smooth muscle.

Structure of the C-terminal subdomain of villin, a protein capable of splitting microfilaments

The structure of a sarcomere, the basic morphological and functional unit of the skeletal muscles that contains actin

Intercalated discs are part of the cardiac muscle cell sarcolemma and they contain gap junctions and desmosomes.

Diagram of a zonula occludens or tight junction, a structure that joins the epithelium of two cells. Actin is one of the anchoring elements shown in green.

Ribbon model of actin from rabbitmuscle. The four subdomains can be seen, as well as the N and C termini and the position of the ATP bond. The molecule is oriented using the usual convention of placing the - end (pointed end) up and the + end (barbed end) down.

F-actin; surface representation of a repetition of 13 subunits based on Ken Holmes' actin filament model

Ribbon model obtained using the PyMOL programme on crystallographs of the prefoldin proteins found in the archaean Pyrococcus horikoshii. The six supersecondary structures are present in a coiled helix “hanging” from the central beta barrels. These are often compared in the literature to the tentacles of a jellyfish. As far as is visible using electron microscopy, eukariotic prefoldin has a similar structure.

Ribbon model of the apical γ-domain of the chaperonin CCT

Microfilament formation showing the polymerization mechanism for converting G-actin to F-actin; note the hydrolysis of the ATP.

Atomic structure of Arp2/3. Each colour corresponds to a subunit: Arp3, orange; Arp2, sea blue (subunits 1 and 2 are not shown); p40, green; p34, light blue; p20, dark blue; p21, magenta; p16, yellow.

An actin (green) - profilin (blue) complex. The profilin shown belongs to group II, normally present in the kidneys and the brain.

The protein gelsolin, which is a key regulator in the assembly and disassembly of actin.

Principal interactions of structural proteins are at cadherin-based adherens junction. Actin filaments are linked to α-actinin and to the membrane through vinculin. The head domain of vinculin associates to E-cadherin via α-catenin, β-catenin, and γ-catenin. The tail domain of vinculin binds to membrane lipids and to actin filaments.

Structure of MreB, a bacterial protein whose three-dimensional structure resembles that of G-actin

Giant nemaline rods produced by the transfection of a DNA sequence of ACTA1, which is the carrier of a mutation responsible for nemaline myopathy

Position of seven mutations relevant to the various actinopathies related to ACTA1

Cross section of a rat heart that is showing signs of dilated cardiomyopathy

Image taken using confocal microscopy and employing the use of specific antibodies showing actin's cortical network. In the same way that in juvenile dystonia there is an interruption in the structures of the cytoskeleton, in this case it is produced by cytochalasin D.

Western blot for cytoplasmic actin from rat lung and epididymis

Nobel Prize winning physiologist Albert von Szent-Györgyi Nagyrápolt, co-discoverer of actin with Brunó Ferenc Straub

Ribbon diagram of an actin monomer from rabbit skeletal muscle, with the molecule's surface shown semi-transparent. The four subdomains as well as the bound ATP and calcium ion are annotated.

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

- Cardiac muscle

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

- Smooth muscle

There are no myofibrils present but much of the cytoplasm is taken up by the proteins of myosin and actin which together have the capability to contract.

- Smooth muscle

Each cell contains myofibrils, specialized protein contractile fibers of actin and myosin that slide past each other.

- Cardiac muscle

Of these, two code for the cytoskeleton (ACTB and ACTG1) while the other four are involved in skeletal striated muscle (ACTA1), smooth muscle tissue (ACTA2), intestinal muscles (ACTG2) and cardiac muscle (ACTC1).

- Actin

3 related topics with Alpha

Skeletal muscle

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Skeletal muscles (commonly referred to as muscles) are organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton.

Types of pennate muscle. A – unipennate; B – bipennate;
C – multipennate

ATPase staining of a muscle cross section. Type II fibers are dark, due to the alkaline pH of the preparation. In this example, the size of the type II fibers is considerably less than the type I fibers due to denervation atrophy.

Structure of muscle fibre showing a sarcomere under electron microscope with schematic explanation.

Diagram of sarcoplasmic reticulum with terminal cisternae and T-tubules.

Human embryo showing somites labelled as primitive segments.

When a sarcomere contracts, the Z lines move closer together, and the I band becomes smaller. The A band stays the same width. At full contraction, the thin and thick filaments overlap.

(a) Some ATP is stored in a resting muscle. As contraction starts, it is used up in seconds. More ATP is generated from creatine phosphate for about 15 seconds. (b) Each glucose molecule produces two ATP and two molecules of pyruvic acid, which can be used in aerobic respiration or converted to lactic acid. If oxygen is not available, pyruvic acid is converted to lactic acid, which may contribute to muscle fatigue. This occurs during strenuous exercise when high amounts of energy are needed but oxygen cannot be sufficiently delivered to muscle. (c) Aerobic respiration is the breakdown of glucose in the presence of oxygen (O2) to produce carbon dioxide, water, and ATP. Approximately 95 percent of the ATP required for resting or moderately active muscles is provided by aerobic respiration, which takes place in mitochondria.

Exercise-induced signaling pathways in skeletal muscle that determine specialized characteristics of slow- and fast-twitch muscle fibers

Jogging is one form of aerobic exercise.

In muscular dystrophy, the affected tissues become disorganized and the concentration of dystrophin (green) is greatly reduced.

Prisoner of war exhibiting muscle loss as a result of malnutrition.

The other types of muscle are cardiac muscle which is also striated and smooth muscle which is non-striated; both of these types of muscle tissue are classified as involuntary, or, under the control of the autonomic nervous system.

The myofibrils are composed of actin and myosin filaments called myofilaments, repeated in units called sarcomeres, which are the basic functional, contractile units of the muscle fiber necessary for muscle contraction.

Muscle contraction

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Activation of tension-generating sites within muscle cells.

In vertebrate animals, there are three types of muscle tissues: 1) skeletal, 2) smooth, and 3) cardiac

Sliding filament theory: A sarcomere in relaxed (above) and contracted (below) positions

Force–velocity relationship: right of the vertical axis concentric contractions (the muscle is shortening), left of the axis eccentric contractions (the muscle is lengthened under load); power developed by the muscle in red. Since power is equal to force times velocity, the muscle generates no power at either isometric force (due to zero velocity) or maximal velocity (due to zero force). The optimal shortening velocity for power generation is approximately one-third of maximum shortening velocity.

Swellings called varicosities belonging to an autonomic neuron innervate the smooth muscle cells.

Key proteins involved in cardiac calcium cycling and excitation-contraction coupling

A simplified image showing earthworm movement via peristalsis

Asynchronous muscles power flight in most insect species. a: Wings b: Wing joint c: Dorsoventral muscles power the upstroke d: Dorsolongitudinal muscles (DLM) power the downstroke. The DLMs are oriented out of the page.

Electrodes touch a frog, and the legs twitch into the upward position

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.

During a concentric contraction, contractile muscle myofilaments of myosin and actin slide past each other, pulling the Z-lines together.

Muscle cell

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Diagram of skeletal muscle fiber structure

A muscle cell is also known as a myocyte when referring to either a cardiac muscle cell (cardiomyocyte), or a smooth muscle cell as these are both small cells.

The thin myofilaments are filaments of mostly actin and the thick filaments are of mostly myosin and they slide over each other to shorten the fiber length in a muscle contraction.