A report on Cardiac muscle and T-tubule

Skeletal muscle fiber, with T-tubule labelled in zoomed in image.
3D rendering showing thick myocardium within the heart wall.
The swirling musculature of the heart ensures effective pumping of blood.
Cardiac muscle
Illustration of a cardiac muscle cell.
Intercalated discs are part of the cardiac muscle cell sarcolemma and they contain gap junctions and desmosomes.
Dog cardiac muscle (400X)

T-tubules (transverse tubules) are extensions of the cell membrane that penetrate into the centre of skeletal and cardiac muscle cells.

- T-tubule

Cardiomyocytes contain T-tubules, pouches of cell membrane that run from the cell surface to the cell's interior which help to improve the efficiency of contraction.

- Cardiac muscle

6 related topics with Alpha

Overall

Types of muscle contractions

Muscle contraction

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Activation of tension-generating sites within muscle cells.

Activation of tension-generating sites within muscle cells.

Types of muscle contractions
In vertebrate animals, there are three types of muscle tissues: 1) skeletal, 2) smooth, and 3) cardiac
Organization of skeletal muscle
Structure of neuromuscular junction.
Sliding filament theory: A sarcomere in relaxed (above) and contracted (below) positions
Cross-bridge cycle
Muscle length versus isometric force
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.
Cardiac muscle
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.

DHPRs are located on the sarcolemma (which includes the surface sarcolemma and the transverse tubules), while the RyRs reside across the SR membrane.

A top-down view of skeletal muscle

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.

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.

A top-down view of skeletal muscle
3D rendering of a skeletal muscle fiber
Muscle types by fiber arrangement
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.
Contraction in more detail
(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.

T tubules are the pathways for action potentials to signal the sarcoplasmic reticulum to release calcium, causing a muscle contraction.

Myofilament

Myofilament

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Myofilaments are the three protein filaments of myofibrils in muscle cells.

Myofilaments are the three protein filaments of myofibrils in muscle cells.

Myofilament
Muscle fiber showing thick and thin myofilaments of a myofibril.

Types of muscle tissue are striated skeletal muscle and cardiac muscle, obliquely striated muscle (found in some invertebrates), and non-striated smooth muscle.

This depolarizes the muscle fiber membrane, and the impulse travels to the muscle's sarcoplasmic reticulum via the transverse tubules.

A cartoon section of skeletal muscle, showing T-tubules running deep into the centre of the cell between two terminal cisternae/junctional SR. The thinner projections, running horizontally between two terminal cisternae are the longitudinal sections of the SR.

Sarcoplasmic reticulum

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Membrane-bound structure found within muscle cells that is similar to the smooth endoplasmic reticulum in other cells.

Membrane-bound structure found within muscle cells that is similar to the smooth endoplasmic reticulum in other cells.

A cartoon section of skeletal muscle, showing T-tubules running deep into the centre of the cell between two terminal cisternae/junctional SR. The thinner projections, running horizontally between two terminal cisternae are the longitudinal sections of the SR.

Cardiac and skeletal muscle cells contain structures called transverse tubules (T-tubules), which are extensions of the cell membrane that travel into the centre of the cell.

There are three types of ryanodine receptor, RyR1 (in skeletal muscle), RyR2 (in cardiac muscle) and RyR3 (in the brain).

Immunohistochemical analysis of L-type calcium channel Cav1.3 (CACNA1D) in human adrenal cortex. Marked immunoreactivity was detected in the zona glomerulosa. In the figure: ZG = zona glomerulosa, ZF = zona fasciculata, AC = adrenal capsule. Immunohistochemistry was performed according to published methods.

L-type calcium channel

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Part of the high-voltage activated family of voltage-dependent calcium channel.

Part of the high-voltage activated family of voltage-dependent calcium channel.

Immunohistochemical analysis of L-type calcium channel Cav1.3 (CACNA1D) in human adrenal cortex. Marked immunoreactivity was detected in the zona glomerulosa. In the figure: ZG = zona glomerulosa, ZF = zona fasciculata, AC = adrenal capsule. Immunohistochemistry was performed according to published methods.
An L-type calcium channel with its subunits labeled along with some drugs known to inhibit the channel.
Alpha subunit of a generic voltage-gated ion channel

L-type calcium channels are responsible for the excitation-contraction coupling of skeletal, smooth, cardiac muscle, and for aldosterone secretion in endocrine cells of the adrenal cortex.

In skeletal muscle, there is a very high concentration of L-type calcium channels, situated in the T-tubules.

Diad

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Structure in the cardiac myocyte located at the sarcomere Z-line.

Structure in the cardiac myocyte located at the sarcomere Z-line.

It is composed of a single t-tubule paired with a terminal cisterna of the sarcoplasmic reticulum.

This way, the wave of depolarization can be coupled to calcium-mediated cardiac muscle contraction via the sliding filament mechanism.