Join us and participate in our Forum discussion: Smooth muscle vs dense regular connective tissue. Smooth muscle is a type of muscle that contracts without any voluntary control, and it is made of a thin form of layers, which is made up of spindle-shaped, unstriated cells with only one nucleus and present in inner organs walls like bladder , intestine, stomach , blood vessels , etc.
These muscles are found all over the body, performing several vital functions of the body, and controlled by the nervous system.
An individual does not have to worry about his or her blood pressure to respond to increased oxygen demands. The nervous system spontaneously controls smooth muscles via hormones , neurotransmitters, and other receptors. These muscles are present in the different organs of the body, such as the gastrointestinal tract where they aid in digestion.
It is also present in the urinary system and performs the electrolyte balance function to eliminate the body toxins effectively. It is also found in the different blood vessels , performing vital roles in controlling the oxygenation of tissues and pressure of blood in the body.
Our body will not be able to perform such vital functions without smooth muscles. Compare: skeletal muscle ; cardiac muscle. Question: Is smooth muscle striated? Answer: Compared to skeletal and cardiac muscles, smooth muscles are not striated. Their name shows that they have a smooth outlook, and such muscles are used in the body system to apply force to vessels of the blood and other body organs.
These muscles stretch under specific stimuli by using adenosine triphosphate as energy, and ATP usage also depends on the strength or intensity of stimuli that allows muscles to have a graded contraction. Question: How smooth muscles are different from other muscles?
Answer: Smooth muscles are different in several ways from other body muscles, but the most notable difference is their capacity to be involuntarily contracted and regulated. How is a muscle tissue different from other tissues? Ask our Expert! Join us and participate in our Forum: Smooth muscle vs dense regular connective tissue. The cytoplasm of smooth muscles is eosinophilic and mostly made up of myofilaments.
At the center of the smooth muscle is the nucleus, appearing as a cigar-like structure when it contracts. A basal lamina anchors these cells and the underlying connective tissue. Unlike in the skeletal muscles, smooth muscle fiber has a spindle-like shape. The fibers form sheets of tissue that work in coordination due to the gap junctions connecting these cells.
Their bundles are not purely parallel and ordered like the skeletal muscles but are composed of a complex structure. These cells can contract even faster than the skeletal muscles. There are thick and thin filaments in the smooth muscle; however, they are not organized into sarcomeres. Thus, the filaments do not form a striated pattern. Under the microscope, it appears homogeneous.
Their cytoplasm includes high concentrations of myosin and actin. Actin and myosin proteins are the primary muscle contraction proteins. The filaments of actin adhere to dense bodies that are scattered across the cell. The filaments of myosin are lying between the filaments of actin. Under an electron microscope, thick bodies may be identified, and they look black. Cardiac muscle cells contract autonomously and involuntarily. Smooth muscle is involuntary. Each cell is a spindle-shaped fiber and contains a single nucleus.
No striations are evident because the actin and myosin filaments do not align in the cytoplasm. Skeletal muscle is composed of very hard working cells. Which organelles do you expect to find in abundance in skeletal muscle cell? You are watching cells in a dish spontaneously contract. They are all contracting at different rates; some fast, some slow. After a while, several cells link up and they begin contracting in synchrony. Discuss what is going on and what type of cells you are looking at.
The cells in the dish are cardiomyocytes, cardiac muscle cells. They have an intrinsic ability to contract. When they link up, they form intercalating discs that allow the cells to communicate with each other and begin contracting in synchrony. Under the light microscope, cells appear striated due to the arrangement of the contractile proteins actin and myosin.
Skip to content The Tissue Level of Organization. Learning Objectives By the end of this section, you will be able to: Identify the three types of muscle tissue Compare and contrast the functions of each muscle tissue type Explain how muscle tissue can enable motion. Each I band has a dense line running vertically through the middle called a Z disc or Z line.
The Z discs mark the border of units called sarcomeres , which are the functional units of skeletal muscle. One sarcomere is the space between two consecutive Z discs and contains one entire A band and two halves of an I band, one on either side of the A band.
A myofibril is composed of many sarcomeres running along its length, and as the sarcomeres individually contract, the myofibrils and muscle cells shorten Figure 3. Myofibrils are composed of smaller structures called myofilaments.
There are two main types of filaments: thick filaments and thin filaments; each has different compositions and locations. Thick filaments occur only in the A band of a myofibril.
Thin filaments attach to a protein in the Z disc called alpha-actinin and occur across the entire length of the I band and partway into the A band. The region at which thick and thin filaments overlap has a dense appearance, as there is little space between the filaments.
The middle of the dark band has a vertical line called the M line, at which accessory proteins hold together thick filaments. Both the Z disc and the M line hold myofilaments in place to maintain the structural arrangement and layering of the myofibril. Thick and thin filaments are themselves composed of proteins. Thick filaments are composed of the protein myosin. The tail of a myosin molecule connects with other myosin molecules to form the central region of a thick filament near the M line, whereas the heads align on either side of the thick filament where the thin filaments overlap.
Skeletal muscles are long and cylindrical in appearance; when viewed under a microscope, skeletal muscle tissue has a striped or striated appearance. The striations are caused by the regular arrangement of contractile proteins actin and myosin. Actin is a globular contractile protein that interacts with myosin for muscle contraction.
Skeletal muscle also has multiple nuclei present in a single cell. Smooth muscle tissue occurs in the walls of hollow organs such as the intestines, stomach, and urinary bladder, and around passages such as the respiratory tract and blood vessels. Smooth muscle has no striations, is not under voluntary control, has only one nucleus per cell, is tapered at both ends, and is called involuntary muscle. Cardiac muscle tissue is only found in the heart, and cardiac contractions pump blood throughout the body and maintain blood pressure.
Like skeletal muscle, cardiac muscle is striated, but unlike skeletal muscle, cardiac muscle cannot be consciously controlled and is called involuntary muscle. It has one nucleus per cell, is branched, and is distinguished by the presence of intercalated disks. Each skeletal muscle fiber is a skeletal muscle cell. The plasma membrane of a skeletal muscle fiber is called the sarcolemma. The sarcolemma is the site of action potential conduction, which triggers muscle contraction.
Within each muscle fiber are myofibrils —long cylindrical structures that lie parallel to the muscle fiber. Myofibrils run the entire length of the muscle fiber, and because they are only approximately 1.
They attach to the sarcolemma at their ends, so that as myofibrils shorten, the entire muscle cell contracts Figure 2. Figure 2.
0コメント