Muscular System or Human Muscle
Muscle cells consist of contractile filaments that move forward away from one another and modify the size of the cell. Muscles are mainly powered by the oxidation of fats and carbohydrates, but anaerobic chemical reactions can also be utilized, especially by fast twitch fibers.These chemical reactions generate adenosine triphosphate (ATP) molecules which are utilized to power the movements of the myosin heads. Muscle could be classified into three types based on structure, function, and location in the body.
Over 600 skeletal muscles function for body motion by means of contraction and relaxation of voluntary, striated muscle fibers. These muscles are connected to our bones, and they are generally under conscious control for locomotion, facial expressions, posture, along with other body movements. Muscles account for approximately 40 percent of bodyweight. One's metabolism that develops within this large mass-produces heat required for the constant maintenance of the body's temperature.
Nearly every muscle comprises one element of a pair of identical bilateral muscles, seen on each side, contributing to around 320 pairs of muscles. On the other hand, the actual number is actually difficult to determine due to the fact various sources group muscles differently, e.g. regarding what is described as different parts of a single muscle or as several muscles.
The muscles of the human body could be classified into a number of groups which include muscles relating to the head and neck, muscles of the torso or trunk, muscles of the upper limbs, and muscles of the lower limbs, but here we will talk about human muscular system.
Cardiac Muscle
Cardiac muscle is a kind of involuntary striated muscle tissue found only within the walls of the heart. This can be a specialised muscle tissue that, while comparable in certain basic approaches to smooth muscle and skeletal muscle, includes a unique structure along with the capability not possessed by muscle tissues anywhere else within the body.
Cardiac muscle, like other muscles, can contract, but it can also carry an action potential (i.e. conduct electricity), like the neurons that make up nerves. In addition, a few of the cells have the capacity to produce actions possibilities, generally known as cardiac muscle automaticity.
As the muscle contracts, it propels blood in to the heart and through the blood vessels of the circulatory system. For a human being, the heart beats about once a second for the entire life of the person, without any opportunity to rest.
It can adjust swiftly for the body's needs, increasing output from five liters of blood per minute to more than 25 liters per minute. The muscles that contract the heart can do so without external stimulation from hormones or nerves, and it does not fatigue or stop contracting if supplied with sufficient oxygen and nutrients.
Cardiac muscle is merely within the heart and balances out the atria and ventricles (heart walls). Like skeletal muscle, cardiac muscle contains striated fibers. Cardiac muscle is known as involuntary muscle simply because conscious thought doesn't manage its contractions. Specialized cardiac muscle cells conserve a constant heartrate.
The muscular tissue of the heart is known as myocardium. The myocardium consists of specialised cardiac muscle, because of its bundles of muscle cells, technically known as myocytes. A myocyte, or muscle fiber, is really a single cell of the muscle.
These muscle fibers consist of numerous myofibrils, the contractile units of muscles. Myofibrils run derived from one of end of your cell to another and therefore are alternating bundles of thin filaments, comprising primarily actin, and thick filaments, comprising primarily the protein myosin. Like smooth and skeletal muscle, cardiac muscle contracts according to a rise of calcium inside the muscle cell, allowing interaction of actin and myosin.
Cardiac and skeletal muscle offer a similar experience for the reason that both seem to be "striated" for the reason that they contain sarcomeres. In striated muscle, for example skeletal and cardiac muscle, the actin and myosin filaments have a particular and constant length around the order of some micrometers, much less expensive than the capacity of the elongated muscle cell (a couple of millimeters when it comes to human skeletal muscle cells).
The filaments are structured into repetitive subunits across the length. These subunits are known as sarcomeres. The sarcomeres are what give skeletal and cardiac muscles their striated look of narrow dark and light bands, due to the parallel arrangement in the actin and myosin filaments. The myofibrils of smooth muscle cells are certainly not organized into sarcomeres. Striated muscle (cardiac and skeletal) contracts and relaxes in short, intense bursts, whereas smooth muscle recieves for a longer time as well as near-permanent contractions.
Smooth Muscle
Smooth muscle is through the entire body, which includes in visceral (internal) organs, blood vessels, and glands. Like cardiac muscle, smooth muscle is involuntary. Unlike skeletal and cardiac muscle, smooth muscle is non-striated (not banded). Smooth muscle, which can be thoroughly inside the walls of digestive tract organs, causes peristalsis (wave-like contractions) that helps in food digestion and transportation.
Smooth muscle is mainly responsible for the contractility of hollow organs, for example blood vessels, the gastrointestinal tract, the bladder, or even the uterus. Its structure is different significantly from that relating to skeletal muscle, even though it may develop isometric force per cross-sectional area that is equivalent to that relating to skeletal muscle. However, the speed of smooth muscle contraction is just a small part of that surrounding skeletal muscle.
Probably the most impressive characteristic of smooth muscle is the possible lack of visible cross striations (and so the name smooth). Smooth muscle fibers are much smaller (2-10 m across) than skeletal muscle fibers (10-100 m ). It really is traditional to categorize smooth muscle as single-unit and multi-unit smooth muscle. The fibers are put together in a different way.
The muscle fibers getting back together the single-unit muscle are collected into dense sheets or bands. Although fibers run nearly parallel, they may be densely and irregularly packed together, usually in order that the narrow portion of one fiber lies up against the broader portion of its neighbor.
These fibers have connections, the plasma membranes of two neighboring fibers form gap junctions that behave as lower resistance pathway for your fast spread of electrical signals through the entire tissue. The multi-unit smooth muscle fibers don't have any internally connected bridges. These are mingled with connective tissue fibers. Except the heart, any action which the entire body executes without having conscious thought is performed by smooth muscle contractions. This consists of varied actions including constricting (closing) the bronchioles (air passages) of the lungs or pupils of the eye or causing goose bumps in cold conditions.
Skeletal Muscle
Skeletal muscles move and support the skeleton. They create up 50 percent of the body weight. There are actually 640 individually named skeletal muscles. A skeletal muscle links two bones throughout its connecting joint. When these muscles contract or shorten, your bone moves.
Muscles are organized in layers within the bones. Those nearest towards the skin are known as superficial muscles. Those nearest to the inside of your body are known as deep muscles. Skeletal muscles are voluntary muscles. These are generally muscles that any of us can consciously control.
A skeletal system has regular, ordered sets of fascicles, muscle fibers, myofibrils, and myofilaments. Epimysium (thick connective tissue) binds groups of fascicles together. A fascicle has muscle fibers; perimysium (connective tissue) envelops the fascicle. Endomysium (connective tissue) surrounds the muscle fibers.
A muscle fiber divides into even smaller parts. Inside of each and every fiber are strands of myofibrils. These long cylindrical structures seem striped because of strands of tiny myofilaments. Myofilaments have two kinds of protein: actin (thin myofilaments) and myosin (thick myofilaments).
The actin and myosin myofilaments align equally, developing dark and light-weight bands around the myofibril. Each dark band depicts a place in which the myofilaments overlap, resulting in the striated appearance of skeletal muscle.
All dark and light-weight bands of the myofilaments have names. In the Z-line, actin strands interweave. The location in between two Z-lines is really a sarcomere, the running unit of skeletal muscle. Muscle contraction takes place when overlapping actin and myosin myofilaments overlap further and shorten the muscle cell. The myofilaments keep their length. The overlapping of myofilaments may be the reason for sliding filament theory of contraction.
Skeletal muscle is really a system of pairs that relax and contract to move a joint. As an example, when front leg muscles contract, the knee extends (straightens) while back leg muscles relax. Conversely, to flex (bend) the knee, back leg muscles contract while front leg muscles relax.
Some muscles are named for their ability to extend or flex a joint; for example, extensor carpiradialis longus muscle and flexor digitorum brevis muscle.
Tendons attach most skeletal muscles to bones. Tendons are strong sheets of connective tissue that are identical with ligaments. Tendons and ligaments differ in function only: tendons attach muscle to bone and ligaments attach bone to bone. Physical activity strengthens the attachment of tendons to bones.
Skeletal muscles have muscle tone (remain partly contracted), which will help sustain body posture. Ongoing signals in the central nervous system to the muscle cells help support tone and readiness for physical exercise.
Skeletal muscle helps with heat generation. During muscle contractions, muscle cells expend much energy, many of which is transformed into heat. In order to avoid getting too hot, glands within the skin produce sweat to cool down the skin; and, the body radiates heat from the blood and tissues through the skin. When the body is cool, shivering causes quick muscle contractions that generate heat.
Skeletal muscles have two kinds of muscle fibers: fast-twitch and slow-twitch. Anaerobic exercise uses fast-twitch fibers. Such exercise includes activities which can be fleeting and require brief high-energy expenditure. Weightlifting, sprinting, and push-ups are types of anaerobic exercise. Because all cells require oxygen to generate energy, anaerobic exercise depletes oxygen reserves within the muscle cells quickly.
The result is an oxygen debt.
To settle the debt, humans breathe deeply and rapidly, which reinstates the oxygen level. Anaerobic exercise produces extra lactic acid (a waste product). By increasing oxygen intake, the liver cells can convert the extra lactic acid into glucose, the main food molecule utilized in cellular metabolism.
Aerobic exercise uses slow-twitch muscle fibers. Such physical exercise includes activities which are prolonged and need constant energy. Long-distance running and cycling are types of aerobic exercise. In aerobic exercise, the muscle cell demands the same amount of oxygen that the body supplies. The oxygen debt is slashed and lactic acid is not really formed.