The muscular system is composed of specialized cells called muscle fibers. Their predominant function is contractibility. Muscles, attached to bones or internal organs and blood vessels, are responsible for movement. Nearly all movement in the body is the result of muscle contraction. Exceptions to this are the action of cilia, the flagellum on sperm cells, and amoeboid movement of some white blood cells.
blank muscular system diagram
Muscle diagrams are a great way to get an overview of all of the muscles within a body region. Studying these is an ideal first step before moving onto the more advanced practices of muscle labeling and quizzes.
Your heart walls are the muscles that contract (squeeze) and relax to send blood throughout your body. A layer of muscular tissue called the septum divides your heart walls into the left and right sides.
The gastrointestinal tract is mostly dependent on smooth muscle for motility. Any damage to the smooth muscle of the intestines may have a devastating effect on the body. The term for this loss of motility is gastroparesis. Many conditions can impact gastric motility, including nerve dysfunction, collagen disease, muscular dystrophies, amyloidosis, thyroid disease, diabetes mellitus, Chagas disease, neuropathy, and so on. A spectrum of disease can occur in these patients; they may present asymptomatic, or they may present in crisis with functional gastric obstruction.[10] Gastric disorders should always immediately raise suspicion that there are potential impacts to smooth muscle physiology.
Duchenne muscular dystrophy (DMD) is a genetic disorder characterized by progressive muscle degeneration and weakness due to the alterations of a protein called dystrophin that helps keep muscle cells intact. DMD is one of four conditions known as dystrophinopathies. The other three diseases that belong to this group are Becker Muscular dystrophy (BMD, a mild form of DMD); an intermediate clinical presentation between DMD and BMD; and DMD-associated dilated cardiomyopathy (heart-disease) with little or no clinical skeletal, or voluntary, muscle disease.
DMD was first described by the French neurologist Guillaume Benjamin Amand Duchenne in the 1860s, but until the 1980s, little was known about the cause of any kind of muscular dystrophy. In 1986, MDA-supported researchers identified a particular gene on the X chromosome that, when flawed (mutated), leads to DMD. In 1987, the protein associated with this gene was identified and named dystrophin. Lack of the dystrophin protein in muscle cells causes them to be fragile and easily damaged.
Every skeletal muscle fiber is supplied by a motor neuron at the NMJ. Watch this video to learn more about what happens at the neuromuscular junction. (a) What is the definition of a motor unit? (b) What is the structural and functional difference between a large motor unit and a small motor unit? Can you give an example of each? (c) Why is the neurotransmitter acetylcholine degraded after binding to its receptor?
This product contains 2 skeletal muscle anatomy diagrams, one anterior and one posterior, in 4 different formats for a total of 8 high quality drawings for your advanced Biology or Anatomy & Physiology students. And, you also get an EDITABLE matching quiz and answer key!
Flatworms are more complex than cnidarians. Cnidarians have two layers of cells, the ectoderm and the endoderm; flatworms have a middle layer called the mesoderm between the other two layers (Fig. 3.16). This extra layer is important because its cells specialize into a muscular system that enables an animal to move around. Beginning with the flatworms, all the animals we will subsequently study have a mesoderm and muscular system. The cells of the ectoderm and endoderm are also more organized than similar cells of cnidarians. For the first time, we see groups of tissues that have evolved to form organs, such as the ones in the digestive, nervous, and excretory systems.
Polychaete (from the Greek root words poly meaning many and chaeta meaning bristle) annelid worms are so named because most of their segments have bristles called chatae or setae. Figure 3.44 shows two examples of polychaete setae. The free-moving (not sessile) polychaetes have muscular flaps called parapodia (from the Greek para meaning near and podia meaning feet) on their sides, and the setae on these parapodia dig into the sand for locomotion. Fireworms are a type of polychaete that have earned their name from stinging bristles on each parapodium (Fig. 3.44 A). These bristles can penetrate human skin, causing irritation, pain and swelling, similar to the irritation caused by exposure to fiberglass.
Almost all multicellular animals depend on muscles to move.[32] Generally, muscular systems of most multicellular animals comprise both slow-twitch and fast-twitch muscle fibers, though the proportions of each fiber type can vary across organisms and environments. The ability to shift their phenotypic fiber type proportions through training and responding to the environment has served organisms well when placed in changing environments either requiring short explosive movements (higher fast twitch proportion) or long duration of movement (higher slow twitch proportion) to survive.[33] Bodybuilding has shown that changes in muscle mass and force production can change in a matter of months.[34] Some examples of this variation are described below.[35]
Muscle also functions to produce body heat. Muscle contraction is responsible for producing 85% of the body's heat.[52] This heat produced is as a by-product of muscular activity, and is mostly wasted. As a homeostatic response to extreme cold, muscles are signaled to trigger contractions of shivering in order to generate heat.[53]
Contraction is achieved by the muscle's structural unit, the muscle fiber, and by its functional unit, the motor unit.[3] Muscle fibers are excitable cells stimulated by motor neurons. The motor unit consists of a motor neuron and the many fibers that it makes contact with. A single muscle is stimulated by many motor units. Muscle fibers aresubject to depolarization by the neurotransmitter acetylcholine, released by the motor neurons at the neuromuscular junctions.[54]
Since three factors affect muscular strength simultaneously and muscles never work individually, it is misleading to compare strength in individual muscles, and state that one is the "strongest". But below are several muscles whose strength is noteworthy for different reasons.
Diseases of skeletal muscle are termed myopathies, while diseases of nerves are called neuropathies. Both can affect muscle function or cause muscle pain, and fall under the umbrella of neuromuscular disease. The cause of many myopathies is attributed to mutations in the various associated muscle proteins.[5][71] Some inflammatory myopathies include polymyositis and inclusion body myositis
Neuromuscular diseases affect the muscles and their nervous control. In general, problems with nervous control can cause spasticity or paralysis, depending on the location and nature of the problem. A number of movement disorders are caused by neurological disorders such as Parkinson's disease and Huntington's disease where there is central nervous system dysfunction.[72]
Symptoms of muscle diseases may include weakness, spasticity, myoclonus and myalgia. Diagnostic procedures that may reveal muscular disorders include testing creatine kinase levels in the blood and electromyography (measuring electrical activity in muscles). In some cases, muscle biopsy may be done to identify a myopathy, as well as genetic testing to identify DNA abnormalities associated with specific myopathies and dystrophies.
A non-invasive elastography technique that measures muscle noise is undergoing experimentation to provide a way of monitoring neuromuscular disease. The sound produced by a muscle comes from the shortening of actomyosin filaments along the axis of the muscle. During contraction, the muscle shortens along its length and expands across its width, producing vibrations at the surface.[73]
Biological factors such as age and hormone levels can affect muscle hypertrophy. During puberty in males, hypertrophy occurs at an accelerated rate as the levels of growth-stimulating hormones produced by the body increase. Natural hypertrophy normally stops at full growth in the late teens. As testosterone is one of the body's major growth hormones, on average, men find hypertrophy much easier to achieve than women. Taking additional testosterone or other anabolic steroids will increase muscular hypertrophy.
The electrical activity associated with muscle contraction is measured via electromyography (EMG). Skeletal muscle has two physiological responses: relaxation and contraction. The mechanisms for which these responses occur generate electrical activity measured by EMG. Specifically, EMG can measure the action potential of a skeletal muscle, which occurs from the hyperpolarization of the motor axons from nerve impulses sent to the muscle. EMG is used in research for determining if the skeletal muscle of interest is being activated, the amount of force generated, and an indicator of muscle fatigue.[82] The two types of EMG are intra-muscular EMG and the most common, surface EMG. The EMG signals are much greater when a skeletal muscle is contracting verses relaxing. However, for smaller and deeper skeletal muscles the EMG signals are reduced and therefore are viewed as a less valued technique for measuring the activation.[83] In research using EMG, a maximal voluntary contraction (MVC) is commonly performed on the skeletal muscle of interest, to have reference data for the rest of the EMG recordings during the main experimental testing for that same skeletal muscle.[84]
Team work can provide greater variety and more evenly distributed muscular work. The whole team is involved in the planning and allocation of the work. Each team member carries out a set of operations to complete the whole product, allowing the worker to alternate between tasks, hence, reducing the risk of WMSDs. 2ff7e9595c
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