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Muscular System

BIO 10 LECTURE
by

Janica Marie Togonon

on 3 October 2012

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Transcript of Muscular System

The Muscular System is an organ system consisting of skeletal, smooth and cardiac muscles. It permits movement of the body, maintains posture, and circulates blood throughout the body. The muscular system in vertebrates is controlled through the nervous system, although some muscles (such as the cardiac muscle) can be completely autonomous.

Muscular System Latin Word(Systema Musculare).

There are approximately 639 skeletal muscles in the human body. TYPES OF MUSCULAR SYSTEM There are three distinct types of muscles: skeletal muscles, cardiac or heart muscles, and smooth (non-striated) muscles. is a form of striated muscle tissue existing under control of the somatic nervous system; that is to say, it is voluntarily controlled. Skeletal muscle is made up of individual components known as myocytes, or "muscle cells", sometimes colloquially called "muscle fibers". They are formed from the fusion of developmental myoblasts (a type of embryonic progenitor cell that gives rise to a muscle cell). These long, cylindrical, multinucleated cells are composed of myofibers.
The myofibers are in turn composed of myofibrils. The myofibrils are composed of actin and myosin myofibrils repeated as a sarcomere, the basic functional unit of the muscle fiber and responsible for skeletal muscle's striated appearance and forming the basic machinery necessary for muscle contraction. The term muscle refers to multiple bundles of muscle fibers held together by connective tissue. Skeletal muscle Heart muscles are distinct from skeletal muscles because the muscle fibers are laterally connected to each other. Furthermore, just as with smooth muscles, they are not controlling themselves. Heart muscles are controlled by the sinus node influenced by the autonomic nervous system called cardiomyocytes or myocardiocyteal muscle cells, can contain one, two, or very rarely three or four cell nuclei. Coordinated contractions of cardiac muscle cells in the heart propel blood out of the atria and ventricles to the blood vessels of the left/body/systemic and right/lungs/pulmonary circulatory systems. This complex of actions makes up the systole of the heart.
Cardiac muscle cells, like all tissues in the body, rely on an ample blood supply to deliver oxygen and nutrients and to remove waste products such as carbon dioxide. The coronary arteries fulfill this function. Cardiac Muscle are controlled directly by the autonomic nervous system and are involuntary, meaning that they are incapable of being moved by conscious thought. Functions such as heart beat and lungs (which are capable of being willingly controlled, be it to a limited extent) are involuntary muscles but are not smooth muscles.
Most smooth muscle is of the single-unit variety, that is, either the whole muscle contracts or the whole muscle relaxes, but there is multiunit smooth muscle in the trachea, the large elastic arteries, and the iris of the eye. Single unit smooth muscle, however, is most common and lines blood vessels (except large elastic arteries), the urinary tract, and the digestive tract.
Smooth muscle is fundamentally different from skeletal muscle and cardiac muscle in terms of structure, function, regulation of contraction, and excitation-contraction coupling. Smooth Muscles The muscular system is the body's network of tissues that controls movement both of the body structures and organs. Without the muscular system, all other essential functions of the body would not be able to take place. Muscular and Skeletal System
Skeletal muscles are attached to bones and allow them to move independently. Because they can only contract, skeletal muscles are typically grouped in pairs around joints, with each muscle in each pair performing antagonistic, or opposite, functions with the other. This means when one muscle in a pair contracts, the other relaxes and vice versa. Muscular and Nervous System
Every muscle in your body is under the direct control of your nervous system, which continuously relays messages to and from your brain through the use of your nerves. Sometimes these messages are in response to your direction, such as when you choose to move a muscle group. Other times, they are in response to outside stimuli. For example, if your body temperature drops, your nerves tell your muscles to contract and relax rapidly to produce heat. Nerves also control all of your automated heart and organ muscle functions. Muscular and Respiratory System
Your respiratory system is controlled by your diaphragm. Your diaphragm is a smooth muscle, but you do have limited control over it and you can deliberately alter your breathing patterns. Your lungs contain no muscles of their own, and your diaphragm actually does all of the work of breathing when you are sedentary. When you breathe hard due to exercise or exertion, muscles in your ribcage help the diaphragm along. Muscular and Digestive System
Powerful muscles in your esophagus push food downward into your stomach. The muscles in your stomach, along with stomach acid, actively churn your food into a soupy mixture and help empty it into the large intestine. Muscles in your intestines push the mixture farther down the intestinal tract. Muscular and Circulatory System
Your heart is arguably the most important muscle in your body. About the size of your fist, your heart powers your entire circulatory system, bringing nutrients and oxygen to each cell in your body. Your heart will beat up to 3 million times in your lifetime. Like other muscles, your heart becomes stronger when it's consistently exercised, so physical activity that keeps your heart rate elevated for an extended period of time will go a long way toward keeping it healthy. "The power of locomotion is that which contracts and relaxes the muscles whereby the members and joints are moved, extended or flexed. This power reaches the limbs by way of the nerves and there are as many forms of power as there are of movement. Each muscle has its own peculiar purpose and it obeys the decree of the composite sense." -- Avicenna, early 11th century

Muscles require, perhaps, less explanation in relation to other parts of the body: most larger muscles are readily visible beneath the skin and their role in the movement of the body was relatively easy to understand. Perhaps because of this fact, careful investigation of the muscles was relatively lacking in ancient and medieval anatomy.

The words that the Scottish medical student John Moir wrote down in 1620, echoing the medieval tradition of knowing the origins of words as a means of anatomizing the body: "Muscle is so called either because of a similarity to the shellfish, or because it resembles a skinned mouse. Muscle is also called lacertus because it resembles a lizard in color and shape."

By the early seventeenth century physicians focused less on the cultural meaning of a man without his skin and began to pay more attention to the actual structure of muscle itself. Fundamentally, this new interest in the muscles related to a widespread fascination about the nature of motion, not only in the body but in the world at large. As physicians and philosophers began to create more mechanistic theories of the body, a study of the musculature became an inquiry into the mechanisms of the body.

Let us consider, for example, how William Harvey in his Lectures on the Whole of Anatomy (1653), built upon the detailed investigations of early Renaissance anatomists to create a rather different picture of the body: "[Muscle] fibers [are] for the sake of motion, sinews, threads. Straight: [1] long longitudinally opening by contraction [2] transverse compressing by contraction. The oblique are unable to detain by tonic motion, because [according to] Fallopius the straight are opened and the transverse are not compressed, by contraction."
Such an account does not quite go as far as Descartes' description of muscles and tendons as "devices and springs which seem to set [nerves] in motion." It was Descartes who, in hisTreatise on Man (written between 1629 and 1633 and published in 1664), provided the ingredients for an utterly mechanist view of the body when he wrote: "I suppose the body to be nothing but a statue or machine made of earth, which God forms with the explicit intention of making it as much as possible like us." In the hands of certain readers, it was easy to remove God entirely from the picture, examining the body as if it were truly a machine -- brute matter in motion. Skeletal Muscles Create Movement
The primary function of skeletal muscle is to produce voluntary gross and fine movements to keep you alive. Large movements include walking, standing, gathering food, cooking food, turning in a chair, running, playing sports and lifting weights. Fine motor skills or smaller movements include chewing, closing your eyes, blinking, typing, writing and talking. Your skeletal muscles will also contract as a reflex to stimuli, like moving your hand from a very hot coffee cup or blinking your eyes when an eyelash lands on the surface of the eye. Skeletal Muscles Protect Organs
The abdominal muscles and the muscles of your lower back help to protect your vital organs. Your abdominal cavity is not protected by bones in the way that your rib cage protects your heart and lungs. Your rectus abdominus, or "six pack" muscle; your obliques, found at the sides of your torso; and your transverse abdominus, running side to side across the front of your abdominal cavity, protect your organs from the front and sides. From the lower back, your lats, quadrates lumborum and your psoas muscles, which run from the bottom area of your ribs to your pelvic bones, protect your organs from the back of your abdominal cavity. Cardiac Muscle Pumps Blood
The contraction of the heart muscle is involuntary and primarily controlled by your heart's own electrical system, with and without influence from factors in the blood. Your heart is responsible for receiving blood back from your muscles, pumping it into your lungs, receiving the blood from the lungs then pumping it out into your arteries to supply your entire body. When your heart muscle does not receive enough blood due to dead heart tissue or lack of sufficient oxygen, you will have a heart attack. Smooth Muscle Aids Digestion
The smooth muscles in your stomach and intestines work to process the food you eat. The involuntary contractions in your stomach and intestines aid in digestion and in moving the food along your digestive tract, ultimately directing indigestible substances to your rectum. Smooth Muscle Ensures Blood Flow
There are smooth muscles in the walls of your blood vessels. When your heart contracts, your arteries expand to accept the blood. The smooth muscles in your arteries contract to push the blood throughout the blood vessel systems in your body, ultimately pushing the blood from your arterioles into your capillaries to return back to the heart. When plaque builds up on the walls of your arteries, your arteries harden and the muscles in your arteries will not contract properly. HISTORY
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