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Muscle system

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    Muscle system Muscle system Presentation Transcript

    • Muscle System Andrew McCaskill – Anatomy/Physiology -CHHS
    • “ Muscular "strength" usually refers to the ability to exert a force on an external object—for example, lifting a weight. By this definition, the masseter or jaw muscle is the strongest. What distinguishes the masseter is not anything special about the muscle itself, but its advantage in working against a much shorter lever arm than other muscles. Interesting Facts: What is the strongest muscle in the human body? Depending on what definition of "strongest" is used, many different muscles in the human body can be characterized as being the "strongest”. If "strength" refers to the force exerted by the muscle itself, e.g., on the place where it inserts into a bone, then the strongest muscles of the body are usually said to be the quadriceps femoris or the gluteus maximus. "Copyright 2003-2004 University of Washington. All rights reserved including all photographs and images. No re-use, re-distribution or commercial use without prior written permission of the authors and the University of Washington." "Musculoskeletal Images are from the University of Washington "Musculoskeletal Atlas: A Musculoskeletal Atlas of the Human Body" by Carol Teitz, M.D. and Dan Graney, Ph.D."
    • Again taking strength to mean only "force", then a shorter muscle will be stronger "pound for pound" (i.e., by weight) than a longer muscle. The uterus may be the strongest muscle by weight in the human body. At the time when an infant is delivered, the human uterus weighs about 40 oz (1.1 kg). During childbirth, the uterus exerts 25 to 100 lbs (100 to 400 N) of downward force with each contraction. The external muscles of the eye are conspicuously large and strong in relation to the small size and weight of the eyeball. It is frequently said that they are "the strongest muscles for the job they have to do" and are sometimes claimed to be "100 times stronger than they need to be". Eye movements, however, probably do "need" to be exceptionally fast.
    • The heart has a claim to being the muscle that performs the largest quantity of physical work in the course of a lifetime. Estimates of the power output of the human heart range from 1 to 5 watts. This is much less than the maximum power output of other muscles; for example, the quadriceps can produce over 100 watts, but only for a few minutes. The heart does its work continuously over an entire lifetime without pause, and thus does "outwork" other muscles. An output of one watt continuously for seventy years yields a total work output of 2 to 3 ×109 joules. The tongue may possibly be the strongest muscle at birth.
    • “ Muscular contraction is one of the most wonderful phenomena of the biological kingdom. That a soft jelly should suddenly become hard, change its shape, and lift a thousand times its weight, and that it should be able to do so several times a second, is little short of miraculous. Undoubtedly, muscle is one of the most remarkable items in nature’s curiosity shop. - Albert Szent-Gyorgyi, 1937 Nobel Laureate in Biology
    • Muscle is contractile tissue of the body and is derived from the mesodermal layer of embryonic germ cells. Its function is to produce force and cause motion , either locomotion or movement within internal organs. Much of muscle contraction occurs without conscious thought (involuntary) and is necessary for survival, like the contraction of the heart, or peristalsis (which pushes food through the digestive system). Voluntary muscle contraction is used to move the body, and can be finely controlled, like movements of the finger, or gross movements like the quadriceps muscle of the thigh. There are approximately 650 skeletal muscles in the human body. Contrary to popular belief, the number of muscle fibers cannot be increased through exercise; instead the muscle cells simply get bigger.
    • Anatomy Muscle is mainly composed of muscle cells (myocyte but usually known as “ muscle fibers “, a single fiber can reach a length of 30cm.). Within the cells are myofibrils ; myofibrils contain sarcomeres , which are composed of actin and myosin . Individual muscle fibres are surrounded by endomysium . Muscle fibres are bound together by perimysium into bundles called fascicles ; the bundles are then grouped together to form muscle, which is enclosed in a sheath of epimysium . Muscle spindles are distributed throughout the muscles and provide sensory feedback information to the central nervous system. Neuromuscular junction 1. Axon 2. Synaptical junction 3. Muscle fiber 4. Myofibrils
    • Myofibrils are cylindrical organelles, found within muscle cells. They are bundles of filaments that run from one end of the cell to the other and are attached to the cell surface membrane at each end. The filaments of myofibrils consist of two types, thick and thin. 1. Thin filaments consist primarily of the protein actin. 2. Thick filaments consist primarily of the protein myosin , held in place by titin filaments.
    • The filaments are organized into repeated subunits along the length of the myofibril. These subunits are called sarcomeres . The sarcomeric subunits of one myofibril are in nearly perfect alignment with those of the myofibrils next to it. This alignment gives rise to certain optical properties which cause the cell to appear striped or striated . In smooth muscle cells, this alignment is absent. Hence there are no apparent striations and the cells are called smooth. A muscle cell, from a biceps, may contain 100,000 sarcomeres.
    • Actin is a globular structural protein that polymerizes in a helical fashion to form an actin filament . Actin is one of the most abundant proteins in many eukaryotic cells.
    • Most myosin molecules are composed of both a head and a tail domain. The head domain binds the filamentous actin , and uses ATP hydrolysis to generate force and to "walk" along the filament towards the (+) end . Myosin are heavy chains, possibly 2000 amino acids in length, which constitute the head and tail domains.
    • Titin , also known as connectin , is a protein that is important in the contraction of striated muscle tissues.. The protein limits the range of motion of the sarcomere in tension, thus contributing to the passive stiffness of muscle. Factoid: Titin is the largest known protein, consisting of 26,926 amino acids. The protein's chemical formula is C132983 H211861 N36149 O40883 S693.
      • Physiology
        • Muscular activity accounts for much of the body's energy consumption. All muscle cells produce adenosine triphosphate (ATP) molecules which are used to power the movement of the myosin heads.
      Adenosine 5'-triphosphate ( ATP ) Within the voluntary skeletal muscles, the glucose molecule is metabolized in a process called glycolysis which produces two ATP molecules in the process. Muscle cells also contain globules of fat, which are used for energy during aerobic exercise. The aerobic energy systems take longer to produce the ATP and reach peak efficiency, and requires many more biochemical steps, but produces significantly more ATP than anaerobic glycolysis. Cardiac muscle on the other hand, can readily consume any of the three macronutrients (protein, glucose and fat) without a 'warm up' period and always extracts the maximum ATP yield from any molecule involved. The heart and liver will also consume lactic acid produced and excreted by skeletal muscles during exercise.
    • Contraction of a muscle fiber. Images from Purves et al., Life: The Science of Biology , 4th Edition, by Sinauer Associates ( www.sinauer.com ) and WH Freeman ( www.whfreeman.com ) Physiological steps of muscle contraction Animation 1 Animation 2
    • There are three type of muscle:
    • Skeletal muscle or "voluntary muscle" is anchored by tendons to bone and is used to affect skeletal movement such as locomotion and in maintaining posture . An average adult male is made up of 40-50% of skeletal muscle and an average adult female is made up of 30-40%. There are two types of fibers for skeletal muscles: Type I and Type II. Type I fibers appear reddish. They are good for endurance and are slow to tire because they use oxidative metabolism ( movements act for a long time but not very fast) . Type II fibers are whitish; they are used for short bursts of speed and power, use anaerobic metabolism, and are therefore quicker to tire ( act quickly, but not for a very long time.) .
    • Muscles are normally arranged in opposition so that as one group of muscles contract, another group 'relaxes' or lengthens, this is called antagonism. How skeletal muscle works Antagonism means that it is impossible to stimulate the contraction of two antagonistic muscles at any one time. In the example of throwing a ball, the biceps contracts to pull the arm upward and create force, while the triceps muscle in the back relaxes in preparation for the throwing action.
    • Skeletal muscles usually have one end (the "origin") attached to a relatively stationary bone, (such as the scapula) and the other end (the "insertion") is attached across a joint, to another bone (such as the humerus). "Copyright 2003-2004 University of Washington. All rights reserved including all photographs and images. No re-use, re-distribution or commercial use without prior written permission of the authors and the University of Washington." "Musculoskeletal Images are from the University of Washington "Musculoskeletal Atlas: A Musculoskeletal Atlas of the Human Body" by Carol Teitz, M.D. and Dan Graney, Ph.D."
    • Cardiac muscle is anatomically different in that the muscle fibers are typically branched like a tree branch, and connect to other cardiac muscle fibers through intercalated disks. Cardiac muscle is a type of involuntary , striated muscle found exclusively within the heart. Its function is to “pump" blood through the circulatory system by contracting.
    • Intercalated Discs Under light microscopy, intercalated discs appear as thin, typically dark-staining lines dividing adjacent cardiac muscle cells. The intercalated discs run perpendicular to the direction of muscle fibers. Unlike skeletal muscle, which contracts in response to nerve stimulation, cardiac muscle is myogenic , meaning that it is self-excitable stimulating contraction without an electrical impulse coming from the central nervous system. This inherent contractile activity is heavily regulated by the autonomic nervous system . If synchronization of cardiac muscle contraction is disrupted for some reason (for example, in a heart attack), uncoordinated contraction known as fibrillation can result .
    • Nuclei (Differences) Cardiac muscle can be distinguished from skeletal muscle because cardiac muscle nuclei are centrally located among the myofibrils, unlike the peripheral nuclei of skeletal muscle . A unique aspect of cardiac muscle is the number of nuclei found inside the cell. Skeletal muscle cells are multinucleated from the fusion of muscle cells, whereas smooth muscle cells are strictly mononucleated , and cardiac muscle cells are predominantly mononucleated in humans.
    • Smooth muscle or "involuntary muscle" is found within the walls of organs and structures such as the esophagus, stomach, intestines, bronchi, uterus, urethra, bladder, and blood vessels, and unlike skeletal muscle, smooth muscle is not under conscious control.
    • Function of smooth muscle The contractile function of this muscle, to a large extent determines the function of the organ. Often smooth muscle containing tissue are very elastic so the tissue can be stretched and still maintain its function. Smooth muscle may contract spontaneously or be induced by a number of physiochemical agents . Smooth muscle contracts slowly and may maintain the contraction for prolonged periods in blood vessels (and sphincters). Smooth muscle in the digestive tract contracts in a rhythmic peristaltic fashion.
    • Nervous control The peripheral nervous system is responsible for conveying commands to the muscles and glands, and is ultimately responsible for voluntary movement . Nerves move muscles in response to voluntary and autonomic (involuntary) signals from the brain.
    • Disease There are many diseases and conditions which cause a decrease in muscle mass, known as atrophy . During aging, there is a gradual decrease in the ability to maintain skeletal muscle function and mass. This condition is called sarcopenia . In addition, there are other diseases which may be caused by structural defects in the muscle (the dystrophies), or by inflammatory reactions in the body directed against muscle (the myopathies). Neuromuscular diseases are those that affect the muscles and/or their nervous control. In general, problems with nervous control can cause paralysis , depending on the location and nature of the problem. A large proportion of neurological disorders leads to problems with movement , ranging from cerebrovascular accident (stroke) and Parkinson’s disease to Creutzfeldt-Jakob disease.
    • Muscles of facial expression Muscle Origin Insertion Action Epicranius (2 parts: frontal and occipital) Occipital bone Skin and muscles around the eye Raises eyebrow Orbicularis oculi Maxilla and Frontal Bones Skin around eye Closes eye (wink/blink) Orbicularis oris Muscles near mouth Skin of lips Closes and protrudes lips (kissing)
    • Muscles of facial expression…continued Muscle Origin Insertion Action Zygomaticus Zygomatic bone Orbicularis oris Raises corner of mouth (smiling effect) Platysma Upper Chest mandible Draws mouth downward (frowning effect)
    • Muscles of Mastication Muscle Origin Insertion Action Masseter Zygomatic arch mandible Closes jaw Temporalis Temporal bone Coronoid process of mandible Closes jaw
    • Muscles that move the Head Muscle Origin Insertion Action Sternocleidomastoid Sternum and clavicle Mastoid process of temporal Pulls head to one side (tilts head), raises sternum (shoulder shrug) Splenius capitus Cervical and thoracic vertebrae Mastoid process of temporal Rotates head
    • "Copyright 2003-2004 University of Washington. All rights reserved including all photographs and images. No re-use, re-distribution or commercial use without prior written permission of the authors and the University of Washington." "Musculoskeletal Images are from the University of Washington "Musculoskeletal Atlas: A Musculoskeletal Atlas of the Human Body" by Carol Teitz, M.D. and Dan Graney, Ph.D." Muscles of the pectoral girdle Muscle Origin Insertion Action Trapezius Occipital bone and cervical and thoracic vertebrae Clavicle and Scapula Raises arm and rotates scapula Pectoralis minor Ends of upper ribs Coracoid process of scapula Raises ribs and pulls scapula downward
    • Muscles that move arm "Copyright 2003-2004 University of Washington. All rights reserved including all photographs and images. No re-use, re-distribution or commercial use without prior written permission of the authors and the University of Washington." "Musculoskeletal Images are from the University of Washington "Musculoskeletal Atlas: A Musculoskeletal Atlas of the Human Body" by Carol Teitz, M.D. and Dan Graney, Ph.D." Muscle Origin Insertion Action Pectoralis Major Clavicle, sternum Humerus Pulls arm anterioraly and across chest Latissimus dorsi Sacrum, thoracic and lumbar vertebrae Humerus, intertubercular groove Extends and adducts arm Deltoid Acromion process, clavicle humerus Abducts arm Subscapularis Scapula, anterior surface Lesser tubercle of humerus Rotates arm medially
    • Muscles that move the forearm! "Copyright 2003-2004 University of Washington. All rights reserved including all photographs and images. No re-use, re-distribution or commercial use without prior written permission of the authors and the University of Washington." "Musculoskeletal Images are from the University of Washington "Musculoskeletal Atlas: A Musculoskeletal Atlas of the Human Body" by Carol Teitz, M.D. and Dan Graney, Ph.D." Muscle Origin Insertion Action Biceps brachii Coracoid process of scapula Radial tuberosity and ulna Flexes forearm at elbow and rotates hand laterally Triceps brachii Lateral and medial surfaces of humerus/scapula Olecranon process of ulna Extends forearm at elbow Supinator Lateral epicondyle of humerus and ulna Medial surface of radius Rotates arm laterally (supinates arm) Pronator teres Medial epicondyle of humerus and ulna Lateral surface of radius Rotates arm medially (pronates arm)
    • Muscles that move the hand! "Copyright 2003-2004 University of Washington. All rights reserved including all photographs and images. No re-use, re-distribution or commercial use without prior written permission of the authors and the University of Washington." "Musculoskeletal Images are from the University of Washington "Musculoskeletal Atlas: A Musculoskeletal Atlas of the Human Body" by Carol Teitz, M.D. and Dan Graney, Ph.D." Muscle Origin Insertion Action Flexor carpi radialis Medial epicondyle of humerus Base of 2 nd and 3 rd metacarpals Flexes and abducts wrist Flexor carpi ulnaris Medial epicondyle Carpal and metacarpal bones Flexes and adducts wrist Extensor digitorum Lateral epicondyle of humerus Posterior surface of phalanges in fingers 2-5 Extends fingers
    • Muscles of the Abdominal Wall Muscle Origin Insertion Action External Oblique lower ribs ilium Tenses abdominal wall Transversus abdominis Lower ribs, lumbar vertebrae Crest of the pubis Tenses abdominal wall and compresses abdominal contents Serratus anterior Outer surface of ribs scapula Pulls scapula downward Rectus abdominus Crest of Pubis Xiphoid Process of sternum Tenses abdominal wall and compresses abdominal contents
    • Muscles that move the thigh: "Copyright 2003-2004 University of Washington. All rights reserved including all photographs and images. No re-use, re-distribution or commercial use without prior written permission of the authors and the University of Washington."Musculoskeletal Images are from the University of Washington "Musculoskeletal Atlas: A Musculoskeletal Atlas of the Human Body" by Carol Teitz, M.D. and Dan Graney, Ph.D." Muscle Origin Insertion Action Psoas major Transverse processes of lumbar vertebrae Lesser trochanter of femur Flexes Thigh Gluteus Maximus Sacrum, coccyx, and posterior surface of ilium Posterior surface of femur Extends Thigh Gluteus minimus Lateral surface of ilium Greater trochanter of femur Abducts and rotates thigh medially
    • "Copyright 2003-2004 University of Washington. All rights reserved including all photographs and images. No re-use, re-distribution or commercial use without prior written permission of the authors and the University of Washington."Musculoskeletal Images are from the University of Washington "Musculoskeletal Atlas: A Musculoskeletal Atlas of the Human Body" by Carol Teitz, M.D. and Dan Graney, Ph.D." Gracilis pubis Medial surface of tibia Adducts thigh, flexes and rotates lower limb medially Adductor Magnus Ischium Medial surface of femur Adducts, extends, and rotates thigh laterally
    • Muscles that move the leg: * Makes up Hamstring Group "Copyright 2003-2004 University of Washington. All rights reserved including all photographs and images. No re-use, re-distribution or commercial use without prior written permission of the authors and the University of Washington."Musculoskeletal Images are from the University of Washington "Musculoskeletal Atlas: A Musculoskeletal Atlas of the Human Body" by Carol Teitz, M.D. and Dan Graney, Ph.D." Muscle Origin Insertion Action Sartorius Iliac spine Medial surface of tibia Flexes leg and rotates leg medially Biceps femoris* Ischium Head of fibula and lateral condyle of tibia Flexes leg, extends thigh Semitendinosus* Ischium Medial surface of tibia Flexes leg, extends thigh Semimembranosus* Ischium Medial condyle of tibia Flexes leg, extends thigh
    • Muscles that move the leg: continued * Quadriceps group "Copyright 2003-2004 University of Washington. All rights reserved including all photographs and images. No re-use, re-distribution or commercial use without prior written permission of the authors and the University of Washington."Musculoskeletal Images are from the University of Washington "Musculoskeletal Atlas: A Musculoskeletal Atlas of the Human Body" by Carol Teitz, M.D. and Dan Graney, Ph.D." Muscle Origin Insertion Action Rectus femoris* Spine of ilium and acetabulum Patella (continues to tibial tuberosity) Extends leg at knee Vastus lateralis* Greater trochanter Patella (continues to tibial tuberosity) Extends leg at knee Vastus medialis* Medial surface of femur Patella (continues to tibial tuberosity) Extends leg at knee Vastus intermedius* Lateral surface of femur Patella (continues to tibial tuberosity) Extends leg at knee
    • Muscles that move the ankle, foot, and toes. "Copyright 2003-2004 University of Washington. All rights reserved including all photographs and images. No re-use, re-distribution or commercial use without prior written permission of the authors and the University of Washington."Musculoskeletal Images are from the University of Washington "Musculoskeletal Atlas: A Musculoskeletal Atlas of the Human Body" by Carol Teitz, M.D. and Dan Graney, Ph.D." Muscle Origin Insertion Action Tibialis anterior Lateral condyle of tibia Cuneiform and first metatarsal Inversion of foot Extensor digitorum longus Lateral condyle of tibia and fibula Dorsal surface of 2 nd and 3 rd phalanges Extension of toes Flexor Digitorum longus Posterior surface of tibia Distal phalanges of four lateral toes Flexes four lateral toes
    • "Copyright 2003-2004 University of Washington. All rights reserved including all photographs and images. No re-use, re-distribution or commercial use without prior written permission of the authors and the University of Washington."Musculoskeletal Images are from the University of Washington "Musculoskeletal Atlas: A Musculoskeletal Atlas of the Human Body" by Carol Teitz, M.D. and Dan Graney, Ph.D." Gastrocnemius Lateral and medial condyles of femur calcaneus Flexes foot and knee Soleus Head and shaft of fibula and posterior surface of tibia calcaneus Flexes foot
    • Conclusion: Muscle as a comprehensive unit! With close to 700 separate muscles tightly interwoven throughout the human body, much of those attached to specific bone projections with unique types of locomotion, it is easy to see the complexity of these two interacting and mutually dependent systems. In short, skeletal muscle and the skeletal system show an amazing example of two systems interacting together with a measure of sophistication that has amazed the most gifted of minds and has left them speechless. In modern terminology, these two systems show irreducible complexity (WPP) in that one system alone would cease to function and/or provide little to no overall function to human body. In 1543, Vesalius published the seven-volume De humani corporis fabrica ( On the fabric of the human body ), a groundbreaking work of human anatomy. The work emphasized the priority of dissection and what has come to be called the "anatomical" view of the body — seeing human internal functioning as an essentially corporeal structure filled with organs arranged in three-dimensional space.
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