Muscular System - Unit 5

MUSCULAR SYSTEM The Muscular System consists of about 600 muscle organs that are typically attached to bones across a joint to produce all voluntary movements. https://www.youtube.com/watch?v=rMcg9YzNSEs General Functions of the Muscular System 1. Movement Gives rigidity for the mus...

MUSCULAR SYSTEM The Muscular System consists of about 600 muscle organs that are typically attached to bones across a joint to produce all voluntary movements. https://www.youtube.com/watch?v=rMcg9YzNSEs General Functions of the Muscular System 1. Movement Gives rigidity for the muscles so that person can pull, walk, run, lift, chew, manipulate objects picking noses and others. 2. Maintenance of Posture Without much conscious control, muscles generate a contractile force that allow us to maintain an erect or seated position. 3. Respiration The muscular system automatically drives movement of air into and out of our body. 4. Heat generation Contraction of muscle tissue generates heat, which is essential for maintenance of temperature homeostasis. 5. Communication Muscle tissue allows us to talk, gesture, write, and convey our emotional state by doing such things as smiling or frowning. 6. Constriction of organs and blood vessels Nutrients move through our digestive tract, urine is passed out of the body, and secretions are propelled out of glands by contraction of smooth muscle. Constriction or relaxation of blood vessels regulates blood pressure and blood distribution throughout the body. 7. Pumping blood/Contraction of the heart Blood moves through the blood vessels because our heart tirelessly receives blood and delivers it to all body tissues and organs. 8. Other functions Muscles help protect fragile internal organs by enclosing them, and are also critical in maintaining the integrity of body cavities. Properties or Characteristics of Muscle Muscles work in pairs!  Types of Muscle Action https://www.youtube.com/watch?v=T00U5lMWAWQ&t=8s Types of Muscle Tissues Features of the skeletal muscle tissue: Muscle attachment Most skeletal muscle run from one bone to another  One bone will move – the other bone remains fixed. The origin is less movable attachment. The insertion is more movable attachment.  Muscles attach to origins and insertions by connection tissue Fleshy attachments – connective tissue fibers that are usually short like the belly’s muscle. Indirect attachments – connective tissue forms a tendon or aponeurosis  Bone markings present where tendons meet bones. Examples: tubercles, trochanter, crests The greater trochanter gives Bone markings are projections and attachment to the gluteus depressions found on bones, which medius and minimus, help us to identify the location of piriformis, obturator internus other body structures like the and externus, and gemelli muscles. muscles),  The iliac crest attaches the hip flexors, the internal and external abdominal oblique muscles, the erector The subscapularis spinae muscles, the latissimus dorsi, the transversus muscle originates at the abdominis, and the tensor fasciae latae. subscapular fossa and inserts into the lesser tubercle of the humerus. Skeletal Muscle Structure Skeletal muscles act not only to produce movement but also to stop movement, like resisting gravity to maintain posture. Muscles also prevent excess movement of the bones and joints, maintaining skeletal stability thus preventing skeletal structure damage or deformation. Skeletal muscles are located throughout the body at the openings of internal tracts to control the movement of various substances.  SKELETAL MUSCLE Each skeletal muscle is an organ that consists of various integrated tissues. Tendon is a fibrous connective tissue which attaches muscle to bone and serves to move the structure. Fascia is connective tissue to provide support, shape, and suspension for most of the soft tissues of the body. Aponeuroses can act as fascia. An aponeurosis is made of layers of delicate, thin sheaths. A skeletal muscle has three layers of connective tissue: (1)the epimysium, (2)the perimysium, and (3)the endomysium Epimysium is the fibrous tissue surrounding the skeletal muscle, allows a muscle to contract or move powerfully while maintaining its structural integrity. It is a layer of dense irregular connective tissue, whose protein fibers gradually merge with the muscular fascia (FASH-ee-ah), the layer of connective tissue between adjacent muscles and between muscles and the skin. These outer layers of connective tissue keep the muscles separate from surrounding tissues and organs. Perimysium is a sheath of connective tissue that groups muscle fibers (cells) into bundles or fascicles which plays in sending / transmitting lateral contractile movements. It serves as passageways for blood vessels and nerves that supply each fascicle Endomysium (meaning within the muscles) is the key element that separates single muscle fibers from one another. Allows autonomous gliding in contraction and is highly deformable tissue Fascicle, a group of muscle fibers “bundled” as a unit within the whole muscle. They are covered by a layer of connective tissue called perimysium. Fascicle arrangements determine what type of movement a muscle can make and they work in tandem. Biceps brachii flexes the forearm and the triceps brachii extends it.  The hamstrings flex the leg, whereas the quadriceps femoris extend it. Every muscle fiber is supplied by the axon branch of a somatic motor neuron, which signals the fiber to contract. Neuromuscular junction (NMJ). Connection between the terminal end of a motor nerve and a muscle (skeletal/ smooth/ cardiac). It is the site for the transmission of action potential from nerve to the muscle. The muscular system is composed of specialized cells called muscle fibers. Their predominant function is contractibility. Each muscle cell is called a muscle fiber. These muscle fiber is surrounded by a plasma membrane called the sarcolemma, which contains sarcoplasm, the cytoplasm of muscle cells. The primary function of the sarcolemma is to conduct electrical signals, signaling the release of calcium Ca2+ ions. Sarcoplasmic Reticulum is a series of closed saclike membranes, that forms a cufflike structure surrounding a myofibril. It serves as the storage of intracellular calcium needed for the initiation of muscle contraction. Myofibrils are made up of thick (myosin) and thin (actin) myofilaments, which help give the muscle its striped appearance. Myofibrils are very long chains of sarcomeres, that are the contractile units of the cell. Along with actin and myosin. There are two other muscle proteins: tropomyosin and troponin. Tropomyosin is a long, fibrous protein that lies in the groove along the fibrous actin strand. In a relaxed muscle, tropomyosin is covering the active sites on the G actin subunits. A muscle cannot contract until the tropomyosin moves to uncover the active sites. Troponin consists of three subunits: (1) a subunit that anchors the troponin to the actin, (2) a subunit that prevents the tropomyosin from uncovering the G actin active sites in a relaxed muscle, and (3) a subunit that binds Ca2+ Skeletal Muscle Contraction Physiology https://www.youtube.com/watch?v=bjyM13pe9NA Energy sources for muscle contraction Breaks the myosin- actin cross bridge Free myosin for the next contraction  Creatine phosphate transfers its phosphate back to Adenosine diphosphate (ADP) Creatine kinase When the muscle starts to contract and needs energy Forming Adenosine triphosphate (ATP) which powers the first few seconds of muscle contraction.  CPK therefore helps in the production of ATP to allow muscle contraction and therefore proper Creatinine phosphokinase function when moving, or promotes the synthesis allowing normal functioning of creatinine phosphate. of the heart. Supply of oxygen gas is important to life. For this, the chemical process inside the cells that consume oxygen to produce usable energy is known as cellular respiration. Aerobic and Anaerobic Respiration https://www.youtube.com/watch?v=WsqP1O7388g Muscle Weakness (muscles loses its ability to contract)  Lactic acid build Lactic Acid up in the bloodstream Accumulation as compared to (prolong relaxation) glucose This burning High lactic acid Intracellular sensation (soreness) is accumulation in the acidosis associated with a buildup blood stream (fatigability) of acid in the muscles Why is lactate bad? Lactate) Muscles burn more CHO which increases breaks down the lactic acid production Hydrogen As the person ions indulge on strenuous activity The build-up of H+ within the muscle lowers the pH and may reduce muscle force by (1) decreasing Ca2+ release from the SR, (2) decreasing the sensitivity of troponin C to Ca2+, and (3) interfering with cross-bridge cycling Muscle Cramps https://www.youtube.com/watch?v=Fb3kmHyXtM4 Causes of Muscle Cramps  Is found in only one place in the body – the heart Like skeletal muscle, cardiac muscle is striated, and like smooth muscle, it is uninucleate and its control is involuntary.  Cardiac Muscle The cardiac cells are cushioned by small amounts of endomysium and are arranged in spiral or figure 8-shaped bundles. Cardiac muscle fibers are branching cells joined by special gap junctions called intercalated discs. Cardiac muscle usually contracts at a fairly steady rate set by the heart’s pacemaker. However, the nervous system can also stimulate the heart to shift into “high gear” for short periods. Myocardium (muscles of the heart) has three types of muscle fibers A. Muscle fibers which form the contractile unit of the (99%) Cardiac muscle, like skeletal muscle, is made up of sarcomeres that allow for contractility, however, unlike skeletal muscle, cardiac muscle is under involuntary control. The cardiac muscle is responsible for the contractility of the heart and, therefore, the pumping action. B. Muscle fibers which form the pacemaker Cardiac muscle cells also called cardiomyocytes are the contractile myocytes of the cardiac muscle. The sinoatrial node (SA) is the heart's natural pacemaker. It's a small mass of specialized cells in the top of the right atrium (upper chamber of the heart). It produces the electrical impulses that cause the heart to beat. https://www.youtube.com/watch?v=v7Q9BrNfIpQ Action Potentials in Pacemaker Cells C. Muscle fibers which form the conductive system The main cardiac conduction system are the: SA node, AV node, bundle of HIS, bundle branches, and Purkinje fibers D. Cardiac muscles are joined to another by intercalated disc (gap junctions) for depolarization between cells and desmosomes to hold the fibers together the fibers when the heart contracts. E. Cardiac muscles are involuntary Cardiac muscles are said to be involuntary because they are not controlled by the mind of the person. The desmosomes provide strong adhesion which is at times exposed to intense mechanical stress like cardiac muscle tissues, bladder tissues, epithelial tissues, and GIT gastrointestinal mucosa.. F. Cardiac muscles are intrinsically controlled (the ability of the heart to control its rate). G. Cardiac muscles are striated. Marked by transverse dark and light bands or long cylindrical fibers. H. Cardiac muscles are branched. Allows cardiac muscle tissue to contract very quickly in a wave-like pattern to effectively pump blood throughout the body. I. Cardiac muscles are single nucleated. Intercalated disks of overlapping cell membrane form between the cardiac muscle cells to lock them together tightly and allow the quick passage of electrochemical signals between cells. Properties of the cardiac muscles A. Electrical a. Excitability (Bathmotropic action) b. Autorhythmicity c. Conductivity (Dromotropic action) B. Mechanical a. Contractility (Inotropic action) b. Refractory period To control the rhythm of the Once an impulse passes heart, there is a special through any area, that area system that generates becomes unresponsive to impulse and spreads all over subsequent stimulation for a the heart. short period. https://www.youtube.com/watch?v=uHKEp4xfhUo&t=46s c. Staircase/Treppe effect When a muscle is With excessive stimulation, the strength stimulated after a increases and reaches a plateau. This long period of rest, phenomenon is called staircase effect. the strength of initial contractions, is less https://www.youtube.com/watch?v=Jg8uz8hAUmM than the usual. https://www.youtube.com/watch?v=6ulvh_ItKcw Understanding Repolarization and Depolarization of the Cardiac Muscles Chemical Composition of a Muscle Types of Body Movements Flexion, movement that decreases the angle between two body parts. Extension, movement that increases the angle, or the distance, between two bones or parts of the body. Rotation, movement of a bone around a longitudinal axis (ball-and-socket joints). Abduction, moving the limb away from the midline, or median plane, of the body. Adduction, it is the movement of a limb toward the body midline. Circumduction is a combination of flexion, extension, abduction, and adduction commonly seen in ball-and-socket joints. Lifting the foot so that its superior surface approaches the shin is called dorsiflexion, whereas depressing the foot is called plantar flexion. Inversion. To invert the foot, turn the sole medially. Eversion. To evert the foot, turn the sole laterally. Supination occurs when the forearm rotates laterally so that the palm faces anteriorly and the radius and ulna are parallel. Pronation occurs when the forearm rotates medially so that the palm faces posteriorly.  The Muscle Song https://www.youtube.com/watch?v=hY2fa6Q98-k Major Skeletal Muscles Muscles that move the face Muscles that move the head Muscles of the abdominal wall Muscles that move the wrist, hand, and fingers Muscles that move the forearm Muscles that move the arm Muscles that move the pectoral girdle Muscles that move the thigh Muscles that move the leg Muscles that move the leg Muscles that move the ankle, foot and toes Muscles that move the ankle, foot and toes Muscles that move the ankle, foot and toes Muscles of the pelvic outlet