Body System: Muscular System PDF

1 Republic of the Philippines EULOGIO “AMANG” RODRIGUEZ INSTITUTE OF SCIENCE AND TECHNOLOGY...

1 Republic of the Philippines EULOGIO “AMANG” RODRIGUEZ INSTITUTE OF SCIENCE AND TECHNOLOGY Cavite Campus General Mariano Alvarez, Cavite ANAPHYLEC: ANATOMY AND PHYSIOLOGY BODY SYSTEM: MUSCULAR SYSTEM INTRODUCTION: As a runner rounds the last corner of track and sprints for the finish line, her arms and legs are pumping as she tries to reach her maximum speed. Her heart is beating rapidly and her breathing is rapid, deep and regular. Blood is shunted away from digestive organs, and a greater volume is delivered to skeletal muscles to maximize the oxygen supply to them. These actions are accomplished by muscle tissue, the most abundant tissue of the body and one of the most adaptable. You don’t have to be running for the muscular system to work. Even when you aren’t moving postural muscles keep you sitting or standing up right, respiratory muscles keep you breathing, the heart continually pumps blood to all parts of the body, and blood vessels constrict or relax to direct blood to organs where it is needed. FUNCTIONS OF THE MUSCULAR SYSTEM: Movement within the body is accomplished by cilia or flagella on the surface of certain cells, by the force of gravity, or by the contraction of muscles. Most of the body's movement results from muscle contraction. There are three types of muscle tissue: skeletal, cardiac, and smooth. This chapter deals primarily with the structure and function of skeletal muscle; cardiac and smooth muscle are described briefly. The major functions of the muscular system are: 1. Body movement. Contraction of skeletal muscles is responsible for the overall movements of the body, such as walking, running, or manipulating objects with the hands. 2. Maintenance of posture. Skeletal muscles constantly maintain tone, which keeps us sitting or standing erect. 3. Respiration. Muscles of the thorax are responsible for the movements necessary for respiration. 4. Production of body heat. When skeletal muscles contract, heat is given off as a by- product. This released heat is critical to the maintenance of body temperature. 5.Communication. Skeletal muscles are involved in all aspects of communication, such as speaking, writing, typing, gesturing, and facial expression. 6. Constriction of organs and vessels. The contraction of smooth muscle within the walls of internal organs and vessels causes constriction of those structures. This constriction can help propel and mix food and water in the digestive tract, propel secretions from organs, and regulate blood flow through vessels. ORGAN SYSTEM: MUSCULAR| © EPZGUADES2015  2 7.Heart beat. The contraction of cardiac muscle causes the heart to beat, propelling blood to all parts of the body. Characteristics of Skeletal Muscle Skeletal muscle with its associated connective tissue, Constitutes approximately 40% of body weight. Skeletal muscle is so named because most skeletal muscle or attach to the skeletal system it’s so also called striated muscles Because of the transverse bands are attach that can be seen in the muscle under the microscope. 1.Contractility is the ability of skeletal muscle to shorten with force. When skeletal muscles contract, they cost movement of the structures to which they are attached. Skeletal muscles shorten forcefully during contraction; open opposing muscle produces a force that pulls on the shortened muscle causing it to lengthen. 2.Excitability is the capability of skeletal muscle to respond to us stimulus. Normally skeletal muscle contracts as a result of stimulation by nerves. 3.Extensibility means that the skeletal muscles can be strengthened to their normal resting length and beyond to a limited degree. 4.Elasticity is the ability of skeletal muscles to recoil to their original resting land after they have been stretched. Structure of skeletal muscle Each skeletal muscle is surrounded by a connective tissue sheath called epimysium or fascia. A muscle is composed of the numerous visible bundle call muscle fasciculi which are surrounded by loose connective tissue called the perymesium. A fasiculus Is compose of several muscle cells or muscle fibers. Each muscle fibers are surrounded by loose connective tissue, called endomysium. A muscle fiber is a single syndical cell that contains several look like located at the periphery of muscle fiber. Muscles contraction is mass easier to understand when we understand the structure of muscle cell. The cytoplasm of each muscle fibers, called the sarcoplasm, contains numerous myofibrils. Each myofibrils is a threadlike structure that extends one consist of two major kind of protein fibers: actin, myosin and myofilaments. The acting and myofilaments are arranged into highly ordered repeating units along the myofibrils called sarcomeres. The sarcomere is the basic structural and functional unit of skeletal muscle because it is the smallest function of skeletal muscles capable of contracting. Each sarcomere extends from one Z disk to another Z disk. Each Z Disk is a network of protein fibers forming an attachment side for actin myofilaments. Actin myofilaments or thin myofilaments, resemble two minutes’ strands of pearls twisted together. Troponin molecules are attached at Specific intervals along the actin myofilaments and provide calcium binding site on the actin myofilaments. Tropomyosin filaments are located along the groove between twisted strand of actin myofilament sub units. ORGAN SYSTEM: MUSCULAR| © EPZGUADES2015  3 ORGAN SYSTEM: MUSCULAR| © EPZGUADES2015  4 Smooth Muscle and Cardiac Muscle Smooth muscle cells are small and spindle-shaped, usually with one nucleus per cell. They contain less actin and myosin than do skeletal muscle cells, and the myofilaments are not organized into sarcomeres. As a result, smooth muscle cells are not striated. Smooth muscle cells contract more slowly than skeletal muscle cells when stimulated by neurotransmitters from the nervous system and do not develop an oxygen debt. Smooth muscle is under involuntary control, whereas skeletal muscle is under voluntary motor control. Some hormones, such as those that regulate the digestive system, can stimulate smooth muscle to contract. Smooth muscle cells are organized to form layers. Most of those cells have gap junctions specialized cell-to-cell contacts, that allow action potentials to spread to all the smooth muscle cells in a given tissue. Thus, all the smooth muscle cells tend to function as a unit and contract at the same time. Cardiac muscle shares some characteristics with both smooth and skeletal muscle. Cardiac muscle cells are long, striated, and branching, with usually only one nucleus per cell. The actin and myosin myofilaments are organized into sarcomeres, but the distribution of myofilaments is not as uniform as in skeletal muscle. As a result, cardiac muscle cells are striated, but not as distinctly striated as skeletal muscle. When stimulated by neurotransmitters, the rate of cardiac muscle contraction is between that of smooth and skeletal muscle. Cardiac muscle contraction is auto rhythmic. Cardiac muscle cells are connected to one another by intercalated (in-ter'kä-lä-ted) disks. Intercalated disks are specialized structures that include tight junctions and gap junctions and that facilitate action potential conduction between the cells. This cell-to-cell connection allows cardiac muscle cells to function as a unit. As a result, an action potential in one cardiac muscle cell can stimulate action potentials in adjacent cells, causing all to contract together. As with smooth muscle, cardiac muscle is under involuntary control and is influenced by hormones, such as epinephrine. ORGAN SYSTEM: MUSCULAR| © EPZGUADES2015  5 SKELETAL MUSCLE ANATOMY GENERAL PRINCIPLES Most muscles extend from one bone to another and cross at least one joint. Muscle contraction causes most body movements by pulling one of the bones toward the other across the movable joint. Some muscles are not attached to bone at both ends, For example, some facial muscles attach to the skin, which moves as the muscles contract. The two points of attachment of each muscle are its origin and insertion. At these attachment points, the muscle is connected to the bone by a tendon. Some broad, sheet like tendons are called aponeuroses. A retinaculum a band of connective tissue that holds down the tendons at each wrist and ankle. The origin, also called the head, is the most stationary end of the muscle, the insertion is the end of the muscle attached to the bone undergoing the greatest movement. Origins are usually, but not always, proximal or medial to the insertion of a given muscle. The part of the muscle between the origin and the insertion is the belly. Muscles are typically grouped so that the action of one muscle or group of muscles is opposed by that of another muscle or group of muscles. For example, the biceps brachii flexes the elbow and the triceps brachii extends the elbow. A muscle that accomplish a certain movement, such as flexion, is called the agonist (ag'ö-nist, agon, a contest). A muscle acting in opposition to an agonist is called an antagonist (an-tag'ö-nist). The biceps brachii is the agonist in elbow flexion, whereas the triceps brachii is the antagonist, which extends the elbow. Nomenclature Most muscles have names that are descriptive. Some muscles are named according to their location, such as the pectoralis (chest) muscles in the chest. Other muscles are named according to their origin and insertion, such as the brachioradialis (brachio, arm) muscle, which extends from the arm to the radius. Some muscles are named according to the number of heads, such as the biceps (bi, two + ceps, head) brachii, which has two heads; and some according to their function, such as the flexor digitorum, which flexes the digits (fingers). Other muscles are named according to their size, such as vast-us, which means large; their shape, such as deltoid, which means triangular; or the orientation of their fasciculi, such as rectus, which means straight. Recognizing the descriptive nature of muscle names makes learning those names much easier. Examining surface anatomy can be a great advantage to the anatomy student in gaining a better understanding of muscle anatomy. ORGAN SYSTEM: MUSCULAR| © EPZGUADES2015  6 ORGAN SYSTEM: MUSCULAR| © EPZGUADES2015  7 ORGAN SYSTEM: MUSCULAR| © EPZGUADES2015  8 ORGAN SYSTEM: MUSCULAR| © EPZGUADES2015  9 ORGAN SYSTEM: MUSCULAR| © EPZGUADES2015  10 ORGAN SYSTEM: MUSCULAR| © EPZGUADES2015  11 ORGAN SYSTEM: MUSCULAR| © EPZGUADES2015  12 ORGAN SYSTEM: MUSCULAR| © EPZGUADES2015  13 Clinical Condition of Muscular System Cramps. are painful, spastic contractions of muscle that are usually the result of an irritation within a muscle. Local inflammation from buildup of lactic acid or connective tissue inflammation can cause contraction of muscle fibers surrounding the irritated region. Fibromyalgia. or chronic muscle pain syndrome, has muscle pain as its main symptom. Fibromyalgia has no known cure, but it is not progressive, crippling, or life-threatening. The pain is chronic and widespread in muscles and muscle-tendon junctions. Hypertrophy and Atrophy Exercise causes muscular hypertrophy which is an enlargement of a muscle resulting from an increase in the number of myofibrils within muscle fibers. Muscle hypertrophy is greater in males than in females, mainly because of greater concentrations of the male sex hormone, testos- muscular atrophy which is a decrease in muscle size because of a decrease in myofilaments within muscle fibers. Severe atrophy involves the permanent loss of skeletal muscle fibers and the replacement Myotonic muscular dystrophy is characterized by the failure of muscles to relax following a forceful contraction, as well as by muscular weakness. The disorder is inherited as a dominant - of those fibers by connective tissue. Important trait in both males and females and bility resulting from damage to the nervous system or casting a broken limb leads to muscular atrophy. If the nerve supply to a muscle is severed, the muscle becomes flaccid (having no tone) and atrophies. Myasthenia gravis is a chronic progressive auto immune disease resulting from the destruction of acetylcholine Are receptors in the neuromuscular junction. Treatment includes anti cholinesterase drugs – or immunosuppressive drugs. Tendinitis implies an inflammation of tendon attachment point it’s usually a cure and lateral overtax the muscle to which tendon is attach. ORGAN SYSTEM: MUSCULAR| © EPZGUADES2015