Human Anatomy & Physiology - Muscular System PDF

Week 3 Human Anatomy & Physiology - 1 (HMG380) MUSCULAR SYSTEM Dr. Merin Thomas [email protected] Office hours : Monday & Wednesday, 3:00pm to 5:00pm Tuesday & Thursday 1:00pm to 3:00...

Week 3 Human Anatomy & Physiology - 1 (HMG380) MUSCULAR SYSTEM Dr. Merin Thomas [email protected] Office hours : Monday & Wednesday, 3:00pm to 5:00pm Tuesday & Thursday 1:00pm to 3:00pm  Learning Objectives Functions & Properties of muscle tissue Types of muscle tissues & their differences Structure of Muscle tissue Neuromuscular Junction Muscle metabolism How muscles produce movement Muscle nomenclature  Levels of Structural Organization - LEVEL 3 - TISSUE LEVEL Epithelial Tissue Connective Tissue Muscular Tissue Nervous Tissue Covers body Connects, supports, and protectsContracts to make body surfaces, lines body organs while distributing parts move & in the Carries information hollow organs & blood vessels to other tissues process generates heat from one part of the cavities, and forms body to another Loose Connective glands. Smooth Muscle through nerve Based onsh ap eof Tissue impulses the cell 2 types of cells Dense Connective Tissue Skeletal Muscle Based on number Cardiac Muscle of layers of cells Special Connective Tissue Three parts: CNS, PNS, ANS  MUSCLE TISSUE - FUNCTION Contractile tissuewhich brings about movement. Muscular tissue has four key functions: 1. Producing body movements 2. Stabilizing body positions 3. Storing and moving substances within the body 4.Generating heat - Thermogenesis  MUSCLE TISSUE - PROPERTIES Muscular tissue has four special properties that enable it to function and contribute to homeostasis: 1. Excitability - the ability to respond to stimuli which maybe delivered from a motor neuron or a hormone. 2. Contractility - the ability of muscular tissue to contract forcefully when stimulated by a nerve impulse. 3. Extensibility - the ability of muscular tissue to stretch, within limits, without being damaged. Normally, smooth muscle is subject to the greatest amount of stretching. 4. Elasticity - is the ability of muscular tissue to return to its original length and shapeafter contraction or extension.  MUSCLE TISSUE - TYPES There areTHREE types of muscles 1 Skeletal Muscle. Smooth Muscle 2 3. Cardiac Muscle.  Location Type of movement Function Structure  SKELETAL MUSCLE - STRUCTURE Skeletal muscle contains connective tissuesurrounding muscle fibers, and blood vessels and nerves. Muscles separated from skin by hypodermis which is is composed o areolar connective tissue and adipose. Fascia is a dense sheet or broad band of irregular connective tissue that lines the body wall and limbs and supports and surrounds muscles and other Three layers of connective tissue extend from t organs of the strengthen body. muscle. skeletal 1. Epimysium 2 Perimysium. Endomysium 3. From Principles of Anatomy and Physiology, by Tortora, Gerard J. And Bryan H Derrickson, Wiley & Sons, 2020,p 308  SKELETAL MUSCLE - STRUCTURE All three layers are continuous with the connective tissue that attaches skeletal muscle to other structures , such as bone or another muscle. All three connective tissue layers may extend be form a rope/cord like tendon that attaches a muscle to the periosteum of bone When the connective tissue elements extend a called an aponeurosis  SKELETAL MUSCLE - STRUCTURE Skeletal muscles are well supplied with nerves and blood vessels. The neurons that stimulate skeletal muscle to c neurons. Each somatic motor neuron has a threadlike axon that extend from the brain or spinal cord to a group of skeletal muscle fiber. Blood are plentiful capillaries in muscular tissue; they bring in oxygen and nutrients and remove heat and the waste products of muscle metabolism.  SKELETAL MUSCLE - MICROSCOPIC STRUCTURE The most important component of a skeletal musclemuscle - fibers The diameter of a mature skeletal muscle fiber ranges from ~10 to 100 μ , with a typical length of about 10 cm. Each muscle fiber has 100 or more nuclei because it arises from the fusio of many myoblasts (developmental). These nuclei lie beneath theSarcolemma, the plasma membrane of the muscle fibre. The cytoplasm of a muscle fiber is called as Sarcoplasm Sarcoplasm has small invaginations extending centre called T-tubules (Transverse tubules) SKELETAL MUSCLE - MICROSCOPIC STRUCTURE  SKELETAL MUSCLE - MICROSCOPIC STRUCTURE Sarcoplasm Glycogen (for ATP synthesis) Myoglobin (protein found only in muscles; binds to oxygen). Mitochondria (Sarcosomes) lie in rows close to the contractile proteins that ATP can be released when energy is needed Sarcoplasmic Reticulum (SR), fluid filled sacs similar to endoplasmic reticulum with dilated ends called Terminal Cisterns. Terminal cisterns push against T - tubules; T ri ad In relaxed muscle fibre SRstores Ca ions Release of Ca ions from terminal cisterns trigger On high magnification, thread like structures seen organelles of skeletal muscle about 2 μm in diameter and extend the entir length of a muscle fiber. From Principles of Anatomy and Physiology, by Tortora, Gerard J. And Bryan H Derrickson, Wiley & Sons, 2020,p 311  SKELETAL MUSCLE - MICROSCOPIC STRUCTURE Sarcoplasm - Myofibrils Within myofibrils, thin filaments called myofilaments. Thin filaments are 8 nm in diameter and 1–2 μm long and composed the proteinactin Thick filaments are 16 nm in diameter and 1–2 μm long and composed the proteinmyosin. Both are directly involved in contractile process Myofilaments do not extend along entire length are arranged in compartments - Sarcomere Basic functional unit of a myofibril Sarcomeres are separated by protein dense material called Z-discs From Principles of Anatomy and Physiology, by Tortora, Gerard J. And Bryan H Derrickson, Wiley & Sons, 2020,p 311  SKELETAL MUSCLE - MICROSCOPIC STRUCTURE Sarcoplasm ; Myofibrils; Sarcomere Sarcomere - Basic functional unit of a myofibril Sarcomeres are separated by protein dense material called Z-discs Dark A band - formed by thick filaments; ends have overlapping thick and thin filaments H band - region in the middle containing onl M line - Supporting proteins that hold the th at the center of the H band Light I band - formed only by thin filaments Z disc lies in the middle of a light band Alternating light and dark bands create the striations hence called striated muscle (skeletal and cardiac) From Principles of Anatomy and Physiology, by Tortora, Gerard J. And Bryan H Derrickson, Wiley & Sons, 2020,p 312  Microscopic structure of skeletal muscle I BAND A BAND SA RC OMER E Thick Filament Z Line M Line Thin Filament H BAND  SKELETAL MUSCLE - MICROSCOPIC STRUCTURE Sarcoplasm ; Myofibrils; Muscle Proteins Myofibrils are built from three kinds of proteins: 1. Contractile proteins, which generate force during contraction. Actin (Thin Filament) & Myosin(Thick Filament). Projecting myosin heads contain act binding and ATP binding sites and are the motor proteins that power muscle contraction. Regulatory proteins, which help switch the 2. contraction process on and off. Tropomyosin & Troponin (Thin Filament) Structural proteins, which keep the thick and thin filaments in the 3. proper alignment, give the myofibril elasticity and extensibility, and link the myofibrils to the sarcolemma and extracellular matrix. Titin (links Z disc to M line and stabilizes thick filament), myomesin (forms M line) nebulin (anchors thin filaments to Z discs and regulates length of thin filaments during development), and dystrophin (links thin filaments to CONTRACTION AND RELAXATION OF SKELETAL MUSCLE  CONTRACTION AND RELAXATION OF SKELETAL MUSCLE The contraction cycle is the repeating sequence of events that causes sliding of the filaments: 1.Myosin ATPase hydrolyzes ATP and becomes energized 2.Myosin head attaches to actin, forming a crossbridge 3.The crossbridgegenerates forceas it rotates toward the center of the sarcomere (power stroke); and. The4.Binding myosin head of ATPagain to thehydrolyzes myosin headthe detaches ATP, returns it from actin to its original position, and binds to a new site on actin as the cycle continues. An increase in Ca 2+ concentration in the sarcoplasm starts filament sliding; a decrease turns off the sliding process.  NEUROMUSCULAR JUNCTION Synapse: The site of transmission of electric nerve impulses between two nerve cells (neurons) or between a neuron and a gland or muscle cell (effector) The neuromuscular junction (NMJ) is a synaptic 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. It is also a site for many diseases and a site of action for many pharmacological drugs  NEUROMUSCULAR JUNCTION The structure of NMJ can be divided into three main parts: 1 A presynaptic part (nerve terminal),. The postsynapticpart (motor endplate), and 2 An area between the nerve terminal and motor endplate (synaptic cleft).. 3.  NEUROMUSCULAR JUNCTION An electrical signal or action potential, arriving from the central nervous system, needs to cross the synaptic cleft. The neuromuscular junction accomplishes this by turning the electrical signal from the nervous system into a chemical signal that can be moved across the synaptic cleft. The chemical in this case is acetylcholine (ACh), an example of a neurotransmitter that allows neurons to communicate with other cells. ACh is stored inside the synaptic end bulb within membrane-enclosed sacs known as synaptic vesicles. As the electrical signal approaches the synaptic end bulb, it stimulates the inflow of calcium (Ca2+) by opening voltage-gated channels in the cell membrane of the neuron. The increase of Ca2+ within the cytosol of the synaptic end bulb causes the synaptic vesicles to move towards and fuse with the neuron’s cell membra Once fused, the synaptic vesicles release their contents – ACh – into the synaptic cleft.  NEUROMUSCULAR JUNCTION The ACh then moves across the synaptic cleft towards the motor end plate of the muscle fiber. The binding of two molecules of ACh to an acetylcholine receptor, opens theIt into ion is channel this influx in of the Na+receptor that and once allows again the initiates influx an of sodium electrical (Na+) impulse or action potential the muscle fiber.that travels outwards from the motor end plate towards both ends of the muscle fiber causing the muscle fiber to contract and shorten.