Muscle Physiology I PDF - BIOL 101 - St. George's University

Anatomy & Physiology BIOL 101 5. Muscle Physiology I Dr. Stephen Onigbinde [email protected] Session ID: dronigbinde  Your Ob...

Anatomy & Physiology BIOL 101 5. Muscle Physiology I Dr. Stephen Onigbinde [email protected] Session ID: dronigbinde  Your Objectives will show here! 1. List and explain the properties and functions of muscular tissue 2. Review the structure and function of the three types of muscle tissue 3. Compare the structure, function, location and distinctive features of the three types of muscle (skeletal, cardiac and smooth muscle) 4. Identify the different types of muscle tissue by histology (skeletal, cardiac and smooth muscle) 5. Describe the connective tissue components 6. Define tendons and aponeuroses 7. Describe the microscopic arrangement of the intracellular components of skeletal muscle fibre 8. Describe the structure and function of the types of proteins found in the skeletal B 101. Lecture 5. Muscle Physiology muscle cell 9. Explain the levels of organization of skeletal muscle (whole muscle to myofilament) 10. Briefly explain the changes that can occur in mature muscle by hypertrophy or atrophy Session ID:  Objective 1 Muscular tissue Consists of elongated cells called muscle fibers or myocytes that can use ATP to generate force. Types: Skeletal Cardiac Smooth Functions: BIOL 101. Lecture 5. Muscle Physiology I Produce body movements Stabilize body position Store and move substances within the body Generate heat Session ID:  Objective 1 Properties of Muscular Tissue Electrical activity: ability to respond to certain stimuli by producing electrical signals called action potentials (impulses) Contractility: the ability of muscular tissue to contract forcefully when stimulated by an action potential Extensibility: the ability of muscular tissue to stretch, within limits, without being damaged BIOL 101. Lecture 5. Muscle Physiology I Elasticity: the ability of muscular tissue to return to its original length and shape after contraction or extension Session ID:  Objective 3,4 Skeletal muscle Description: consists of long, cylindrical, striated fibers. A muscle fiber is a rough cylindrical, multinucleated cell with nuclei at the periphery Striated: alternating light and dark protein bands Location: Attached to bones Make up 40% of body weight Function: locomotion, facial expressions, posture, respiratory movements, and other types of body movement, heat production Voluntary (somatic) in action: controlled by somatic motor neurons BIOL 101. Lecture 5. Muscle Physiology I  Objective 3,4 Cardiac muscle Description: consists of branched, striated fibers with usually only one centrally located nucleus. Attach end to end by transverse thickenings of plasma membrane called intercalated discs (desmosomes and gap junctions). Location: Heart Function: Pumps blood to all parts of the body, Autorhythmic Controlled involuntarily by endocrine and autonomic nervous system BIOL 101. Lecture 5. Muscle Physiology I  Objective 3,4 Smooth muscle Description: consists of nonstriated fibers. A small spindle-shaped cell containing a single, centrally located nucleus. Contains a lot of gap junctions. Location: Iris of eyes; walls of hollow internal structures such as blood vessels, airways to lungs, stomach, intestines, gallbladder, urinary bladder and uterus. Function: Involuntary powerful contraction that cause motion such as constriction of blood vessels and airways, propulsion of foods through digestive canal, contraction of urinary bladder and gallbladder. Controlled involuntarily by endocrine and autonomic nervous system. BIOL 101. Lecture 5. Muscle Physiology I  Objective 5 Connective Tissue Sheaths of skeletal muscle Epimysium: The outer layer, encircling the entire muscle Consists of dense irregular connective tissue Perimysium: Layer of dense connective tissue surrounding groups of 10-100 or more muscle fibers BIOL 101. Lecture 5. Muscle Physiology I Separates fibers into bundles called fascicles Endomysium: Reticular fibers penetrating the interior of each fascicle Separates individual muscle fibers from one another BIOL 101. Lecture 5. Muscle Physiology I Objective 5  Objective 6 Tendon Cord of dense, regular connective tissue formed by the three layers of connective tissue sheath of the skeletal muscle Attaches muscle to the periosteum of a bone Example: Calcaneal tendon (Achilles) of the gastrocnemius BIOL 101. Lecture 5. Muscle Physiology I muscle Aponeurosis Tendon that extends as a broad, flat layer Example: external oblique aponeurosis  Objective 7 Microscopic Anatomy of a Skeletal Muscle Fiber Each muscle fiber is a single multinucleated, long, cylindrical cell and is surrounded by a plasma membrane (sarcolemma) Sarcoplasm: Muscle cell cytoplasm, Contains myoglobin which binds oxygen molecule T tubules: BIOL 101. Lecture 5. Muscle Physiology I Tiny invaginations of the sarcolemma Quickly spread the muscle action potential to all parts of the muscle fiber almost instantaneously  Objective 7 Sarcotubular System Consists of T tubules and sarcoplasmic reticulum. Surrounds the muscle fibers. Appears in electron micrographs as vesicles and tubules. BIOL 101. Lecture 5. Muscle Physiology I  Objective 7 Sarcoplasmic Reticulum The smooth endoplasmic reticulum found in myocytes Forms an irregular curtain around each of the fibrils. It has enlarged terminal cisterns in close contact with the T system at the junctions between the A and I bands BIOL 101. Lecture 5. Muscle Physiology I Stores calcium ions in a relaxed muscle Release of calcium ions triggers muscle contraction  Objective 7 Transverse tubules Extensive tubular network Opens to the extracellular space Carry the depolarization (action potential) from the sarcolemma to the cell interior BIOL 101. Lecture 5. Muscle Physiology I A single T-tubule and the 2 terminal cisternae form a triad  Objective 7 Sarcomere Functional unit of skeletal muscle Each myofibril is made up of filaments (thick and thin). - These filaments are arranged in compartments called sarcomeres BIOL 101. Lecture 5. Muscle Physiology I BIOL 101. Lecture 5. Muscle Physiology I Objective 7  Objective 8 Muscle proteins Myofibrils are built from three kinds of proteins: 1. Contractile proteins: generate force during contraction Myosin, actin 2. Regulatory proteins: help switch the contraction process on and off Troponin, tropomyosin BIOL 101. Lecture 5. Muscle Physiology I 3. Structural proteins: Keep the thick and thin filaments in the proper alignment Give myofibrils elasticity and extensibility Link the myofibrils to the sarcolemma and extracellular matrix Titin, myomesin, nebulin, dystrophin  Objective 8 Contractile Proteins Proteins that generate force during muscle contractions Myosin: contractile protein that makes up thick filaments Molecule consists of a tail and two myosin heads Actin: contractile protein that is the main component of thin filament Each actin molecule has a myosin-binding site where myosin head of thick filament binds during muscle contraction BIOL 101. Lecture 5. Muscle Physiology I  Objective 9 Levels of organization within a skeletal muscle BIOL 101. Lecture 5. Muscle Physiology I  Objective 9 Levels of organization within a skeletal muscle BIOL 101. Lecture 5. Muscle Physiology I  Objective 10 Muscle Hypertrophy Muscle growth from heavy training Increases diameter of muscle fibers Increases number of myofibrils Increases mitochondria, glycogen reserves BIOL 101. Lecture 5. Muscle Physiology I  Objective 10 Muscle Atrophy Lack of muscle activity Reduces muscle size, tone, and power BIOL 101. Lecture 5. Muscle Physiology I BIOL 101. Lecture 5. Muscle Physiology I