Principles of Animal Physiology Muscle Physiology Introduction The ability to use chemical energy to produce force is present to some extent in most living cells but in muscle cells the chemical apparatus has its greatest development Principles of Animal Physiology Muscle Physiology Introduction On the basis of structure contractile properities and control mechanisms three types of muscles can be identified Skeletal Smooth Cardiac Principles of Animal Physiology Muscle Physiology Introduction Muscles can Perform purposeful locomotory movement of the whole body of parts of the body Manipulate external objects Propell contents through various hollow internal organs Empty the contents of certain organs Produce heat Produce sound Principles of Animal Physiology Muscle Physiology Introduction They differ in cell structure location function and mode of activation Know how they differ by Appearance Fiber arrangement Fiber proteins Control Nervous control Hormonal influences Location Morphology Contraction speed Force generated Principles of Animal Physiology Muscle Physiology Introduction Know their similarities Elongated contraction depends on two kinds of myofilaments actin and myosin microfilaments Principles of Animal Physiology Muscle Physiology Introduction Muscle function Produce movement Skeletal muscles for locomotion and manipulation cardiac muscle responsible for moving blood throughout system smooth muscles to squeeze and propel substances through hollow organs and tracts Maintain posture Some muscles are continuously activated to enable us to remain erect or seated Stabilizing joints Pull on bones to maintain articulating surfaces Generating heat Tissue most responsible for maintiang body temperature Principles of Animal Physiology Muscle Physiology Introduction Functional characteristics of muscles Excitability Ability to receive and respond to a stimulus Contractility Ability to shorten forcibly when stimulated Sets muscles apart from other tissues Extensibility Ability of muscle to be stretched or extended Elasticity Ability to return to original length after being stretched or after contracting Principles of Animal Physiology Muscle Physiology Introduction Categorization of muscle Principles of Animal Physiology Muscle Physiology Skeletal Muscle Account for at least 40 of body mass 40 in men and 32 in women Smooth cardiac muscle account for 10 of total weight Fish 20 50 muscle Barracudas 55 65 Contains obvious stripes called striations and under voluntary control Made up of muscle fibers nerves blood vessels and connective tissue Principles of Animal Physiology Muscle Physiology Skeletal Muscle Attached to bones by tendons Origin closest to body or more stationary bone Insertion more distal or mobile attachment Joint flexible connection where two bones meet Flexor muscle that bring bones closer together Extensor muscle that move bones away from each other Flexor extensors pairs are called antagonistic muscle group Principles of Animal Physiology Muscle Physiology Skeletal Muscle Organization of skeletal muscle Principles of Animal Physiology Muscle Physiology Introduction Organization of cylindrical muscle fibers Striated muscle characteristic light and dark bands oriented perpendicular to the long axis of the fibers Striated pattern due to cylindrical elements 1 2 known as myofibrils Muscle fiber single skeletal muscle cell Myoblast formed by fusion of undifferentiated mononucleated cells during development Muscle collection of muscle fibers bound together by connective tissue Principles of Animal Physiology Muscle Physiology Skeletal Muscles Levels of Organization Principles of Animal Physiology Muscle Physiology Skeletal Muscles Levels of Organization Myofibril Sarcomere Principles of Animal Physiology Muscle Physiology Skeletal Muscles Myofibril composed of thick and thin filaments arranged in a repeating pattern along its length One of these units is known as a sacomere Thick filaments composed entirely of myosin Thin filaments composed of actin troponin and tropomyosin Motor unit a motor neuron and all the muscle fibers it controls Principles of Animal Physiology Muscle Physiology Skeletal Muscles Titin huge elastic protein molecule Extends from Z disk to next M line Stabilizes position of the contractile filaments Its elasticity returns stretched muscles to their resting length Nebulin inelastic giant protein Attaches to Z disk Aligns the actin filaments to the sarcomere Principles of Animal Physiology Muscle Physiology Skeletal Muscles Levels of Organization Internal arrangement A band I band H zone M line Z line Sarcomere The area between two adjecent Z lines The functional unit of skeletal muscle Smallest component capable of contraction Principles of Animal Physiology Muscle Physiology Skeletal Muscles Levels of Organization thick thin filaments Principles of Animal Physiology Muscle Physiology Skeletal Muscles Levels of Organization Xsection of myofibril Principles of Animal Physiology Muscle Physiology Skeletal Muscles Myosin and thick filaments Principles of Animal Physiology Muscle Physiology Skeletal Muscles Thin Filament Principles of Animal Physiology Muscle Physiology Skeletal Muscles Role of calcium in cross bridging Principles of Animal Physiology Muscle Physiology Skeletal Muscles Muscle contraction Sliding filament mechanism Thin filaments slide toward M line Z discs move closer together Sarcomere shortens H zone becomes smaller and may disappear A band unchanged Principles of Animal Physiology Muscle Physiology Skeletal Muscles Cross bridge activity Principles of Animal Physiology Muscle Physiology Skeletal Muscles Transverse tubule T tubule Runs around perimeter of each myofibril at Z line Continuous with neighboring myofibrils Anatomical link between surface membrane and deep myofibrils Sarcoplamic reticulum collar wrapped around each myofibril from one Z line to another Sequesters Ca using Ca pumps 10 7 M Principles of Animal Physiology Muscle Physiology Skeletal Muscles T tubule sarcoplasmic reticulum Principles of Animal Physiology Muscle Physiology Skeletal Muscles Calcium release during excitation contraction coupling Principles of Animal Physiology Muscle Physiology Skeletal Muscles Cross bridge cycle Principles of Animal Physiology Muscle Physiology Skeletal Muscles During shortening The crossbridges attach to the thin filament Movement of crossbridge causing movement of the thin filament Detachment of crossbridge from thin filament