Topic 5 Muscle Structure and Function PDF

RFD13803 MUSCLES STRUCTURE & FUNCTION LEARNING OBJECTIVES At the end of the lesson, students should be able to: 1 2 3 Identify the Describe the Explain the elements of muscle function effect of injury musc...

RFD13803 MUSCLES STRUCTURE & FUNCTION LEARNING OBJECTIVES At the end of the lesson, students should be able to: 1 2 3 Identify the Describe the Explain the elements of muscle function effect of injury muscle structure to muscles  MUSCLES Muscles are vital tissues in our bodies that enable movement by contracting (shortening) and relaxing (lengthening). Muscles allowing us to perform various activities.  MUSCLES When you decide to move, your brain sends signals to the skeletal muscles, which are attached to your bones. For example, to raise your arm, the muscles in your arm contract, pulling on the bones to lift it. TYPES OF MUSCLE TISSUE  SKELETAL MUSCLE Skeletal muscles have a striated appearance because of the way their fibers are organized. Voluntary: Contraction can be controlled. These muscles attach to bones throughout the body, enabling us to move. Made up of 1/3 of total human body mass.  CARDIAC MUSCLE Cardiac muscles have a striation, branched and interconnected. Cardiac muscles work involuntarily, continuously contracting to pump blood through the heart. It is autorhytmic fibers providing stimulation leading to contraction. SMOOTH MUSCLE Smooth muscles do not have striations. These muscles operate involuntarily. They are found in the walls of hollow organs such as the stomach, intestines, blood vessels, and bladder. 2 types: visceral (single unit) and multi unit. COMPARING THE MUSCLE TISSUE Type of Muscle Appearance Contraction Location Striated Skeletal Voluntary Between bones Non- branching Striated Cardiac Involuntary Heart Branching Vessels, Non striated Smooth Involuntary Intestine, Non-branching Organs SKELETAL MUSCLE STRUCTURE  STRUCTURE Long, cylindrical, multinucleated cell with various length and width Has highly organized structure of muscle fibers  STRUCTURE Actin and myosin myofilaments are stacked and overlapped to form sarcomeres Actin and myosin filaments slide against each other and responsible for muscle contraction. STRUCTURE Z disc - separation between sarcomere I band – The thin filament location H zone – area where only thick filament is found A band - length of thick filament M line – midline of the sarcomere SHAPE SKELETAL MUSCLE FIBER SKELETAL MUSCLE FIBER SKELETAL MUSCLE FUNCTION  TERMINOLOGIES Terminologies related to muscle action: ⚬ Agonist: initiate and execute the movement. ⚬ Antagonist: muscle or muscle group that have opposite action of a particular muscle. ⚬ Synergist: muscle that cooperate during execution or works with agonist.  MUSCLE ACTIVATION Isometric Contraction ⚬ Change in tension ⚬ Muscle length is constant  MUSCLE ACTIVATION Isotonic Contraction ⚬ Tension remains constant ⚬ Change in muscle length.  MUSCLE ACTIVATION Concentric Isotonic Contraction ⚬ Tension increases to meet resistance as the muscles shortens.  MUSCLE ACTIVATION Eccentric Isotonic Contraction ⚬ Muscle lengthens as the resistance becomes greater than force of the muscle is producing. LENGTH TENSION RELATIONSHIP Forcefulness of a muscle contraction depends on the length of a sarcomere before contraction. CONTROL OF MUSCLE TENSION A single nerve impulse elicits a single muscular action potential. Force of a muscle fiber depends on: ⚬ Frequency of stimulation. ⚬ Amount of stretch before a contraction is elicited. ⚬ Availability of nutrients: glucose, oxygen, and ATP. LENGTH TENSION RELATIONSHIP EXPLANATION  TWITCH CONTRACTION A brief contraction of all the muscle fibers in a motor unit. Latent period Contraction period Relaxation period  MOTOR UNIT A group of muscle fibers and a motor neuron that work together to produce a movement. A basic functional unit of skeletal muscle A muscle have several hundreds of motor neurons and each motor neuron may innervates several thousand muscle fibers.  MOTOR UNIT RECRUITMENT Recruitment is responsible for producing smooth muscle movements. Different motor units are activated at various times. Weak motor units are recruited first and stronger ones later as needed. Recruitment of different motor units also reduces fatigue. EFFECT OF AGING AND INJURY  EFFECT OF AGING & INJURY Loss of skeletal muscle mass is replaced by fibrous connective and adipose tissue. Muscle decreases in strength, speed and flexibility. Slow oxidative fibers increase Aerobics and strength training can slow or reverse decline in muscular performance  THANK YOU! I hope you learn something new today!  REFERENCES Pamela K.L., Cynthia C.N. Joint Structure and Function; A Comprehensive Analysis (4th Edition). F.A Davis Company. Nigel P., Derek F., Roger S. Anatomy and Human Movement; Structure and Function (5th Edition). Elsevier Butterworth Heinemann.