KHP450 Lecture 1: Structure and Function of Body Systems PDF

Structure and Function of the Muscular, Neuromuscular, Cardiovascular, and Respiratory chapter 1 Systems KHP450 – Lecture 1 Structure and Function of Body Systems Eli Mizelman  Chapte...

Structure and Function of the Muscular, Neuromuscular, Cardiovascular, and Respiratory chapter 1 Systems KHP450 – Lecture 1 Structure and Function of Body Systems Eli Mizelman  Chapter Objectives Macrostructure and microstructure of muscle and bone The sliding-filament theory The specific physiological characteristics of different muscle fiber types and their involvement in different sports The characteristics of the cardiovascular and respiratory systems  Skeletal System Composed of 206 bones in the adult body Provides leverage, support, and protection Pulled on by muscles to allow the body to push or pull against external objects  Skeletal System (continued) – (a) Front view of an adult male human skeleton – (b) Rear view of an adult male human skeleton  Axial Versus Appendicular Skeleton Axial: Consists of the skull, vertebral column (C1-coccyx), ribs, and sternum Appendicular: Consists of shoulder girdle; bones of the arms, wrists, hands, and pelvic girdle; and bones of the legs, ankles, and feet  Types of Joints Joint: Junctions of bones Fibrous: Allow virtually no movement – Example: Sutures of the skull Cartilaginous: Allow limited movement – Example: Intervertebral Synovial: Allow considerable movement – Example: Elbows and knees  Types of Joints (continued) Uniaxial: Operate as a hinge, rotate about one axis – Example: Elbow Biaxial: Operate in two perpendicular axes – Example: Ankle and wrist Multiaxial: Allow movement in all three axes – Example: Shoulder and hip  Vertebral Column Vertebral bones separated by flexible disks that allow for movement – Cervical vertebrae (neck region): 7 – Thoracic vertebrae (upper back): 12 – Lumbar vertebrae (lower back): 5 – Sacral vertebrae (make up rear of pelvis): 5 – Coccygeal vertebrae (form vestigial tail extending down from the pelvis): 3-5  Muscular System Macrostructure and microstructure – Each skeletal muscle is an organ that contains muscle tissue, connective tissue, nerves, and blood vessels. – Fibrous connective tissue, or epimysium, covers the body’s more than 430 skeletal muscles.  Schematic Drawing of a Muscle Three types of connective tissue: Epimysium (the outer layer) Perimysium (surrounding each fasciculus, or group of fibers) Endomysium (surrounding individual fibers)  Motor Unit – A motor unit consists of a motor neuron and the muscle fibers it innervates. – There are typically several hundred muscle fibers in a single motor unit.  Muscle Fiber – Sectional view of a muscle fiber Figure 1.5  Myosin and Actin – A detailed view of the myosin and actin protein filaments in muscle. – The arrangement of myosin (thick) and actin (thin) filaments gives skeletal muscle its striated appearance.  Key Point The discharge of an action potential from a motor nerve signals the release of calcium from the sarcoplasmic reticulum into the myofibril, causing tension development in muscle.  Muscular System Sliding-filament theory of muscular contraction – States that the actin filaments at each end of the sarcomere slide inward on myosin filaments, pulling the Z-lines toward the center of the sarcomere and thus shortening the muscle fiber  Contraction of a Myofibril – (a) In stretched muscle the I-bands and H-zone are elongated, and there is low force potential due to reduced crossbridge–actin alignment.  Contraction of a Myofibril – (b) When muscle contracts (here partially), the I-bands and H-zone are shortened.  Contraction of a Myofibril – (c) With completely contracted muscle, there is low force potential due to reduced crossbridge–actin alignment.  Muscular System Sliding-filament theory of muscular contraction – Resting phase – Excitation–contraction coupling phase – Contraction phase – Recharge phase – Relaxation phase  Key Points The number of crossbridges that are formed between actin and myosin at any instant in time dictates the force production of a muscle. Calcium and ATP are necessary for crossbridge cycling with actin and myosin filaments.  Neuromuscular System Activation of muscles – Arrival of the action potential at the nerve terminal causes the release of acetylcholine. Once a sufficient amount of acetylcholine is released, an action potential is generated across the sarcolemma, and the fiber contracts.  Neuromuscular System (continued) Activation of muscles – The extent of control of a muscle depends on the number of muscle fibers within each motor unit. Muscles that function with great precision may have as few as one muscle fiber per motor neuron. Muscles that require less precision may have several hundred fibers served by one motor neuron.  Key Term all-or-none principle: All of the muscle fibers in the motor unit contract and develop force at the same time. There is no evidence that a motor neuron stimulus causes only some of the fibers to contract. Similarly, a stronger action potential cannot produce a stronger contraction.  Stimulated Motor Unit – Twitch, twitch summation, and tetanus of a motor unit: a = single twitch b = force resulting from summation of two twitches c = unfused tetanus d = fused tetanus  Neuromuscular System Muscle fiber types – Type I (slow-twitch) – Type IIa (fast-twitch) – Type IIx (fast-twitch)  Key Point Motor units are composed of muscle fibers with specific morphological and physiological characteristics that determine their functional capacity.  Neuromuscular System Motor unit recruitment patterns during exercise – The force output of a muscle can be varied through change in the frequency of activation of individual motor units or change in the number of activated motor units.  Key Point The force output of a muscle can be varied through change in the frequency of activation of individual motor units or change in the number of activated motor units.  Key Point Proprioceptors are specialized sensory receptors that provide the central nervous system with information needed to maintain muscle tone and perform complex coordinated movements.  Proprioception Muscle spindles When a muscle is stretched, deformation of the muscle spindle activates the sensory neuron, which sends an impulse to the spinal cord, where it synapses with a motor neuron, causing the muscle to contract.  Proprioception Golgi tendon organs (GTO) – Golgi tendon organs are proprioceptors located in tendons near the myotendinous junction. – They occur in series (i.e., attached end to end) with extrafusal muscle fibers.  Golgi Tendon Organ – When an extremely heavy load is placed on the muscle, discharge of the GTO occurs. – The sensory neuron of the GTO activates an inhibitory interneuron in the spinal cord, which in turn synapses with and inhibits a motor neuron serving the same muscle.  Neuromuscular System How can athletes improve force production? – Incorporate phases of training that use heavier loads in order to optimize neural recruitment. – Increase the cross-sectional area of muscles involved in the desired activity. – Perform multimuscle, multijoint exercises that can be done with more explosive actions to optimize fast- twitch muscle recruitment.  Cardiovascular System Heart – The heart is a muscular organ made up of two interconnected but separate pumps. The right ventricle pumps blood to the lungs. The left ventricle pumps blood to the rest of the body.  Heart and Blood Flow – Structure of the human heart and course of blood flow through its chambers  Cardiovascular System Heart – Valves Tricuspid valve and mitral (bicuspid) valve Aortic valve and pulmonary valve Valves open and close passively, depending on the pressure gradient – Conduction system Controls the mechanical contraction of the heart  Electrical Conduction System – The electrical conduction system of the heart  Cardiac Conduction Rhythmicity and conduction properties of myocardium – Influenced by cardiovascular center of medulla – Signals transmitted through sympathetic and parasympathetic nervous systems – Bradycardia (100 beats/min)  Cardiovascular System Heart – Electrocardiogram Recorded at the surface of the body A graphic representation of the electrical activity of the heart  Electrocardiogram – Normal electrocardiogram  Cardiovascular System Blood vessels – Blood vessels operate in a closed-circuit system. – The arterial system carries blood away from the heart. – The venous system returns blood toward the heart.  Distribution of Blood – The arterial (right) and venous (left) components of the circulatory system. – The percent values indicate the distribution of blood volume throughout the circulatory system at rest.  Cardiovascular System Blood vessels – Arteries – Capillaries – Veins (continued)  Cardiovascular System (continued) Blood – Hemoglobin transports oxygen and serves as an acid–base buffer. – Red blood cells facilitate carbon dioxide removal.  Key Point The cardiovascular system transports nutrients and removes waste products while helping to maintain the environment for all the body’s functions. The blood transports oxygen from the lungs to the tissues for use in cellular metabolism; and it transports carbon dioxide from the tissues to the lungs, where it is removed from the body.  Respiratory System – Gross anatomy of the human respiratory system  Respiratory System Exchange of respiratory gases – The primary function of the respiratory system is the basic exchange of oxygen and carbon dioxide.  Respiratory System (continued) Exchange of air – The amount and movement of air and expired gases in and out of the lungs are controlled by expansion and recoil of the lungs.  Respiratory System (continued) Pleural pressure – Pressure in the narrow space between the lung pleura and the chest wall pleura Membranes enveloping the lungs and lining the chest walls  Respiratory System (continued) Alveolar pressure – Pressure inside the alveoli when the glottis is open and no air is flowing into or out of the lungs – To cause inward flow of air during inspiration, the pressure in the alveoli must fall to a value slightly below atmospheric pressure – During expiration, alveolar pressure must rise above atmospheric pressure  Respiratory System (continued) Exchange of respiratory gases – The process of diffusion is a simple random motion of molecules moving in opposite directions through the alveolar capillary membrane.