Ch. 1 - Structure and Function of Body Systems 2024 PDF

KINESIOLOGY Structure and Function of Body Systems KINESIOLOGY Structure and Function of Body Systems KINESIOLOGY Objectives 1. Identify macrostructure and microstructure of muscle and...

KINESIOLOGY Structure and Function of Body Systems KINESIOLOGY Structure and Function of Body Systems KINESIOLOGY Objectives 1. Identify macrostructure and microstructure of muscle and connective tissue. 2. Describe the sliding-filament theory of muscle contraction. 3. Describe physiological characteristics of muscle fiber types. 4. Identify structures of cardiovascular and respiratory systems and their function during exercise. KINESIOLOGY KINESIOLOGY Musculoskeletal System Bones, muscles, and connective tissue Muscles pull on bones to create pushing or pulling forces against external objects KINESIOLOGY KINESIOLOGY Skeletal System Joints – junction of bones Joints can be classified by: – Degree of movement Fibrous joint – no movement Cartilaginous joint – allows limited movement Synovial joint – allows greatest movement – Number of directions in which rotation can occur KINESIOLOGY Skeletal System Synovial joints: – Hyaline cartilage – Synovial capsule with fluid – Supporting connective tissue (i.e. ligaments) Types of synovial joints: – Non-axial – Uniaxial – Biaxial – Multiaxial KINESIOLOGY Skeletal Muscle What is the largest organ system in the body? KINESIOLOGY Skeletal Muscle KINESIOLOGY Skeletal Muscle Muscle fiber – muscle cell Muscle fascicles – bundles of muscle fibers Muscles – an organ that contains contractile proteins, connective tissue, nerves, and blood vessels. KINESIOLOGY KINESIOLOGY Skeletal Muscle Epimysium – outer fibrous covering of the muscle Perimysium – covers muscle fascicles Endomysium – covers muscle fibers Contiguous with the muscle tendon – Attaches to bone periosteum KINESIOLOGY KINESIOLOGY KINESIOLOGY KINESIOLOGY How does foam rolling work? KINESIOLOGY KINESIOLOGY Institute ofofHuman Anatomy Myofascial Anatomy Release Institute of Human Anatomy Anatomy of Myofascial Release KINESIOLOGY Skeletal Muscle Sarcolemma – outer membrane – Contiguous with endomysium Sarcoplasm – fluid portion (cytoplasm) of the muscle fiber – contains proteins, glycogen, lipids, enzymes, and other organelles KINESIOLOGY Skeletal Muscle Myofibrils – groups of contractile proteins Mitochondria – metabolic center of the muscle fiber KINESIOLOGY Skeletal Muscle Sarcoplasmic reticulum: – tubule system running parallel to myofibrils – Storage cite of calcium Transverse tubules (T-tubules): – tube system that extends from the sarcolemma to sarcoplasmic reticulum – Important for transmitting electrical impulses KINESIOLOGY Skeletal Muscle Nucleus – organelle that contains gene information – Skeletal muscle is multi-nucleic Satellite cells – cells that can donate a nuclei to the muscle fiber – Important for muscle growth and repair KINESIOLOGY KINESIOLOGY Skeletal Muscle Sarcomere – smallest contractile unit of skeletal muscle – Repeated longitudinally throughout the muscle fiber – Made up of protein myofilaments Myosin – protein containing a globular head and polypeptide tails – Thick filament Actin – two polypeptide protein strands arranged in a double helix – Thin filaments KINESIOLOGY KINESIOLOGY Six actin filaments surround one myosin filament, while each actin filament is surrounded by three myosin filaments. KINESIOLOGY Skeletal Muscle Tropomyosin – tube-shaped protein twisted around the actin filament and lies in the groove between the double-helix – Responsible for inhibiting the actin and myosin coupling Troponin – protein embedded at regular intervals along actin and tropomyosin – High affinity for calcium ions (Ca2+) – Regulates tropomyosin KINESIOLOGY Z-line: anchors actin filaments – Sarcomere extends from z-line to z-line I-band: region where only actin is located – Light portion H-zone: region where only myosin is located – Dark portion A-band: region where myosin and actin overlap – Dark portion KINESIOLOGY KINESIOLOGY Muscle Contraction Motor unit – a motor neuron and the muscle fibers that it innervates – One motor neuron may innervate a few fibers up to thousands KINESIOLOGY Muscle Contraction Neuromuscular junction – location where motor neuron and muscle fiber innervate – Motor end plate – sarcolemma pocket formed around motor neuron – Synaptic cleft – gap between neuron and muscle fiber – Acetylcholine – neurotransmitter released from motor neuron to stimulate muscle fiber KINESIOLOGY Muscle Contraction Video Explanation KINESIOLOGY Muscle Contraction Actin filaments slide inward over myosin filaments Z-lines pulled together, shortening the sarcomere Relaxed Contracting Fully Contracted KINESIOLOGY Muscle Contraction The number of crossbridges between actin and myosin dictates the force production of the muscle. Length-Tension Relationship KINESIOLOGY KINESIOLOGY Muscle Contraction Step 1: Action potential from alpha motor neuron Step 2: Release of acetylcholine into the NMJ – ACh binds to receptors Step 3: Depolarization across sarcolemma – Action potential travels down T-tubules Step 4: Ca2+ released from sarcoplasmic reticulum Step 5: Ca2+ binds to troponin – Troponin causes shift in tropomyosin – Myosin biding sites uncovered KINESIOLOGY Muscle Contraction Step 6: Myosin binds to actin to form crossbridge Step 7: ATP split and energy produces power stroke Step 8: New ATP binds to myosin – Crossbridge released Step 9: Steps 6-8 continue if: – Sufficient Ca2+ and ATP Step 10: Motor neuron stimulation ceases – Calcium pumped back into sarcoplasmic reticulum – Muscle relaxes; sarcomere returns to resting state KINESIOLOGY Muscle Contraction Resting Phase – Low calcium binding → minimal crossbridge formation Excitation-Contraction Coupling Phase – Action potential → increased calcium release → crossbridge formation Contraction Phase – ATP hydrolysis → power stroke → sarcomere shortens Relaxation Phase – Decreased motor neuron activation → calcium pumped back into SR → myosin detachment → sarcomere returns to resting state KINESIOLOGY Muscle Contraction Sliding Filament Video 1 Sliding Filament Video 2 KINESIOLOGY Neuromuscular Activation Muscle control depends on number of fibers in motor unit – Muscles with fine motor skills may have as few as one fiber per unit – Muscles with less precision may have several hundred fibers All or none principle – All muscle fibers in a motor unit will contract when stimulated KINESIOLOGY Neuromuscular Activation Each action potential produces a brief contraction: – a twitch – Calcium is released and removed quickly If second twitch is elicited before muscle relaxes, the two twitches summate – Force is greater than single twitch If twitch frequency becomes high enough, the twitches fuse a = single twitch – Tetanus b = summation of two twitches – Individual twitches blend into sustained contraction c = unfused tetanus d = fused tetanus KINESIOLOGY KINESIOLOGY Muscle Fiber Types Muscles contain fibers of different morphological and physiological characteristics Common classification is based on twitch time – Slow-twitch: develops force and relaxes slowly long twitch time – Fast-twitch: rapid force production and relaxation short twitch time KINESIOLOGY Muscle Fiber Types Biochemical classification – Classified by ability to supply and utilize energy for contraction Aerobic capacity – Number of capillaries – Number of mitochondria – Amount of myoglobin – Enzyme content – Fiber size (amount of contractile proteins) KINESIOLOGY Muscle Fiber Types Mechanical classification – Force production capacity – Speed of contraction and relaxation – Power output (force × velocity) – Fatigue resistance KINESIOLOGY Muscle Fiber Types Type I fibers – Slow-twitch – Aerobic fibers Type IIa – Fast-twitch – Aerobic-anaerobic fibers Type IIx Light Blue = Type I fibers – Fast-twitch Green = Type IIa fibers Dark Blue = Type IIx fibers – Anaerobic fibers KINESIOLOGY KINESIOLOGY Muscle Fiber Types Endurance Strength/Power 70% Slow; 30% Fast 70% Fast; 30% Slow Inter-individual variability Differences between muscles Adapted from S&Cresearch.com KINESIOLOGY KINESIOLOGY Motor Unit Recruitment Force production can be varied through: – Frequency of activation (rate coding) – Number of motor units activated Size principle KINESIOLOGY KINESIOLOGY KINESIOLOGY Comparison of paused vs. touch and go reps during bench press * Mean Velocity (m∙s-1) * * * % of 1RM * significantly different from TNG reps (p < 0.05). Osborn and Gwaltney, in prep KINESIOLOGY Can an athlete vertical jump higher with a countermovement or in a static squat position? KINESIOLOGY Proprioception Muscle spindles – Aka intrafusual fibers – Detect rate and changes in muscle length – Feedback sent to spinal cord (afferent) – Alpha motor neuron stimulation (efferent) – Aids in activities such plyometrics Stretch-shortening cycle (SSC) – Stretch-reflex (muscle spindles) – Series elastic component KINESIOLOGY Proprioception Golgi Tendon Organ (GTO) – Located in musculotendinous junction – Senses tension – Activation → muscle inhibition – Desensitized through training KINESIOLOGY Cardiovascular System CV system: – Heart (pump) – Circulatory system (vessels) – Blood (fluid) Functions: – Delivery of nutrients – Removal of metabolic byproducts – Transport of hormones – Temperature regulation KINESIOLOGY Cardiovascular System Chambers – atria – ventricles Valves – Atrioventricular valves: tricuspid – right mitral – left – Semilunar valves pulmonary – right aortic - left KINESIOLOGY KINESIOLOGY Sinoatrial (SA) node – intrinsic control (approx. 60-80 bpm) – location where electrical impulses are initiated Atrioventricular (AV) node – Location where impulse is delayed before passing to ventricles Atrioventricular (AV) bundle – Transmits impulses to the ventricles Left and right bundle branches – Branches of the AV bundle transmitting the impulse to the ventricles – Contains Purkinje fibers which transmits impulses throughout the ventricles KINESIOLOGY KINESIOLOGY Autonomic Control Cardiovascular control center in medulla transmits signals via: – Sympathetic nervous system – Parasympathetic nervous system Sympathetic nervous system – Cardiac accelerator nerves – Increases heart rate by stimulating the SA node (chronotropic effect) – Increase heart rate > 200 bpm Parasympathetic nervous system – Vagus nerve – Decreases heart rate by inhibiting the SA and AV node (vagal tone) – Decrease heart rate as low as 30 bpm KINESIOLOGY KINESIOLOGY P-wave – Atrial depolarization QRS complex – Ventricular depolarization – Atrial repolarization T-wave – Ventricular repolarization KINESIOLOGY KINESIOLOGY KINESIOLOGY Cardiovascular System Close-circuit system – Arterial system – carries blood from the heart Arteries and arterioles Strong, muscular walls; high pressure – Venous system – carries blood to the heart Veins and venules Low pressure Skeletal muscle pump; One-way valves – Capillaries Exchange of O2, CO2, nutrients, fluids, etc. KINESIOLOGY Skeletal Muscle Pump KINESIOLOGY KINESIOLOGY Blood – Plasma Liquid portion Contains proteins, hormones, etc. – Cells Red blood cells – Contains hemoglobin White blood cells – Immune function Platelets – Blood clotting KINESIOLOGY Respiratory System Nose and nasal cavity – Purifies, humidifies, and warms air Transport into lungs Pharynx → larynx (vocal) → trachea → bronchi → bronchioles Alveoli – Location of gas exchange in the lungs KINESIOLOGY KINESIOLOGY Respiratory System Lungs recoil and expand – Diaphragm and muscles around the rib cage Inspiration Diaphragm contracts (depresses and flattens) Vacuum to pull air into the lungs Expiration Diaphragm relaxes (elevates) Elastic recoil forces air out of the lungs Rest vs. Exercise – Diaphragm controls air exchange during rest – Heavy exercise requires muscles around the rib cage to assist Inspiration: external intercostals, SCM, anterior serratus, and scalenes Expiration: rectus abdominus, obliques, transverse abdominus, internal intercostals KINESIOLOGY Respiratory System Pleural pressure – Pressure in the narrow space between the lung pleura and chest wall pleura – Pleura – membrane enveloping the lungs and lining the chest wall – Expansion of rib cage: Pressure decreases Increases air flow into lungs – Depression of rib cage Pressure increases Forces air out of lungs KINESIOLOGY Respiratory System Alveolar pressure – Pressure in the alveoli Inspiration – Alveolar pressure decreases below atmospheric pressure Expiration – Alveolar pressure increases above atmospheric pressure KINESIOLOGY KINESIOLOGY Respiratory System Diffusion – Movement of molecules in opposite directions through the alveolar capillary membrane KINESIOLOGY Respiratory System High concentration to low concentration – partial pressure of O2 is approx. 60 mmHg higher than pulmonary capillaries at rest O2 easily diffuses into capillaries to be transported – Partial pressure of CO2 is lower than pulmonary capillaries CO2 diffuses into aveoli to be exhaled KINESIOLOGY KINESIOLOGY KINESIOLOGY KINESIOLOGY KINESIOLOGY KINESIOLOGY Next: Biomechanics of Resistance Exercise