Neuromuscular Physiology PDF

Neuromuscul ar Physiology Muscles are cool!  01 Skeletal Muscle Structure QUIZ!! A. What are the three types of muscle throughout the human body? B. What are the two main types of skeletal muscle? C. What is the lowest contractile unit of muscle? Muscle C...

Neuromuscul ar Physiology Muscles are cool!  01 Skeletal Muscle Structure QUIZ!! A. What are the three types of muscle throughout the human body? B. What are the two main types of skeletal muscle? C. What is the lowest contractile unit of muscle? Muscle Characteristics Excitable The motor neuron will use action potentials to stimulate contraction Muscle Characteristics Excitable The motor neuron will use action potentials to stimulate contraction Contractile Will forcibly shorten due to changes in membrane potential Muscle Characteristics Extensible Excitable The motor neuron will stretching beyond use action potentials normal resting to stimulate point contraction Contractile Will forcibly shorten due to changes in membrane potential Muscle Characteristics Extensible Excitable The motor neuron will stretching beyond use action potentials normal resting to stimulate point contraction Contractile Elastic Will forcibly shorten the ability of due to changes in stretched muscle to membrane potential retract back to normal/resting Muscle Characteristics Extensible Excitable The motor neuron will stretching beyond use action potentials normal resting to stimulate point contraction Contractile Elastic Will forcibly shorten the ability of due to changes in stretched muscle to membrane potential retract back to normal/resting Muscle Functions Producing Movement producing movement is dependent on certain muscle contracting together to move Muscle Functions Producing Movement producing movement is dependent on certain muscle contracting together to move Posture to maintain posture against gravity, muscles need to be stabilizing Muscle Functions Stabilize Joints Producing Movement muscles wrap around joints and producing movement create stabilization is dependent on certain muscle contracting together to move Posture to maintain posture against gravity, muscles need to be stabilizing Muscle Functions Stabilize Joints Producing Movement muscles wrap around joints and producing movement create stabilization is dependent on certain Produce Heat muscle contracting by product of together to move cellular Posture respiration is heat; also, shivering = to maintain posture quivering against gravity, contractions to muscles need to be generate heat stabilizing Muscle Functions Stabilize Joints Producing Movement muscles wrap around joints and producing movement create stabilization is dependent on certain Produce Heat muscle contracting by product of together to move cellular Posture respiration is heat; also, shivering = to maintain posture quivering against gravity, contractions to muscles need to be generate heat stabilizing  Smallest contractile unit of muscle  Smallest contractile unit of muscle  Somatic motor neurons of PNS carry neural messages from spinal cord to muscles Motor unit motor neuron and the muscle fibers it innervates smallest functional unit in muscle Motor Unit and Fiber Types 2b? Type Type Type 1 2a 2x Motor Unit and Fiber Types Type Type Type 1 2a 2x Motor Unit and Fiber Types Slow Fast Fast Oxidative Oxidative Glycolytic (SO) Glycolytic (FG) (FOG) Motor Unit and Fiber Types Properties I (SO) 2a 2x (FG) (FOG) Contraction Slow Fast Fastest Velocity Relaxation Slow Fast Fast Time Force Low High High Production Fatigability Resistan Fatigabl Most t e Motor Unit and Fiber Types Properties I (SO) 2a (FOG) 2x (FG) PCR Stores Low High High Glycogen Stores Low High High Lipid Stores High Medium Low Glycolytic Low Medium High Enzymes Oxidative High Medium Low Enzymes Motor Unit and Fiber Types Properties I (SO) 2a (FOG) 2x (FG) Fiber Diameter Small Medium Large Hypertrophic Small Medium Large Potential Mitochondrial High Medium Low Density Capillary Density High Medium Low Fiber to motor unit ratio low ratio in SO: more fine control muscles in eye = 23:1 ratio higher in FG & FOG: gross control biceps = 150:1 or gastrocnemius = 2000:1  02 What defines a fiber type? Lance & Landmesser 1978 2 1 Surgically switched the location of two muscle masses before nerve outgrowth Outgrowing axons detoured and innervated the 1 2 correct muscles Muscles signaled the nerves  Buller & Eccles Fast motor nerve Slow motor nerve 1960 Surgically reattached a motor nerve from a fast- contracting muscle to a slow-contracting muscle Muscles began to switch characteristics Why? SL OW Slow Fast How to determine? Direct: Biopsy and staining Indirect: Various exercise tests How to determine? Direct: Biopsy and staining Indirect: Various Fatigue Index exercise tests Wingate and fiber types Type Type Type 1 2a 2x Low PP High PP and FI and FI MU patterns in elite athletes Sport % Type % Type 1 2 Endurance 60-70 30-40 Sprinters 20-25 75-80 Weightlifters 40-45 55-60 Gen pop Non-athletes 47-53 47-53 Recruitme Size nt Principle FG FOG SO Review Quiz 1. What fiber type is only found in mice? 2. Describe the size principle? 3. What is one indirect test that can help give an estimate of fiber type composition?  Sex Differences in Fiber Types  Greater proportion of Type 1 fibers in females Sort of….. Miller et al., 1993 Female Male Bicep VL How might this impact training?  Male More reps 2-4 reps at 90% of 1RM with the same Female 3-6 reps at percentag 90% of 1RM e! Differences are primarily with lower body or single joint exercises!  02 Review The Neuromuscular Syste m  Sensory neuron Sense s Organ Somatic motor neuron ta l Sk e l e le M us c Autonomic motor neuron scle oo t h mu Sm scle ar d iac M u C s Gland Start of Action Potential Action Potential: All or None Theory  Na Na Na K K Na Na Na Na K Na K K K Na K K K Na RMP = -70mv Na Na Na K Na Na Na K K  Na Na Na K K Na Na Na Na K Na K K K Na K K K Na TP = -55mv Na Na Na K Na Na Na K K Na K K Na Na Na K Na K Na K Na Na K Na Na Na K Na Na K K Na +30mv Na K Na K K Na K K Na Na Approximately -90mv Na Na Na K Na Na Na Na Na K Na Na K Na Na K K K K K Na K K  Na Na Na K K Na Na Na Na K Na K K K Na K K K Na RMP = -70mv Na Na Na K Na Na Na K K Ca Ca Ca +30mv Synaptic Vesicles filled with Ach Ca Ca Ca Ca Ca Action Potential: All or None Theory Na+ influx K+ efflux Na/K Pump Action Potential: All or None Theory Absolute refractory period Action Potential: All or None Theory Relative refractory period  03 Excitation Contraction Coupling Neuromuscular Junction  Neuromuscular Junction What happens at the neuromuscular junction??  AP enters muscle through t-tubule Troponin moves tropomyosin to expose the active site on actin Myosin can now bind strongly to actin Ca2+ binds troponin Ca2+ is released when “triad”region depolarizes  Types of Contractions Isometric Isokinetic Isotonic Concentric Eccentric Concentric Eccentric  Isotonic Contractio n External load stays the same  Isokinetic Contractio n Speed of contraction stays the same  Isokinetic Contractio n Speed of contraction stays the same Isometric Contractio n Position stays the same Isometric Contractio n Position stays the same Types of Contractions: Strength Eccentric Isometric Concentric Concentric >30lbs 30lbs isometric =30lbs 30lbs Eccentric ≤ 29lbs 30lbs An eccentric muscle contraction, on the other hand, is the stretching of a muscle in response to an opposing force on that muscle, in which the opposing force (weight being lifted) is greater than its current force production. When the myofilaments of a muscle fiber are stretched while contracting (i.e, doing an eccentric contraction), Herzog and colleagues (2008) propose there may be a decreased rate of cross- bridge detachments (thus an increased PERCENTAGE of cross-bridges remain attached) leading to greater force production on the eccentric bout. In addition, Herzog et al. add that there is an increase in the stiffness of the titin protein during the eccentric contraction. Titin adds a passive (i.e., a tautness) force enhancement to the muscle's force production while being lengthened (under load). Herzog and colleagues speculate that other, not fully elucidated, metabolic force enhancement changes in the sarcomere are also occurring during eccentric muscle actions. Examples of eccentric muscle contractions are walking down a hill, or resisting the force of gravity while lowering a weight or object. Eccentric actions place a stretch upon the sarcomere to the point at which the myofilaments may experience sarcomere strain, or damage referred to as exercise-induced delayed onset muscle soreness (DOMS).  Force Velocity Curve Ability to generate force is related to velocity of contraction High velocities limit cross- bridging Low velocities increase cross-bridging Length Tension Relationship