S chapter10


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S chapter10

  1. 1. Chapter 10Skeletal Muscle Tissue and the Muscular System ▪3 types of muscle; cardiac, smooth, skeletal ▪Functions of skeletal muscles:Anatomy of skeletal muscle ▪Organization of Connective Tissues (from outer to inner) ▫Epimysium ▫Perimysium ▫Fascicle ▫Edomysium -Myosatellite cells- 1
  2. 2. ▫all “–mysium” join together to form tendons and aponeuroses▪Blood Vessels and Nerves ▫Connective tissues of the epimysium and perimysium contain the blood and nerves that supply the muscle fibers.▪Skeletal Muscle Fibers ▫Sarcolemma ▫Sarcoplasm ▫Transverse Tubules (T tubules) ▫Myofibrils ▫Sarcoplasmic reticulum -Terminal cisternae -Triad ▫Sarcomere -A band- dArk band 2
  3. 3. -M line -H zone -Zone of Overlap-I band- lIght band -Z line (disc)- -Actinins- -Titin--two transverse tubules encircle each sarcomere, triads are found on 2+either side of the M line. Allows Ca to enter where thin and thickfilaments can interact.-Thin Filaments- contains 4 proteins -F actin 3
  4. 4. -G actin contains an active site that binds to a myosin head -Nebulin -Tropomyosin- -Troponin- -Thick Filaments- has a head end and a tail end -Tail is two myosin subunits twisted together -Head projects toward nearest thin filament. -Cross-bridges- ▪Sliding Filament Theory- The explanation of muscle contraction. ▫Describes that the thin filaments move along the thick filaments toward the center of the sarcomere.The Contraction of Skeletal Muscle ▪Control of Skeletal Muscle Activity 4
  5. 5. ▫Neuromuscular junction ▫Acetyelcholine (ACh) ▫Synaptic cleft ▫Motor end plate ▫Acetylcholinesterase (AChE) *Use figure 10-11 to work through the steps of a neuron stimulating a muscle fiber*▪Excitation-contraction coupling 2+ ▫When the action potential reaches the triad, it triggers the release of Ca from the cisternae of SR. 2+ ▫This release lasts only 0.03 seconds, yet increases the Ca levels around the sarcomere a hundred fold. 2+ ▫Since the terminal cisternae are located at the zone of overlap, the Ca reaches the myofilaments almost instantly. 5
  6. 6. 2+ ▫troponin binds with Ca , causing tropomyosin to move aside revealing the active sites for myosin head binding. ▫This action is the beginning of the contraction cycle. *Use figure 10-12 to work through the 5 steps of the contraction cycle* ▪Relaxation ▫Outside forces must act on the contracted muscle fiber to return it to its original length.Tension Production ▪Tension Production by Muscle Fibers ▫Muscle fibers contract in an all-or-none mechanism ▫Tension production by muscle fibers can vary, depending on two things: 1. 2. ▫Length-Tension Relationships 6
  7. 7. ▫Frequency of stimulation -Twitch -Treppe- -Wave summation- -Incomplete tetanus- -Complete tetanus-▫The amount of tension produced by a whole muscle is determined by the 1. 2.▫Motor Units 7
  8. 8. -Recruitment ▫Muscle Tone ▫Isotonic Contractions -Concentric contraction -Eccentric contraction ▫Isometric ContractionsEnergy Use and Muscular Activity ▪ATP and CP Reserves- ATP and CP are both high energy compounds ▫ATP phophorylates creatine to produce creatine phosphate ▫When muscle contraction occurs, dephosphorylated ATP (ADP) is then rephophorylated by CP. ▫ATP reserves last about _____ seconds 8
  9. 9. ▫CP reserves last about _____ seconds▪ATP Generation ▫Aerobic metabolism ▫Glycolysis▪Energy Use and the Level of Muscle Activity*Use figure 10-20 to see the relationship between energy use and muscle activity.*▪Muscle Fatigue- ▫Muscle fatigue is cumulative▪The Recovery Period- conditions in muscle fibers return to normal, pre-exertion levels. 9
  10. 10. ▪Hormones and Muscle Metabolism ▫Growth hormone and testosterone stimulate the synthesis of contractile proteins and the enlargement of skeletal muscles. ▫Thyroid hormones elevate the rate of energy consumption by resting and active skeletal muscles. ▫Epinephrine stimulates muscle metabolism during a sudden crisis.Muscle Performance ▪Types of Skeletal Muscle Fibers ▫Fast Fibers (majority of skeletal muscles) -Large in diameter -Densely packed myofibrils -Large glycogen reserves -Relatively few mitochondria -Fatigue rapidly, build up of lactic acid 10
  11. 11. -Also called: white muscle fibers, fast-twitch glycolytic fibers, type II-A. ▫Slow Fibers -Half diameter of fast fibers -Extensive capillary network, high oxygen supply -Abundant myoglobin -Smaller glycogen reserves -Many mitochondria -Continued contraction without fatigue. -Also called: red muscle fibers, slow-twitch oxidative fibers, type I. ▫Intermediate Fibers- characteristics between fast and slow.▪Muscle Performance and the Distribution of Muscle Fibers ▫Percentage of fast and slow fibers is genetically determined, presence of intermediate fibers can changed resulting in athletic training.▪Muscle Hypertrophy 11
  12. 12. ▪Physical Conditioning ▫Anaerobic endurance- ▫Aerobic endurance-Cardiac Muscle ▪Structural Characteristics of Cardiac Muscle Tissue ▪Functional Characteristics of Cardiac Muscle TissueSmooth Muscle ▪Structural Characteristics of Smooth Muscle 12
  13. 13. ▪Functional Characteristics of Smooth Muscle Tissue: ▫Excitation-Contraction coupling ▫Length-Tension Relationships -Plasticity ▫Control of Contraction -multiunit smooth muscle cells- -visceral smooth muscle cells- 13