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HHP Ch 12
Muscle Physiology
| Question | Answer |
|---|---|
| Compare the different characteristics of skeletal, smooth, and cardiac muscle | Skeletal muscle: move bones, S, V, (Somatic) myo-act, Ca-tro Cardiac muscle: heart, S, IV (ANS), myo-actin, Ca-tro, gap juntions Smooth muscle: hollow organs and tubes, US, IV, Ca-cal, gap |
| Describe the different levels of muscle structure | Molecular level — actin and myosin Microscopic level — sarcomere and myofibrils Cell level — myoblasts and myofibers Tissue level — neuromuscular junctions and fascicles Organ level — major skeletal muscles of the body |
| Describe the function of skeletal muscle | – Movement of body – Posture – Genera7on of body heat – Movement of substances (ex Urinary tract ) – Nutrient reserves – Support soI 7ssues and organs |
| Define the A band, I band, Z band, H zone, and M line | Z-bounds each sacromere M-down center of sac, thru middle of myo fils I-only thin fil H- only thick fil A-both thick and thin, span thick fil (end of thick-beginning of thin) |
| Describe the structure of myosin | • Component of thick filament • Heads form cross bridges between thick and thin filaments • On myosin heads: - Actin Binding site - ATP Binding Site - ATPase |
| Explain the roles of troponin and tropomyosin | • Regulatory proteins on Actin Tropomyosin (Restng, covers myosin binding sites blocking interaction Troponin 3 binding units (tropomyosin, actin, Ca2+ ) |
| Describe a sarcomere | – Functional unit of contraction – Between 2 Z lines – Regions • A band: • H zone: • M line: • I band: |
| Describe motor units, and motor end plate. | – Motor unit = single motor neuron and all the muscle fibers it innervates – Motor end plate= area of the muscle fiber sarcolemma where a motor neuron stimulates skeletal muscle • Neutransmitter:Acetylcholine |
| Explain the power stroke, cross-bridge cycle and the sliding filament theory of contraction | PS- swiveling of myo head (MH) CBC- ADP+Pi on MH, Pi released when MH-actin, Pi release-> MHpowerstroke and ADP released. ATP-MH :. actin release. ATP hydrolyzed (ATPase) to ADP+Pi on MH (restart). FtC- powerstroke pull think (actin) to M line->contract |
| Explain the function of T tubules | passes AP to interior of muscle cell |
| Explain excitation-contraction coupling in skeletal muscles | AP->depolarized sacrolemm->membrane potential change-> detected by Ca V channel dihydropyridine receptor (DHPR)-> signal Ca channel ryanodine receptor (RyR1) in SR membeane-> releases Ca2+ ions for contraction. |
| Describe muscle relaxation. | -AP stops -Active reuptake of Ca2+ into sarcoplasmic reticulum (SR) – Ca++ATP pump |
| Explain the roles of ATP in muscle contraction | 1. Split of ATP by myosin ATPase provides energy for power stroke 2. Bind of new ATP to myosin->cross bridge detach from actin so cycle repeat 3. Active transport Ca2+ back to SR ->return to resting state |
| Define load and tension as it pertains to skeletal muscle contraction | – Tension=Force exerted on an object by contracting muscle – Load=Force exerted on the muscle by weight of object |
| Describe a muscle twitch including the different phases | *response of a single muscle fiber to a single AP latent, contraction, relaxation*** |
| Describe skeletal muscle summation | Repeated twitch contractions, where the previous twitch has not relaxed completely |
| Define tetanus and the mechanism leading to tetanus | If the frequency of these contractions increases to the point where maximum tension is generated and no relaxation is observed then the contraction is termed a tetanus |
| Compare isotonic and isometric muscle contractions | TON:Change in muscle length MET:Muscles can’t shorten because the load is too great |
| Compare eccentric and concentric muscle contractions | CC: Muscle shortens EC: Muscle lengthens |
| Describe the control of muscle tension, including the role of the nervous system and the role of muscle | CNS Freq of stim -twitch slow compared to AP :. many AP for one contraction motor unit (generation of force>single twitch) -^#=^tension+velocity MUSC properties of skel. m -fiber length at onset of contr -type -fatigue extent -Xsection |
| Explain the significance of recruitment of motor units. | All muscle fibers in a single motor unit are the same fiber type. different needs signal diff units/fiber types |
| Explain the length tension relationship of skeletal muscles | *graphLength of fiber at onset of contraction |
| Explain the force velocity curve of skeletal muscle | *image. – For muscles to contract, they must generate force that is greater than the opposing forces. – The greater the force, the slower the contrac7on. |
| Distinguish the different types of skeletal muscle fibers and how they are distinguished | – Slow-oxidative (type I) – Fast-oxidative Glycolytic (type IIa) – Fast-glycolytic (type IIx) 1. Maximal velocity of shortening – Contain different myosin enzymes 2. Major pathway used to form ATP 3. Characteristics*** |
| Describe the order of recruitment of muscle fiber types | Slow Ox, Fast Ox, Fast Glyco AKA Type I, IIa, IIx |
| Describe the effects of cross-sectional area on muscle tension | * expand. why affect TENSION Peak force production is to the physiological cross sectional area |
| Describe the components of the muscle spindle | - Parallel to extrafusal muscle fibers - Contains intrafusal muscle fibers - Innervated by gamma motor neurons |
| Describe the function of muscle spindle | sense muscle length. Purpose is to resist tendency for passive stretch of muscles by gravitational forces when person is upright – Stretch of muscle->increases firing->leads to contraction gamma posture, hold basic form |
| Explain the patellar knee jerk reaction as it relates to muscle spindles | strike patellar ligament->stretch tendon->spindle stretched:.activate sens. neruon->S neuron activates alpha motorneuron-> Amotor stimulates extrafusal fibers to contract |
| Describe the effects of Golgi tendon organs. | sense muscle tension. Activation results in: – Inhibitory synapses on motor neurons of the contracting muscle – Excitatory synapses on motor neurons of ipsilateral antagonists. |
| Explain alpha and gamma co-activation | a way the muscle maintains proper tension/length afferent input from sensory endings of spindle fiber->alpha mn simulate extrafusal->gamma stimulate intrafusal to maintain proper tension |
| Describe energy sources for skeletal muscle(how does muscle form ATP?) | Creatine Phosphate (CP) phosphorylates ADP – Utilized at onset of contractile activity – Limited by CP stores • Oxidative phosphorylation • Glycolysis |
| Describe muscle fatigue and the causes | Decline in muscle tension as result of previous contractile activity, even though stimulation continues Dependent on: – Type of skeletal muscle – Intensity/duration – Individual fitness |
| Explain how endurance training affects skeletal muscles | – Increased ability to use fatty acids as fuel and ^intracellular triglyceride storage – ^ capillary density (^O2) – ^ number of mitochondria (^ATP synth) – Increase Krebs Cycle Enzymes (^ATP shuttled to ETC) – Muscle X change size |
| Explain the roles of creatine and creatine phosphate (CP) in muscle physiology. phosphate (P) creatine (C) | CP- molecule storing E in P bonds. Resting muscle, excess ATP transfers P to C :. ADP + CP, acting as E reserve to quickly create more ATP. When the muscle starts to contract and needs E, CP transfers P back to ADP, forming ATP and C. enzyme Ckinase |
| Define hypertrophy and atrophy | Muscle atrophy is a decrease in muscle mass; muscle hypertrophy is an increase in muscle mass due to an increase in muscle cell size. |
| Describe structure of myocardium | mass of cardiac muscle cells connected to each other via gap junctions. |
| Explain the function of gap junctions in cardiac muscle cells | allows it to behaves as a single functional unit. Action potentials that occur at any cell in a myocardium can stimulate all the cells in the myocardium. |
| Distinguish between multi-unit and single unit smooth muscle | – Single-‐unit smooth muscle • Cells electrically linked by gap junctions • Act as one unit – Multiunit smooth muscle • Units must be separately stimulated by nerves to contract |
| Describe the structure of smooth muscle | 3 filaments-thick myo, thin actin, intermediate TA- no troponin I- supports shape, X participate in contraction |
| Describe excitation-contraction coupling in smooth muscle | 1. ^ intracellular Ca (some from DR, most by opening voltage gated Ca channels) 2. Ca-calmodulin (rather than tropo) 3. Ca-cal -> myosin light chain kinase (MLCK) 4. MLCK phosphorylates myo light chains 5. P.lated myo forms Xbridge w actin -> contract |
| What is in high demand for ATP for muscle contraction and relaxation? | – Myosin ATPase(70%) – Ca++ pump |
| Specific factors influencing fatigue by E metabolism? | – Internal acidity – K+ accumulation – Glycogen Depletion – Reduced SR calcium release – Central fatigue |
| Explain how resistance training affects skeletal muscles | – Resistance training promotes hypertrophy of fast glycolytic fibers (IIx) – Skeletal muscles atrophy when not used. |
| Characteristics of Muscle Fibers | – Speed of contraction – Fatigue resistance – Myoglobin Content – Mitochondria – Oxidative Phosphorylation Capacity – Enzymes – Glycogen content – Size Differences |
| Characteristics of Muscle Fiber I | more myoglobin content, more mitochondria, oxidative phosphorylation capacity, smaller, slower, weaker but resistant to fatigue |
| Characteristics of Muscle Fiber IIa | high speed of contraction, oxidative phosphorylation capacity, more glycogen content, bigger, faster, stronger |
| Characteristics of Muscle Fiber IIx | high speed of contraction, enzymes specific to construction are fast, more glycogen content, bigger, faster, stronger, |
| What determines fiber type? | genetics, motor unit |
| role of gamma motor and alpha neurons. | gamma- efferent. involuntary reflex like stretch alpha- efferent. voluntary **bVoluntary a so knee jerk spindle first, no extrafusal? |
| What leads to excitation-contraction coupling? | Ap travels down somatic motor neuron. At axon terminal, release of ACh, which binds to and opens Nicotinic ACh receptors, causing end plate potential which induces AP in sacrolemma. |
| Intensities of muscle ATP systems | CP -very high power, very low capacity glycolysis - high power, low capacity aerobic system - low power, very high capacity |
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kellyyrosse
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