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35 Cards in this Set
- Front
- Back
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Skeletal muscle functions
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1-produce skeletal movement
2-maintain body position 3-support soft tissues 4-guard openings 5-maintain body temp 6-store nutrient reserves |
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skeletal muscle structures
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-muscle tissue
-connective tissue -nerves -blood vessels |
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3 layers of connective tissues
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-Epimysium-exterior collagen layer
-Perimesium-surround fascicles -blood vessel/nerve supply to ^ -Endomysium-individual muscle fibers |
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Nerves & Blood vessels
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Nerves-control voluntary muscles(CNS)
Blood vessels-supply large amounts 02 -supply nutrients -carry away wastes |
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Sarcolemma
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-Cell membrane of muscle fibers
-surrounds sarcoplasm |
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Transverse Tubules (T Tubules)
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-Transmit action pot. thru cell
-Allow entire muscle fiber to contract simultaneously |
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Myofibrils
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-Subdivisions w/in muscle fiber
-Made up of myofilaments |
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Myofilaments
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-Responsible for muscle contraction
-thin filaments -> actin -thick filaments -> myosin |
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Sarcoplasmic Reticulum (SR)
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-Membrane around each myofibril
-Helps transmit action pot. to ^ -Forms chambers (terminal cisternae) attached to T Tubules |
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Triad
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Forbed by 1 TTubule/2 Terminal Cist.
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Terminal cisternae
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-concentrate Ca
-release Ca into sarcomeres to begin contraction |
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Sarcomere
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-contractile unit of muscle
-structural unit of myofibril -Alternating thick (A band)/thin (I band) |
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M line
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center of A band, midline of sarcomere
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Z lines
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centers of I bands, @ 2 ends of sarcomere
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Zone of overlap
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Densest, darkest area of sarcomere, overlap of thin/thick filaments
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H band
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Area around M line
-thick filaments, no thin filaments |
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Titin
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Strands of protein that reach from thick filaments to Z line
-Stabilize filaments |
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F-Actin
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-2 twisted rows of G-actin
-active site that binds to myosin |
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Tropomyosin
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-covers active sites on G-actin
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Troponin
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-Binds to tropomyosin - forms troponin-
tropomyosin complex -binds to G-actin to hold complex in place -binds to/controlled by Ca |
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Sliding Filament Theory
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-Thin filaments slide toward M line
-Width of A band stays the same -Z lines move closer together -Myosin Xbridges cyclically attach, rotate & detach from actin filaments -energy provided by ATP |
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5 Steps of contraction cycle
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1-Exposure of active sites
2-Xbridge formation 3-pivot of myosin heads (powerstroke) 4-detachment of Xbridges 5-Reactivation of myosin |
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Tension of a single muscle fiber depends on...
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-# of pivoting Xbridges
-Fibers resting length @ time of stim. -Frequency of stimulation |
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3 phases of twitch
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1-Latent period before contraction
-action potential moves thru sarcolem -causes Ca release 2-Contraction phase 3-relaxation phase - Ca levels fall |
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Wave summation/summation of twitches
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-Increasing tension
-repeated simulations b4 end of relax. |
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Incomplete tetanus
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-Twitches reach max tension w/ simultaneous stimulation
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Isometric contraction
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Constant length
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Isotonic Contraction
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Change length -> motion
1-concentric: tension>load -shortening 2-eccentric: tension<load -lengthening |
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Recovery Period
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def:time req'd after exertion for muscles to return back to normal
-02 becomes available, mitoch. activity resumes -Cori cycle, 02 debt |
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Cori Cycle/02 Debt
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-CC: Recycling of lactic acid to pyruvic acid
-02: body needs more 02 than usual to normalize metabolic activity ->heavy breathing |
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Hormones & Muscle Metabolism
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-Growth hormone (anabolic)
-Testosterone (anabolic) -Thyroid hormones (Inc. metabolism) -Epinephrine (substrate mobilization) |
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Fast Muscle Fibers
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-Contract quickly
-large diameter -large glycogen reserves -few mitochondria -strong contractions, fatigue quickly |
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Slow Muscle Fibers
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-Slow to contract and fatigue
-small diameter, more mitochondria -High 02 supply -contain myoglobin ->red pigment that binds 02 |
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Characteristics of Cardiac Muscle Tissue
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-small, mononucleate
-short, wide T Tubules -no triads, no terminal cisternae in SR -aerobic (high in myoglobin/mitochond) -interculated discs ->cell junctions |
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Functions of cardiac tissue
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1-automaticity-controlled by pacemaker cells, not nerves
2-variable contraction time-controlled by nervous system 3-extended contraction time-10x as long as skeletal muscle 4-Prevention of wave summation & tetanic contractions by cell membranes->long refractory pd. |
