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HKIN 303 midterm Exam | Questions And Answers Latest {} A+ Graded | 100% Verified
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HKIN 303 midterm Exam | Questions And Answers Latest {} A+ Graded | 100% Verified
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HKIN 303 midterm Exam | Questions And Answers Latest {2024- 2025} A+ Graded | 100%Verified
skeletal system - -composed of 206 bones in adult body
-provides leverage, support and protection
-pulled on by muscles to allow thebody to push or pull against external objects
axial skeleton - Portion of the skeletal system that consists of the skull, rib cage, and vertebral column
appendicular skeleton - bones of the shoulder, pelvis, and upper and lower extremities
joint - junction of bones
types of joints - fibrous: allow virtually no movement
cartilaginous: allow limited movement
synovial: allow considerable movement
uniaxial:operate as a hinge, rotate about one axis
biaxial: operate in two perpendicular axes
multiaxial: allow movement in all three axis
Vertebral column - vertebral bones seperated by flexible disks that allow for movement
muscular system - macrostructure and microstructure
-each skeletal muscel is an organ that contains muscle tissue, connective tissue, nerves, and blood
vessels
-fibrous coneective tissue, or epimysium, covers teh body's more than 430 skeletal muscles
muscle structure - three types of connective tissue:
-epimysium (outer layer)
, -perymysium (surrouding each faciculus, or gropu of fibers)
-endomysium (surrounding individual fibers)
Motor unit - -a motor unit consists of a motor neuron and the muscle fibers it innervates
-there are typically several hundred muscle fibers in a single motor unit
myosin and actin - The arrangement of myosin (thick) and actin (thin) filaments gives skeletal muscle its
striated appearance.
the discharge of an action potential from a motor nerve signals the release of calcium from the
sarcoplasmic reticulum into the myofibril, causing tension development in muscle -
sliding-filament theory of muscular contraction - states that the actin filaments at each end of the
sarcomere slide inward on myosin filaments, pulling the Z-lines toward the center of the sarcomere and
thus shortening the muscle fiber
Contraction of a Myofibril - - in streched muscle the I bands and H zone are elongated, and there is low
force potential due ot reduced cross bridge - actin alignment
-when muscle contracts, hte I bandsand H zone are shortened
-with completely contracted muscle, there is low force potential due to reduced corssbridge- actin
alignment
all-or-none principle - all of the muscle fibers in the motor unit contract and develop force at the same
time. there is no evidence that a motor neuron stimulus causes only some of the fibers to contract.
Similarly, a stronger action poetential cannot porduce a stronger contraction
Muscle Fiber Types - Type I (slow-twitch)
Type IIa (fast-twtich)
Type IIx (fast-twitch) or Type IIb
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