unit-1: skeletal system and properties
TRANSCRIPT
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Unit-1: Neuromuscular Aspect
of Movement-2
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Contents of the lesson • All or none law
• Strength of Contraction
• Group Action of Muscles
• Reciprocal Innervation
• Muscular Fatigue
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All or None Law • This law states that:
“ When a stimulus of minimum threshold is sent to
the motor unit then all the muscle fibers, within unit,
are recruited and contracted to their full extent.”
• Full response or No response.
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All or None Law
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Strength of Contraction Certain important terms to understand:
• Phasic Contraction:
Muscle’s response to a single stimulus of sufficient
magnitude.
• Twitch:
a single contraction of a muscle fiber in response to brief
threshold stimulation.
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Strength of Contraction • Latent Period
Short Period of time b/w stimulation and tension
development. “ Reaction time of muscle fiber”
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Strength of Contraction • Relaxation Period
the time during which the tension is removed from
the muscle fiber.
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Strength of Contraction • Multiple Wave Summation
The summation of multiple stimuli and their tensions
from twitches when subsequent stimulus arrives before
the complete relaxation period in a muscle fiber.
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Strength of Contraction • Tetany or Tetnus Contraction
A sustained contraction resulting from multiple wave
summation.
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Strength of Contraction • Strength of Contraction = Tension generated.
• So, in terms of strength;
Fused tetany> Unfused Tetany> Multiple Wave summation> twitch
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Strength of contraction
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Group Action of Muscles • “Coordination among the contraction and activities
of motor muscles to effectively execute a motor
action. “
Gro
up
Act
ion
of
Mu
scle
Agonist: prime movers
Antagonist: contralateral muscle
Stabilizers
Synergist
Neutralizers
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Reciprocal Innervation • Sherrington’s Law of Reciprocal Inhibition
• “For the initiation of any motor action, motor
neurons carry exciting impulse to agonist muscle
and inhibitory impulse to antagonist muscles.”
• Important for neuromuscular coordination and
delaying fatigue.
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Muscle Fatigue • “ State of discomfort and decline in the efficiency
and functioning capacity of the muscle due to
prolonged or excessive exertion”
• “ Failure to execute voluntary contraction”
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Causes of Muscle Fatigue • Lack of Na+ ion in the motor nerve.
• Decline in the release of AcH from Neuromuscular
Junction.
• Accumulation of Lactic Acid.
• Reduction in ATP-CP stores.
• Reduction in muscle glucose
• CNS fails to initiate and relay nerve impulse to the
muscle.
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References • https://www.wikiwand.com/en/All-or-none_law
• http://www.unm.edu/~jimmy/muscle3_notes.htm
• Shaw,Dhananjoy. (1998).Biomechanics and
kinesiology of human
motion.Khelsahityapublication. Newdelhi
• Floyed ,R.T.(2009). manual of structural
kinesiology.,USA,ed.16. humankinetics
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Doubts?
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Topics to be revised for the next lesson
• Moment of Inertia
• Center of gravity and balance
• Levers and mechanical advantage
• Linear and angular Momentum
• Principle of conservation of Angular Momentum
• Motor Action and it’s Characteristics
• Fluid drag