SKELETAL MUSCLE PHYSIOLOGY IN Rana pipiens

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SKELETAL MUSCLE PHYSIOLOGY IN Rana pipiens

• BIOL 305L

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ANNOUNCEMENTS

• Lab Quizzes
• Next Week
• ½ quiz Qs based on Sciatic exercise
• Other half based on G. Muscle exercise

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ANNOUNCEMENTS

• Midterm Exam
• Friday, March 13th Noon 2 pm in LH 7
• No calculators
• Format short ans, essay, fill in blank, T/F
• No labs that week!
• NO MAKEUP EXAM UNLESS UNIVERSITY APPROVED
  EMERGENCY

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REVIEW THE SCIATIC NERVE

• Main Points

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NEXT WEEK SKELETAL MUSCLE PHYSIOLOGY

• The Dissection
• Isolation of frog
• Instrumentation Equipment

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SKELETAL MUSCLE PHYSIOLOGY
The Stimulus iWorx Unit Stimulating
Electrode
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SKELETAL MUSCLE PHYSIOLOGY

• The Response
• Force of muscle contraction measured by
  deflection of force transducer blade

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SKELETAL MUSCLE PHYSIOLOGY

• Vertebrate
• Motor Unit
• Unit of contraction in skeletal muscle
• Composed of
• AP in neuron almost always results in contraction

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slice from spinal chord
motor neuron axons in a nerve leading from spinal
chord
muscle
neuromuscular junction
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SKELETAL MUSCLE PHYSIOLOGY

• Recruitment of Muscle Fibers
• A motor unit contracts in all-or-none manner
• Still, muscles can create contractions of varying
  force and duration! HOW???

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SKELETAL MUSCLE PHYSIOLOGY

• Recruitment
• Controlled by CNS
• The more motor units recruited, the greater the
  force generated

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SKELETAL MUSCLE PHYSIOLOGY

• Force of Contraction
• In lab, well observe the stimulus-response
  properties of skeletal muscle by stimulating the
  sciatic nerve with increasing stimulus intensity

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SKELETAL MUSCLE PHYSIOLOGY
Single twitch

• Force of Contraction
• Single Twitches
• In lab, well also observe relationship between
  stimulus frequency and force of contraction

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SKELETAL MUSCLE PHYSIOLOGY

• Force of Contraction
• Summation
• Sustained contraction
• The result of continuous APs from CNS

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SKELETAL MUSCLE PHYSIOLOGY

• Summation
• Summation of single twitches ? more forceful
  contraction

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SKELETAL MUSCLE PHYSIOLOGY

• Tetanus
• State of maximum contraction
• Reached when
• APs stimulate muscle repeatedly at high freq.

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SKELETAL MUSCLE PHYSIOLOGY

• Fatigue
• Occurs after prolonged, high freq. stimuli
• Muscle cannot generate / sustain expected output
  (force)