ANNOUNCEMENTS Lab Quizzes: • Next Week: • ½ quiz Qs based on Sciatic exercise • Other half based on G. Muscle exercise
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 ANNOUNCEMENTS
REVIEW: THE SCIATIC NERVE Main Points:
NEXT WEEK: SKELETAL MUSCLE PHYSIOLOGY The Dissection: • Isolation of frog: Instrumentation & Equipment:
SKELETAL MUSCLE PHYSIOLOGY • The Stimulus: • iWorx Unit • Stimulating • Electrode
SKELETAL MUSCLE PHYSIOLOGY The Response: • Force of muscle contraction measured by deflection of force transducer blade
SKELETAL MUSCLE PHYSIOLOGY Vertebrate Motor Unit: • Unit of contraction in skeletal muscle • Composed of: • AP in neuron almost always results in contraction
slice from spinal chord motor neuron axons in a nerve leading from spinal chord muscle neuromuscular junction
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???
SKELETAL MUSCLE PHYSIOLOGY Recruitment: • Controlled by CNS: • The more motor units recruited, the greater the force generated
SKELETAL MUSCLE PHYSIOLOGY Force of Contraction: • In lab, we’ll observe the stimulus-response properties of skeletal muscle by stimulating the sciatic nerve with increasing stimulus intensity
SKELETAL MUSCLE PHYSIOLOGY Single twitch Force of Contraction: • Single Twitches • In lab, we’ll also observe relationship between stimulus frequency and force of contraction
SKELETAL MUSCLE PHYSIOLOGY Force of Contraction: • Summation • Sustained contraction • The result of continuous APs from CNS
SKELETAL MUSCLE PHYSIOLOGY Summation: • Summation of single twitches more forceful contraction
SKELETAL MUSCLE PHYSIOLOGY Tetanus: • State of maximum contraction • Reached when: • APs stimulate muscle repeatedly at high freq.
SKELETAL MUSCLE PHYSIOLOGY Fatigue: • Occurs after prolonged, high freq. stimuli • Muscle cannot generate / sustain expected output (force)