Section 40: Muscle Mechanics Section 40: Muscle Mechanics 40-1 - PowerPoint PPT Presentation

Section 40: Muscle Mechanics Section 40: Muscle Mechanics 40-1

40-2 From: Hamill

•Smallest MU recruited at lowest stimulation frequency stimulation frequency •As frequency of stimulation of smallest MU increases, force of its contraction increases contraction increases •As frequency of stimulation continues to increase, but not before maximum contraction of smallest MU, another MU will be recruited •Etc. 40-3 From: Brown

Recruitment proceeds from smallest fibers to largest ( the size principle ) ( the size principle ) 40-4 From: Hamill

40-5 From: Garner Nigg & Herzog, 1998

40-6 From: Garner Nordin & Frankel (1989)

Wave summation & tetanization Critical frequency Critical frequency 40-7 From: Ju

Muscle Function • Force – length relationship 40-8 From: Legh

40-9 From: Seeley

interference of overlapping thin myofilaments yields force drop deformation of thick myofilament deformation of thick myofilament (and possible inhibited activation) yields rapid force drop Frog skeletal muscle: thick filament = 1.60 μ m thin filament = 0.95 μ m Z-disc (at end of thin) = 0.1 μ m H-zone (middle of thick) = 0.2 μ m zero-force sarc length = 3.6 μ m peak-force sarc length = 2.0-2.2 μ m drop-force sarc length = 1.7 μ m zero-force sarc length = 1.3 μ m 40-10 From: Garner Nigg & Herzog, 1998