Physiology Flashcards
motor unit
motorneuron + muscle fibers it innervates
anisotropic (A) band
dark band
thick
ALWAYS same length
isotropic (I) band
light band
thin
Z line
middle of I band
sarcomere
one Z line to the next
thick filaments
myosin heavy chain
thin filaments
actin
tropomyosin
troponin C, T, I
tropomyosin
blocks myosin binding site on actin
troponin C
binds Ca2+
troponin T
binds tropomyosin
troponin I
keeps troponin in position so that tropomyosin covers myosin binding site on action
isometric twitch
one AP
tension increases
length stays the same
isotonic twitch
one AP
energy is expended to move weight instead of developing greater tension
peak isometric twitch tension
velocity = 0
max velocity of shortening
force =0
theoretical
fast motor unit
- large motorneuron
- more rapid time to peak tension and more rapid half-relaxation time
- greater isometric twitch tension
- more fibers
- greater cross-sectional area
- require more active excitatory synapses for depolarization
- tetanic tension reached at higher frequency AP firing
- AP fire after slow
- fewer mitochondria
- ATP from glycogenolysis
- cannot sustain
slow motor unit
- small motorneuron
- slow to peak tension and slow half relaxation time
- smaller isometric twitch tension and tetanic tension
- fewer fibers
- smaller cross section
- requires fewer active excitatory synapses for depolarization
- tetanic tension reached at lower frequencies
- AP fire first
- lots of mitochondria and myoglobin
- ATP produced by oxidative phosphorylation
- can sustain: postural muscles
tetanic tension
tension reaches maximum
and contractions are fused upon the previous contractions
graded contraction
more motor units recruited as more force it required and already recruited units increase frequency of contraction
How is ATP regenerated that is consumed by myosin?
donation of high energy phosphate from creatine phosphate
creatinine
metabolic product of creatine
