Muscle Physiology Flashcards
What connects muscles to bone?
tendons
A band
dark band & thick filaments
H zone
thick filaments only
M line
links thick filaments
I band
light band & thin filaments
Z line
links thin filaments
What is the contractile protein?
Actin
What is the structure of thin filament?
actin, tropomyosin, troponin
What regulates skeletal muscle contraction?
Ca2+ binding to troponin
What is the structure of thick filament?
myosin tail toward M line, myosin head toward I band, has myosin binding sites
What is titin?
provides structural support & elasticity, anchors thick filaments between M line & Z line
How do muscles generate force?
crossbridge cycling
How are muscle contractions regulated?
excitation-contraction coupling
How do mycoytes provide ATP to drive cross bridge cycling?
muscle cell metabolism
Sliding-Filament model
thick & thin filaments overlap & slide past each other; neither of them shorten
A band stays the same length
I band, H zone, sarcomere shortens
What is a twitch?
contraction in a muscle fiber in response to a single action potential
What happens during latent period of a twitch?
excitation-contraction coupling
What happens during contraction phase of a twitch?
crossbridge cycling
What happens during relaxation phase of a twitch?
Ca2+ reuptake
What are the contractile elements of a twitch?
sarcomeres
What do contractile elements generate?
active tension
What are the series elastic elements of a twitch?
connective tissue & tendons
What do series elastic elements generate?
passive tension
What factors affect the force generated by individual muscle fibers?
number of crossbridges per sarcomere
diameter of fiber
stimulation frequency
intracellular Ca2+ concentration
length of fiber
What is optimal length?
length where fiber has maximum overlap of thick & thin filament, max crossbridge formation, & length where fiber can develop greatest tension
What factors affect the force generated by whole muscles?
motor unit size
motor unit recruitment
How is velocity of shortening calculated?
shortened distance (mm)/ change in time (msec)
What are fast fibers?
myosin with fast ATPase activity
contract & relax faster
What are slow fibers?
myosin with slow ATPase activity
Which muscle types are involuntary?
smooth & cardiac
What is smooth muscle innervated by?
autonomic nervous system
