muscle fiber
myofibrils
thick filaments
myosin
thin filaments
actin
banding
A band
H zone
M line
I band
Z line
sarcomere
transverse tubules at A-I junction
sarcoplasmic reticulum
lateral cisternae
thick filament
actin binding site
myosin ATPase site
thin filament
actin
G actin
F actin
tropomyosin
troponin
binding sites
actin
tropomyosin
Ca2+
sliding filament mechanism
power stroke
excitation-contraction coupling
| 1. | ATP hydrolyzed by ATPase |
| ADP & Pi attached to myosin | |
| energy stored in cross-bridge | |
| 2. | Ca2+ released at excitation |
| actin disinhibited | |
| actin-myosin binding | |
| 3. | Power stroke of cross-bridge |
| ADP & Pi released | |
| 4. | Fresh ATP binds to myosin head |
| myosin detaches from actin | |
| GoTo 1 |
rigor mortis
relaxation
sarcoplasmic reticulum Ca2+-pump
contractile activity
latent period: <10 msec
contraction time: ~50 msec
relaxation time ~50 msec
determinants of whole-muscle tension
twitch
number of fibers contracting
size of muscle
number of motor units recruited
number of muscle fibers per motor unit
tension developed by each contracting fiber
frequency of stimulation
twitch summation
tetanic contraction
length-tension relationship
extent of fatigue
duration of activity
asynchronous recruitment of motor units
type of fiber
oxidative, fatigue-resistant
glycolytic, fatigue-prone
thickness of fiber
hypertrophy
atropy
types of contraction
isotonic
isometric
Energy sources for ATP
existing ATP
creatine phosphate
oxidative phosphorylation: aerobic
glycolysis: anaerobic
muscle fiber types
| Characteristic | Slow Oxidative ( Type I ) |
Fast Oxidative ( Type IIa ) |
Fast Glycolytic ( Type IIb ) |
|---|---|---|---|
| myosin ATPase activity | low | high | high |
| speed of contraction | slow | fast | fast |
| resistance to fatigue | high | intermediate | low |
| oxidative phosphorylation capacity |
high | high | low |
| enzymes for anaerobic glycolysis |
low | intermediate | high |
| fiber color | red | red | white |
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[ Anatomy & Physiology 1 syllabus ] [ Page created 25 July 1999 ][ Last update 21 June 2004 ] [ Questions about this lecture? E-mail me ] |