Create an account
functions of skeletal muscle
force production for locomotion and breathing
fore production for postural support
heat production during cold stress
human body contains over... skeletal muscles which accounts for...% body weight
400, 40-50% total body weight
threadlike strands within muscle fibers (cells). actin (thin filament), myosin (thick filament)
connects Z band to M line
passive component force
assists in maintaing shape of cell
Within the sarcoplasm
Sarcoplasmic reticulum: Storage site for calcium
The Neuromuscular Junction
Where motor neuron meets the muscle fiber
Motor end plate
The sliding filament model
Muscle shortening occurs due to movement of the actin filament over the myosin filament
Formation of cross-bridges between actin and myosin filaments--> "power stroke"
1. Rest; cross-bridges weakly bound (no Ca++)
2. Ca++ binds; cross-bridges strongly bound (to troponin)
3. Pi released; movement starts
4. ADP released; movement finishes
5. ATP attaches; weak binding state. ATP breakdown-->cross-bridge "energized"
Ca++ removal-->weak binding state (rest)
Depolarization of motor end plate (excitation) is linked to contraction: Nerve impulse travels down T-tubles and causes release of Ca** from SR
Ca** binds to troponin and causes position change in tropomyosin, exposing active sites on actin
Permits strong binding state between actin and myosin, and contraction occurs
Continues until Ca** is removed
ATP is required for muscle contraction
1. Myosin ATPase breaks down ATP as fiber contracts
2. Calcium ATPase breaks down ATP for calcium pump in SR
3. Sodium-potassium pump on sarcholemma re-establishes membrane potential
contractile properties of muscle fibers
maximal force production, speed of contraction, muscle fiber efficiency (economy)
regulation of muscle force is dependent on
1. Size of the muscle
2. Number of motor units recruited (recruitment)
3. Rate at which they are recruited ("rate coding")
relative lack of strength in an unfatigued muscle. strength is measured as the force of power produced during a maximum voluntary contraction (MVC)
acute fall of maximum force generating capacity of the muscle in response to muscular activity. measured as decrease in mvc as a result of contraction(s)
lack of dystrophin (structural protein that helps transmit force developed by actin and myosin to connective tissue to move limb)
Please allow access to your computer’s microphone to use Voice Recording.
Having trouble? Click here for help.
We can’t access your microphone!
Click the icon above to update your browser permissions and try again
Reload the page to try again!Reload
Press Cmd-0 to reset your zoom
Press Ctrl-0 to reset your zoom
It looks like your browser might be zoomed in or out. Your browser needs to be zoomed to a normal size to record audio.
Please upgrade Flash or install Chrome
to use Voice Recording.
For more help, see our troubleshooting page.
Your microphone is muted
For help fixing this issue, see this FAQ.
Star this term
You can study starred terms together