Phys - Skeletal Muscle Flashcards
Which regions shorten during contraction?
H zone (disappears) I band
Troponin T
Binds troponin complex to tropomyosin
Troponin I
Binds myosin to actin
Troponin C
Binding site for Ca++
Titin
Connects Z line to M line
Connectin
Acts as a spring, contributes to elasticity of muscle
Dystrophin
Scaffolding for myofibrils
Associated with transmembrane sarcoglycans
Skeletal muscle resting Em
-90mV
Action potentials of skeletal muscles
What is released?
Receptors?
Acetylcholine is released
Nicotinic receptor
Cross-bridge cycling
- Actin binding
- Power stroke
- ATP binding and cross bridge detachment
- ATP hydrolysis
What happens to the cross bridges?
They do not detach
Rigor
What happens if Ca++ transported into the SR is inhibited?
The muscle remains contracted
What causes the myosin head to “re-cock”?
ATP hydrolysis to ADP and Pi
The velocity of muscle shortening is inversely related to the ___
Initial load
Isometric contraction
No external shortening
Velocity = 0
The load exceeds the ability to create tension
Twitch contraction
Single contractile event
Isotonic contraction
External shortening
The load is less than the ability to create tension
Concentric contraction
Eccentric contraction
Contraction with external lengthening
Example: going down stairs
What is a motor unit?
A single alpha motor neuron and all the muscle fibers it innervates
Motor neurons and muscle fibers are recruited from ___ to ____
Smallest to largest
*this permits development of smooth, graded increases in muscle tension
Are action potentials more easily elicited in small or large neuron cell bodies?
Small
