AA
What is the range of transmembrane potential?
-10mV to -100mV
Where in the body are slow fibers not found?
Eyes or hands
Separates muscle from surrounding tissues
Epimysium
Define motor unit
All muscle fibers controlled by single motor neuron
What helps pull filaments back to their original shape/position?
Titin
Tension produced by skeletal muscles depends on
Tension produced by stimulated muscle fibers
Total number of muscle fibers stimulated
What kind of process is contraction?
Active
Of the three connective tissue coverings, which contains myosatellite cells that repair damage
Endomysium
What is the optimum overlap?
It produces the greatest amount of tension during contraction
What is the perimysium?
Surrounds muscle fiber bundles (fascicles)
What are the six functions of skeletal muscle tissue?
Produce skeletal movement
Maintain posture and body position
Support soft tissues
Guard entrances and exits
Maintain body temperature
Store nutrient reserves
Change in _____________ begins muscle contraction
Transmembrane potential
Anaerobic glycolysis produces what as a waste product?
Lactic acid
Fixed muscular contraction shortly after death
Rigor mortis
What does the amount of tension being generated by a muscle fiber depend on?
Number of pivoting cross-bridges
Muscle fiber's resting length at time of stimulation
Frequency of stimulation
Define twitch
Single stimulus-contraction-relaxation sequence in muscle fiber
Contraction duration depends on
Duration of stimulation by neuron
Concentration of Ca2+ in sarcoplasm
Availability of ATP
What occurs when muscles can no longer perform required activities?
Muscle fatigue
Explain incomplete tetanus
Rapid stimulation continues and muscle is not allowed to complete relaxation
Twitches reach maximum level of tension BELOW total maximum force/tension that can be generated
Cell membrane of muscle fiber
Sarcolemma
Isotonic contraction vs Isometric contraction
Isotonic --> skeletal muscle changes length resulting in motion
Isometric --> skeletal muscle develops tension, but is prevented from changing length
During rest in aerobic respiration muscle fibers metabolize ____________
Fatty acids
What are pacemaker cells?
Specialized cardiac muscle cells
What are multiunit smooth muscle cells connected to?
Involuntary motor neurons
Explain steps of muscle contraction
1. LMN propagates action potential
2. action potential causes opening of calcium channels at the axon terminal
3. calcium flows into the axon terminal and binds to ACh vesicles
4. causes exocytosis of ACh and it goes into the synapse
5. ACh binds to ACh receptors on motor end plate of the sarcolemma
6. ACh receptor tied to sodium channels and opens channels
-AChE breaks down ACh to reset the membrane potential
7. sodium flows into the muscle cell/fiber; causing depolarization (becomes less negative)
8. sodium travels into the T-tubules until it reaches SR
9. voltage gated channels detect the (+) change and open/release calcium
10. calcium binds to troponin and “unlocks” actin active site by moving tropomyosin
11. cross-bridges form as myosin heads bind to actin
12. myosin heads pivot which pulls thin filaments towards M line
13. myosin heads detach and actin active site open for another cross-bridge formation
14. cycle repeats to produce further filament sliding causing muscle fiber to shorten