EC 380 STUDY EXAMS GUIDE ALL QUESTIONS
AND ANSWERS SURE A+
✔✔Sliding filament theory - ✔✔Step 1: calcium released into sarcoplasm, binds to
troponin C, conformation change, moves tropomyosin from actin binding sites, actin
binding sites exposed to myosin
Step 2: myosin extends to bind actin
Step 3: power stroke release of ADP and Pi from MHC, sarcomere shortening,
formation of the rigor complex
Step 4:release of actin from myosin, ATP dependent process
Step 5: ATP hydrolyzed and myosin reset
Step 6: Ca++ removed from sarcoplasm SERCA
✔✔Motor unit - ✔✔Single motor neurons divide into multiple axon terminals
Each axon terminal innervates a single fiber
All fibers are innervated by a single nerve share a phenotype
MHC profile
determines rate of ATP hydrolysis
Determines contraction speed
✔✔Recruitment - ✔✔Stimulation additional motor units
Increases strength of contracting by activating larger numbers of fibers
Small motor units (low threshold) for precise movement
, add large motor units (high threshold) for powerful movements
High threshold difficult to activate in untrained individuals
✔✔Factors affecting muscle contraction - ✔✔frequency of stimulation, number of motor
units recruited, degree of muscle stretch
✔✔Twitch - ✔✔single stimulus-contraction-relaxation sequence in a muscle fiber
Activation= 5msec
Physical movement = 95msec
phases
latent period
contraction
relaxation
no refractory period in muscle
✔✔temporal summation - ✔✔Multiple impulses result in:
increases Ca++ exposure to myofilamets
greater force development
✔✔Pre tightening of sarcomeres - ✔✔twitch
unfused tetanus
fused tetanus
fatigue
✔✔Rate coding - ✔✔alerting CNS impulse frequency modulates muscle force
least stable at low forces
✔✔Spatial Stimulation - ✔✔All contractions are fused providing steady control
-Sequential recruitment of motor units from small to large amounts allows for fine control
of muscle force
✔✔Muscle mechanics - ✔✔Length tension relationship
isometric muscle contraction
single fibers
✔✔Length tension curve - ✔✔Only applies to isometric contractions
Cannot describe whole muscle moving through a range of motion
✔✔Force velocity relationship - ✔✔Isotonic actions (concentric and eccentric)
Clinically important for rehabilitation
✔✔Length tension- velocity relationship - ✔✔Reflects actual movement
Series of length tension curves overlaying a serious of velocity curves
At high velocity little force is developed regardless of sarcomere length
At low velocity, force can be developed and is related to sarcomere length
AND ANSWERS SURE A+
✔✔Sliding filament theory - ✔✔Step 1: calcium released into sarcoplasm, binds to
troponin C, conformation change, moves tropomyosin from actin binding sites, actin
binding sites exposed to myosin
Step 2: myosin extends to bind actin
Step 3: power stroke release of ADP and Pi from MHC, sarcomere shortening,
formation of the rigor complex
Step 4:release of actin from myosin, ATP dependent process
Step 5: ATP hydrolyzed and myosin reset
Step 6: Ca++ removed from sarcoplasm SERCA
✔✔Motor unit - ✔✔Single motor neurons divide into multiple axon terminals
Each axon terminal innervates a single fiber
All fibers are innervated by a single nerve share a phenotype
MHC profile
determines rate of ATP hydrolysis
Determines contraction speed
✔✔Recruitment - ✔✔Stimulation additional motor units
Increases strength of contracting by activating larger numbers of fibers
Small motor units (low threshold) for precise movement
, add large motor units (high threshold) for powerful movements
High threshold difficult to activate in untrained individuals
✔✔Factors affecting muscle contraction - ✔✔frequency of stimulation, number of motor
units recruited, degree of muscle stretch
✔✔Twitch - ✔✔single stimulus-contraction-relaxation sequence in a muscle fiber
Activation= 5msec
Physical movement = 95msec
phases
latent period
contraction
relaxation
no refractory period in muscle
✔✔temporal summation - ✔✔Multiple impulses result in:
increases Ca++ exposure to myofilamets
greater force development
✔✔Pre tightening of sarcomeres - ✔✔twitch
unfused tetanus
fused tetanus
fatigue
✔✔Rate coding - ✔✔alerting CNS impulse frequency modulates muscle force
least stable at low forces
✔✔Spatial Stimulation - ✔✔All contractions are fused providing steady control
-Sequential recruitment of motor units from small to large amounts allows for fine control
of muscle force
✔✔Muscle mechanics - ✔✔Length tension relationship
isometric muscle contraction
single fibers
✔✔Length tension curve - ✔✔Only applies to isometric contractions
Cannot describe whole muscle moving through a range of motion
✔✔Force velocity relationship - ✔✔Isotonic actions (concentric and eccentric)
Clinically important for rehabilitation
✔✔Length tension- velocity relationship - ✔✔Reflects actual movement
Series of length tension curves overlaying a serious of velocity curves
At high velocity little force is developed regardless of sarcomere length
At low velocity, force can be developed and is related to sarcomere length
