2
Myosin Myofilaments
• Myosin= thick myofilaments
• M-lines
• Cross-bridge
• ATPase
Actin Myofilaments
• Actin + accessory proteins= thin myofilaments
• Active sites (attachment sites)
• Z discs
Sarcomere
Sliding Filament Model
Ion Channels
Resting Membrane Potential
Action Potentials
Action Potential Propagation
Neuromuscular Junction
Synaptic Transmission
Excitation-Contraction Coupling
Cross Bridge Cycle
Relaxation
• Relaxation requires ATP
– Acetylcholinesterase breaks down Ach and action potential stops
– Na
+
/K
+
pump returns to and maintains resting membrane potential
– Detach myosin heads and return them to resting position
– Active transport Ca
2+
back into sarcoplasmic reticulum
Muscle Contraction Summary
3
Motor Units
• High precision vs low precision
• All-Or-None Law
– Sub-threshold stimulus= no action potential and no contraction
– Threshold stimulus: action potential and contraction
• Recruitment
Graded Contractions
• Twitch
• Summation
• Tetanus= fused or unfused
• Myogram: aka electromyograph or EMG
Muscle Metabolism
• Anaerobic
– Creatine phosphate
– Glycolysis
• Lactic acid
• Aerobic cellular respiration
Muscle Fatigue
• Contributing factors
– Buildup of lactic acid
– Unable to make enough ATP
– Insufficient Ca
2+
– Failure of action potential to release enough Ach
• Oxygen Use After Exercise
– Converts lactic acid back to glucose in liver
– Resynthesizes creatine phosphate and ATP
– Replaces oxygen removed from myoglobin
Types of Muscle Contractions
• Isometric: no change in length but increased tension
– Ex. postural muscles of body
• Isotonic: change in length but tension constant
– Concentric: muscle overcomes opposing resistance and shortens
– Eccentric: muscle lengthens while maintaining tension
• Muscle tone= hypotonia vs hypertonia
Types of Skeletal Muscle Fibers
• Red muscle fibers: high in myoglobin
– Slow oxidative (SO) fibers: slow, least powerful, endurance
• Postural muscles
– Fast oxidative glycolytic (FOG) fibers: fast, intermediate in power and
endurance
• Leg muscles
White muscle fibers: low in myoglobin
– Fast glycolytic (FG) fibers: fast, most powerful, fatigue easily
• Arm muscles
Toxins and Poisons Effecting Muscles
• Contract
– Tetanus: bacterium Clostridium tetani; “lockjaw“
– Strychnine: neurotoxin from seeds of strychnine tree
• Relax
– Curare: South American paralytic
• Blocks acetylcholine receptors
– Botulism: bacterium Clostridium botulinum
Muscular Diseases
Rigor Mortis
• Rigor Mortis: stiff muscles after death
– Results from inadequate amounts of ATP and calcium leakage into muscle
tissue
• Begins 3-4 hours after death and lasts ~24 hours (ends when filaments begin to
decay)
• Used to estimate the time of death
Muscle Attachment and Arrangement
• Origin
• Insertion
• Action
• Muscle arrangements
– Agonist/prime mover
– Antagonist
– Synergists
– Fixators
• Tendons= connect muscle to bone
• Ligaments= connect bone to bone
Muscle Names
1. Location: pectoralis, gluteus, brachial
2. Size: maximus, minimus, longus, brevis
3. Shape: deltoid, quadratus, teres
4. Orientation: rectus
5. Origin and insertion: sternocleidomastoid, brachioradialis
6. Number of heads: biceps, triceps
7. Function: abductor, adductor, massete
Knowt
Note
Studied by 48 people
