Anatomy & Physiology Study Guide — Martini 12th Edition
Chapters 10 & 11: Muscle Tissue and The Muscular System
MUSCLE STRUCTURE & ORGANIZATION
• Three Muscle Types:
• Skeletal – striated, multinucleate, voluntary.
• Cardiac – striated, branched, intercalated discs, involuntary.
• Smooth – non-striated, spindle-shaped, involuntary.
• Four Key Properties: Excitability, Contractility, Extensibility, Elasticity.
• Fiber Anatomy:
• Sarcolemma – muscle cell membrane.
• Sarcoplasm – cytoplasm with glycogen & myoglobin.
• SR (Sarcoplasmic Reticulum) – Ca²⁺ storage.
• T-tubules – carry signals deep into cell.
• Myofibrils – bundles of actin & myosin filaments.
• Sarcomere Components:
Z-line → Z-line (functional unit)
o A band: thick filaments (myosin) – constant length.
o I band: thin filaments (actin) – shortens in contraction.
o H zone: center of A band – disappears in contraction.
o M line: midline of sarcomere – anchors myosin.
🩻 Example: Biceps brachii = voluntary striated muscle.
MUSCLE FUNCTION & CONTRACTION PHYSIOLOGY
• Sliding Filament Theory:
Myosin heads attach to actin and pull thin filaments toward the M-line → sarcomere
shortens.
A band constant; I band shortens.
• Cross-Bridge Cycle:
Ca²⁺ binds troponin → tropomyosin moves.
, Myosin head attaches to actin.
Power stroke (pulls actin).
ATP binds → myosin detaches.
ATP hydrolysis → head re-cocks.
• Excitation–Contraction Coupling:
Motor neuron → ACh release → sarcolemma AP → T-tubules → SR releases Ca²⁺ →
contraction.
• Neuromuscular Junction (NMJ):
o Synaptic cleft
o ACh receptors on motor end plate
o Acetylcholinesterase destroys ACh (post-signal)
Clinical: Botulinum toxin blocks ACh → paralysis.
ENERGY & METABOLISM
• ATP Sources (chronological):
Creatine phosphate – immediate, < 10 s.
Anaerobic glycolysis – fast, short (30-60 s).
Aerobic respiration – slow, sustained (minutes-hours).
• Muscle Fatigue: low ATP, ion imbalance, acid buildup.
• Oxygen Debt: extra O₂ after exercise to restore ATP and CP.
• Fiber Types:
Energy
Type Color Speed Example
Source
Postural muscles
Type I (Slow Oxidative) Red Slow Aerobic
(back)
Type IIa (Fast Oxidative) Pink Intermediate Both Sprint/walk
Type IIb (Fast Glycolytic) White Fast Anaerobic Jump/punch
Chapters 10 & 11: Muscle Tissue and The Muscular System
MUSCLE STRUCTURE & ORGANIZATION
• Three Muscle Types:
• Skeletal – striated, multinucleate, voluntary.
• Cardiac – striated, branched, intercalated discs, involuntary.
• Smooth – non-striated, spindle-shaped, involuntary.
• Four Key Properties: Excitability, Contractility, Extensibility, Elasticity.
• Fiber Anatomy:
• Sarcolemma – muscle cell membrane.
• Sarcoplasm – cytoplasm with glycogen & myoglobin.
• SR (Sarcoplasmic Reticulum) – Ca²⁺ storage.
• T-tubules – carry signals deep into cell.
• Myofibrils – bundles of actin & myosin filaments.
• Sarcomere Components:
Z-line → Z-line (functional unit)
o A band: thick filaments (myosin) – constant length.
o I band: thin filaments (actin) – shortens in contraction.
o H zone: center of A band – disappears in contraction.
o M line: midline of sarcomere – anchors myosin.
🩻 Example: Biceps brachii = voluntary striated muscle.
MUSCLE FUNCTION & CONTRACTION PHYSIOLOGY
• Sliding Filament Theory:
Myosin heads attach to actin and pull thin filaments toward the M-line → sarcomere
shortens.
A band constant; I band shortens.
• Cross-Bridge Cycle:
Ca²⁺ binds troponin → tropomyosin moves.
, Myosin head attaches to actin.
Power stroke (pulls actin).
ATP binds → myosin detaches.
ATP hydrolysis → head re-cocks.
• Excitation–Contraction Coupling:
Motor neuron → ACh release → sarcolemma AP → T-tubules → SR releases Ca²⁺ →
contraction.
• Neuromuscular Junction (NMJ):
o Synaptic cleft
o ACh receptors on motor end plate
o Acetylcholinesterase destroys ACh (post-signal)
Clinical: Botulinum toxin blocks ACh → paralysis.
ENERGY & METABOLISM
• ATP Sources (chronological):
Creatine phosphate – immediate, < 10 s.
Anaerobic glycolysis – fast, short (30-60 s).
Aerobic respiration – slow, sustained (minutes-hours).
• Muscle Fatigue: low ATP, ion imbalance, acid buildup.
• Oxygen Debt: extra O₂ after exercise to restore ATP and CP.
• Fiber Types:
Energy
Type Color Speed Example
Source
Postural muscles
Type I (Slow Oxidative) Red Slow Aerobic
(back)
Type IIa (Fast Oxidative) Pink Intermediate Both Sprint/walk
Type IIb (Fast Glycolytic) White Fast Anaerobic Jump/punch
