Download Muscle

The Muscular System
 Produce movement or tension via shortening
(contraction)
 Generate heat - body temp
 3 types:
 Skeletal - moves bone, voluntary
 Smooth
 Cardiac
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Skeletal Muscle Characteristics
 Voluntary
 Most are attached by tendons to bones
 Synergistic: groups work together
 Antagonistic: groups oppose each other
 Origin, insertion points on opposite sides of
joints
 Cells are multinucleate, striated
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Muscle Structure
 Whole muscle
 Fascicles: bundles of
cells, CT covering on
each one
 Muscle cells = fibers
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Figure 6.3
Microscopic Anatomy of Skeletal Muscle
 Muscle cells
 multinucleate, striated –visible banding
 Myofibril - bundles of filaments
Figure 6.3a
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Skeletal Muscle Contractile Unit
Sarcomere
Actin and myosin
Z Lines:
attachment points
for sarcomeres
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Figure 6.5
Nerve Stimulus to Muscles
 Skeletal muscles
must be stimulated
by a nerve to
contract
 Motor unit
 One neuron
 Muscle cells
stimulated by
that neuron
Figure 6.4a
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Nerve Stimulus to Muscles
 Neuromuscular junctions – association site of
nerve and muscle
Figure 6.5b
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Nerve Activation of Muscle Cells
Acetylcholine
released from
motor neuron
Electrical
impulse
transmitted
along T tubules
Calcium
released from
sarcoplasmic
reticulum
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Figure 6.6
QuickTime™ and a
Cinepak decompressor
are needed to see this picture.
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Calcium Initiates the Sliding Filament
Mechanism
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Figure 6.7
Mechanism of Muscle Contraction (cont.)
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Figure 6.8
QuickTime™ and a
Cinepak decompressor
are needed to see this picture.
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Muscle Relaxation
 Nerve activation ends, contraction ends
 Calcium pumped back into sarcoplasmic
reticulum
 Calcium removed from troponin
 Myosin-binding site covered
 No calcium = no cross-bridges
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Energy Required for Muscle Activity
 Principle source of energy: ATP
 ATP replenished by:
 Creatine phosphate
 Stored glycogen
 Aerobic metabolism of glucose, fatty
acids, and other high-energy molecules
 Anaerobic use of glucose
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Aerobic metabolism
 3 stages to convert energy of glucose to ATP
High-energy electrons
High-energy
electrons
carried by NADH
carried by NADH
GLYCOLYSIS
GLYCOLYSIS
Glucose
Glucose
Pyruvic
Pyruvic
acid
acid
KREBS
KREBS
CYCLE
CYCLE
Cytoplasmic
Cytoplasmic
fluid
fluid
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ELECTRON
ELECTRON
TRANSPORT
CHAIN
TRANSPORT
CHAIN
AND CHEMIOSMOSIS
AND CHEMIOSMOSIS
Mitochondrion
Mitochondrion
Muscle Fatigue and Oxygen Debt
 A fatigued muscle is unable to contract
 anaerobic metabolism produces lactic acid
 Increasing acidity (from lactic acid) and lack of
ATP causes the muscle to contract less
GLYCOLYSIS
2 Pyruvic
acid
Glucose
 Oxygen is required to get rid of lactic acid
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2 Lactic
acid
Contraction of a Skeletal Muscle
 Muscle fiber contraction is “all or none”
 Within a skeletal muscle, not all fibers may be
stimulated during the same interval
 Graded responses due to:
- number of muscle cells in each motor unit
- number of muscle cells stimulated
- frequency of muscle stimulation
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Muscle Contraction: Myogram
 Latent period
 Contraction
 Relaxation
 Summation
vs. tetanus
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Figure 6.10
Types of Muscle Contractions
 Isotonic contractions
 Myofilaments slide past each other
 muscle shortens
 Isometric contractions
 Tension in muscles
 muscle is unable to shorten
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Muscle Activity
 Slow twitch vs. fast twitch fibers
 Slow twitch: endurance, long duration
contraction, contain myoglobin
 Jogging, swimming, biking
 Fast twitch: strength, white muscle, short
duration contraction
 Sprinting, weight lifting, tennis
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Exercise Training
 Strength training
 Resistance training
 Short, intense
 Builds more fast-twitch myofibrils
 Aerobic training
 Builds endurance
 Increases blood supply to muscle cells
 Target heart rate at least 20 minutes, three times a
week
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Features of Cardiac and Smooth Muscles
 Activation of cardiac and smooth muscles
 Involuntary
 Specialized adaptations
 Speed and sustainability of contractions
 Arrangement of myosin and actin filaments
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Smooth Muscle Characteristics
 Has no striations
 Spindle-shaped cells
 Single nucleus
 Involuntary – no
conscious control
 Found mainly in the
walls of hollow
organs
Figure 6.2a
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Cardiac Muscle Characteristics
 Has striations
 Branched cell with a
single nucleus
 Joined to another
muscle cell at an
intercalated disc
 Involuntary
 Muscle bundles
wrapped around
heart
Figure 6.2b
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Diseases and Disorders of the Muscular
System
 Muscular dystrophy
 Tetanus
 Muscle cramps
 Pulled muscles
 Fasciitis
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Superficial Muscles: Anterior
Figure 6.21
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Superficial Muscles: Posterior
Figure 6.22
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Body Movements
Flexion
Extension
Rotation
Figure 6.13a–c
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Body Movements
Abduction
Adduction
Circumduction
Figure 6.13d
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