Date post: | 24-Dec-2015 |
Category: |
Documents |
Upload: | osborne-jonathan-nicholson |
View: | 217 times |
Download: | 1 times |
Lecture Outline• Functions of Skeletal Muscle
• Structural Hierarchy of Muscle
• Sarcomere Structure– Thick Filaments – myosin– Thin filaments – actin, troponin and tropomyosin
• Sliding Filaments and Cross-bridge Cycling
• Neuromuscular Junction and Causes of Muscle Contraction
• Force Production in Skeletal Muscle– Single Muscle Fibers– Whole Muscles
Functions of Skeletal Muscles
• Produce skeletal movement
• Maintain body position
• Support soft tissues
• Guard openings
• Maintain body temperature
• Store nutrient reserves
A cross section through a sarcomere shows that:• each myosin can interact with 6 actin filaments, and• each actin can interact with 3 myosin filaments.
Single Fiber Force Production• The all–or–none principle
• Tension of a Single Muscle Fiber– Depends on
• Number
• Length
• Frequency
Whole Muscle Force Production
• Whole Muscle Force depends on:– Contraction Type
– Velocity
– Muscle Fiber Type
– Muscle Architecture
Types of Muscle Contraction
• Four Types of Skeletal Muscle Contraction
– Isotonic contraction
– Isometric contraction
– Eccentric Contraction
– Concentric Contraction
Muscle Fiber Types
• Three Types of Skeletal Muscle Fibers
– Fast Glycolytic (FG)
– Slow Oxidative (SO)
– Fast Oxidative Glycolytic (FOG)
Slow-oxidative skeletal muscle responds well to repetitive stimulation without becomingfatigued; muscles of bodyposture are examples.
Fast-oxidative skeletal muscle responds quickly and to repetitive stimulation without becoming fatigued; muscles used in walking are examples.
Fast-glycolytic skeletal muscle is used for quick bursts ofstrong activation, such as muscles used to jump or to run a short sprint.
Mos
t ske
leta
l mus
cles
incl
ude
all t
hree
type
s.
Muscle Fiber Types• Muscle Hypertrophy– Muscle growth from heavy training
• Muscle Atrophy– Lack of muscle activity
Muscle Fiber Types• Physical Conditioning– Improves both power and endurance• Anaerobic activities (e.g., 50-meter dash, weightlifting):
• Aerobic activities (prolonged activity):
Muscle Fiber Types• What you don’t use, you lose
• Muscle fibers break down proteins, become smaller and weaker
• With prolonged inactivity, fibrous tissue may replace muscle fibers
Muscle Properties that Affect ForceCross Sectional Area
• Muscle Force is proportional to muscle cross-sectional area
• The greater a muscles cross-sectional area the greater the force
Muscle Architecture – Parallel or Fusiform
Long muscles made up of in-series, parallel fibers
Design for muscles that undergo shortening contractions that produce work
Muscles usually contract over long distances
Muscle Architecture - Pennate• Designed to have large
cross-sectional area
• Designed to produce force
• Three types– Unipennate– Bipennate– Multipennate
Summary• Functions of Skeletal Muscle
• Structural Hierarchy of Muscle
• Sarcomere Structure– Thick Filaments – myosin– Thin filaments – actin, troponin and tropomyosin
• Sliding Filaments and Cross-bridge Cycling
• Neuromuscular Junction and Causes of Muscle Contraction
• Force Production in Skeletal Muscle– Single Muscle Fibers– Whole Muscles