Skeletal Muscle Physiology How do contractions occur? Remember that muscles are excitable.
Chapter 6 - Muscle system · Chapter 6 – Muscular System BIO 105 What do all these muscle types...
Transcript of Chapter 6 - Muscle system · Chapter 6 – Muscular System BIO 105 What do all these muscle types...
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Chapter 6 – Muscular System
BIO 105
What do all these muscle types have in common?
1. Muscles are excitable
2. Muscles have the ability to contract.
3. Muscles are extensible.
4. Muscles are elastic.
Organization of skeletal muscle
The muscles that we use for locomotion are attached to bones by __________.
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Muscle origins and insertions
(a) Flexion
The relaxed triceps
is stretched.
The biceps contracts
and pulls the forearm
up, flexing the arm.
Origin of muscle:
attachment of muscle to less moveable bone
Insertion of muscle:
attachment of muscle to more moveable bone
extension
(b) Extension
The triceps contracts and
pulls the forearm down,
extending the arm.
The relaxed biceps
is stretched.
Structure of skeletal muscle
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skeletal muscle
(c) A diagram and
electron micrograph
of a myofibril
(d) A sarcomere, the contractile unit of a skeletal muscle, contains actin and
myosin myofilaments.
Z line
Z line
Z line
Actin
Myosin
One sarcomere
One sarcomere
Thick & thin myofilaments Skeletal muscle contraction
Sliding filament model – muscle contracts
when actin filaments slide along the myosin filaments, increasing the degree of
overlap between actin and myosin, and
thus shortening the sarcomere.
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What stimulates skeletal muscle
contraction?Neuromuscular Junction
Amyotrophic Lateral Sclerosis (ALS)
Degeneration of the motor neurons that control skeletal muscle.
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Muscular Dystrophy
Progressive degeneration
of skeletal muscle fibers
Motor Units and RecruitmentTypes of Skeletal Muscle Fibers
Slow - twitch
• Slow speed of contraction
• Slow to fatigue
• Many mitochondria & blood vessels
Fast - twitch
• Fast speed of contraction
• Fast to fatigue
• Fewer mitochondria & blood vessels
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A muscle twitch is a single contraction-
relaxation cycle that occurs in a muscle fiber in response to a
single action potential.
Where does this wealth of ATP come from?
1. ATP stored in muscle cells
2. The breakdown of creatine phosphate
3. Cellular respiration
4. Fermentation
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How does aerobic vs. anaerobic exercise affect your muscles?
• Aerobic exercise facilitates the
development of new blood vessels, more mitochondria, cardiac & respiratory
improvement
• Anaerobic exercise increases muscle size