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Muscular
System
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Skeletal Muscle Structure
Skeletal Muscle: The muscle that moves the
body. (including arm/leg movement and facial
expressions)
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Skeletal Muscle
Parts of the Skeletal muscle:
• Made up of bundles of long multinucleated
cells called fibers
• These fibers are enclosed in a membrane
called the sarcolemma
• Inside the sarcolemma are tiny myofilaments
(Myofibril = 1 )
The Muscle Fiber
Myofilament (myofibril) Up Close
Two kinds of myofilaments:
-actin: thin filaments
-myosin: thick filaments
These two filaments overlap forming striations
giving it a striped appearance
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Zones on the Myofilament
Z lines: Anchor the filaments.
Sacromere: The area between the anchors
Sliding-Filament Theory
• Explains how muscles contract.
Steps to contracting a muscle:
1) Muscles shorten by the sliding movement of
the actin filaments over the myosin filaments
Sliding-Filament Theory
2) This sliding brings the two myosin closer
together this brings the Z lines closer as well
How do the actin and myosin filaments slide
over each other?
Sliding-Filament theory
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Sliding-Filament Theory
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Sliding-Filament Theory
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Sliding-Filament Theory
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Sliding-Filament Theory
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Sliding-Filament Theory
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ATP and Sliding-Filament theory
ATP:
• The energy needed to power the sliding
filaments.
• This energy is required to allow the cross
bridge to release
• Without ATP the muscle will not be able to
contract.
Muscle Fatigue
Causes of Muscle Fatigue:
1) Lack of energy
2) Build up of waste
Energy Demand from Muscles: Most ATP comes
from cellular respiration by the breakdown of
glucose.
The role of creatine phosphate:
Muscle Fatigue
Causes of Muscle Fatigue:
1) Lack of energy
2) Build up of waste
Energy Demand from Muscles: Most ATP comes
from cellular respiration by the breakdown of
glucose.
The role of creatine phosphate: Found in all muscle
cells. It acts as a supply of phosphate for ADP so
it can be converted into ATP
When Supply Does not Meet Demand
When More ATP is needed then your muscle
cells can make: Lactic acid builds up in muscle
tissues creating a burning sensation. This is
known as oxygen debt.
When Supply Does not meet demand
When More ATP needed then your muscle cells
can make: Lactic acid builds up in muscle
tissues creating a burning sensation. This is
known as oxygen debt.
This build up of acidic fluid eventually stops
muscle contractions. Rapid breathing after
exercise is the bodies way of trying to increase
the oxygen content in the muscle.
Assignment pg 902 8-12