p Muscular System Skeletal Muscle Structure Skeletal Muscle

p Muscular System -

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 j

Sliding-Filament Theory j

Sliding-Filament Theory j

Sliding-Filament Theory j

Sliding-Filament Theory j

Sliding-Filament Theory j

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