Chapter 2 - Basic Exercise Science: Muscular System Flashcards Preview

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Flashcards in Chapter 2 - Basic Exercise Science: Muscular System Deck (47):
1

The Muscular System

The device that the NS can command to move the skeletal system

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3 Major Muscle Types in Body

Skeletal, cardiac, and smooth muscle

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Skeletal Muscle Make-Up

Made up of individual muscle fibers

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Muscle Definition

Multiple bundles of muscle fibers held together by connective tissue

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1st Bundle of Muscle Fiber

Actual muscle itself wrapped by an outer layer of CT called fascia and an inner layer called epimysium

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Epimysium

Outermost layer
-Layer of CT that is underneath the fascia and surrounds the muscle

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2nd Bundle of Muscle Fiber

Fascicle
-Each fascicle wrapped by perimysium

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Perimysium

Middle layer
-Surrounds the fascicles

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Endomysium

Deepest layer of CT that surrounds individual muscle fibers

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Fascia Definition

Outer layer of CT that wraps the actual muscle

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Fascicle Definition

The compartments that contain bundles of muscle cells, surrounded by perimysium

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Tendons

Connective tissues that attach muscle to bone and provide an anchor for muscles to produce force

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Sarcolemma

Plasma membrane that encases muscle fibers

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Sarcoplasma

Cellular plasma within muscle fiber

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Sarcoplasma Elements

Contains glycogen, fats, minerals, and oxygen-binding myoglobin, as well as nuclei, and mitochondria

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Myofibrils

Structure of muscle fibers that contain myofilaments that are actual contractile components of muscle tissue
-Actin and Myosin

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Actin

Thin filaments

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Myosin

Thick filaments

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Sarcomere

The functional unit of muscle that produces muscular contraction and consists of repeating sections of actin and myosin

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Two Lines of Sarcomere

Z Lines
-Each Z line denotes another sarcomere along the myofibril

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2 Protein Structures Important to Muscle Contraction

Tropomyosin and Troponin

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Tropomyosin

Located on the actin filament and keeps myosin from attaching to actin when the muscle is in a relaxed state

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Troponin

Plays a role in muscle contraction by providing binding sites for both calcium and tropomyosin on the actin filament when a muscle needs to contract

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Neural Activation Definition

The contraction of a muscle generated by neural stimulation

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Neuromuscular Junction

The point at which the motor neurons meets an individual muscle fiber

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Motor Unit Definition

A motor neuron and all of the muscle fibers it innervates

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Synapse Definition

Small gap between the nerve and muscle fiber

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Action Potentials

Electrical impulses that are transported from the CNS down the axon of the neuron

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Impulse Reaching End of Axon (Axon Terminal)

Neurotransmitters are released

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Neurotransmitters

Chemical messengers that cross the synapse to transmit electrical impulses from the nerve to the muscle

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Acetylcholine (ACh)

The neurotransmitter used by the neuromuscular system
-Stimulates the muscle fibers to go through a series of steps that initiates muscle contractions

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Sliding Filament Theory

Describes how thick and thin filaments within the sarcomere slide past one another, shortening the entire length of the sarcomere and thus shortening the muscle and producing force

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Excitation-Contraction Coupling

The process of neural stimulation creating a muscle contraction
-A series of steps that start with the initiation of a neural message and end with a muscle contraction

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Motor Units and the "All or Nothing" Law

Motor units cannot vary the amount of force they generate, they either contract maximally or not at all.

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Strength of Skeletal Muscle Contraction

Depends on size of motor unit recruited and number of motor units that are activated at a given time

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Size of Motor Units Related to Function of Muscle

Large muscle required to general more powerful movements will have much more muscle fibers in each of their motor units, vice versa

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Muscle Fiber Types

Type I and Type II

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Type I Muscle Fibers

Slow-Twitch
-More capillaries, mitochondria, and myoglobin
-Increased oxygen delivery
-Smaller in size
-Less force produced
-Slow to fatigue
-Long-term contraction (stabilization)

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Type II Muscle Fibers

Fast-Twitch
-Fewer capillaries, mitochondira, and myoglobin
-Decreased oxygen delivery
-Larger in size
-More force produced
-Quick to fatigue
-Short-term contractions (force and power)

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Type II Muscle Fibers

Subdivided into Typer IIa and Type IIx based on their chemical and mechanical properties

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Type IIx

Low oxidative capacity and fatigue quickly

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Type IIa (Combination of Type I and Type II)

Higher oxidative capacity and fatigue more slowly
-Intermediate fast-twitch fibers as they can use both aerobic and anaerobic metabolism almost equally to create energy

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Muscles as Movers

Agonist, Synergist, Stabilizer, Antagonist

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Agonist

Prime movers, most responsible for the movement

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Synergist

Assist prime movers during movement

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Stabilizer

Support and stabilize while prime mover and synergist work

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Antagonist

Perform opposite action of prime mover