Physiology of Exercise
Chapter 1: Structure & Function of Exercising Muscle
Chapter 1: Structure & Function of Exercising Muscle
Kartei Details
| Karten | 36 |
|---|---|
| Sprache | English |
| Kategorie | Chemie |
| Stufe | Universität |
| Erstellt / Aktualisiert | 02.09.2016 / 07.05.2021 |
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Motor neuron
nerve cell that connects with and innervates many muscle fibers.
Motor Unit
A single motor neuron and all the muscle fiers it directly signal
Neuromuscular junction
Synapse or gap between the a-motor neuron and a muscle fiber. Where communication between nervous and muscular systems occurs.
Excitation-contraction coupling
begins with the excitation of a motor nerve and results in contraction of the muscle fibers.
Sliding Filament Theory
Myosin cross-bridges are activated, bind to actin resultin in conformation change in cross-bridge, causes the myosin head t tilt and to drag thin filament toward the cener of sarcomere
Power Stroke
Tilting of the myosin head to tilt
Adenosine triphosphate (ATP)
Energy molecule. Myosin molecule must bind with ATP for muscle contraction to occur
Adenosine triphosphatade (ATPase)
Enzyme located on myosin head, splits ATP to yield ADP, inorganic phosphate, and energy.
Type I fibers
slow-twitch
take approx 110 ms to reach peak tension when stimulated
Most muscles composed of 50% type I fibers
high level of aerobic endurance
Type II fibers
fast twitch
reach peak tension in about 50ms
most muscles composed 25% type IIa fibers
poor aerobic endurance
Principle of Orderly Recruitment
Motor units within a given muscle appear to be ranked.
tyoe I -->type IIa --> type IIx
Size principle
the order of recruitment of motor units is directly related to the size of their motor neuron.
Motor units with smaller motor neurons will be recruited first.
Type II motor units are recruited as force needed to perform the movement increases.
concentric contraction
shortening of muscle
considered a dnamic contractions
Static/ Isometric Muscle Contraction
Muscles act without moving
Muscles generates force but its length remain static (unchanged), because joint angle does not change
Eccentric Contraction
Muscles exert force while lengthening
a dynamic contraction
musculoskeletal system
Skeletal muscles together with the bones of the skeleton make this us.
Epimysium
outer layer connective tissue covering entire muscle and functions to hold it together.
Perimysium
Connective tissue sheath surrounding each fasiculus
Muscle Fiber
Single muscle cell
Endomysium
connective tissue covers each muscle fiber
Plasmalemma
Individual muscle fiber surrounded by a plasma membrane
Sarcolemma
composed of the plasmalemma and the basement membrane.
Satellite cells
located between the plasmalemma and the basement membrane.Involved in the growth and development of skeletal muscle and in muscle adaptation to injury, immoblization, and training.
Sarcoplasm
gelatin-like substance fills spaces within and between the myofibrils. Contains mainly dissolved proteins, minerals, glycogen, fats and necessary organells.
Transverse tubules (t-tubules)
extensions of the plasmalemma that pass laterally through the muscle fiber. Interconnected as pass among myofibrils, allowing nerve impulses received by plasmalemma to be transmitted rapidly to individual myofibrils
Sarcoplasmic Reticulum
longitudinal network of tubules found within muscle fiber. Serves as a storage site for calcium, essential for muscle contraction.
Myofibrils
muscle fiber contains several hundred-thousand of these. Made up of the basic contactile elements of skeletal muscle- the sarcomeres.
Sarcomere
basic functional unit of a myofibril and basic contractile unit of muscle. Each myofibril is composed of numerous sarcomeres joined end to end at Z disks.
Sarcomere includes what is found between each pair of Z-disks
An I-band (light zone)
An A band (dark zone)
an H zone ( middle of A band)
an M-line in middle of H zone
the rest of A band
a second I-band
Actin
thinner filaments
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