Chapter 50.5 Flashcards
Skeletal Muscle
Vertebrate skeletal muscle moves bones and the body and is characterized by a hierarchy of smaller and smaller units
Myofibrils
Each muscle fiber is itself a bundle of smaller myofibrils arranged longitudinally
Myofilament:
Thin Filaments
myofibrils are composed of two kinds of myofilaments
Thin filaments consist of two strands of actin and two strands of a regulatory protein
Myofilament:
Thick Filaments
myofibrils are composed of two kinds of myofilaments
Thick filaments are staggered arrays of myosin molecules
Striated Muscle
Skeletal muscle is also called striated muscle because the regular arrangement of myofilaments creates a pattern of light and dark bands
Sarcomere
The functional unit of a muscle is called a sarcomere and is bordered by Z lines
Sliding-Filament Model
According to the sliding-filament model, filaments slide past each other longitudinally, producing more overlap between thin and thick filaments
Tropomyosin & The Troponin Complex
Tropomyosin is a regulatory protein
The regulatory protein tropomyosin and the troponin complex, a set of additional proteins, bind to actin strands on thin filaments when a muscle fiber is at rest
Transverst (T) Tubules
Action potentials travel to the interior of the muscle fiber along transverse (T) tubules
Sarcoplasmic Reticulum (SR)
The action potential along T tubules causes the sarcoplasmic reticulum (SR) to release Ca2+
Moor Unit
A motor unit consists of a single motor neuron and all the muscle fibers it controls
Tetanus
Tetanus is a state of smooth and sustained contraction produced when motor neurons deliver a volley of action potentials
Oxidative & Glycolitic Fibers
These fibers have many mitochondria, a rich blood supply, and a large amount of myoglobin
Slow-Twitch Fibers
Contract more slowly but sustain longer contractions
All slow-twitch fibers are oxidative
Fast-Twitch Fibers
Contract more rapidly but sustain shorter contractions
can be either glycolytic or oxidative
