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32 Cards in this Set

  • Front
  • Back
What are the three major functions of the skeletal muscles?
(a) endomysium, (b) perimysium, (c) epimysium
Name some features of the muscle cell that are not found in other types of cells
Excitability, contractibility, and extensibility
What causes the striations observed in skeletal muscle fibers?
The striations r a result of the A bands of sarcomeres appearing as relatively wide, dark stripes under the microscope, which alternate with narrower, lighter colored stripes formed by the I bands
Why is the triad relationship between T tubules and the SR important
The triad allows an electrical impulse traveling along a T tubule to stimulate the membranes of adjacent sacs of the SR
Describe the structure of thin and thick myofilaments, and name the kinds of proteins that compose them
Thin filament (actin, troponin,& tropomyosin): molecules strung 2gether like beads 2 form 2 fibrous strands that twist around each other.
Describe the structure of thin and thick myofilaments, and name the kinds of proteins that compose them
Thick filament (myosin): shaped like golf clubs,w/ their long shafts bundled together 2 form a thick filament & their “heads” sticking out from the bundle
What is the role of calcium ions (Ca++) in muscle contraction?
Calcium ions released from the SR bind to troponin in the thin filament allow tropomyosin 2 shift frm its position blcking the active sites of actin molecules, thus initiating the chemical reactions that produce contractions
Where does the energy stored in ATP come from?
Catabolism of foods
What is the role of myoglobin in muscle fibers?
Myoglobin attracts oxygen molecules and holds them temporarily. When the oxygen concentration inside a muscle fiber decreases rapidly, it can be quickly resupplied from the myoglobin
What are the three phases of a twitch contraction?
Latent period, contraction phase, and relaxation phase
What is tetanus? Is it normal?
tetanus is a smooth, sustained contraction. Yes, tetanus is the kind of contraction exhibited by normal skeletal muscle organs most of the time
What is meant by the term muscle tone?
Muscle tone (tonic contraction) is a continual, partial contraction in a muscular organ
Name four factors that influence the strength of a skeletal muscle contraction
Metabolic condition of individual muscle fibers, recruitment of motor units, length-tension relationship, amount of load imposed on the muscle
What is meant by the phrase “recruitment of motor units
Number of muscle fibers activated
How do slow, separate, autorhythmic contractions of cardiac muscle make it well suited to its role in pumping blood?
Cardiac muscle does not normally run low on ATP and thus does not experience fatigue
What produces the striations in cardiac muscle?
Each myofibril comprises sarcomeres that give the whole fiber a striated appearance
How are myofilaments arranged in a smooth muscle fiber?
Thin arrangements of myofilaments crisscross the cell and attach at their ends to the cell’s plasma membrane.
Isometric contraction
type of muscle contraction in which muscle does not alter the distance between two bones; see isotonic contraction
Isotonic contraction
type of muscle contraction in which the muscle sustains the same tension or pressure and a change in the distance between two bones occurs
Motor unit
functional unit composed of a single motor neuron with the muscle cells it innervates
Muscle tone
tonic contraction; characteristic of muscle of a normal individual who is awake
very fine longitudinal fibers found in skeletal muscle cells; composed of thick and thin filaments
ultramicroscopic, threadlike structures found in myofibrils; composed of myosin (thick) and actin (thin)
Neuromuscular Junction
point of contact between nerve endings and muscle fibers; see motor endplate
plasma membrane of a striated muscle fiber
contractile unit of muscle cells; length of a myofibril between two Z disks
cytoplasm of muscle fibers
Sarcoplasmic reticulum
network of tubules and sacs in muscle cells; similar to endoplasmic reticulum of other cells
T Tubules
transverse tubules unique to muscle cells; formed by inward extensions of the sarcolemma that allow electrical impulses to move deeper into the cell
smooth, sustained muscular contraction caused by high-frequency stimulation
Threshold Stimulus
minimal level of stimulation required to cause a muscle fiber to contract
Anatomy & Physiology Chapter 11 Physiology of the Muscular System
Anatomy & Physiology Chapter 11 Physiology of the Muscular System