Glossary of Bio lecture test 7

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muscle fibers
long smooth and skeletal muscle cells
the muscle equivalents of the actin or myosin-containing filaments
skeletal muscle
organs that attach to and cover the bony skeleton
smooth muscle
muscle in the walls of hollow, visceral organs
cardiac muscle
muscle in the walls of the heart
ability to receive and respond to a stimulus
ability to shorten forcibly
ability to be stretched or extended
ability of a muscle fiber to recoil and resume its length after being stretched
fine sheath of connective tissue consisting of reticular fibers which surrounds each muscle fiber
bundles of endomysium-wrapped muscle fibers
layer of fibrous connective tissue surrounding each fascicle
layer of dense irregular connective tissue surrounding the entire muscle
deep fascia
connective tissue which lies between neighboring muscles or the superficial fascia deep to the skin
plasma membrane surface of a muscle fiber
nonfibular cytoplasm of a muscle fiber which contains large amounts of glycosomes and substatial amounts of myoglobin
red pigment that stores oxygen
rodlike bundle of contractile filaments found in muscle cells
A bands
the darker bands which represent thick filaments and never shorten
I bands
light bands which represent thin filaments
H zone
Lighter stripe in the A band's midsection which represents a place with no actin and are visible only in relaxed muscle fibers
M line
dark line bisecting H zone vertically and contains fine protein strands which hold the adjacent thick filaments together
Z disc
darker area interrupting I band composed of the protein nebulin which anchors the thin filaments and connets each myofibril to the next and is a network of titin
region of a myofibril between two z discs which contains an A band flanked by half and I band at each end and is the smallest contractile unit of a muscle fiber and the functional unit of skeletal muscle
thick filament
filament exteding the entire length of the A band composed primarily of myosin
thin filament
filament extending across the I band and partway into the A band composed chiefly of actin
sarcoplasmic reticulum
elaborate smooth endoplasmic reticulum whose interconnecting tubules surround each myofibril and it regulates intracellular levels of ionic calcium
terminal cisternae
channels formed by perpendicular tubules crossing normal tubules at the A-I band junctions that always occur in pairs in the sarcoplasmic reticulum
T tubules
elongated tube formed by the penetration fo the sarcolemma into the cell interior at the A-I band junction
successive groupings of the 3 membranous structures- terminal cisternae, t tubule, terminal cisternae
muscle tension
force exerted by a contracting muscle on an object
muscle load
opposing force exerted by the weight of an object on a muscle
motor unit
motor neuron and all the muscle fibers it supplies
a graphic recording of contractile activity
muscle twitch
response of a motor unit to a single action potential of its motor neuron
latent period
first few milliseconds following contraction coupling is ocurring when muscle tension is beginning to increase but there is no myogram response
period of contraction
when cross-bridges are active from the onset to the peak of tension develoopment and myogram rises to a peak
period of relaxation
initiated by the reentry of calciurm into the sarcoplasmic reticulum, muscle tension decreases to zero and the tracing ends
graded response
variations in the degree of muscle contraction by changing either the frequency or strength of the stimulus
wave summation
when the second twitch appears to ride on the first on the myogram
incomplete tetanus
sustained but quivering contraction caused by shortening twitches, rise of clacium, and greater degree of summation
complete tetanus
smooth, sustained contraction as muscle contractions disappear
multiple motor unit summation
increasing voltage to the muscle which causes more and more muscle fibers into play and controls force of contraction precisely
threshold stimulus
stimulus at which the first observable contraction occurs
maximal stimulus
strongest stimullus that produces increased contractile force
staircase pattern caused by muscle contractions half as strong as those that occur later
muscle tone
relaxed muscles are almost always slightly contracted due to alternalte stimulating of motor units
isotonic contraction
muscle length changes and moves the load
isometric contraction
tension builds to the muscle's peak tension-producing capacity, but the muscle neither shortens nor lengthens
aerobic enducance
length of time a muscle can continue to contract using aerobic pathways
anaerobic endurance
point at which muscle metabolism converts to anaerobic glycolysis
muscle fatigue
state of physilogical inability to contract even while still receiving stimuli
states of continuous contraction which result because cross-bridges are unable to detach
embryonic mesoderm cells which develop all muscle tissues

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