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89 Cards in this Set

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skeletal muscle
Striated muscle attached to bone or skin and responsible for skeletal movements and facial expression; controlled by somatic nervous system
smooth muscle
Nonstriated muscle that surrounds hollow organs and tubes; see also multiunit smooth muscle, single-unit smooth muscle
cardiac muscle
Heart muscle
muscle fiber
Muscle cell
myoblasts
Embryological cell that gives rise to muscle fibers
satellite cells
Undifferentiated cells found within skeletal muscle tissue that can fuse and develop into new muscle fibers following muscle injury.
hypertrophy
Enlargement of a tissue or organ due to increased cell size rather than increased cell number.
muscle
Number of muscle fibers bound together by connective tissue
tendons
Collagen fibre bundle that connects skeletal muscle to bone and transmits muscle contraction force to the bone.
striated muscle
Muscle having transverse banding pattern due to repeating sarcomere structure; see also cardiac muscle, skeletal muscle
myofibrils
Bundle of thick or thin contractile filaments in cytoplasm of striated muscle; myofibrils exhibit a repeating sarcomere pattern along longitudinal axis of muscle.
sarcomere
Repeating structural unit of myofibril; composed of thick and thin filaments; extends between two adjacent Z lines
thick filaments
Myosin filament in muscle cell
thin filaments
Actin filament in muscle cell
actin
Globular contractile protein to which myosin cross-bridges bind; located in muscle thin filaments and in microfilaments of cytoskeleton.
A band
One of the transverse bands making up repeated striations of cardiac and skeletal muscle; region of aligned myosin-containing thick filaments.
Z line
Structure running across myofibril at each end of striated muscle sarcomere; anchors one end of thin filaments and titin
I band
One of transverse bands making up repeating striations of cardiac and skeletal muscle; located between A bands of adjacent sarcomeres and bisected by Z line.
H zone
One of the transverse bands making up striated pattern of cardiac and skeletal muscle; light region that bisects A band.
M line
Transverse stripe occurring at the center of the A band in cardiac and skeletal muscle; location of energy-generating enzymes and proteins connecting adjacent thick filaments.
titin
Protein that extends from the Z line to the thick filaments and M line of skeletal muscle.
contraction
Operation of the force-generating process in a muscle cell.
relaxation
Return of muscle to a low force-generating state, caused by detachment of cross-bridges.
sliding-filament mechanism
Process of muscle contraction in which shortening occurs by thick and thin filaments sliding past each other.
heavy chains
Painrs of large, coiled polypeptides that make up the rod and globular head of a myosin molecule.
light chains
Pair of small polypeotides bound to each globular head of a myosin molecule; function is to modulate contraction.
cross-bridge cycle
Sequence of events between binding of cross-bridge to actin, its release, and reattachment during muscle contraction.
power stroke
The step of a cross-bridge cycle involving physical rotation of the globular head.
rigor mortis
Stiffness of skeletal muscles after death due to failure of cross-bridges to dissociate from actin because of loss of ATP.
troponin
Regulatory protein bound to actin and tropomyosin of striated muscle thin filaments; site of calcium binding that initiates contractile activity
tropomyosin
Regulatory protein capable of reversibly converting binding sites on actin; associated with muscle thin filaments.
excitation-contraction coupling
In muscle fibers, mechanism linking plasma membrane
sarcoplasmic reticulum
Endoplasmic reticulum in muscle fiber; site of storage and release of calcium ions.
lateral sacs
Enlarged region at end of each sarcoplasmic reticulum segment; adjacent to transverse tubule.
transverse tubule (T-tubule)
Tubule extending from striated-muscle plasma membrane into the fiber, passing between opposed sarcoplasmic reticulum segments; conducts muscle action potential into muscle fiber.
junctional feet “foot proteins”
Large extension of sarcoplasmic reticulum calcium channels (ryanodine receptors), which connect them to the T-tubule membrane and mediate excitation-contraction coupling in skeletal muscle; also known as junctional feet
dihydropyridine (DHP) receptor
Nonconducting calcium channels in the T-tubule membranes of skeletal muscle cells, which act as voltage sensors in excitation-contraction coupling
ryanodine receptor
Calcium-release channel found in the lateral sas of the carcoplasmic reticulum in skeletal muscle cells.
motor neurons
Somatic efferent neuron, which innervates skeletal muscle.
motor unit
Motor neuron plus the muscle fibers it innervates.
acetylcholine (ACh)
A neurotransmitter released by pre- and post-ganglionic parasympathetic neurons, preganglionic sympathetic neurons, somatic neurons, and some CNS neurons.
motor end plate
Specialized region of muscle cell plasma membrane that lies directly under axon terminal of a motor neuron
neuromuscular junction
Synapse-like junction between an axon terminal of an efferent nerve fiber and a skeletal muscle fiber.
end-plate potential (EPP)
Depolarization of motor end plate of skeletal muscle fiber in response to acetylcholine; initiates action potential in muscle plasma membrane
acetylcholinesterase
Enzyme that breaks down acetylcholine into acetic acid and choline.
tension
Force; see also muscle tension
load
External force acting on muscle.
Isometric contraction
Contraction of muscle under conditions in which it develops tension but does not change length
isotonic
Containing the same number of effectively nonpenetrating solute particles as normal extracellular fluid
Isotonic contraction
Contraction of muscle under conditions in which load on the muscle remains constant but muscle shortens
concentric contraction
Muscle activity that involves shortening of muscle length.
Lengthening contraction (eccentric contraction)
Contraction as an external force pulls a muscle to a longer length despite opposing forces generated by the active cross-bridges.
twitch
Mechanical response of muscle to single action potential
latent period
Period lasting several milliseconds between action potential initiation in a muscle fiber and beginning of mechanical activity
contraction time
Time between beginning of force development and peak twitch tension by the muscle.
summation
Increase in muscle tension or shortening in response to rapid, repetitive stimulation relative to single twitch
tetanus
Maintained mechanical response of muscle to high-frequency stimulation; also the disease lockjaw
unfused tetanus
Stimulation of skeletal muscle at a low-to-moderate action potential frequency that results in oscillating, submaximal force
fused tetanus
Skeletal muscle activation in which action potential frequency is sufficiently high to cause a smooth, sustained, maximal strength contraction.
creatine phosphate (CP)
Molecule that transfers phosphate and energy to ADP to generate ATP.
oxygen debt
Decrease in energy reserves during exercise that results in an increase in oxygen consumption and an increased production of ATP by oxidative phosphorylation following the exercise.
muscle fatigue
Decrease in muscle tension with prolonged activity
Fatigue from high-intensity, short duration exercise is thought to involve at least three different mechanisms
Conduction failure, lactic acid buildup, inhibition of cross-bridge cycling
lactic acid
Three-carbon molecule formed by glycolytic pathway in absence of oxygen; dissociates to form lactate and hydrogen ions.
central command fatigue
Muscle fatigue due to failure of appropriate regions of cerebral cortex to excite motor neurons.
fast fibers
Skeletal muscle fiber that contains myosin having high ATPase activity.
slow fibers
Muscle fiber whose myosin has low ATPase activity.
oxidative fibers
Muscle fiber that has numerous mitochondria and therefore a high capacity for exidative phosphorylation; red muscle fiber
myoglobin
Muscle fiber protein that binds oxygen.
red muscle
Muscle having high oxidative capacity and large amount of myoglobin.
glycolytic fibers
Skeletal muscle fiber that has a high concentration of glycolytic enzymes and large glycogen stores; white muscle fiber.
white muscle
Muscle lacking appreciable amounts of myoglobin
slow-oxidative fibers
Type of skeletal muscle fiber that has slow intrinsic contraction speed but fatigues very slowly due to abundant capacity for production of ATP by aerobic oxidative phosphorylation.
fast-oxidative fiber
Type of skeletal muscle fiber that has high intrinsic contraction speed and abundant capacity for production of ATP by aerobic oxidative phosphorylation.
fast-glycolytic fiber
Type of skeletal muscle fiber that has high intrinsic contraction speed and abundant capacity for production of ATP by anaerobic glycolysis.
recruitment
Activation of additional cells in response to increased stimulus strength; increasing the number of active motor units in a muscle.
flexion
Bending a joint
extension
Straightening a joint
antagonists
(muscle) muscle whose action opposes intended movement; (drug) molecule that competes with another for a receptor and binds to the receptor but does not trigger the cell’s response.
hypocalcemia
The condition of low blood (and interstitial) calcium concentration.
dense bodies
Cytoplasmic structure to which thin filaments of a smooth muscle fiber are anchored.
myosin light-chain kinase
Smooth-muscle protein kinase; when activated by Ca-calmodulin, phosphorylates myosin light chain.
myosin light-chain phosphatase
Enzyme that removes high-energy phosphate from myosin; important in the relaxation of smooth muscle.
latch state
Contractile state of some smooth muscles in which force can be maintained for prolonged periods with very little energy use; cross-bridge cycling slows to the point where thick and thin filaments are effectively “latched” together.
smooth muscle tone
Smooth-muscle tension due to low-level cross-bridge activity.
pacemaker potential
Spontaneous gradual depolarization to threshold of some nerve and muscle cells’ plasma membrane
Varicosity
Swollen region of axon; contains neurotransmitter-filled vesicles; analogous to presynaptic ending
single-unit smooth muscles
Smooth muscle that responds to stimulation as single unit because gap junctions join muscle fibers.
multiunit smooth muscles
Smooth muscle that little, if any propagation of electrical activity from fiber to fiber and whose contractile activity is closely coupled to its neural input.