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89 Cards in this Set
- Front
- Back
The branch of motor system that controls skeletal muscle.
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somatic
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Consists of thin filaments composed of polymerized actin and thick filaments composed of aggregations of myosin.
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contractile machinery
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Protein component of the sarcomere. The thin polymerized filaments in the contractile machinery of all muscle.
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actin
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Protein component of the sarcomere. Aggregations of filaments in the contractile machinery of all muscle.
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myosin
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The basic functional unit of the contractile machinery of
striated muscle. |
sarcomere
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Contained within heart muscle that are spontaneously active and can serve as pacemakers for the entire heart.
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nodal fibers
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Some heart muscle fibers that are spontaneously active.
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pacemakers
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Muscle not connected by gap junctions and typically is not
spontaneously active. Such muscle is found in the iris of the eye and in the arrector pili muscles attached to individual hairs. |
multiunit smooth muscle
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A type of smooth muscle that contains extensive gap junction
connections, making it possible for a large number of neighboring cells to contract simultaneously as if they were one unit. Such muscle is found in the GI tract and in blood vessels. |
single-unit smooth muscle
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Stem cells that fuse to form skeletal muscle during embryonic development, with the result that the mature cells are long cylinders with multiple nuclei.
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myoblasts
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A layer of connective tissue that wraps each individual muscle fiber.
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endomysium
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Bundles of fibers enclosed in connective tissue sheaths of perimysium.
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fascicles
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A covering that surrounds all of the fascicles.
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epimysium
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The attachment of muscle to bone may be direct, or the connective tissue may extend beyond the muscle to form a cord-like tendon or a sheet-like _________..
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aponeurosis
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When the arrangement of the fascicles converge from a broad origin toward a tendon so that the muscle has a fan shape.
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convergent
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The arrangement of the muscle looks like a feather with the
fascicles (the barbs of the feather) projecting at an angle from a tendon (the shaft of the feather) that runs the whole length of the muscle. |
pennate
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The central principle of leverage is: effort × length of effort arm= load × length of load arm.
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leverage
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Leverage using a small force operating over a large distance to move a heavy load a short distance.
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mechanical advantage
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Leverage allowing a strong force to move a light load rapidly through distance.
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mechanical disadvantage
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The fulcrum lies between the effort and the load so that moving the effort arm in one direction moves the load in the
other direction. |
first class lever
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The load is attached between the effort and the fulcrum. The closer the load is to the fulcrum relative to the position of the effort, the greater the mechanical advantage.
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second class lever
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Effort is applied between the load and the fulcrum. The load is moved rapidly, but with a mechanical disadvantage—the disadvantage increases with the length of the load arm.
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third class lever
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Muscles that are responsible for a particular movement.
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agonists
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Muscles that oppose or reverse a movement.
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antagonist
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A motor neuron, together with its muscle fibers.
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motor unit
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The connection between a motor neuron and a skeletal muscle fiber.
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neuromuscular junction
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A neurotransmitter. When _________ interacts with receptors on the muscle fiber, an action potential is initiated in
the muscle fiber membrane. |
acetylcholine
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Rapid, brief (several msec in duration) changes in the membrane potential of a neuron or muscle cell.
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action potential
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Each skeletal muscle fiber either contracts maximally or not at all.
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all-or-nothing principle
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A process that will result in a detectable mechanical response
of the muscle, as the action potential sweeps across the muscle cell surface. |
excitation-contraction coupling
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A measurable delay between muscle excitation and the onset of tension development or shortening in the muscle.
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latent period
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Follows each action potential.
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refractory period
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Early in the refractory period a period restimulation is effectively impossible.
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absolute refractory period
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A period during which it is more difficult to restimulate the muscle.
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relative refractory period
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The force summation in muscle generated by the newly added motor units to increase force production summates with the
force produced by the units already active. |
spatial summation
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The force delivered by a muscle may increase in proportion to
the intensity of the stimulus delivered to its motor nerve, even though each motor neuron and each muscle fiber obeys the allor- nothing rule. |
graded strength principle
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The muscle is not allowed to shorten, although tension does develop in the muscle.
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isometric contraction
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The muscle is allowed to shorten and lift a load.
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isotonic contraction
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Part of the contractile machinery of the muscle to which thin filaments are attached.
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Z discs
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Double strands of polymerized actin.
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thin filaments
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A theory of muscle contraction that states that each thick filament has one end overlapping slightly with the thin filaments of one Z disc and the other end among the thin filaments of the other Z disc. Shortening of the distance
between the hairbrushes occurs as the thick filaments pull both sets of thin filaments toward the center. |
sliding filament theory
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Structural proteins associated with thin filaments; serves as a molecular yardstick that limits the length of thin filaments.
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nebulin
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Connects the ends of thick filaments to Z disc to prevent
sarcomeres from falling apart; believed to be largely responsible for the series elastic properties of muscle |
titin
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Forms the Z discs.
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CapZ
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Attaches thin filaments to Z disc and determines their spacing.
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alpha actinin
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Attachments made by myosin heads to actin binding sites that generate force during muscle contraction.
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crossbridges
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A rotation of the head that applies force to the thin filament.
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power stroke
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Can be determined by subtracting the predetermined passive tension curve from the total tension curve.
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active tension
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Skeletal muscles that are removed from the body assume a standard length.
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rest length
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The curve of ____________ of a muscle has a value of zero at
rest length and rises as the length is made greater than rest length. |
passive tension
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Can be determined by subtracting the predetermined passive tension curve from the total tension curve.
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active tension
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The curve shows that the active tension is maximal when the muscle is near its rest length.
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length-tension curve
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The optimal range of contractile performance created by the leverage arrangements imposed by the skeleton that restricts muscle lengths.
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operating range
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The site within the cell where Ca++ is stored.
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sarcoplasmic reticulum (SR)
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A vessel formed by the SR, near the Z disc of each sarcomere.
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terminal cisterna
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Finger-like projections of plasma membrane (T tubules) that project into the interior of the muscle fiber and pass close to each terminal cisterna.
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transverse tubules
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Formed by T tubules lying between two terminal cisternae.
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muscle triad
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The protein components of the endfeet that sense the action potential passing along the T tubule.
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voltage sensors
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Stretch components that are part of the contractile machinery.
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series elastic elements
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A form of summation in muscle contraction: If the muscle is
restimulated within a few tens of msec, the force or shortening generated in the second twitch can summate, or add on top of, the initial one, making a stepwise increase in tension or decrease in length. |
temporal summation
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A smooth rise in muscle tension or decrease in length resulting
from the further reduction of the interval between successive impulses. |
tetanus
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A tetanic contraction of all of the fibers of a muscle—almost never occurs
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complete tetanus
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An incomplete tetanus that does not involve all of the fibers of the muscle at any one time.
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a typical contraction
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The force summation in muscle generated by the newly added
motor units to increase force production summates with the force produced by the units already active. |
spatial summation
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Muscle activity requires _______ ?
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ATP
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The enzyme that catalyzes the transfer of phosphate groups
from CrP to ADP and from ATP to Cr. |
creatine phosphokinase
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ATP + Cr =
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ADP + CrP
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Skeletal muscle fibers can be divided into two major categories:
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slow twitch (Type I) and fast twitch (Type II).
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Type I muscle expresses a myosin that cycles less rapidly than that expressed by Type II fibers.
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slow twitch (Type I)
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Type II muscle expresses a myosin that cycles more rapidly than that expressed by Type I fibers.
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fast twitch (Type II) Skeletal muscle fibers.
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An intracellular oxygen carrier.
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myoglobin
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Type I fibers that are a red color due to myoglobin.
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red fibers
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Slowly fatiguing Type IIa fibers that contain some myoglobin
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pink fibers
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Rapidly fatiguing Type IIb fibers contain some myoglobin.
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white fibers
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A sustained increase in oxygen uptake that follows exercise.
In order to incur an oxygen debt, the exercise must be of such intensity that it demands significant recruitment of Type IIb fibers. |
oxygen debt
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Involuntary contractions of skeletal muscles initiated when the
core body temperature falls below its central setpoint, resulting in an increase in heat production. |
shivering
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Defined as the mass of the load multiplied by the distance it is moved.
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Work
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Defined as a set of adaptive changes that occurs in response to exercise
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Conditioning
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With conditioning skeletal muscles undergo adaptive changes
that are visible mainly as an increase in the size of the cells. |
hypertrophy
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An increase in the number of muscle cells.
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hyperplasia
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A dramatic loss of muscle mass due to long-term immobilization of a muscle.
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disuse atrophy
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Structures that make durable end-to-end connections between
the plasma membranes of adjacent fibers in cardiac muscle. |
intercalated discs
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Attaches some of the network of actin thin filaments within the
interior of smooth muscle cells. These bodies are the functional equivalent of the Z disc in striated muscle. |
dense bodies
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Electrical excitation results in the opening of plasma membrane Ca++ channels that induce Ca++ release from the SR.
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elecromechanical route,
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The second messages set in motion by autonomic transmitters
may control release of Ca++ from the intracellular stores without involvement of a change in membrane potential |
pharmacomechanical route
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An enzyme that phosphorylates a portion of the myosin head.
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myosin light-chain kinase (MLCK)
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Removal of the phosphate by an enzyme called ___________ serves as a turn-off pathway that can be initiated by an inhibitory autonomic signal
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myosin light chain phosphatase
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A type of smooth muscle that contains extensive gap junction
connections, making it possible for a large number of neighboring cells to contract simultaneously as if they were one unit. Such muscle is found in the GI tract and in blood vessels. |
single-unit smooth muscle
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Muscle not connected by gap junctions and typically is not
spontaneously active. Such muscle is found in the iris of the eye and in the arrector pili muscles attached to individual hairs. |
multiunit smooth muscle
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