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Definition
| Can be determined by subtracting the predetermined passive tension curve from the total tension curve. |
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Definition
| Rapid, brief (several msec in duration) changes in the membrane potential of a neuron or muscle cell. |
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Definition
| Muscles that are responsible for a particular movement. |
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Definition
| Each skeletal muscle fiber either contracts maximally or not at all. |
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Term
| Absolute refractory period |
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Definition
| Early in the refractory period a period restimulation is effectively impossible. |
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Definition
| The thin polymerized filaments in the contractile machinery of all muscle. |
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Definition
| When acetylcholine interacts with receptors on the muscle fiber, an action potential is initiated in the muscle fiber membrane. |
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Definition
| Attaches thin filaments to Z disc and determines their spacing. |
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Definition
| The enzyme that catalyzes the transfer of phosphate groups from CrP to ADP and from ATP to Cr. |
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Definition
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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 this. |
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Definition
| Actin and myosin, protein components of the sarcomere. |
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Definition
| The parts of the voltage sensors that face the interior of the cell make a close connection with the second component of the endfeet, the Ca++ release channels in the membrane of the sarcoplasmic reticulum. In the unexcited state the voltage sensors block block them. Excitation causes the voltage sensors to unblock them, releasing Ca++ into the surrounding myofibrils. |
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Definition
| 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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Definition
| Consists of thin filaments composed of polymerized actin and thick filaments composed of aggregations of myosin. |
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Definition
| Attachments made by myosin heads to actin binding sites that generate force during muscle contraction. |
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Definition
| 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. |
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Definition
| Bundles of fibers enclosed in connective tissue sheaths of perimysium. |
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Definition
| A covering that surrounds all of the fascicles. |
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Definition
| Skeletal muscle fibers. This type of muscle expresses a myosin that cycles rapidly. |
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Definition
| A dramatic loss of muscle mass due to long-term immobilization of a muscle. |
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Term
| Excitation-contraction coupling |
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Definition
| A process that will result in a detectable mechanical response of the muscle, as the action potential sweeps across the muscle cell surface. |
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Definition
| 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. |
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Definition
| A layer of connective tissue that wraps each individual muscle fiber. |
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Definition
| Structures that make durable end-to-end connections between the plasma membranes of adjacent fibers in cardiac muscle. |
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Definition
| The muscle is allowed to shorten and lift a load. |
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Definition
| With conditioning skeletal muscles undergo adaptive changes that are visible mainly as an increase in the size of the cells. |
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Definition
| The curve shows that the active tension is maximal when the muscle is near its rest length. |
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Definition
| The muscle is not allowed to shorten, although tension does develop in the muscle. |
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Definition
| A measurable delay between muscle excitation and the onset of tension development or shortening in the muscle. |
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Term
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Definition
| An increase in the number of muscle cells. |
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Term
| Graded strength principle |
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Definition
| 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 all-or-nothing rule. |
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Definition
| Leverage allowing a strong force to move a light load rapidly through distance. |
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Definition
| Leverage using a small force operating over a large distance to move a heavy load a short distance. |
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Term
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Definition
| 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. |
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Term
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Definition
| Effort length of effort arm = load length of load arm. |
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Definition
| A motor neuron, together with its muscle fibers. |
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Definition
| Formed by T tubules lying between two terminal cisternae. |
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Definition
| Protein component of the sarcomere. Aggregations of thick filaments in the contractile machinery of all muscle. |
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Term
| Myosin light-chain kinase (MLCK |
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Definition
| An enzyme that phosphorylates a portion of the myosin head. |
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Definition
| The connection between a motor neuron and a skeletal muscle fiber. |
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Definition
| 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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Definition
| An intracellular oxygen carrier. |
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Definition
| Structural proteins associated with thin filaments; serves as a molecular yardstick that limits the length of thin filaments. |
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Definition
| Contained within heart muscle that are spontaneously active and can serve as pacemakers for the entire heart. |
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Term
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Definition
| Each fiber contains a number of parallel structures that constitute the actual contractile machinery of the fiber. Each is composed of a highly orderly arrangement of macromolecular filaments organized in repeating units called sarcomeres. |
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Definition
| 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. |
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Term
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Definition
| The curve of passive tension of a muscle has a value of zero at rest length and rises as the length is made greater than rest length. |
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Term
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Definition
| The optimal range of contractile performance created by the leverage arrangements imposed by the skeleton that restricts muscle lengths. |
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Term
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Definition
| Some heart muscle fibers that are spontaneously active. |
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Definition
| Slowly fatiguing Type IIa fibers that contain some myoglobin. |
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Term
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Definition
| 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. |
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Term
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Definition
| 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. |
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Term
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Definition
| The less movable attachment of a muscle. |
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Term
| Relative refractory period |
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Definition
| A period during which it is more difficult to restimulate the muscle. |
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Term
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Definition
| Follows each action potential. |
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Term
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Definition
| Skeletal muscles that are removed from the body assume a standard length. |
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Definition
| Type I fibers that are a red color due to myoglobin. |
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Definition
| 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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Term
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Definition
| A rotation of the head that applies force to the thin filament. |
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Term
| Sarcoplasmic reticulum (SR) |
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Definition
| The site within the cell where Ca++ is stored. |
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Term
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Definition
| The basic functional unit of the contractile machinery of striated muscle. |
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Term
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Definition
| Skeletal muscle fibers. Expresses a myosin that cycles slowly. |
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Term
| Single-unit smooth muscle |
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Definition
| 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. |
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Term
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Definition
| One of three types of muscle, these muscles are attached to the skeleton and controlled by the somatic motor branch of the nervous system. |
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Term
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Definition
| Stretch components that are part of the contractile machinery. |
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Term
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Definition
| The branch of motor system that controls skeletal muscle. |
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Term
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Definition
| 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. |
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Term
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Definition
| Involuntary contractions of skeletal muscles initiated when the core body temperature falls below its central setpoint, resulting in an increase in heat production. |
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Term
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Definition
| 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. |
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Term
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Definition
| 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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Term
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Definition
| Double strands of polymerized actin. |
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Term
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Definition
| A protein component of sarcomeres, consisting of nebulin, titin, CapZ, and alpha actinin. |
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Term
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Definition
| 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. |
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Term
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Definition
| Muscle that has a striped appearance due to being tightly organized sarcomeres, as in skeletal muscle and cardiac muscle. |
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Term
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Definition
| 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 |
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Term
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Definition
| A vessel formed by the SR, near the Z disc of each sarcomere. |
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Term
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Definition
| A smooth rise in muscle tension or decrease in length resulting from the further reduction of the interval between successive impulses. |
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Term
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Definition
| Rapidly fatiguing Type IIb fibers contain some myoglobin. |
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Term
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Definition
| The protein components of the endfeet that sense the action potential passing along the T tubule. |
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Term
| Transverse tubules (T Tubules) |
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Definition
| Finger-like projections of plasma membrane that project into the interior of the muscle fiber and pass close to each terminal cisterna. |
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Term
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Definition
| Part of the contractile machinery of the muscle to which thin filaments are attached. |
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