Term
| What is a neuromuscular junction |
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Definition
| a synapse between a motor neuron and muscle fiber |
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Term
| what is a motor end plate |
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Definition
| the portion of muscle fiber membrane that lies just below or next to the terminal button of the motor axon |
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Term
| what happens when an AP is generated in an axon terminal button |
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Definition
| VG Ca channel opens; Ca influx; exocytosis and diffusion of Ach; Ach binds to nicotinic cholinergic receptors; channel opens; Na influx (graded potential); depolarization leads to end plate potential (EPP); VG Na channels open; Na influx; membrane reaches threshold; AP in muscle fiber; Ach degraded |
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Term
| what does Acetylcholinesterase do |
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Definition
| it is an enzyme in the motor end plate membrane that degrades Ach |
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Term
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Definition
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Term
| Microanatomy properties of a skeletal muscle fiber |
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Definition
| each fiber has multiple nuclei; elongated; abundant mitochondria; multiple myofibrils; thin and thick filaments; A band; M line; H-zone; I band; Z line; sarcomere |
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Term
| what is the thin filament also known as |
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Definition
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Term
| what is the thick filament also known as |
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Definition
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Term
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Definition
| dark band; spans length of thick filament; has an H-zone in the center |
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Term
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Definition
| the region of an A band (center) in which there is no overlap with thin filaments |
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Term
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Definition
| it runs down the center of the H-zone; it is a system of proteins that anchors thick filaments |
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Term
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Definition
| it contains the portion of thin filaments that do not overlap with thick filaments |
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Term
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Definition
| it is the area between 2 Z lines; it is also the functional unit of skeletal muscle contraction |
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Term
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Definition
| it is the middle of an I band; protein structure that anchors thin filaments |
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Term
| Microanatomy properties of a skeletal muscle fiber |
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Definition
| each fiber has multiple nuclei; elongated; abundant mitochondria; multiple myofibrils; thin and thick filaments; A band; M line; H-zone; I band; Z line; sarcomere |
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Term
| what is the thin filament also known as |
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Definition
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Term
| what is the thick filament also known as |
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Definition
|
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Term
|
Definition
| dark band; spans length of thick filament; has an H-zone in the center |
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|
Term
|
Definition
| the region of an A band (center) in which there is no overlap with thin filaments |
|
|
Term
|
Definition
| it runs down the center of the H-zone; it is a system of proteins that anchors thick filaments |
|
|
Term
|
Definition
| it contains the portion of thin filaments that do not overlap with thick filaments |
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|
Term
|
Definition
| it is the area between 2 Z lines; it is also the functional unit of skeletal muscle contraction |
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Term
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Definition
| it is the middle of an I band; protein structure that anchors thin filaments |
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Term
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Definition
| it is the PM of muscle fibers |
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Term
| what are transverse-tubules (T-tubules) |
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Definition
| they are invaginations of PM that run through the muscle fiber |
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Term
| What is the sarcoplasmic reticulum |
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Definition
| it is a highly developed and modified ER with terminal cisternas (expanded rgions of SR surrounding the T-tubules) |
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Term
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Definition
| one thick filament composed of multiple myosin molecs; myosin molec composed of 2 subunits with tails intertwined into a helix; heads are the binding site for actin, myosin ATPase site (form myosin cross bridges) |
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Term
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Definition
| actin subunits form into strands that twist into a helix; each actin subunit has a site to bind MCB; contain tropomyosin and troponin |
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Term
| Structure and function of tropomyosin |
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Definition
| threadlike protein; lies alongside groove of actin spiral in relaxed state obscuring MCB binding sites on actin subunits |
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Term
| Structure and function of troponin |
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Definition
| globular protein made up of 3 subunits; when Ca is present in the ICF the Ca binds to troponin which results in a conformational change in troponin uncovering the MCB binding sites on the actin |
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Term
| what do the 3 subunits in troponin bind to |
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Definition
| 1 binds to actin; 1 binds to tropomyosin; 1 binds to Ca ions |
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Term
| What is the sliding filament theory |
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Definition
| thick and thin filaments do not shorten; during contract, thin filaments are pulled towards center of sarcomere; when MCB binds to actin it is in a high energy "cocked" position; once bound the MCB goes from high energy to low energy position; New ATP binds to MCB causing detachment from actin |
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Term
| What happens during excitation/contraction coupling |
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Definition
| generation of AP in muscle fiber; AP spreads along entire sarcolemma (includes T-tubules); causes release of Ca from lateral sacs; Ca binds to troponin changing the conformation; tropomyosin uncovers MCB binding sites on actin; MCB binds to actin |
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Term
| What happens during excitation/contraction coupling |
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Definition
| generation of AP in muscle fiber; AP spreads along entire sarcolemma (includes T-tubules); causes release of Ca from lateral sacs; Ca binds to troponin changing the conformation; tropomyosin uncovers MCB binding sites on actin; MCB binds to actin |
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Term
| What happens during cross bridge cycling |
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Definition
| When MCB is in energized position if Ca is present, MCB binds to actin and performs a powerstroke; a new molecule of ATP binds to myosin ATPase detaching MCB from actin; ATP is split re-energizing MCB into high energy position; if excitation continues (Ca still present) the cycle can repeat |
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Term
| What causes MCB to be in a high energy position |
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Definition
| ADP and P are bound to the MCB |
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Term
| what happens during a powerstroke |
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Definition
| ADP and P are released by the MCB |
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Term
| What occurs during relaxation |
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Definition
| motor neuron stops firing; no Ach released at terminal; EPPs stop; AP stops; stops release of Ca from lateral sacs; SR has active Ca ATPase pumps; Ca no longer binds to troponin; tropomyosin moves back and covers binding sites on actin; thin filaments return to initial position |
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Term
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Definition
| a brief contraction in a single muscle fiber due to one single AP |
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Term
| what is the contraction time |
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Definition
| the onset of contraction until peak tension |
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Term
| what is the relaxation time |
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Definition
| peak tension to complete relaxation |
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Term
| how long is the refractory period for skeletal muscle fibers |
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Definition
| relatively short; possible to generate another AP prior to relaxation |
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Term
| what does the strength of whole muscle contraction depend on |
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Definition
| the number of muscle fibers contracting; amount of tension developed in each contracting fiber; number of muscle fibers contracting |
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Term
| what determines the amount of tension developed in each contracting fiber |
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Definition
| frequency of stimulation; length of fiber; extent of fatigue; thickness of fiber |
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Term
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Definition
| the motor neuron and all the muscle fibers it innervates |
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Term
| what does motor unit recruitment mean |
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Definition
| the strength of contraction increases with increasing number of motor units excited |
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Term
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Definition
| if a second AP occurs prior to relaxation, the twitches can sum to produce a contraction of greater force |
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Term
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Definition
| a smooth, sustained contraction of max force |
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Term
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Definition
| results from rapid stimulation with no relaxation between twitches |
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Term
| what is the optimal length (lo) theoretically |
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Definition
| length at which max tension can be generated if the muscle fiber is stimulated to teanus |
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Term
| what happens if at lengths greater than optimal length |
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Definition
| thin filaments are pulled out from the thick filaments; decreased number of actin sites available for cross-bridge binding |
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Term
| what happens at lengths less than optimal length |
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Definition
| less tension; thin filaments overlap in center of sarcomere; decrease MCB actin binding; ends of thick filaments forced up against z-lines; less Ca is released from lateral sacs |
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Term
| what is the normal length of muscle fibers compared to optimal length |
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Definition
| between 70% and 130% of the optimal length |
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Term
| what determines the thickness of muscle fibers |
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Definition
| the amount of thick and thin filaments |
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Term
| what are the different types of contractions |
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Definition
| Isotonic (concentric, eccentric); Isometric; Concentric |
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Term
| Properties of isotonic contractions |
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Definition
| constant tension; changing length; 25% efficiency doing work |
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Term
| what do concentric contractions do |
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Definition
|
|
Term
| what do eccentric contractions do |
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Definition
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|
Term
| what happens in isometric contractions |
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Definition
| tension develops at constant length (no work is done) |
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Term
| properties of concentric contractions |
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Definition
| inverse relationship (increased load, decreased velocity of shortening) |
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Term
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Definition
| the tension required to overcome the load |
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Term
| What is the role of ATP in muscles |
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Definition
| detachment of MCB from actin; energizes MCB; power the Ca ATPase pump at SR |
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Term
| What are the metabolic sources of ATP |
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Definition
| creatine phospate and ADP which produce ATP and creatine |
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Term
| what is oxidative phosphorylation |
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Definition
| the main source of ATP when oxygen is present and adequately delivered |
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Term
| what is glycolysis role in ATP production |
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Definition
| it is the main source when oxygen is not being adequately delivered; rapid source; consumes a lot of glucose (2ATP/glucose); lactic acid build up |
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Term
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Definition
| the inability of muscles to maintain muscle contractile activity |
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Term
| what occurs during muscle fatigue |
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Definition
| loss of contraction despite maintained stimulus; increase in local P and ADP; possible increase in lactic acid; local accumulation of K ions in ECF (may cause decrease in Ca released in SR); depletion of energy stores |
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Term
| What happens during central fatigue |
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Definition
| CNS no longer stimulates motor neurons that innervate muscle fibers; psychologically based pain,tiredness, boredom; oxygen debt |
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Term
| what occurs during oxygen debt |
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Definition
| excess post-exercise oxygen consumption (increase in elevated resp rate and depth to satisfy oxygen demand); oxygen used to replenish ATP (ATP used to restore creatine and convert lactic acid); nutrient replenishment may be necessary if prolonged activity |
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Term
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Definition
| the storage protein for oxygen |
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Term
| in general how many of the 3 fiber types do most muscles contain |
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Definition
| all 3 (slow-oxidative, fast-oxidative, fast-glycolytic) |
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Term
| what type of fiber is predominant in muscles used for low-intensity but prolonged function |
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Definition
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|
Term
| what types of fiber is predominant in muscles used in burst-like activities |
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Definition
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|
Term
| what does aerobic training require |
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Definition
| maintaining a level of activity that consumes ATP at a rate that oxygen delivery is sufficient to produce ATP aerobically |
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Term
| what increases in muscles as a result of aerobic training |
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Definition
| number of mitochondria in muscle fibers; vasculature; capillaries |
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Term
| what does anaerobic training cause in muscle fibers |
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Definition
| an increase in the number of thick and thin filaments |
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Term
|
Definition
|
|
Term
|
Definition
| when muscles are not used |
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Term
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Definition
| a decrease in muscle mass |
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Term
|
Definition
| when muscles are not used even though nerves are intact |
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Term
| what is denervation atrophy |
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Definition
| when muscles are not used due to nerve loss |
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Term
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Definition
| awareness of body position |
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Term
| properties of muscle spindles |
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Definition
| composed of intrafusal fibers; noncontractile portions; stretched during contraction and can detect changes in muscle length; associated with peripheral endings of afferent neurons |
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|
Term
| properties of golgi tendon organs |
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Definition
| located in tendons; respond to changes in tension; during contraction the tendon is stretched which stimulates impulses in associated afferent fiber |
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Term
| properties of smooth muscle |
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Definition
| not striated; single nucleus |
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|
Term
| properties of multiunit smooth muscle |
|
Definition
| neurogenic; fibers function as separate units independent of nearby muscle cells |
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|
Term
| what does neurogenic mean |
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Definition
| must be stimulated by autonomic nervous system and certain hormones |
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Term
| properties of visceral/single unit muscle |
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Definition
| self excitable and rhythmic; muscle fibers connected by gap junctions; AP impulse can spread to adjacent cells causing entire muscle to contract as a single unit |
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