somatic motor division
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| Neurotransmitter/receptor at neuron-target synapse | ACh/nicotinic
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| target tissue | skeletal muscle
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| structure of axon terminals | boutons like a round button
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| effects on target tissue | excitatory only: muscle contracts
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| peripheral components found outside the CNS | axons only
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| function of somatic division | skeletal movement
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| neuromuscular junction | synapse of a somatic motor neuron on a muscle fiber
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| the neuron orginates | CNS
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| location of ACh neurotransmitter of a somatic motor neuron | somatic vessels in the mitochondria
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| ACh receptors/nicotinic | chemically gated ion channels with two binding sites for ACh. Net Na+ entry into the muscle fiber depolarizes it, triggering an action potential that causes contraction of the skeletal muscle cell
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| location of nicotinic receptors | skeletal muscle membrane
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| number of binding sites for ACh on nicotinic receptors | 2
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| 3 components of the neuromuscular junction | motor neuron's presynaptic axon terminal filled w/ synaptic vesicles and mitochondria, the synaptic cleft, and the post synaptic membrane of the skeletal muscle fiber
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| motor end plate | a region of muscle membrane that contains high concentrations of ACh receptors
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| acetylcholinesterase: AChe | the enzyme that rapidly deactivates ACh by degrading it into acetyl and choline
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| skeletal muscles are attached to bones by? | tendons
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| origin of muscle | end of the muscle that is attached closest to the stationary bone
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| insertion of muscle | is the more distal or mobile attachment
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| joint | attaches the bone to the muscle
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| flexor | when the bones come closer together when the muscle contracts
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| extensor | when bones move farther away from each other when the muscle contracts
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| antagonistic muscle groups | flexor-extensor pairs
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| the three types of muscle tissue | smooth, skeletal, and cardiac
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| striated muscles | skeletal and cardiac
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| cardiac muscle | found only in the heart and moves blood flow
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| smooth muscle | primary muscle of internal organs and tubes such as the stomach or urinary bladder
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| involuntary muscles | smooth and cardiac
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| voluntary muscle | skeletal
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| motor unit | groups of muscle fibers that function and the motor neuron that controls them
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| the largest cells in the body | skeletal muscle fibers
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| sarcolemma | cell membrane
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| sarcoplasm | cytoplasm
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| myofibrils | main intracellular structures
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| sarcoplasmic reticulum | like endoplasmic reticulum
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| terminal cisternae | concentrate and sequester Ca2+
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| transverse tubules | the membranes of the t-tubules, are a continuation of the4 muscle fiber membrane. The lumen of the tubules are continuous with the extracellular fluid.
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| triad | one t-tubule with its flanking terminal cisternae
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| myosin | thick filaments
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| actin | thin filaments
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| crossbridges | myosin heads that loosely bind to the actin filaments
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| z disks | zigzag structures are made of proteins that serve as the attachment site for thin filaments. 2 z disks per sacromere
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| I bands | thin filaments
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| A bands | thick and thin filaments
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| H zone | part of a band that only has thick filaments
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| M line | goes through the middle of the A band; holds thick filaments only
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| titin | largest protein in the body
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| nebulin | an inelastic giant protein that lies by thin filaments and attaches to the z-disks. Helps align the actin filaments of the sacromere
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| muscle tension | the force created by the contracting muscles
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| load | weight or force that opposes the contracting muscle
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| events at the neuromuscular junction | converts a chemical signal from a somatic motor neuron into a electrical signal in the muscle fiber
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| Excitation-contraction coupling | process in which muscle action potentials initiate calcium signals. The calcium signals then activate the contraction-relaxation cycle.
1)somatic motor neuron releases ACh at neuromuscular junction 2)net entry of Na+ through ACh receptorchannel initiate
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| con't | a muscle action potential. 3)action potential in t-tubules alters conformation of DHP receptor. 4)DHP receptor opens Ca2+ release channels in SR and Ca2+ enters cytoplasm. 5)Ca2+ binds to troponin, allows strong actin myosin binding6powerstroke.7)AF slide
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| sliding filament theory | overlapping muscle fibers of thick and thin filaments of fixed length slide past each other in an energy requiring process, resulting in muscle contraction
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| muscle in relaxed state | a sacromere has a large I band and an A band that have the same length
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| when a muscle contracts | the sacromere shortens, the two z disks at each end move closer together while the I bands and the H zone almost disappear
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| what are the two binding sites on myosin | one for ATP molecule and one for actin
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| power stroke | movement of the flexible myosin crossbridges pushes actin filaments toward the center of the sacromere. At the end of the power stroke, the myosin head releases its bound actin, then swings back a binds to another actin molecule
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| in a muscle fiber what causes movement of the myosin molecules? | the energy from ATP
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| myosin; a motor protein | converts the chemicalbond energy then becomes the powerstroke that moves actin
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| "red muscle" | slow twitch fibers, has large amounts of myoglobin, a red oxygen-binding pigment
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| "white muscle" | fast twitch muscles, has a lower myoglobin content
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| charateristics of muscle fiber types | slowtwitch oxidative redmuscle
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| metabolism | oxidative;p aerobic has large mitochondria / glycolytic but becomes moreoxidative with endurance training / glycolytic; more anaerobic
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| color | dark red / red / pale
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| phosphocreatine | back up energy source created from creatine and ATP when muscles are at rest
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| musle fatigue | condition in which a muscle can not generate or sustainthe expected power output
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| central fatigue | a rise in the central nervous system, feelings of tiredness and wanting to quit an activiity
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| peripheral fatigue | anywhere between the neuromuscular junction and the contractile elements of the muscle
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| muscle fatigue; theories, inorganic phosphate | elevated inorganic phosphate may slow Pi release from myosin and alter the power stroke. A new theory suggests that elevated phosphate decreases Ca2+ release because the phosphate combines with Ca2+ to become calcium phosphate
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| Potassium K+ can cause fatigues during exercise | during maximal exercise K+ leaves the cell with each action potential, and K+ concentrations increase in extracellular fluid of t0tubules, it is believed to decrease Ca2+ release from SR
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| summation in muscle fibers | it means that the force of the fiber increases with repeated acion potentials
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| recruitment | force of a contraction can be increased in skeletal muscle by recruiting additional motor units
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| motor unit | (blank)
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| temporal summation in neurons | graded potentials increase
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| tetanus | maximal contraction of a muscle
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| incomplete or unfused tetanus | the stimulation rate of muscle fiber is slower, and the fiber relaxes slightly b/w stimuli
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| complete or fused tetanus | stimulation rate is fast enough that the muscle fiber does not have time to relax
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