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what are the layers of connective tissue?
epimysium, perimysium, endomysium
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what are the 4 functions of connective tissue?
- 1. perimysium provides a conduit for blood vessels and nerves
- 2. resist passive stretching
- 3. distribution of contractile forces
- 4. elasticity enables the muscle belly to regain shape when forces are removed
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where is most of the calcium stored?
terminal cisternae
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satellite cells are responsible for what?
replacing damaged fiber/muscle
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what are myotubes?
immature muscle fibers
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what is proliferation?
satellite cells are activated resulting in the formation of myoblasts
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what is differentiation?
myoblasts fuse together to form a multi-nucleated cell type called a myotube
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what is maturation?
myotubes grow to form myofiber
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what are the stages of myogenesis?
satellite cells - proliferation - myoblasts - differentiation - myotubes - maturation - myofibers
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name 3 cytoskeletal proteins
contractile (actin and myosin), regulatory (troponin and tropomyosin) and structural
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where are troponin and tropomyosin found?
actin (thin filament)
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what are the 4 functions of exosarcomeric proteins?
- 1. link sarcomeres to the sarcolemma
- 2. transmission of contractile force to the sarcolemma
- 3. spatial arrangement of the myofibrils
- 4. anchor for organelles
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what is dystrophin?
cytoseletal filaments that cross together combined with actin and spectrin
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what is the function of endosarcomeric proteins?
- 1. transmission of contractile forces to the Z lines
- 2. spatial arrangement of the actin and myosin filaments
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what are considered endosarcomeric proteins?
nebulin (helps align actin), titin (provides elasticity and stability to myosin expanding from one Z disk to the M line)
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explain the steps to a power stroke
- 1. myosin head engergized before attaching to actin
- 2. cross bridge to actin
- 3. releasing of Pi causes change in myosin
- 4. power stroke causes fliaments to slide, ADP is released
- 5. new binding of ATP to myosin allows the release of actin
- 6. ATP is hydrolyzed causing cross bridge to return to its original orientation
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what provides the energy for cross bridge formation?
hydrolysis of ATP
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what does calcium do for the myosin?
exposes the binding site by binding to the troponin complex
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2 types of ion channels and what they respond to
- 1. voltage - membrane potentials
- 2. chemically - neurotransmitters
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where are voltage ion channels found?
axon of motor neurons and sarcolemma
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where are chemically regualted ion chennels found?
dendrite and motor end plate
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what is the axon hillock?
region of a neuron capable of generating an action potential
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how does the action potential travel?
always from axon hillock to axon terminal
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what is a refractory period?
degree of readiness of an axon to generate an action potential
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what is absolute refractory period?
portion is incapable of generating an action potential
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what is relative refractory period?
portion is capable of generating an action potential provided that the stimulus is strong enough
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what part of the motor neuron is exposed to extracellular fluid?
the axon at the node of ranvier
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what are the components of the neuromuscular junction?
axon terminal, synaptic cleft, motor end plate
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what happens to ACH at a NMJ?
released from axon terminal, binds to receptor on motor end plate resulting in entry of Na, then degraded by acetylcnolinesterase which is found on the endomyosium
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T-tubules contain what receptor?
dihydropyridine (DHP)
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what is the channel called that is connected from the T-tubule to the SR?
ryanodine channel
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when Ca is released from the ryanodine channel, what happens?
power stroke
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type 1 muscle fiber
slow twitch
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type 2a muscle fiber
fast twitch (anaerobic/aerobic)
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type 2b muscle fiber
fast twitch (anaerobic)
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small motor unit innervates what muscle fiber?
type 1
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fast fatigue resistant innervates what muscle fiber?
type 2a
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fast fatigable innervates what muscle fiber?
type 2b
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what muscle type has a high glycogen content?
type 2b
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why are there differences in twitch contraction times?
motor neuron conduction velocity, myosin ATPase activity
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which muscle fiber generates the fastest twitch tension? why?
type 1 - smaller motor units
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what are the anaerobic capacity differences in the fatigue index?
creatine phosphate and glycolytic enzymes activity
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what are the aerobic capacity differences in the fatigue index?
oxidative enzymes, myoglobin content, number of mitochondria, capillaries
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