Muscle Tissue Flashcards
Functions of muscle tissue - 4
Produce body movement
Stabilize body position
Storing and moving substances within body. Store=sphincter
Generating heat
Types of muscle tissue - 3
Skeletal - move bones, striated, voluntary
Cardiac - pumps blood, striated, involuntary, pacemaker autorhythmicity
Smooth - hollow internal structures, no striations, involuntary, some have autorhythmicity
Properties of muscle tissue - 4
Electrical excitability - action potential, autorhythmic from within muscle, chemical - neurotransmitter
Contractibility - contract when stimulated by action potential
Extensibility - stretch within limits without damage
Elasticity - return to original shape
Muscle proteins 2,2,5
Contractile: myosin, actin
Regulatory (switch contraction process on and off)
Tropomyosin, troponin
Structural (keep thick and thin filaments in alignment, give myofibrils elasticity and extensibility, link myofibrils to sarcolemma)
Titin - connect z disc to m line, elastic
(Alpha)actinin - connect z disc to actin to titin
Myomesin - forms m line
Nebulin - wraps around actin, anchor to z disc
Dystrophin - links actin to sarcolemma to connective tissue
Muscle contraction cycle (4)
Atp hydrolysis to produce adp and phosphate on myosin head
Attachment of myosin to actin to form cross bridges
Power stroke moves thin fibers
Detachment of myosin from actin, myosin binds new atp
Excitation contraction coupling - 5 steps
Muscle action potential along sarcolemma into T tubules
Sarcoplamsic reticulum opens Ca2 release channels
Ca2 flows out of SR onto myofibrils
Ca2 combines with troponin, changes shape, tropomyosin uncovers myosin binding sites on actin.
Myosin heads bind with actin cross bridges, muscle contracts.
Neuromuscular junction terminology
Synapse
Synaptic cleft
Neurotransmitter - acetylcholine ACh is one
Axon terminal, synaptic end bulbs, on motor neuron
Synaptic vesicles
Muscle - motor end plate, ACh receptors, junctional folds
Nerve AP to muscle AP - 4 steps
Release of ACh by electical potential causing Ca2 channel to open, Ca2 to flow in causing synaptic vesicles to do exocytosis.
Activation of ACh receptor - ACh binds with receptors on motor end plate opening ion channel to let Na into muscle cell
Na makes inside more positive, triggering muscle AP
ACh then broken down by acetylcholinesterase
Twitch contraction, latent period
20-200 msec
Latent period 5 msec for AP to propogate, Ca to move out
Refractory period, muscle and nerve
Excitability lost just after excited. 5 msec for muscle.
Wave summation
Second stim before all relaxed produces larger force
Unfused tetanus 20-30 AP per second. Jagged line force.
Fused tetanus 80-100 AP per second solid high force.
Types of skeletal muscle fibers (3)
Slow oxidative SO - lots of myoglobin and mitochondria, so red muscle. ATPAse slow to hydrolyze ATP, slow contraction, slow to fatigue.
Fast oxidative-glycolytic FOG - largest, lots of myoglobin and mitochondria. Fast to hydrolyze ATP. Anaerobic and aerobic.
Fast glycolytic FG - white meat, lots of glycogen, anaerobic. Strong and quick, fast twitch. Fatigue more quickly.
Cardiac muscle
Actin myosin bands zones Z discs like skeletal
Intercalated discs to help spread AP with gap junctions and desmosomes.
Endomysium and perimysium but no epimysium
Ca comes from SR and interstitial fluid
Contractions 10-15 times longer
Autorhythmic instead of ACh.
Lots of mitochondria, aerobic. Can make ATP from lactic acid.
Physiological enlarged heart from exercise.
Smooth muscle types 2
Visceral single unit, one nerve AP spreads through gap junctions
Multiunit, each fiber needs nerve ending.
Smooth muscle anatomy
Filaments thick, thin, intermediate
Caveolae instead of T tubules, contain Ca
Dense bodies instead of Z discs
Contraction causes shortening and twist like helix
