Muscular system anna edited Flashcards
Entire muscle
Wrapped in epimysium
Runs from origin to insertion
Made of many fascicles
Fascicles
Bundles of muscle fibers
Wrapped in perimysium
Muscle fibers
- Individual muscle cells made of myofibrils
- Wrapped in endomysium
- multinucleated
Sarcolemma
Excitable plasma membrane
Responds to electrical stimulus
Membrane proteins that
conduct ions
T-tubules that extend deep into cell
Triad
contains t-tubule and 2 terminal cisternae of the SR
Tendon
Extension of mysiums
Attaches muscle to bone
myoblast
creates muscle cells
Sarcoplasm
typical organelles + contractile proteins
Terminal cisternae
large chambers in the SR that store calcium ions and release them to cause muscle contraction
Sarcomere
basic unit of contractile muscle, composed of protein filaments actin and myosin
Myofilaments
Contractile proteins within myofibrils
myosin and actin
tropomyosin and troponin
actin
thin filaments
myosin binding sites
myosin
thick filaments
myosin heads
I band
Light regions of actin
A band
Dark regions of myosin
Z discs
- Hold sarcomeres together
- sarcomere boundrie
Neuromuscular Junction
a synaptic connection between the terminal end of a motor nerve and a muscle. It is the site for the transmission of action potential from nerve to the muscle.
resting membrane potential
-90mV
ECF positively charged, ICF negatively charged maintained by sodium-potassium pumps
Neural Control of Skeletal Muscle
-Neuron fires
-Calcium channels on synaptic knob open
-Influx of calcium causes Ach to be released
-ACh diffuses across synaptic cleft
-ACh binds to receptors at motor end plate of sarcolemma
Depolarization
- ACh triggers action potential along sarcolemma and t-tubules
- sodium gates open
- Sodium rushes into the muscle cell
- ICF becomes less negative (≤+30mV)
Excitation-Contraction Coupling
- Action potential reaches triad
- calcium channels and calcium-release channels of SR open
- Calcium diffuses throughout muscle fiber.
Sarcomere Crossbridge Cycling
- calcium binds to tropoin
- tropoin and tropomyosin shift off binding site of actin, exposing binding site. Myosin heads attach to binding sites of actin forming crossbridge.
1. Crossbridge formation
2. Power stroke
3. Release
4. Reset
5. Cycling continues if calcium and ATP are available
Repolarization
Sodium gates close
Potassium gates open (potassium rushes out of cell)
returns to -90mV
Skeletal muscle contraction order
resting
motor neuron fires and releases ACh
ACh triggers motor end plate of sarcolemma
Depolarization
Excitation-contraction Coupling
Crossbridge cycling
Repolarization
Refractory period
Skeletal Muscle Relaxation
- Termination of nerve signal and ACh release; hydrolysis of residual ACh by acetylcholinesterase.
- ACh receptors close; cessation of motor end plate potential.
- No further action potential generated.
- Closure of SR calcium channels and calcium release channels.
- Return of calcium to SR via pumps.
- Return of troponin and tropomyosin to original position, blocking actin’s binding sites.
- Return of muscle to original length.
Tetanus
- Spastic paralysis caused by toxin found in soil and feces
- Results in overstimulation of muscles
- Vaccination prevents symptoms
Botulism
- Muscular paralysis
- Prevents release of ACh
- Recovery in 90% of cases
Creatine phosphate
Phosphate group is transferred to ADP to form ATP
Anaerobic, occurs in cytosol
lasts for about 30 seconds
Glycolysis
Breakdown of glucose by enzymes, releasing energy and pyruvic acid
Anaerobic
Fast; yields 2 ATP molecules/glucose molecule
Aerobic Respiration
Slower; yields 32 ATP molecules/glucose molecule
- uses oxygen
Oxygen debt
Amount of oxygen needed after exercise to restore pre-exercise conditions
Muscle Fiber Type I
Slow-twitch oxidative fibers
High endurance; ATP supplied aerobically
Red due to myoglobin
Muscle Fiber Type IIA
“Intermediate”; aerobic/glycolytic
Faster, fatigue more quickly
Light red; some myoglobin
Muscle Fiber Type IIB
Fast-twitch glycolytic fibers
Fastest, fatigue quickest
White due to lack of myoglobin
