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3 types of vertebrate muscle
- 1.Skeletal:voluntary movement
- 2.Cardiac:beating of the heart
- 3.Smooth:Involuntary, movement of internal organs
Skeletal muscle cells are...
- 1.Muscle fibers
- -large and multinucleate
Skeletal muscles form from....
fusion of embryonic myoblasts
wrap around muscle
wraps around Fasicles
wraps the muscle fibers
How does Muscle get activated?
- 1.Brain sends signals to muscles fiber
- 2.Axon of neuron binds to skeletal muscle fibers
Fine motor control
one axon to one muscle fiber
gross motor control
one axon to many muscle fibers
Bundles of actin and myosin filament
How actin filaments surround one myosin filament?
1. Repeating units of overlapping actin and myosin filaments
each sarcomere is bounded by...
what anchors actin?
- 2.Contains myosin and no actin
1.Actin, yet no myosin are present
- where actin and myosin do not overlap
- -myosin but no actin
the largest protein in the body
holds the myosin together
What is muscle contraction initiated by?
1.Initiated by action potentials from motor neuron at neuromuscular junction
- 1.Two polypeptide chains coiled together
- 2.Globular head
- Long twisted molecule
- -tropomyosin twists around it
all the muscle fibers activated by one motor neuron
To increase strength of muscle contraction....
- 1.Increase rate of firing of motor neuron
- 2.Recruit more motor neurons to fire
what blocks the binding sites on actin?
at rest, tropomyosin blocks the binding sites on actin
Steps of muscle contraction
- 1.Neuron action potential arrives at end of motor neuron
- 2. ACH is released
- 3. ACh binds to receptors on motor end plate
- 4.Permeability of sarcolemma changes (Na rushes in)(an action potential is produced)
- 5.Muscle action potential sweeps into the T tubules
- 6. triggering release of Ca from the sarcoplasmic reticulum
- 7.CA binds to troponin
- 8.Troponin changes shape and shifts tropomyosin to expose binding sites of actin
- 9. myosin binds to actin (ADP released from myosin)
- 10. Myosin head pivots (pulling actin)
- 11. Myosin releases from actin
- 12. Myosin re-extends (ATP---ADP)
what cells initiate and coordinate heart contractions>
Pacemaker and conducting cells
Heartbeat is myogenic, generated by the heart muscle itself
Smooth muscles have electrical contact by...
Smooth muscle contraction
- 1.Ca2+ influx tp sarcoplasm, stimulated by stretching
- 2.Ca2+ binds with calmodulin
- 3.Activates myosin kinases, which phosphorylates myosin heads
- 4.Bind and release actin
minimum unit of contraction
Tension generated by entire muscle depends on:
- • Number of motor units activated
- • Frequency at which motor units are firing
action potentials arrive so rapidly that the sarcoplasmic reticulum does not have time to reclaim the calcium ions.
How long muscle fiber can sustain tetanic contraction depends on
To maintain contraction, actin-myosin bonds have to keep....
ATP is needed to break the
actin-myosin bonds, and“re-cock” the myosin heads
- 1.Oxidative or red muslce
- 2.Contain myoglobin:oxygen binding protein
- 1.Have reserves of glycogen and fat
- 2.Can produce ATP if oxygen is available
muscles with high proportions of ______ are good for aerobic workout (e.g., long distance running, cycling, swimming, etc.).
- 1.Glycolytic or white muscle
- 2.Fewer mitochondria, few blood vessels
- 3. Good for sprints, fatigue quickly
- 4.Largely genetic
Muscles have three systems for supplying ATP for contractions:
- 1.immediate system: uses preformed ATP and creatine phosphate
- 2.Glycolytic system: metabolizes carbohydrates to lactic acid and pyruvate
- 3.Oxidative system: metabolizes carbohydrates or fats to H2O and CO2