-
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
-
Epimysium
wrap around muscle
-
-
Perimysium
wraps around Fasicles
-
Endomysium
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
-
-
-
Myofibrils
Bundles of actin and myosin filament
-
How actin filaments surround one myosin filament?
6
-
Sarcomeres
1. Repeating units of overlapping actin and myosin filaments
-
each sarcomere is bounded by...
Z lines
-
what anchors actin?
Z lines
-
A band
- 1.Center
- 2.Contains myosin and no actin
-
I band
1.Actin, yet no myosin are present
-
H zone
- where actin and myosin do not overlap
- -myosin but no actin
-
Titin
the largest protein in the body
-
M band
holds the myosin together
-
What is muscle contraction initiated by?
1.Initiated by action potentials from motor neuron at neuromuscular junction
-
Myosin structure
- 1.Two polypeptide chains coiled together
- 2.Globular head
-
Actin structure
- Long twisted molecule
- -tropomyosin twists around it
-
Motor unit
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
-
Myogenic
Heartbeat is myogenic, generated by the heart muscle itself
-
Smooth muscles have electrical contact by...
gap junctions
-
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
-
Twitch
minimum unit of contraction
-
Tension generated by entire muscle depends on:
- • Number of motor units activated
- • Frequency at which motor units are firing
-
Tetanus
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
ATP supply
-
To maintain contraction, actin-myosin bonds have to keep....
cycling
-
ATP is needed to break the
actin-myosin bonds, and“re-cock” the myosin heads
-
Slow-twitch fibers
- 1.Oxidative or red muslce
- 2.Contain myoglobin:oxygen binding protein
-
Slow-twitch fibers
- 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.).
slow-twitch fibers
-
Fast-twitch fibers
- 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
|
|
