1. Muscle Physiology
Muscle contractions

2. The Muscle Cell Sarcolemma- plasma membrane
T tubules are inward projections of sarcolemma
Sarcoplasm- cytoplasm
Sarcoplasmic reticulum- similar to ER
Myofibrils-bundles of thick and thin filaments which allow for contraction

3. The Muscle Cell Sarcomere- functional unit of contraction
Z lines attach actin(thin) filaments together
M line attaches myosin(thick) filaments together
A band is section of thick filaments
H zone with out thin filaments
I band area without thick filaments

5. Muscle Cell Contraction
Actin filament are made of actin, troponin and tropomyosin
Myosin filaments have golf club shaped heads that are attracted to active sites in the actin
Tropomyosin-troponin complex block the actin active sites thus preventing contraction.

6. Muscle Cell Contraction
Nerves release acteylcholine at synapse which stimulates the sarcolemma to release Ca++ ions into the sarcoplasm.
Ca++ binds to the troponin and frees up active sites
Myosin heads attach to active sites (forming crossbridges) and pulls actin in causing contraction.
ATP is required to loosen attachment.

7. Muscle Cell Contraction
Motor neurons synapse with muscle cells to form a motor unit
The lower the ratio of nerves fibers to muscle fibers the greater the dexterity of that muscle

8. Muscle Cell Contraction

9. Energy Sources
ATP is neccessary for resetting the myosin heads for contraction.
ATP cannot be stored in large amount, must be synthesized constantly via glucose catabolism
O2 can be stored in small amounts by the protein myoglobin.
O2 is usually the limiting factor in aerobic respiration.

10. Types of Muscle Fibers
Myoglobin gives muscle tissue its dark red color.
Slow twitch fibers have more myoglobin and area called red fibers.
Fatigue very slowly, seen in higher amounts in endurance athletes and in postural muscles.
Fast twitch fibers are called white fibers.
Fatigue quickly, move quickly seen in places like the eye and hand.
Intermediate are a mix between slow & fast.

11. Muscle Tone Hypertrophy Atrophy Endurance
Muscle tone is a result of muscles being in a constant state of contraction.
Flaccid muscles have less than normal tone, spastic muscles too much.
Strength training can cause increase in myofibrils thus increase size.
Aerobic training increases myoglobin content, mitochondria and blood vessels.

12. Isotonic is contraction of muscle with movement.
Isotonic & Isometric
Isotonic is contraction of muscle with movement.
Picking up a book.
Isometric is contraction without movement.
Holding a book up.