1. Muscles & Motion

2. Evolution of Movement 1) epitheliomuscular cells in Cnidarians
epithelial cells w/ contractile protein arrays
(actin & myosin)
2) epitheliomuscular
cells sank below
surface into
connective tissues
and became muscle

3. Vertebrate Skeletal Muscle
Bundles of muscle cells fuse together inside a covering of connective tissue
Bundles of fused muscle cells form muiltinucleate muscle fibers
The connective tissue covering extends past the muscle fibers to attach to bones = tendons

5. Neuromuscular Junctions
CNS sends action potential down motor neuron
Synaptic Vesicles release Ach (acetylcholine)
Ach diffuses across synapse
Ach binds membrane receptors & trigger action potential that spreads through muscle fiber along T-tubules
T-tubules are in-foldings of cell membrane
(signaling molecule/ cell communication essay topic)

7. Sarcoplasmic Reticulum (SR)
Action Potential in T-tubule activates SR
1. SR releases Ca+ into muscle fiber
2. Ca+ binds to
Troponin
3. Troponin moves
Tropomyosin
4. Muscle contracts

8. Lack of Action Potential
Sarcoplasmic Reticulum actively uptakes Ca+
Low Ca+ levels in muscle fiber makes
Tropomyosin block myosin binding sites
Muscles relax

10. Sarcomeres: myofibril subunits
Joined at borders called Z line

12. Sarcomeres: myofibril subunits
Each myofibril is made of many sarcomeres
Sarcomeres contain
Thick Myosin in the middle
Thin Actin attached to Z line

14. Regulatory Proteins Tropomyosin – blocks myosin binding sites on actin
Troponin complex – move tropomyosin out of the way so myosin can bind to the actin ….activated by Ca

15. Myosin heads primed by ATP

16. Binding site blocked by tropomyocin
Ca bonding to troponin Δ its shape
Δ troponin moves tropomyocin out of
binding site
Myosin binds
to actin

18. Myosin releases ADP and P and bends toward center of sarcomere
Actin pulled toward center
ATP binds myosin & resets myosin head