1. Alpha motoneuron

2. AN ACTION POTENTIAL

3. Neuromuscular Junction

4. Skeletal Muscle Macrostructure

5. Sarcoplasmic Reticulum and T-Tubule System

6. Skeletal Muscle Microstructure

7. ARRANGEMENT OF FILAMENTS IN A SARCOMERE

8. AN ACTIN FILAMENT Filamentous actin-entire strand
Globular actin- each globule
Tropomyosin situated in a groove along the actin
Troponin situated each seventh G-actin

9. EVENTS LEADING TO MUSCLE ACTION

10. CONTRACTING MUSCLE FIBER

11. Each crossbridge moves independently of the other crossbridges
At any given moment during contraction, typically 50% of myosin is attached to actin

12. Architectural Factors and Force Development
Muscle fibers in series mean increased velocity w/ lower force
Pennate arrangement means increased maximal force due to increased x sectional area w/ decreased max velocity

13. FORCE-VELOCITY RELATIONSHIP
The less force applied, the quicker the shortening when stimulated until there is no movement (maximal isometric tension).
More and more force is required to increase the velocity of eccentric contraction, as a greater amount of force is necessary to detach cross-bridges during muscle lengthening.

14. Motor Unit Recruitment Patterns
Number (AND SIZE‚ of motor units stimulated affects force production
Patterns are additive, not sequential

15. Proprioceptors

16. Muscle Spindles Parallel to muscle fibers
Larger concentration in muscles involving complex movements
Important for maintaining posture
Respond to stretch by initiating reflexive contraction (stretch reflex)
Example: Patellar tendon stretch

17. Golgi Tendon Organs High threshold
Function to protect the muscle and connective tissue from injury
Are stimulated with excessive tension during muscle shortening or when the muscle is stretched passively
Cause a reflex inhibition of the muscle