2. Neuron

3. Motor Unit Is one motor neuron and all muscle fibers its branches innervate. Delicate control - a few muscle fibers per motor unit. Stimulates 6 to ___ fibers.Eye Gross movement have over ______ muscle fibers per unit. All fibers in a motor unit contract when stimulated with a threshold stimulus.

4. NEUROMUSCULAR JUNCTION  ____ -the junction between a motor neuron ending and a muscle fiber.  Composed of a motor neuron, and muscle fiber.  Has a motor end plate.  Motor end plate is the junction between the muscle fiber and the axon terminals.

6. Nerve Action 1. Action potential moves down the axon 2. Increase in _____causes acetylecholine to be released. 3.Acetylecholine moves synaptic gap 4.Acetylecholine reaches motor end plate 5.Acetylecholine _______ with receptors

8. Nerve Action 6. Repolarized 7. Acetylecholine to _______ 8. Acetylecholine is broken down to A_____ and C______. 9. Ready again to receive an impulse.

9. Single Muscle Contraction 3 phases  Latent period  Contraction period  Relaxation period  Followed by recovery(refractory period)

10. ISOTONIC Equal + tension Force used to produce work and work is ______. Object moves and muscle shortens

11. Isometric Muscle produces heat but _______work is done Muscle does not shortens Examples  Standing  Holding a door

12. Oxygen Debt A_____ of extra oxygen needed to metabolize the accumulated lactic acid and restore normal ______ levels.

13. Fatigue Lactic acid builds up and makes the muscle to feel _________. Body needs oxygen to change lactic acid into carbon dioxide and water.

14. Aerobic With ________ Pyruvic acid + oxygen = CO2 + H2O + _________.

15. Anaerobic Without oxygen Pyruvic Acid is changed to lactic acid.

16. Contraction speed Classified:  Fast-twitch (type II fiber)  Slow-twitch (type I fibers)

17. Fast-twitch Relaxation cycle is about 30msc More mitochondrea than slow-twitch Pale in color - _______ muscle Fast quick movement Example  Eye - Hand  Sprinter

18. Slow-twitch Relaxation cycle is about 3000msc Fewer mitochondrea than fast-twitch _______ Muscle Prolonged, steady contractions Example  Back muscle  Long distance runners

19. Smooth Muscle Appear smooth Involuntary muscles Contract and relation periods are slower than skeletal muscle Action is ____________ Contraction may last ____ sec or longer Examples - stomach, intestine, bladder, uterus during child birth.

20. Smooth Muscle Poorly organized sarcoplasmic reticulum NO Z line or T tubules Types  Single unit - sphincters, pacemaker cells  Multiunit - iris of eye, goose bumps

21. Cardiac Muscle Found only in the __________! Huge #’s of mitochondrea Well developed sarcoplasmic reticulum and T tubules Intercalated disk Refractory period is ______msc, almost as long as the contraction

22. Cardiac Muscle Never stops beating in a life time ____________beats a day At 70 years old your heat would have pumped 2.5 billion times. If oxygen is deprived _____ sec, cardiac muscle cells may stop contracting, resulting in heart failure.

23. When things Go WRONG! Muscle injuries Skeletal muscle - satellite cells under the endomysium cause cell division. Smooth muscle - causes the proliferation of cells. Pregnancy enlarging of uterus. Cardiac muscle - childhood can regenerate but in adults is replaced by connective tissue.