1. Muscular System Part 2 adapted from www.biologycorner.comwww.biologycorner.com

2. Review

9. Behavioral Properties of Muscle Extensibility: ability to be stretched Elasticity: the ability to return to normal after being stretched Irritability: ability to respond to stimuli (like a nerve impulse) Contractility: ability to shorten

10. Tension and Types of Contractions A contraction is when tension has developed in a muscle Using biceps and triceps and action of flexing as examples Agonist: prime mover Antagonist: opposing muscle group Concentric: when muscle develops tension and shortens; tension in biceps when flexing Eccentric: when muscle develops tension but weight being lifted is too heavy so gravity, not triceps, lengthens biceps Isometric: tension in both agonist and antagonist (biceps and triceps) is equal; no change in muscle length

11. How Muscles Work with the Nervous System NEUROMUSCULAR JUNCTION - where a nerve and muscle fiber come together

12. 1. Neuron 2. Sarcolemma (or motor end plate) 3. Vesicle 4. Synapse 5. Mitochondria Motor Unit or Neuromuscular Junction

13. The neurotransmitter that crosses the gap is ACETYLCHOLINE. This is what activates the muscle. Acetylcholine is stored in vesicles

15. SLIDING FILAMENT THEORY (MODEL) The theory of how muscle contracts is the sliding filament theory. The contraction of a muscle occurs as the thin filament slide past the thick filaments. The sliding filament theory involves five different molecules and calcium ions. The five molecules are: myosin actin tropomyosin troponin ATP

16. ANIMATION OF SLIDING FILAMENT http://www.blackwellpublishing.com/matthews/myosin.html

17. Sarcomere in a relaxed Muscle Cell

18. What will happen to each part of the sarcomere when the muscle contracts?

19. Energy Source -ATP is produced by CELLULAR RESPIRATION which occurs in the mitochondria -Creatine phosphate increases regeneration of ATP * Only 25% of energy produced during cellular respiration is used in metabolic processes - the rest is in the form of HEAT. -maintains body temperature.

20. Terms Acetylcholine: neurotransmitter for skeletal muscle that carries the message to contract across the synaptic cleft. Synaptic vesicles: They are in the axonal terminal and hold the acetylcholine until it is released Calcium ions: Is stored in the sarcoplasmic reticulum. When released it removes the blocking proteins from the actin and myosin so they can slide across each other, causing contraction. Sarcoplasmic reticulum: Stores the calcium ions. Actin and Myosin: are contractile proteins in the muscle cell that slide across each other resulting in muscle contraction

21. 1. Threshold Stimulus Minimal strength required to cause a contraction Motor neuron releases enough acetylcholine to reach threshold 2. All-or-None Response Fibers do not contract partially, they either do or don't

22. 3. Motor Unit The muscle fiber + the motor neuron 4. Recruitment more and more fibers contract as the intensity of the stimulus increases 5. Muscle Tone Sustained contraction of individual fibers, even when muscle is at rest