1. Do Now • What happens when you work out within your muscles? (Think back to Bio and the topic of cellular respiration!)

2. Muscular responses

3. objectives • To explain what happens during muscular fatigue • To identify different muscular responses • To label and explain the different stages of contraction

4. Muscle fatigue • Cells undergo both aerobic and anaerobic respiration too supply ample atp (lactic acid fermentation) • Lactic acid creates an oxygen debt because the liver cells must now use oxygen to break down the lactic acid (can take several hours) • Lactic acid lowers the ph, which diminishes the muscle fibers response to stimulation • More exercise = more glycolytic enzymes = increased capacity for glycolysis= increased capacity for aerobic respiration!! … start working out 

5. Muscle contraction • A muscle fiber will contract after threshold stimulus has been reached. • Once stimulated, the entire fiber completely contracts which is called the all-or-none response. • *the extent of shortening depends on resistance.

6. myogram • Twitch= single muscle contraction • Latent period: time between stimulation and response • Period of contraction: muscle is contracted • Relaxation: fiber returns to former length

7. Hypertrophy vs. atrophy • Hypertrophy- muscles respond to exercise and enlarge • Slow twitch fibers activated by low intensity exercise such as swimming or running, develop more mitochondria and capillaries, prolonging fatigue • Fast twitch fibers activated by weight lifting can produce new myofilaments & enlarge the muscle (they are still fatigable) • Atrophy- when regular exercise stops, capillary networks shrink, mitochondria decrease, actin & myosin decrease, and muscle shrinks.

8. Types of graphs • Twitch- full contraction • Summation- force of each twitch combines Incomplete tetanus- minimal amt. of relaxation after each stimulus • Complete tetanus- no relaxation, continuous calcium ion deposit

9. tetanus • Caused by Clostridium bacteria present in soil • Bacteria produces a neurotoxin which blocks the release of inhibitory neurotransmitters.

10. Isometric vs. isotonic • Isometric- no change in muscle length • Isotonic- muscle length changes