MUSCULAR SYSTEM NOTES

 Byproduct is lactic acid  Occurs when muscle cells have used all the oxygen available to them (muscles bulge during intense exercise which compresses blood vessels)  Pathway is glycolysis  lactic acid fermentation  Uses large amounts of glucose to produce small amounts of ATP  Lactic acid buildup in cells leads to muscle soreness ANAEROBIC METABOLISM

 95% of energy during rest/light muscle activity comes from aerobic metabolism  Provides 38 ATP total from 1 glucose molecule  Slow process compared to anaerobic metabolism AEROBIC METABOLISM

 Physiological inability to contract despite still receiving stimulus  Different than psychological/central fatigue (flesh able, but we are wimps)  Depleted levels of ATP lead to contractures (state of continuous contraction)  Cross bridge unable to detach without ATP available  Rigor mortis  Accumulation of lactic acid leads to fatigue (changes shape of contractile proteins)  Ion imbalances (K+ accumulates in T tubules) MUSCLE FATIGUE

 Defined as the extra amount of oxygen that the body must take in for the body to replenish its supplies  Body must convert lactic acid to pyruvic acid, ATP must be resynthesized, glycogen stores replenished OXYGEN DEBT

 Major function of muscular system  Comes from muscle contraction (friction) as actin and myosin move across one another  40% of energy released from ATP is converted to work energy  Remaining 60% is released as heat energy  To compare, only about 15% of energy in gasoline is used to move the vehicle, other 85% is released as heat and sound  Shivering causes quick contractions of the muscle fibers, creates large amounts of heat while using minimal energy HEAT PRODUCTION

 Slow twitch  Fast twitch  Main difference is in the speed of ATPase (enzyme that breaks down ATP during muscle contraction) TYPES OF MUSCLE FIBERS

 Contracts relatively slowly (slow ATPase)  Depends on oxygen delivery (functions through aerobic processes)  Fatigue resistant (high endurance)  Fibers are thin  Small amount of contractile power (limited myofibrils)  Multiple mitochondria  Lots of capillaries  Very red SLOW TWITCH FIBERS

 Contracts rapidly  Depends on glycogen reserves  Fewer mitochondria  Low capillary density  White color  Very dense and large compared to slow twitch fibers  Prone to fatigue quickly  Very powerful contractions for short times FAST TWITCH FIBERS

 Fast twitch are used in short spurts (sprinting)  Slow twitch are used in longer exercises (running a mile)  Light meat vs dark meat  Muscles that maintain posture (erectors) have slow twitch fibers, while muscles that are used for propelling (quads, gastrocnemius) are fast twitch fibers  All muscles have a mixture of slow and fast fibers, but are usually predispositioned towards one or the other SLOW TWITCH VS FAST TWITCH

 Aerobic exercise leads to muscles working longer before becoming fatigued  More mitochondria are formed in each cell  More capillaries surround the cells  Result in much more efficient metabolism MUSCLE ENDURANCE

 Isotonic contraction: muscle length changes  Concentric contractions: when a muscle shortens and does work (kicking a stupid soccer ball)  Eccentric contractions: when a muscle generates force as it lengthens  Useful for walking and coordination  Microtears occur during this form of contraction (muscle soreness)  Isometric contraction: muscle length stays the same ISOTONIC VS ISOMETRIC CONTRACTION

 Come up with 2 examples of an isotonic and isometric contraction (not ones I gave you)  Compare and contrast slow twitch fibers with fast twitch fibers (venn diagram) ACTIVITY