Thursday, Oct 25Friday, Oct 26 Saturday Afternoon, Oct 27 Sunday, Oct 28 in Acorn Cafe 9-11 am Biology Office Suite with Sharon Guffy 1-2 pm Biology Office Suite Miranda Stockman and Brooks Owens by appointment with Polly Ketcham ail.wofford.edu with Miranda Stockman 2-4 with Polly Ketcham 4-6 with Brooks Owens 6-8 with Becca Bryson Abstract Reviewers Schedule Abstract due Monday At start of class.

1QQ # 19 for 10:30 Convert to a correct statement or if true, write true. 1.Skeletal myofibers have muscarinic acetylcholine receptors. 2.Skeletal myofibers have adrenergic receptors, but the binding of EPI does not cause contraction. 3.After a powerstroke, ATP must bind to the myosin head before the crossbridge can detach from actin. 4.The duration of a muscle twitch depends on how rapidly Ca++ is actively transported back into the T- tubule. 5.A drug that activates ryanodine receptors would cause a skeletal muscle to contract.

1QQ # 19 for 11:30 Convert to a correct statement or if true, write true. 1.Skeletal myofibers have muscarinic acetylcholine receptors. 2.Skeletal myofibers have adrenergic receptors, but the binding of EPI does not cause contraction. 3.After a powerstroke, ATP must bind to the myosin head before the crossbridge can detach from actin. 4.The duration of a muscle twitch depends on how rapidly Ca++ is actively transported back into the T- tubule. 5.There are two isozymes of actin which hydrolyze ATP at different rates.

3 Sources of ATP in muscle Creatine phosphate, then oxidative phosphorylation (OP) from glycogen, then OP from blood glucose, then blood fatty acids. If intense, switch to glycolysis… then take a breather… oxygen debt Powerstroking & Disconnecting crossbridges S 7

S 8 Would creatine supplementation benefit endurance runners?

Muscle Fatigue Central Fatigue Psychological drive Protective reflexes – Chemoreceptors in muscles? Peripheral Fatigue Less ACh release Less AChR activation AP conduction failure in T-tubles Leaking Ca++ from SR Less Ca++ released from SR Disturbed Ca++ binding to Troponin Depletion Hypotheses – Depletion of phosphocreatine – Depletion of ATP – Depletion of glycogen Accumulation Hypotheses – Accum of H+ – Accum of inorganic phosphate – Accum of lactate Many factors are associated with muscle fatigue. Factors that cause muscle fatigue are still uncertain.

Classes of Myofibers based on Twitch Duration Each muscle fiber express only one of two different myosin isozymes: Fast twitch = rapid hydrolysis of ATP means crossbridges cycle faster Slow twitch = slower hydrolysis, isozyme catalyzes the reaction slower Myosin Isozymes not modified by athletic training but metabolic pathway enzymes are! S 5 Contraction velocity also affected by load!

S 10

Skeletal Myofiber Types CharacterType I (Slow Ox)Type II A (FOG)Type II B (FG) Myosin ATPaseslowfast MetabolismOxidative (aerobic)oxidative & glycolytic glycolytic Ca++ ATPasemoderatefastFast MitochondrianumerousmoderateFew Myofiber diametersmallmediumLarge ColorDark red (myoglobin) redpale Capillary densityhighmoderateLow Recruitmentfirstsecondthird EnduranceFatigue resistant Easily fatigued UsageMost used. postureWalking, standingLeast used: jumping, quick fine movements

Duck Chicken Muscles (the organs) consist of various proportions of all three myofiber types depending on the usage of that muscle.

Running from Saturday June 29 th to Sunday July 21 th 2013, the 100 th Tour de France will be made up of 21 stages and will cover a total distance of 3,479 kilometres (before ratification). These stages have the following profiles: 7 flat stages 5 hilly stages 6 mountain stages with 4 summit finishes 2 individual time trial stages 1 team time trial stage 2 rest days Tour de France

Skeletal Myofiber Types CharacterType I (Slow Ox)Type II A (FOG)Type II B (FG) Myosin ATPaseslowfast MetabolismOxidative (aerobic)oxidative & glycolytic glycolytic Ca++ ATPasemoderatefastFast MitochondrianumerousmoderateFew Myofiber diametersmallmediumLarge ColorDark red (myoglobin) redpale Capillary densityhighmoderateLow Recruitmentfirstsecondthird EnduranceFatigue resistant Easily fatigued UsageMost used. postureWalking, standingLeast used: jumping, quick fine movements

Response to training Resistance training Type II change enzyme profiles: II A to II B Type II add more actin and myosin Type II increase cross-sectional area (hypertrophy) Endurance training – Type I increases vascularity – Type I increase number of mitochondria S 7

Fig b Read section of King et al., 1999 that deals with analysis of muscle biopsy material in subjects taking Andro or placebo while resistance training. What changes were expected? What changes were observed? S 8

Fig Motor unit = a single somatic motor neuron and all the muscle fibers in innervates S 14

S 15 But each motor unit has myofibers of the same type: I or IIA or IIB.

Fig Relationship between recruitment and motor unit type S 17 Size of somatic motoneuron cell body The Size Principle