Thursday, Oct 25 Friday, Oct 26 Saturday

Afternoon, Oct 27

Sunday, Oct 28in 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

ketchampd@email.wofford.edu

12- 2 with Miranda Stockman2-4 with Polly Ketcham4-6 with Brooks Owens6-8 with Becca Bryson

Abstract Reviewers Schedule

Abstract due MondayAt start of class.

1QQ # 19 for 10:30Convert 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 11:30Convert 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 TypesCharacter Type I (Slow Ox) Type II A (FOG) Type II B (FG)

Myosin ATPase slow fast fast

Metabolism Oxidative (aerobic) oxidative & glycolytic

glycolytic

Ca++ ATPase moderate fast Fast

Mitochondria numerous moderate Few

Myofiber diameter small medium Large

Color Dark red (myoglobin)

red pale

Capillary density high moderate Low

Recruitment first second third

Endurance Fatigue resistant Fatigue resistant Easily fatigued

Usage Most used. posture Walking, standing Least 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 29th to Sunday July 21th 2013, the 100th 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 stages5 hilly stages6 mountain stages with 4 summit finishes2 individual time trial stages1 team time trial stage2 rest days

Tour de France

Skeletal Myofiber TypesCharacter Type I (Slow Ox) Type II A (FOG) Type II B (FG)

Myosin ATPase slow fast fast

Metabolism Oxidative (aerobic) oxidative & glycolytic

glycolytic

Ca++ ATPase moderate fast Fast

Mitochondria numerous moderate Few

Myofiber diameter small medium Large

Color Dark red (myoglobin)

red pale

Capillary density high moderate Low

Recruitment first second third

Endurance Fatigue resistant Fatigue resistant Easily fatigued

Usage Most used. posture Walking, standing Least used: jumping, quick fine

movements

Response to training

• Resistance trainingType II change enzyme profiles: II A to II BType II add more actin and myosinType II increase cross-sectional area (hypertrophy)

• Endurance training– Type I increases vascularity– Type I increase number of mitochondria

S 7

Fig. 09.24bRead 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. 09.13

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. 09.26Relationship between recruitment and motor unit type

S 17

Size of somatic motoneuron cell body

The Size Principle