1. 26 October 2010 This Week in Physiology: Lab: Frog Muscle Physiology
Lectures: Wednesday: Ch. 9 Muscle Physiology Friday Finish Muscle, then Ch. 10 Control of Movement
Abstracts due Friday
Test on Monday
Coverage to be posted to Website
Starts with Nervous System
Ends with Muscle Physiology

2. 1QQ # 22 for 8:30 am
1. What events occur during the latent period before a muscle develops tension?
2. Once a muscle is stretched greater than 120% of its optimal length, what happens?
3. As a muscle contracts,
a) A bands get narrower
b) I bands get narrower
c) H bands get narrower
d) Z lines move closer together
e) M lines move closer together

3. 1QQ # 22 for 9:30 am
1. What term applies to the type of muscle contraction where the tension developed is less than the load on the muscle?
2. What are the three roles of ATP in skeletal myofibers?
3. What causes a muscle contraction to end?

4. Fig
S 1
Motor unit = a single somatic motor neuron and all the muscle fibers in innervates
09.13.jpg

5. S 2
Size Principle

6. Increasing tension in a whole muscle
Frequency of stimulation of motor neuron
Activate larger motor units
Recruitment: activate more motor units
These factors also influence actual tension
Fiber length (length-tension) relationship
Fiber diameter
Level of fatigue (state of activity)

7. Muscle Metabolism Fiber types
Speed of myosin ATPase (fixed for a cell)
Slow isozyme = slow twitch = Type I
Fast isozyme = fast twitch = Type II
Metabolic sources of ATP
Oxidative phosphorylation
Glycolytic
Timing of fatigue
Oxidative = fatigue resistant
Glycolytic = fatigue quickly (but recover quickly)

8. Classes of Myofibers based on Twitch Duration
Each muscle fiber express only one of two different myosins isozymes:
Fast twitch = rapid hydrolysis of ATP means crossbridges cycle faster
Slow twitch = slower hydrolysis, isozyme catalyzes the reaction slower
Isozymes not modified by athletic training!
Contraction velocity also affected by load!

9. S 5
Lifting a load and contraction velocity

10. S 7
Comparison of contraction time (measured?): extraocular muscle (IR, internal rectus), gastrocnemius (G), and soleus (S)
Whole muscles consist of many motor units.
Each motor unit has myofibers of only one type (I, IIA or IIB)

11. Classes of Myofibers based on Metabolism and Enzyme profiles
Oxidative: at peak activity rely on full aerobic cellular respiration
many mitochondria, enzymes for oxidative phosphorylation, numerous capillaries, lots of myoglobin (red)
Glycolytic: at peak activity rely on glycolysis
few mitochondria, many glycolytic enzymes, large store of glycogen, fewer capillaries, little myoglobin (white)

12. Fig
S 9
Type I
Type II A
Type II B
09.03.jpg

13. 3 Sources of ATP in muscle
Powerstroking &
Disconnecting crossbridges
09.22.jpg
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

14. Use of Creatine as a Nutritional Supplement
                                                                                  
A 1998 Review on the
Use of Creatine as a Nutritional Supplement

15. Type I Type IIA Type IIB S 12 What are the causes of fatigue?
Depends on the type of activity…

16. Causes of fatigue High intensity, short duration exercise
Conduction failure in t-tubules
Lactic acid accumulation
Accumulation of ADP and inorganic phosphate
Low intensity, long duration exercise
As above, and
Depletion of muscle glycogen
Low plasma glucose (hypoglycemia)
Dehydration
Control pathways: “willpower”
Common in couch potatoes

17. Fig. 09.26 S 14 Relationship between recruitment and fiber type
09.26.jpg

18. S 15

19. Fig b
S 16
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?
09.24b.jpg