1. 19 October 2011 This Week in Physiology: Lab: Visual System Part 2,
Somatosensory Data Collection Vestibulocochlear system PPT
Lectures: Ch. 9 Muscle Physiology
Next Week in Physiology:
Lab: Frog muscle physiology Lectures: Ch. 10 Control of Body Movement
Abstracts due Friday
Instructions on Website! About midterm grades….. About Take Home portion of Test 1

2. 1QQ # 19
Write a question that you were prepared to answer today and provide the answer to that question.
A more challenging/sophisticated/thought-provoking question with its correct answer earns more points than a simple memorization-type question.

3. Muscle kinetics
Link to cytosolic calcium concentration, release, and reuptake?
S 1
09.10.jpg

4. Fig
S 2
09.16.jpg

5. S 3
Fig
Why does this plateau?
09.20.jpg
So….. Tension produced by a single myofiber varies depending on frequency of Action Potentials.

6. Muscle Metabolism Classification of Myofiber types
Speed of myosin ATPase
Metabolic sources of ATP
Fatigability

7. 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
Myosin isozymes not modified by athletic training!

8. Classes of Myofibers based on Metabolic 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)
Metabolic profiles CAN BE modified by athletic training!

9. 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

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

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

12. S 10

13. Type I Type IIA Type IIB S 11 What are the causes of fatigue?
Depends on the type of activity…

14. 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

15. S 13
So what are the ways a muscle (consisting of many myofibers) increases tension?

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

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

18. 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)

19. Fig. 09.26 S 17 Relationship between recruitment and motor unit type
The Size Principle
Size of somatic motoneuron cell body
09.26.jpg