1. 25 October 2010 This Week in Physiology: Lab: Frog Muscle Twitches
Lectures: Ch. 9 Muscle Physiology & Ch. 10 Body Movement
Friday: Abstracts Due
Next Week in Physiology:
Monday: Test # 2
Lectures: Ch. 12 Cardiovascular Physiology

2. 1QQ # 21 for 8:30 Compare and contrast EPPs and EPSPs.
Which are characteristics of smooth muscle?
Cylindrical shape
Multinucleated
Attached to tendons
Connected to each other by intercalated disks
Can be excited or inhibited

3. 1QQ # 21 for 9:30
What is the cause of myasthenia gravis and what are the symptoms?
Which are characteristics of cardiac muscle?
Cylindrical shape
Multinucleated
Attached to tendons
Connected to each other by intercalated disks
Can be excited or inhibited

4. How does AP in sarcolemma cause twitch?
Fig a
S 5
Capillaries
Oxygen,
Nutrients, hormones,
waste
How does AP in sarcolemma cause twitch?
09.01a.jpg

5. Types of Contractions S1 Isotonic = Same tension Isometric =
Same length
Look at contractile properties of individual skeletal myofiber and then at whole muscles (hundreds or thousands of myofibers.)

6. Terms: Myofiber, myofibril, myofilament
Fig b
Terms: Myofiber, myofibril, myofilament
09.11b.jpg
Thick myofilament = myosin Thin myofilament = actin

7. Fig a
S 3
09.11a.jpg

8. Fig
S 4
High fAP leads to accumulation of Ca++ in sarcoplasm because Ca++ ATPase doesn’t return all Ca++ to SR quickly enough.
The concentration of free calcium is directly related to force of contraction in skeletal muscle
Thus we need to understand the cellular mechanism of contraction… cell biology flashbacks…
09.12.jpg

9. S5
YouTube Videos Role of ATP in muscle Creepy Muscle demo Sarcomere contraction Powerstoke in muscle I Powerstroke in muscle II
09.09.jpg

10. Energy for powerstroke & Necessary for detaching myosin from actin
Fig
S 6
2 roles of ATP:
Energy for powerstroke &
Necessary for detaching myosin from actin
Crossbridge cycling continues as long as ATP and Ca++ present.
09.08.jpg

11. dArk band = aligned myosin filaments
Fig
S 7
dArk band = aligned myosin filaments
lIght band = absence of myosin filaments
09.02.jpg

12. S 8

13. Fig
S 9
09.03.jpg

14. Fig
S 10
09.04.jpg

15. Fig a
S 11
09.05a.jpg

16. Fig b
S 12
Contracted
09.05b.jpg

17. Fig a
S 13
09.05a.jpg
Image if the sarcomeres were stretched? How would the number of cross bridges be affected? And the tension produced?

18. Length-tension Relationship
09.21.jpg
So….. Tension produced by a single myofiber varies depending on sarcomere length.

19. Muscle kinetics
Link to cytosolic calcium concentration, release, and reuptake?
S 15
09.10.jpg

20. Fig
S 16
09.16.jpg

21. Fig a
S 17
Twitch
Twitch
Twitch
09.19a.jpg

22. Fig b
S 18
Summation
09.19b.jpg
Tension is a result of the temporal control of cytosolic calcium concentration

23. Fig c
S 19
09.19c.jpg

24. S 20
Fig
Why does this plateau?
09.20.jpg
So….. Tension produced by a single myofiber varies depending on frequency of Action Potentials.

25. S 21
So what are the ways a muscle (consisting of many myofibers) increases tension (force)?

26. Fig
S 22
Motor unit = a single somatic motor neuron and all the muscle fibers in innervates
09.13.jpg

27. S 23

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

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

30. Muscle Metabolism Fiber types Muscles in action Speed of myosin ATPase
Metabolic sources of ATP
Timing of fatigue
Muscles in action
Causes of Fatigue
Training and fiber type
Creatine supplements

31. S 27

32. S 28