Lecture 14, 14 Oct 2003 Chapter 10, Muscles Chapter 11, Movement and Behavior

1. Lecture 14, 14 Oct 2003 Chapter 10, Muscles Chapter 11, Movement and Behavior Vertebrate Physiology ECOL 437 University of Arizona Fall 2003 instr: Kevin Bonine t.a.: Bret Pasch

2. Vertebrate Physiology 437 1. Muscles (Ch10) 2. Announcements old exam, review sheet exam next Tuesday papers due today mid-semester evaluations seminars etc. 3. Behavior and Movement (CH11)

3. UA Undergrad Conservation Biology Internships

4. Muscle Energetics and Mechanics Randi B. Weinstein, Ph.D. Department of Physiology University of Arizona randiw@cs.arizona.edu

5. Cyclic Contractions In cyclic motions muscle contractions are not purely isometric or isotonic. Instead, muscles shorten and lengthen during each cycle. How much work does a muscle do during one cycle?

6. Flex -biceps shortens Extend -biceps lengthens Cyclic Contractions Example: repeatedly lifting load -biceps develops more tension as it shortens than when it lengthens -biceps does net positive work Flexor vs Extensor

7. servomotor Experimentalsetup Muscle lever controls muscle length and measures force Electrical stimulation pattern synchronized with muscle length (rate ~EMG data) Muscle is moved along its linear axis

8. Time Work Loops - positive net work example See text Fig. 10-38 shortening (contraction) lengthen Length 0.2 mm shorten 20 mN Force Stimulation 25 cycles/s Josephson, 1985 (insect flight muscle)

9. Work Loops - positive net work example 0.2 mm Length 20 mN Force Work output during shortening 20 mN Force 0.2 mm Length

10. Time Work Loops - positive net work example lengthening (relaxation) lengthen Length 0.2 mm shorten 20 mN Force Stimulation 25/s

11. Work Loops - positive net work example 0.2 mm Length 20 mN Force Work input to lengthen Work output during shortening 0.2 mm 20 mN Force Length Length

12. Work Loops - positive net work example 0.2 mm Length 20 mN Force Work input to lengthen Work output during shortening Net work per cycle 0.2 mm 20 mN Force Length Length Length

13. 0.2 mm 20 mN Work Loops - positive net work example 0.2 mm Length 20 mN Force Stimulation 25 cycles/s (0.04 s/cycle) Net work per cycle = 4.5 µNm Net work/cycle Cycle duration Force Net power = 4.5 µNm 0.04 s = Length = 113 µNm/s Muscle generates power!

14. Flex Cyclic Contractions Example: repeatedly lowering load -biceps develops more tension as it lengthens than when it shortens -biceps does net negative work Extend

15. -4.5 µNm Work Loop - negative net work example 0.2 mm Length 20 mN Force phase shift Stimulation 25/s Work output during shortening Net work per cycle Work input to lengthen Force Length Length Length Muscle absorbs energy!

16. Work Loop Examples Dickinson et al., 2000

17. Cardiac Muscle (the other striated muscle) -Small muscle fiber cells with only one nucleus -Individual fibers are connected to neighbors electronically via gap junctions -Two types of fibers: 1. Contractile (similar to skeletal muscle) 2. Conducting (including pacemaker cells) Do not contract, but transmit electrical signal -Cardiac contraction myogenic (arises within heart) Can be influenced by autonomic nervous system (alpha, beta adrenoreceptors increase [Ca2+]) -Long-lasting AP with long plateau phase, and long refractory period - why?

18. Fig. 10-18 Randall et al. 2002 Skeletal muscle Cardiac muscle Fig. 10-49 Randall et al. 2002

19. Cardiac Muscle (the other striated muscle) -Intracellular calcium from SR and across plasma membrane(unlike in skeletal) -Dihydropyridine receptors in T-tubules are voltage-activated calcium channels -Ryanodine receptors then release more calcium from SR into the cytoplasm (calcium-induced calcium release) -During relaxation, Calcium pumped actively back into SR and out across plasma membrane

20. Smooth Muscle -Lacks sarcomeres, isn’t striated -Walls of hollow organs – visceral functions (GI tract, urinary bladder, uterus, blood vessels) -Heterogenous -Innervated by autonomic NS -Each fiber is individual cell with one nucleus -No T-tubules -Organized into bundles of actin and myosin anchored to dense bodies or to the plasma membrane -Can be single-unit or multi-unit Neurogenic (walls of blood vessels, iris) -Myogenic and electronically linked via gap junctions (peristaltic waves in GI tract)

21. Smooth Muscle -Autonomic NT released from varicosities along axon, not at motor endplate, affecting many cells -Poorly developed SR, calcium mostly across plasma membrane -Several ways to regulate calcium concentration (no troponin) -One is via calcium-calmodulin complex that then binds to caldesmon, removing caldesmon from blocking actin binding sites -Some smooth muscle responds to stretch (vessels, GI) -Processes all very slow and require little energy

22. Smooth Muscle -Latch state prolonged contraction, low energy use (0.3% striated) Low rate of cross-bridge cycling Mechanism not well-understood Fig. 10-53 Randall et al. 2002

23. 11 Species of Phrynosomatidae Sceloporus Group Uta stansburiana Sceloporus magister Sceloporus undulatus Sceloporus virgatus Uma notata Callisaurus draconoides Cophosaurus texanus Holbrookia maculata Phrynosoma cornutum Phrynosoma modestum Phrynosoma mcallii - - Sand Horned

24. High-Speed Treadmill

25. Muscle Fiber-Type Composition Twitch Speed (SPRINTING) FG= Fast Glycolytic FOG= Fast-Oxidative Glycolytic Oxidative Capacity (ENDURANCE) SO= Slow Oxidative FOG= Fast-Oxidative Glycolytic

26. Histochemistry Iliofibularis muscle IF Dorsal view of lizard hindlimb Iliofibularis Muscle (IF) cross-section with darker oxidative core that appears red in fresh tissue

27. Histochemistry IF Cross Section of Hindlimb at Mid-Thigh Femur

28. Succinic Dehydrogenase (SDH) Myosin ATPase Histochemistry Iliofibularis Muscle (IF)

29. Histochemistry mATPase (fast-twitch) SDH (oxidative) Serial sections stained for: FOG (fast-twitch oxidative glycolytic; dark mATPase and dark SDH) FG (fast-twitch glycolytic; dark mATPase, light SDH) SO (slow-oxidative; light mATPase, dark SDH)

30. Proportional area of all three fiber types sums to 1. FG +FOG+ SO= 1

31. 11 Species of Phrynosomatidae Sceloporus Group Uta stansburiana Sceloporus magister Sceloporus undulatus Sceloporus virgatus Uma notata Callisaurus draconoides Cophosaurus texanus Holbrookia maculata Phrynosoma cornutum Phrynosoma modestum Phrynosoma mcallii - - Sand Horned

32. What are the Potential Sources of Muscle Variation? 1. Whole-leg muscle area 2. Proportion of a muscle in the thigh 3. Change in size of individual fibers 4. Variation in fiber-type composition

33. Which Muscle Components May Predict Speed Differences? 1. Whole-leg muscle area 2. Proportion of a muscle in the thigh 3. Change in size of individual fibers 4. Variation in fiber-type composition Focus on the Iliofibularis muscle

34. Scelop. Group Sand Lizards Horned Lizards Horned lizards have marginally slimmer thighs, but relative iliofibularis size does not vary among subclades (mm2)

35. Scelop. Group Sand Lizards Horned Lizards Iliofibularis fiber size varies with respect to fiber type and mass, butnot subclade µm2 µm2 SO FG

36. Scelop. Group Sand Lizards Horned Lizards Iliofibularis FG and FOG compositions vary among phrynosomatid subclades; composition of SO fibers does not vary % Slow Oxidative (SO) %Fast Glycolytic (FG)

37. Because slow oxidative (SO) composition is rather stable, FG and FOG trade-off (but only AMONG subclades) Fast Glycolytic fiber proportional area P < 0.001 conventional r = -0.95 phylogenetic r = -0.89 Scelop. Group Sand Lizards Horned Lizards 0 0.2 0.4 0.6 0.8 1 Fast-Oxidative Glycolytic fiber proportional area

38. Which Muscle Components May Predict Speed Differences? 1. Whole-leg muscle area Horned lizards may have slim thighs 2. Proportion of iliofibularis in thigh does not vary among subclades 3.Change in size of individual fibers correlates with body mass, not speed 4. Variation in fiber-type composition likely explains speed differences

39. Scelop. Group Sand Lizards Horned Lizards Proportion offast glycolyticfibers and relative hindlimb span predictspeed log sprint speed (m/s) hindlimb span/SVL proportion FG area in iliofibularis muscle

40. Fiber-type composition has evolved dramatically since the Sand–Hornedsplit:

41. Horned Scelop. Sand Cnemidophorus FG FG

42. Cnemidophorus FOG

43. Fast GlycolyticandFast-Oxidative Glycolytic fiber compositions exhibit a trade-off (because of the constant Slow Oxidative proportion) Do Speed and Endurance trade-off similarly?

44. The Speed - Endurance trade-off question is unresolved Trade-off? depends NO NO NO NO YES YES Inter/Intra Intra Interspecific Intra Intra Intra Interspecific Interspecific Reference Heinrich 1985 Garland et al. 1988 Brodie and Garland 1993 Tsuji et al. 1989 Sorci et al. 1995 Huey et al. 1984 Vanhooydonck et al. 2001 Taxa Humans 18 mammal spp. Garter snakes 1 Sceloporus 1 Lacertid 4 Lacertids 12 Lacertids

45. Speed and Endurance are positively correlated Residuals (from regressions on body mass) Speed and Endurance do not trade-off r2 = 0.187 p = 0.039 23 Species (Adult Males)

46. The evolution of both speed and endurance does not seem to be constrained across a broad range of lizard taxa.

47. 1. Fast glycolyticfibers and relative hindlimb span predictspeed 2. The evolution of Slow Oxidative fiber composition appears constrained 3. FG and FOG composition trade-off (and proportion FG fibers predicts speed) 4. Speed and Endurance do not trade-off, indicating that evolution has either overcome a hypothetical constraint, or that constraint never existed

48. 1. Chap. 11 ~Behavior Initiation Fig. 11-12 Randall et al. 2002

49. Chapter Eleven Animal Behavior, Neurobiology ~Behavior Initiation Complex Bring together nervous, endocrine, muscular systems, etc. Respond to situation(s) Parallel Processing Complicated Neuronal Circuitry Reflexes / Learned / Plasticity

50. End