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

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Presentation on theme: "Lecture 14, 14 Oct 2003 Chapter 10, Muscles Chapter 11, Movement and Behavior Vertebrate Physiology ECOL 437 University of Arizona Fall 2003 instr: Kevin."— Presentation transcript:

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 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 Randi B. Weinstein, Ph.D. Department of Physiology University of Arizona Muscle Energetics and Mechanics

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

7 Experimental setup 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 servomotor

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

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

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

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

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

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

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

15 Work Loop - negative net work example Force Length Force 0.2 mm 20 mN Stimulation Work output during shortening Length Work input to lengthen Net work per cycle Length 25/s -4.5 µNm phase shift 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 Skeletal muscle Cardiac muscle Fig Randall et al Fig 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 -Myogenic and electronically linked via gap junctions (peristaltic waves in GI tract) Neurogenic (walls of blood vessels, iris)

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 -Some smooth muscle responds to stretch (vessels, GI) -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 -Processes all very slow and require little energy

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

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

24 High-Speed Treadmill

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

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

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

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

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

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

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

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 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 Which Muscle Components May Predict Speed Differences?

34 (mm 2 ) Horned lizards have marginally slimmer thighs, but relative iliofibularis size does not vary among subclades Scelop. Group Sand Lizards Horned Lizards

35 µm 2 Iliofibularis fiber size varies with respect to fiber type and mass, but not subclade Scelop. Group Sand Lizards Horned Lizards FG µm 2 SO

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

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

38 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 Which Muscle Components May Predict Speed Differences?

39 Scelop. Group Sand Lizards Horned Lizards proportion FG area in iliofibularis muscle hindlimb span/SVL log sprint speed (m/s) Proportion of fast glycolytic fibers and relative hindlimb span predict speed

40 Fiber-type composition has evolved dramatically since the Sand – Horned split:

41 Cnemidophorus FG Horned Scelop.Sand

42 Cnemidophorus FOG

43 Fast Glycolytic and Fast-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 Taxa Humans 18 mammal spp. Garter snakes 1 Sceloporus 1 Lacertid 4 Lacertids 12 Lacertids Trade-off? depends NO YES Inter/Intra Intra Interspecific Intra Interspecific Reference Heinrich 1985 Garland et al Brodie and Garland 1993 Tsuji et al Sorci et al Huey et al Vanhooydonck et al. 2001

45 Speed and Endurance are positively correlated 23 Species (Adult Males) Residuals (from regressions on body mass) Speed and Endurance do not trade-off r 2 = p = 0.039

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

47 2. The evolution of Slow Oxidative fiber composition appears constrained 1. Fast glycolytic fibers and relative hindlimb span predict speed 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 Randall et al. 2002

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

50 End


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