Lecture 14, 14 Oct 2003Chapter 10, Muscles

Chapter 11, Movement and Behavior

Vertebrate PhysiologyECOL 437

University of ArizonaFall 2003

instr: Kevin Boninet.a.: Bret Pasch

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)

UA Undergrad Conservation Biology Internships

Randi B. Weinstein, Ph.D.Department of Physiology

University of Arizona

randiw@cs.arizona.edu

Muscle Energetics and Mechanics

Cyclic ContractionsIn cyclic motions muscle contractions are not purely isometric or isotonic.

Instead, muscles shorten and lengthenduring each cycle.

How much work does a muscle do duringone cycle?

Cyclic ContractionsExample: 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

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

servomotor

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 textFig. 10-38

Work Loops - positive net work example

Force

Length

Force

0.2 mm

20 mN

Work outputduring shortening

Length

20 mN

0.2 mm

Work Loops - positive net work example

Length

Force

Stimulation

Time

0.2 mm

20 mN

lengthen

shorten

lengthening (relaxation)

25/s

Work Loops - positive net work example

Force

Work outputduring shortening

Length

20 mN

Length

Force

0.2 mm

20 mN

Length

Work inputto lengthen

0.2 mm

Work Loops - positive net work example

Force

Work outputduring shortening

Length

20 mN

Length

Force

0.2 mm

20 mN

Length

Work inputto lengthen

0.2 mm

Net workper cycle

Length

Work Loops - positive net work example

Force 20 mN

Length

Force

0.2 mm

20 mN

0.2 mm

Net workper cycle

Length

Stimulation 25 cycles/s (0.04 s/cycle)= 4.5 µNm

4.5 µNm0.04 s

Net power =Net work/cycleCycle duration

=

= 113 µNm/sMuscle generates power!

Cyclic Contractions Flex

Extend

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

Work Loop - negative net work example

Force

Length

Force

0.2 mm

20 mNStimulation

Work outputduring shortening

LengthLength

Work inputto lengthen

Net workper cycle

Length

25/s

-4.5 µNm

phaseshift

Muscle absorbs energy!

Work Loop Examples

Dickinson et al., 2000

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?

Skeletal muscle

Cardiac muscle

Fig. 10-49Randall et al. 2002

Fig. 10-18Randall et al. 2002

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

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)

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

-Latch state prolonged contraction, low energy use (0.3%

striated)

Smooth Muscle

Low rate of cross-bridge cycling

Mechanism not well-understood

Fig. 10-53Randall et al. 2002

--

Uta stansburiana

Sceloporus magister

Sceloporus undulatus

Sceloporus virgatus

Uma notata

Callisaurus draconoides

Cophosaurus texanus

Holbrookia maculata

Phrynosoma cornutum

Phrynosoma modestum

Phrynosoma mcallii

SceloporusGroup

Sand

Horned

11 Species of Phrynosomatidae

High-Speed Treadmill

Twitch Speed (SPRINTING)

SO = Slow OxidativeFOG = Fast-Oxidative Glycolytic

Muscle Fiber-Type Composition

FG = Fast GlycolyticFOG = Fast-Oxidative Glycolytic

Oxidative Capacity (ENDURANCE)

Iliofibularis muscle

Iliofibularis Muscle (IF)cross-section with darker oxidative core that appears red in fresh tissue

Dorsal view oflizard hindlimb

IF

Histochemistry

Femur

Cross Section of Hindlimb at

Mid-Thigh

Histochemistry

IF

Iliofibularis Muscle (IF)

SuccinicDehydrogenase

(SDH)H

isto

chem

istr

yMyosin ATPase

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)

HistochemistrySerial sections stained for:

Proportional area of all three fiber types sums to 1.

FG + FOG + SO = 1

--

Uta stansburiana

Sceloporus magister

Sceloporus undulatus

Sceloporus virgatus

Uma notata

Callisaurus draconoides

Cophosaurus texanus

Holbrookia maculata

Phrynosoma cornutum

Phrynosoma modestum

Phrynosoma mcallii

SceloporusGroup

Sand

Horned

11 Species of Phrynosomatidae

What are the Potential Sourcesof 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

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?

0

10

20

30

40

50

60

1 10 100Body Mass (g)

Thig

h M

uscl

e X-

Sect

iona

l Are

a

0

4

8

12

16

1 10 100

Body Mass (g)

Iliof

ibul

aris

as

% o

f Thi

gh M

uscl

e

(mm

2 )Horned lizards have marginally

slimmer thighs, but relative iliofibularis size does not vary among subclades

Scelop. Group Sand Lizards Horned Lizards

0

100

200

300

400

500

600

1 10 100

Body Mass (g)

Size

of S

ingl

e

F

iber

µm2

0

100

200

300

400

500

600

1 10 100

Body Mass (g)

Size

of S

ingl

e

F

iber

Iliofibularis fiber size varies with respect to fiber type and mass, but not subclade

Scelop. Group Sand Lizards Horned Lizards

FG

µm2

SO

0

10

20

30

40

50

60

70

80

1 10 100

Body Mass (g)

% F

ast-G

lyco

lytic

0

10

20

30

40

50

60

70

80

1 10 100Body Mass (g)

% S

low

-Oxi

dativ

e

Iliofibularis FG and FOG compositionsvary among phrynosomatid subclades;composition of SO fibers does not vary

Scelop. Group Sand Lizards Horned Lizards

% F

ast G

lyco

lytic

(FG

)

% S

low

Oxi

dativ

e (S

O)

0

0.2

0.4

0.6

0.8

1

proportion FOG fibers

prop

ortio

n FG

fibe

rs

Because slow oxidative (SO) composition is rather stable,

0 0.2 0.4 0.6 0.8 1

Scelop. Group Sand Lizards Horned Lizards

Fast-Oxidative Glycolyticfiber proportional area

Fast

Gly

coly

ticfib

er p

ropo

rtion

al a

rea FG and FOG

trade-off(but only AMONG subclades)

P < 0.001conventional r = -0.95phylogenetic r = -0.89

1. Whole-leg muscle areaHorned lizards may have slim thighs

2. Proportion of iliofibularis in thighdoes not vary among subclades

3. Change in size of individual fiberscorrelates with body mass, not speed

4. Variation in fiber-type compositionlikely explains speed differences

Which Muscle Components May Predict Speed Differences?

0.200.35

0.500.65

0.80

1.251.50

1.752.00

0.00

0.20

0.40

0.60

0.80

Scelop. Group Sand Lizards Horned Lizards

proportion FG area

in iliofibularis muscle

hindlimb span/SVL

log

sprin

t spe

ed (m

/s) Proportion

of fast glycolytic fibers and

relative hindlimb

span predict speed

Fiber-type composition has evolved dramatically since

the Sand – Horned split:

Cnemidophorus

FG

FG

Horned Scelop. Sand

Cnemidophorus

FOG

Fast Glycolytic and Fast-Oxidative Glycolytic fiber compositions exhibit a trade-off (because of the

constant Slow Oxidative proportion)

Do Speed and Endurancetrade-off similarly?

The Speed - Endurance trade-offquestion is unresolved

Taxa

Humans18 mammal spp.

Garter snakes

1 Sceloporus1 Lacertid

4 Lacertids12 Lacertids

Trade-off?

dependsNONO

NONO

YESYES

Inter/Intra

IntraInterspecific

Intra

IntraIntra

InterspecificInterspecific

Reference

Heinrich 1985Garland et al. 1988

Brodie and Garland 1993

Tsuji et al. 1989Sorci et al. 1995

Huey et al. 1984Vanhooydonck et al. 2001

-0.4

-0.3

-0.2

-0.1

0

0.1

0.2

0.3

0.4

-1 -0.5 0 0.5 1

log Endurance (s)

log

Sprin

t Spe

ed (m

/s)

SceloporusSandHornedCrotaphytidaeAgamidaeTeiidaeLacertidaeScincidaeAnguidae

Speed and Endurance are positively correlated

23 Species(Adult Males)

Residuals(from regressions

on body mass)Speed and Endurance

do not trade-off

r2 = 0.187p = 0.039

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

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

1. Chap. 11 ~Behavior Initiation

Fig. 11-12Randall et al. 2002

~Behavior InitiationChapter Eleven

Bring together nervous, endocrine, muscular systems, etc.

Complex

Reflexes / Learned / Plasticity

Respond to situation(s)Parallel Processing Complicated

NeuronalCircuitry

Animal Behavior,Neurobiology

End