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
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
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