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8/8/2019 Ch 09 Lecture Outline c
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PowerPoint Lecture Slidesprepared byJanice Meeking,
Mount Royal College
C H A P T E R
Copyright 2010 Pearson Education, Inc.
9Muscles andMuscleTissue: Part C
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Copyright 2010 Pearson Education, Inc.
Force of Mus cle Contraction
The force of contraction is affected by:
Number of muscle fibers stimulated(recruitment)
Relative size of the fibershypertrophy of cells increases strength
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Copyright 2010 Pearson Education, Inc. Fig u re 9.21
Largen umb er of
mus clefib er s
activated
Contractile force
Highfreq u ency of s timu lation
Largemus clefib er s
Mus cle ands arco m ere
s tretched to s lightly over 100%of re s ting length
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Copyright 2010 Pearson Education, Inc. Fig u re 9.22
S arcomeresgreatly
shortened
S arcomeres atresting length
S arcomeres excessivelystretched
170%
Op tim al s arco m ereo p erating length(80%120% of re s ting length)
100%75%
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V elocity and Du ration of Contraction
Influenced by:
1. Muscle fiber type
2. Load3. Recruitment
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Mus cle Fib er Typ e
2. Metabolic pathways for ATP synthesis:
Ox idative fibersuse aerobic pathways
Glycolytic fibersuse anaerobic glycolysis
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Mus cle Fib er Typ e
Three types:
Slow o x idative fibers
Fast ox
idative fibersFast glycolytic fibers
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Copyright 2010 Pearson Education, Inc. Ta b le 9.2
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Copyright 2010 Pearson Education, Inc. Fig u re 9.23
P redo m inanceof fa s t glycolytic(fatiga b le) fib er s
P redo m inanceof s low oxidative(fatig u e-re s is tant)
fib er s
Sm all load
Contractilevelocity
Contractileduration
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Copyright 2010 Pearson Education, Inc. Fig u re 9.24
FO
FG
SO
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Copyright 2010 Pearson Education, Inc.
Effect s of Exerci s e
Aerobic (endurance) e x ercise:
Leads to increased:
Muscle capillaries
Number of mitochondria
Myoglobin synthesis
Results in greater endurance, strength, andresistance to fatigue
May convert fast glycolytic fibers into fast o x idativefibers
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Copyright 2010 Pearson Education, Inc.
Effect s of Re s is tance Exerci s e
Resistance e x ercise (typically anaerobic)results in:
Muscle hypertrophy (due to increase in fiber size)
Increased mitochondria, myofilaments,glycogen stores, and connective tissue
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Copyright 2010 Pearson Education, Inc.
The Overload P rinci p le
Forcing a muscle to work hard promotesincreased muscle strength and endurance
Muscles adapt to increased demands
Muscles must be overloaded to producefurther gains
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Sm ooth Mus cle
Found in walls of most hollow organs(e x cept heart)
Usually in two layers (longitudinal andcircular)
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Copyright 2010 Pearson Education, Inc. Fig u re 9.26
Sm allinte s tine
(a) (b ) Cross section of the
intestine showing thesmooth muscle layers(one circular and theother longitudinal)running at rightangles to each other.
Mu co s a
Longitudinal layer of smooth muscle(s how s sm ooth mus cle fib er s in cro ss s ection)
Circular layer of
smooth muscle(s how s longit u dinalview s of sm ooth mus cle fib er s )
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Copyright 2010 Pearson Education, Inc. Ta b le 9.3
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Copyright 2010 Pearson Education, Inc.
Innervation of Sm ooth Mus cle
Autonomic nerve fibers innervate smoothmuscle at diffuse junctions
Varicosities (bulbous swellings) of nerve fibersstore and release neurotransmitters
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Copyright 2010 Pearson Education, Inc. Fig u re 9.27
Sm oothmus clecell
V aricosities relea s etheir ne u rotran sm itter sinto a wide s yna p tic cleft (a diff us e ju nction) .
S yna p ticve s icle s
Mitochondrion
Autonomicnerve fi b ersinnervatem o s t sm ooth
mus cle fib er s.
Varico s itie s
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Copyright 2010 Pearson Education, Inc.
Myofila m ent s in Sm ooth Mus cle
Ratio of thick to thin filaments (1:13) is muchlower than in skeletal muscle (1:2)
Thick filaments have heads along their entirelength
No troponin comple x ; protein calmodulin bindsCa 2+
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Copyright 2010 Pearson Education, Inc.
Myofila m ent s in Sm ooth Mus cle
Myofilaments are spirally arranged, causingsmooth muscle to contract in a corkscrewmanner
Dense bodies: proteins that anchor noncontractile intermediate filaments tosarcolemma at regular intervals
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Copyright 2010 Pearson Education, Inc. Fig u re 9.2 8a
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Copyright 2010 Pearson Education, Inc. Fig u re 9.2 8b
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Copyright 2010 Pearson Education, Inc.
Contraction of Sm ooth Mus cle
Slow, synchronized contractions
Cells are electrically coupled by gap junctions
Some cells are self-e x citatory (depolarizewithout e x ternal stimuli); act as pacemakersfor sheets of muscle
Rate and intensity of contraction may bemodified by neural and chemical stimuli
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Contraction of Sm ooth Mus cle
Sliding filament mechanism
Final trigger is o intracellular Ca 2+
Ca2+
is obtained from the SR and e x tracellular space
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Copyright 2010 Pearson Education, Inc. Ta b le 9.3
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Copyright 2010 Pearson Education, Inc. Ta b le 9.3
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Copyright 2010 Pearson Education, Inc. Fig u re 9.29
Calci um ion s (Ca 2+ )enter the cyto s ol fro mthe EC F via voltage-de p endent or voltage-inde p endent Ca 2+channel s, or fro mthe s cant SR.
ATP
P i P i
Extracell u lar flu id (EC F)
ADP
Ca 2+
Ca 2+
Ca 2+
P la sm a m emb rane
Sarco p la sm icretic u lum
Inactive cal m od u lin
Inactive kina s e
Inactivem yo s in m olec u le
Activated (p ho sp horylated)m yo s in m olec u le
Activated kina s e
Activated cal m od u lin
Cyto p la sm
Ca 2+ b ind s to andactivate s cal m od u lin .
Activated cal m od u linactivate s the m yo s inlight chain kina s eenzy m e s.
The activated kina s e enzy m escatalyze tran s fer of p ho sp hateto m yo s in , activating the m yo s inATP as es.
Activated m yo s in for ms cro ssb ridge s with actin of the thinfila m ent s and s hortening b egin s.
Thinfila m ent
Thic kfila m ent
1
2
3
4
5
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Copyright 2010 Pearson Education, Inc. Fig u re 9.29, s te p 1
Calci um ion s (Ca 2+)enter the cyto s ol fro mthe EC F via voltage-de p endent or voltage-inde p endent Ca 2+channel s, or fro mthe s cant SR.
Extracellular fluid (ECF)
Ca 2+
Ca 2+
P la sm a m e mb rane
S arco p la sm icretic u lum
Cytoplasm
1
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Copyright 2010 Pearson Education, Inc. Fig u re 9.29, s te p 2
Ca 2+
Inactive cal m od u lin Activated cal m od u lin
Ca 2+ b ind s to andactivate s cal m od u lin .
2
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Copyright 2010 Pearson Education, Inc. Fig u re 9.29, s te p 3
Inactive kina s e Activated kina s e
Activated cal m od u linactivate s the m yo s inlight chain kina s eenzy m e s.
3
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Copyright 2010 Pearson Education, Inc. Fig u re 9.29, s te p 4
ATP
P i
P i
ADP
Inactivem yo s in m olec u le
Activated (p ho sp horylated)m yo s in m olec u le
The activated kina s e enzy m e scatalyze tran s fer of p ho sp hateto m yo s in , activating the m yo s inATP a s e s.
4
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Copyright 2010 Pearson Education, Inc. Fig u re 9.29, s te p 5
Activated m yo s in for ms cro ssb ridge s with actin of the thinfila m ent s and s hortening b egin s.
Thinfila m ent
Thic kfila m ent
5
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Copyright 2010 Pearson Education, Inc. Fig u re 9.29
Calci um ion s (Ca 2+ )enter the cyto s ol fro mthe EC F via voltage-de p endent or voltage-inde pendent Ca 2+channel s, or fro mthe s cant SR.
ATP
P i P i
Extracell u lar flu id (EC F)
ADP
Ca 2+
Ca 2+
Ca 2+
P la sm a m e mb rane
Sarco p la sm icretic u lum
Inactive cal m od u lin
Inactive kina s e
Inactivem yo s in m olec u le
Activated (p ho sp horylated)m yo s in m olec u le
Activated kina s e
Activated cal m od u lin
Cyto p la sm
Ca 2+ b ind s to andactivate s cal m od u lin .
Activated cal m od u lin
activate s the m yo s inlight chain kina s eenzy m es.
The activated kina s e enzy m escatalyze tran s fer of p ho sp hateto m yo s in , activating the m yo s inATP as es.
Activated m yo s in for ms cro ssb ridge s with actin of the thinfila m ent s and s hortening b egin s.
Thinfila m ent
Thic kfila m ent
1
2
3
4
5
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Copyright 2010 Pearson Education, Inc.
Contraction of Sm ooth Mus cle
Very energy efficient (slow ATPases)
Myofilaments may maintain a latch state for prolonged contractions
Rela x ation requires:
Ca 2+ detachment from calmodulin
Active transport of Ca 2+ into SR and ECF
Dephosphorylation of myosin to reducemyosin ATPase activity
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Reg u lation of Contraction
Neural regulation:
Neurotransmitter binding p o [Ca 2+] insarcoplasm; either graded (local) potential or action potential
Response depends on neurotransmitter released and type of receptor molecules
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Reg u lation of Contraction
Hormones and local chemicals:
May bind to G proteinlinked receptors
May either enhance or inhibit Ca 2+ entry
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Sp ecial Feat u re s of Sm ooth Mus cle Contraction
Stress-rela x ation response:
Responds to stretch only briefly, then adaptsto new length
Retains ability to contract on demandEnables organs such as the stomach andbladder to temporarily store contents
Length and tension changes:Can contract when between half and twice itsresting length
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Sp ecial Feat u re s of Sm ooth Mus cle Contraction
Hyperplasia:
Smooth muscle cells can divide and increasetheir numbers
Ex ample:
estrogen effects on uterus at puberty andduring pregnancy
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Copyright 2010 Pearson Education, Inc. Ta b le 9.3
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Typ e s of Sm ooth Mus cle
Single-unit (visceral) smooth muscle:
Sheets contract rhythmically as a unit (gap junctions)
O ften e x hibit spontaneous action potentials
Arranged in opposing sheets and e x hibitstress-rela x ation response
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Typ e s of Sm ooth Mus cle: Mu ltiu nit
Multiunit smooth muscle:
Located in large airways, large arteries,arrector pili muscles, and iris of eye
Gap junctions are rare
Arranged in motor units
Graded contractions occur in response toneural stimuli
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Develo pm ental Asp ect s
Female skeletal muscle makes up 36% of body mass
Male skeletal muscle makes up 42% of bodymass, primarily due to testosterone
Body strength per unit muscle mass is thesame in both se x es
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Mus c u lar Dys tro p hy
Group of inherited muscle-destroyingdiseases
Muscles enlarge due to fat and connectivetissue deposits
Muscle fibers atrophy
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Mus c u lar Dys tro p hy
Duchenne muscular dystrophy (DMD):
Most common and severe type
Inherited, se x -linked, carried by females and
e x pressed in males (1/3500) as lack of dystrophinVictims become clumsy and fall frequently; usually dieof respiratory failure in their 20s
No cure, but viral gene therapy or infusion of stemcells with correct dystrophin genes show promise