Muscle

1
Muscle

• Chapter 16

2
Roles of Muscle

• Biological Motor (effector)
• maintains posture
• does work
• produces heat
• Regulates Physiological processes
• controls movement of substances through tubular
  structures
• expel substances from body at proper time
• pump

3
Muscle categorization

• visceral muscles- lines walls of internal organs
• smooth muscle- can be found in intestines
• cardiac muscle- found in heart
• skeletal muscle- voluntary muscle that controls
  conscious movement and behavior

4
Muscle Control

• Voluntary muscle- moved by conscious thought
• involuntary- not controlled by thought
  (breathing)
• Stimulated and regulated by the CNS, ANS,
  hormones, or environmental factors (internal
  metabolic)

5
Voluntary control
Skeletal muscle
Striated structure
Cardiac muscle
Smooth structure
Visceral muscle
Involuntary control
fig 16-1, pg 479
6

• Table. Comparison of Muscle Types                 
                                                    
                                                   
                                                    
              Muscle Type                           
                                         Characteri
  stic            Skeletal                          
    Cardiac                            
   Smooth                             
      Nuclei                      Multinucleated  
               Single nucleus centrally    Single
  nucleus centrally                               
    peripherally located         located            
                     located
• Banding                    Actin and myosin
  form     Actin and myosin form        Actin and
  myosin no                                
  distinctive bands              distinctive
  bands                 distinctive bands
• Z disks                       Present             
                  Present                           
      Z disks not present                         
                                                    
                                            
  cytoplasmic dense bodies                         
                                                    
                                            are
  present T tubules                  T tubules at
  A-I                 T tubules at Z
  disk             No T tubules no
  triads                                 junction
  triads                  diads present             
          or diads caveolae are                   
                 present                            
                                             
  present Cellular                     No
  junctional                    Intercalated
  disks               Gap junctio
  junctions                        complexes   
• Neuromuscular          Present                    
           Not present contraction     Not
  present contraction      junctions              
                                            is
  intrinsic            is intrinsic, neural, or 
                                                   
                                                    
                       hormonal Ca
  2-binding           Troponin                     
       Troponin                            Calmoduli
  n
• Regeneration            Limited satellite
  cells       None                                
  High                                     

7
Gross Structure

• skeleton works w/muscle as a lever system
• Tendon- connects muscle to bone
• origin- more stationary proximal attachment
• insertion- distal end of attachment
• belly- wide thick central portion of muscle

8
Muscle Force 10 x 35/5 70 kg-wt
Biceps has double origin and a single insertion
Tendon Velocity 7 x 5/35 1 cm/s
Tendons
Origin
Bicepts (agonist muscle)
Flexor- closes joint Extensor- opens joint
Tricept (antagonist muscle)
10 kg
Flexion
Fulcrum for lever
10 kg
Insertion
Extension
Hand force 10 kg-wt
5 cm
35 cm
Lever ratio 535 or 17
fig 16-2, pg 480
9
fig 16-3, pg 481
10

• Muscle cell muscle fiber
• endomysium- delicate connective tissue sheet that
  surrounds ind muscle fibers
• fasciculi- bundles of muscle fibers
• perimysium- surrounds muscle bundle
• epimysium- connective tissue that surrounds
  entire muscle

11
Cellular structure
fig 16-3, pg 481
12
Contractile apparatus
Z line
Z line
Longitudinal
Thin filaments
Thick Filaments at M line
Thick filaments
Thick and thin filaments
Relaxed sarcomere
Cross sectional
M line
Z line
Z line
H zone
I band
I band
A band
I band
I band
fig 16-5, pg 483
Contracted sarcomere
13
Width of a myofibril
Sarcoplasmic reticulum
H
Mitochondria
Z
Thin filaments
Thick filaments
A
T-tubule
I
Width of a myofibril
Sarcomere
M
fig 16-4, pg 482
14
Vocab

• Crossbridge- projections from thick filaments
  that reach directly toward thin filaments
• z-line- marks boundary of sarcomere, on center of
  I-band
• H-zone- center region of A-band, no thin
  filaments
• Titin- large protein extending from Z-line

15
(a) Thin filament
Troponin subunits
TnT
Tnl
TnC
Tropomyosin
Troponin Tropomyosin Regulatory complex
Functional actin filament
Actin
fig 16-6a, pg 485
16
(b) Thick filament
Light chains
End view of myosin filament
Head region of myosin binds ATP and actin
Myosin heads project of crossbridges
Bare zone tail portions only
Myosin filaments packed tail-to-tail
Assembled myosin filament
fig 16-6b, pg 485
17
(C) Functional assembly of myofilaments
Thick filaments (myosin)
Thin filament (actin, troponin And tropomyosin)
Crossbridge- free region
Functional overlap region
Functional overlap region
fig 16-6c, pg 485
18
Muscle Fiber internal membrane

• Participate in control of contraction and
  relaxation
• sarcolemma- outer covering of cell
• SR-run at right angles to the t-tubules and down
  length of sarcomere
• triad- consist of t-tubules and enlarged end
  portions of SR

19
T-tubule interior arrangement
T-tubule openings
Sarcolemma
Basal lamina
Mitochondria
Terminal cisternae
Longitudinal element Of sarcoplasmic reticulum
Cut away of Myofibril illustrating Myofibril
arrangement
fig 16-7, pg 486
20
Cardiac muscle

• Cells of cardiac muscle are smaller than skeletal
  muscle cells
• Cardiac cells have single centrally located
  nucleus
• have intercalated disk
• desmosome
• gap junctions
• intracellular organization most like skeletal
  muscle
• have dyad rather than triad

21
Intercalated disc
fig 16-8a, pg 487
22
Sacrolemma
Basal lamina
Myofibrils
Longitudinal system
Mitochondria
Transverse tubule
Nucleus
Intercalated disc
Myofibril
Opening of Transverse tubule
fig 16-8b, pg 487
23
Thin filament
Z-disc
Z-disc
M line
Thick filament
I- Band
I- Band
H zone
A-Band
Sarcomere
fig 16-8c, pg 487
24
Rough Endoplasmic reticulum
Glycogen granules
Nucleus
Mitochondria
Thin filament
Thick filament
Dense bodies
Plasma membrane
fig 16-9a, pg 479
25
Rough Endoplasmic reticulum
Nucleus
Mitochondra
Dense bodies
Plasma membrane
Collagen fibers
Schwann cell
Axon
Epinephrine vesicles
fig 16-9b, pg 479
26
Contractions and Tension

• Isotonic
• Isometric
• Length v. tension

27
ISOMETRIC CONTRACTION
Agonist tenses but does not shorten
Force of muscle contraction equals counterforce
of weight
Force of muscle contraction equals counterbalance
of opposing muscle contraction
Opposing muscles contract simultaneously
No movement
No movement
Greater force of muscle contraction
States of contraction
States of relaxation
Agonist shortens
Antagonist relaxes by reflex action
Lesser counter- force of weight
ISOTONIC CONTRACTION
Movement takes place
fig 16-11a, pg 490
28
Oscilloscope
Length scale
Rigid support
Length
Muscle (isometric contraction)
Force
Time
Length adjustment
Force transducer
Stimulator
fig 16-11b, pg 490
29
Total
F ORCE
Active
Passive
Length (cm) WHOLE MUSCLE
F ORCE
Length (microns) SINGLE SARCOMERE
fig 16-12, pg 492
30
fig 16-13, pg 493
31
Oscilloscope
Length
Rigid support
Length transducer
Lever
Length
Pivot
Force
Afterload support
Muscle (isotonic contraction)
Time
Length adjustment
Force transducer
Stimulator
fig 16-14, pg 493
32
Slope indicates velocity
Length
A
Force
B
C
D
200 msec
100 msec
300 msec
Time
Limit of Force shortening
A
B
C
Force
Velocity
D
Length
Force
fig 16-15, pg 494
33
Optimal power output
A
(F1, V1)
Lower power output
C
Lower power output
Shortening velocity
B
(F0, V0)
(F2, V2)
Muscle force
fig 16-16, pg 495
34
Longitudinal sarcoplasmic reticulum
Sarcolemma
T-tubules
Terminal cisternae
Myofilaments
fig 16-17a, pg 498
35
Longitudinal sarcoplasmic reticulum
Sarcolemma
T-tubules
Terminal cisternae
Myofilaments
fig 16-17b, pg 498
36
Longitudinal sarcoplasmic reticulum
Sarcolemma
T-tubules
Myofilaments
fig 16-17c, pg 498
37
Longitudinal sarcoplasmic reticulum
Sarcolemma
T-tubules
Myofilaments
fig 16-17d, pg 498
38
Actin
Binding sites exposed
Tropomyosin
Covered
Ca2
Ca2
Tropomyosin
Troponin complex
fig 16-18a, pg 499
39
Myosin
Myosin
Add calcium
Remove calcium
Muscle contracted Ca2gt10-5 M Ca2 bound to
troponin
Muscle contracted Ca2gt10-9 M no Ca2 for troponin
Actin
Actin
Ca2
Tropomyosin blocking binding sites interaction
inhibited
Tropomyosin shifted interaction permitted
Troponin complex
Tropomyosin
fig 16-18b, pg 499
40
In the muscle fiber the contraction begins with
the release of Ca2
1
Ca2 binds to the TnC subunit of the
Troponin-Tropomyosin complex. This initiates a
conformation change which ultimately shifts
tropomyosins position and exposes the myosin
binding site on actin. P1 is then released.
Membrane depolarization by action potential
causes release of Ca2 ions from the sarcoplasmic
reticulum
If Ca2 is present, crossbrdige cycles continue.
The release of P1 triggers the power stroke of
contraction, the energy being supplied by the
hydrolysis of ATP?ADPP1E. During the power
stroke the myosin head rotates 45º bringing the Z
line closer to the thick filament. ADP is them
released.
If Ca2 is taken away, the cycle stops here and
the muscle relaxes.
2
If ATP is taken away crossbridges remain attached
and rigor mortis will occur. Cycle stops here.
4
ATP binds to the myosin head releasing the
crossbridge. It remains bound as the hydrolyzed
from of ADP and Pi.
Membrane repolariza- tion allows uptake of Ca2
ions by the sarcoplasmic reticulum
Myosin remains in the bound position until ATP
binds to the myosin head or Ca2 is removed.
3
As long as Ca2 and ATP are resent the cycle
continues. The Z line is pulled closer and
closer to the ends of the thick filaments.
fig 16-19, pg 501
41
? ACTIVATION OF MCLK
Calcium ions taken up
Calcium bound to calmodulin
CAM
CAM
CAM
RELAXATION
CONTRACTION
MLCK
MLCK
MLCK
Enzyme inactive
Enzyme inactive
? REGULATION OF MYOSIN
Non-phosphorylated Myosin (inactive)
ATP
P
Phosphatase
Phosphorylated myosin
ADP
? CROSSBRIDGE CYCLE
P1
ATP
ADP
fig 16-20, pg 502
ATP from cellular energy sources
42
Nerve action potentials
Em
Contractions
Force
Em
Twitches
Tetanus
Time
fig 16-21, pg 503
43
fig 16-22, pg 506
44
Vesicles containing acetylcholine
Mitrochondria
Ach vesicle
Nicotinic receptors at neuromus-clar junction
15mV
End-plate potential (stationary)
fig 16-23a, pg 507
45
Action potential (moving)
Action potential (moving)
fig 16-23b, pg 507
46
Creatine phosphate
1
A
ADP
Replacement of ATP
Consumption of ATP
Coupled reactions
Contraction
Net energy exchange
Myosin ATPase
ATP
Creatine
ATP
ATP
2
ATP
B
Creatine phosphate pool (energy buffer)
ATP supply
Sarcoplasmic reticulum Ca2 pump
Relaxation
ATP
ATP
Cellular amino acids
3
O2
Citric acid cycle
ATP
ATP
C
Fatty acids
4
Other metabolic functions
Glycolysis
Lactic acid
Glycogen
Glucose
fig 16-24, pg 511