This document provides an overview of muscular tissue and muscle contraction. It discusses the three main types of muscle tissue - skeletal, cardiac, and smooth muscle - and their structural characteristics. The sliding filament theory of muscle contraction is explained, involving the interaction of the thick and thin filaments during the cross-bridge cycling of actin and myosin. Calcium release from the sarcoplasmic reticulum in response to the muscle action potential triggers contraction by exposing myosin binding sites on actin. Relaxation occurs when calcium is sequestered back into the sarcoplasmic reticulum.

1. 1
Muscular
Tissue
BIOL
121:
A&P
I
Chapter
10
Rob
Swatski
Associate
Professor
of
Biology
HACC
–
York
Campus
Textbookimages-Copyright©2014JohnWiley&Sons,Inc.Allrightsreserved.

2. 2
Myology
MoHlity
ContracHon
RelaxaHon
Chemical
energy
à
Mechanical
energy

3. 3
Muscle
Tissue
Skeletal
muscle
Cardiac
muscle
Smooth
muscle

4. 4
Skeletal
Muscle
A4ached
to
bone,
skin,
fascia
Striated
&
voluntary
Parallel
fibers

5. 5
Cardiac
Muscle
Heart
muscle
Striated,
involuntary,
autorhythmic
Branching
fibers

6. 6
Smooth
Muscle
In
walls
of
viscera
Nonstriated
&
involuntary
Tapered
individual
cells

7. 7
FuncHons
of
Muscle
Tissue
Movement
Stability
Storing
and
TransporHng
Substances
Thermogenesis

8. 8
ProperHes
of
Muscle
Tissue
Excitability
Extensibility
ContracHlity
ElasHcity

9. 9
Skeletal
Muscle
Whole
muscle
=
organ
MulQnucleated
muscle
cell
=
fiber
Fascicle
Muscle
belly
à
Tendon
à
Bone

10. 10
ConnecHve
Tissue
Components
of
Muscle
Epimysium
Perimysium
Endomysium

11. Perimysium around
fascicle
Satellite cell
Mitochondrion
Endomysium
Myofibril
Muscle fiber
Sarcolemma
Sarcoplasm
Nucleus
OrganizaHon
of
a
fascicle

12. 12
Tendons
Extensions
of
CT
A4ach
muscle
to
bone
or
to
other
muscle
Dense
regular
CT
Aponeurosis

13. 13
Nerve
&
Blood
Supply
of
Muscle
Nerve,
artery,
1-­‐2
veins
per
muscle
Motor
neuron
supplies
several
fibers
Neuromuscular
juncHon
(NMJ)

14. 14

15. 15
Structure
of
Muscle
Fibers
Sarcolemma
Transverse
(T)
tubules
Sarcoplasm:
glycogen
&
myoglobin
Mitochondria

16. Sarcoplasmic reticulum
Sarcolemma
Myofibril
Sarcoplasm
Nucleus
Thick
filament
Thin
filament
Z disc
Details
of
a
muscle
fiber
Triad:
Transverse tubule
Terminal cisterns
Mitochondrion
Sarcomere

17. 17
Myofibrils
Create
striaHons
Surrounded
by
sarcoplasmic
reHculum
(SR)
Thick
&
thin
contracHle
filaments

18. 18

19. 19
Sarcomeres
Organized
contracQle
units
Separated
by
z-­‐
discs
Thick
&
thin
filaments
overlap

20. 20

21. 21
Sarcomere
Structure
M-­‐line
H-­‐zone
A-­‐band
I-­‐band
Z-­‐disc

22. 22

23. 23

24. 24

25. 25
Myofibril
Proteins
ContracHle
proteins
Regulatory
proteins
Structural
proteins

26. 26
ContracHle
Proteins
AcHn
Myosin

27. Myosin-binding site (covered by tropomyosin)
PorHon
of
a
thin
filament
Actin Troponin Tropomyosin

28. 28

29. 29

30. 30

31. 31
Regulatory
Proteins
Troponin
Tropomyosin

32. 32
Structural
Proteins
Nebulin:
alignment
TiHn:
extensibility
&
elasQcity
Myomesin:
anchorage
Dystrophin:
transmits
tension

33. 33

34. Sarcolemma Sarcoplasmic
reticulum (SR)
Transverse
tubule
Terminal
cistern of SR
Sarcoplasm
Membrane
protein
Nucleus
Z
disc
Dystrophin
Thin filamentThick filament
Sarcomere
SimplisHc
representaHon
of
a
muscle
fiber
Myofibril
= Ca2+
Key:
= Ca2+ release
channels
= Ca2+ active
transport pumps
Glycogen granulesMyoglobinMitochondrion
Z
disc

35. 35
Sliding
Filament
Mechanism
of
ContracHon

36. 36
NMJ
Axon
terminal
of
motor
neuron
SynapHc
end
bulb
Motor
end
plate
Synapse
SynapHc
cleW

37. Neuromuscular
juncHon
Axon collateral of
somatic motor neuron
Axon terminal
Synaptic end bulb
Neuromuscular
junction (NMJ)
Sarcolemma
Myofibril in
muscle fiber
Muscle fiber

38. 38
Muscle
ContracHon
Nerve
impulse
reaches
axon
terminal
at
NMJ
SynapHc
vesicles
à
ACh
into
cle
ACh
à
receptors
on
sarcolemma
(motor
end
plate)
Na+
channels
OPEN
Na+
“soaks”
into
muscle
fiber

39. Enlarged
view
of
the
neuromuscular
juncHon
Axon terminal
Nerve impulse
Synaptic vesicle
containing
acetylcholine
(ACh)
SYNAPTIC END
BULB
Synaptic cleft
(space)
Ca2+
Voltage-gated
Ca2+ channel
Sarcolemma
MOTOR END
PLATE

40. Binding
of
acetylcholine
to
ACh
receptors
in
the
motor
end
plate
ACh is released
from synaptic
vesicle
Synaptic cleft
(space)
ACh binds to ACh
receptor
Junctional fold
Synaptic end bulb
ACh is broken down
MOTOR END PLATE
Muscle action
potential is produced
Na+
Ca2+
1
2
4
3

41. Nerve impulse arrives at axon
terminal of motor neuron and
triggers release of
acetylcholine (ACh).
1
ACh diffuses across
synaptic cleft, binds
to its receptors in the
motor end plate, and
triggers a muscle
action potential (AP).
Acetylcholinesterase in
synaptic cleft destroys ACh
so another muscle action
potential does not arise
unless more ACh is released
from motor neuron.
ACh receptor
Synaptic
vesicle filled
with ACh
Muscle action
potential
Transverse tubule
Muscle AP traveling along
transverse tubule opens Ca2+
release channels in the
sarcoplasmic reticulum (SR)
membrane, which allows calcium
ions to flood into the sarcoplasm.
SR
Ca2+
Ca2+ binds to troponin on the thin filament,
exposing the binding sites for myosin.
Elevated Ca2+
Contraction: power strokes use
ATP; myosin heads bind to actin,
swivel, and release; thin filaments
are pulled toward center of
sarcomere.
Muscle relaxes.
Troponin–tropomyosin complex slides
back into position where it blocks the
myosin binding sites on actin.
Ca2+ active
transport pumps
Ca2+ release channels in
SR close and Ca2+
active transport pumps use
ATP to restore low level of
Ca2+ in sarcoplasm.
Ca2+
Nerve impulse
2
3
4
5
67
8
9

42. 42
Muscle
ContracHon
Muscle
acHon
potenHal
à
sarcolemma
&
T-­‐
tubules
SR
à
Ca+2
into
sarcoplasm
Ca+2
binds
to
troponin

43. 43
Muscle
ContracHon
Tropomyosin
swivels
open
Exposes
myosin-­‐
binding
sites
(on
acQn)
ContracHon
Cycle
begins

44. 44
ContracHon
Cycle
1.
ATP
hydrolysis
at
myosin
head
2.
Binding
of
myosin
heads
to
acHn
(crossbridges)
3.
ContracHon
=
power
stroke
4.
Detachment
of
myosin
heads

45. 45
1.
ATP
hydrolysis

46. 46
2.
Binding
of
myosin
heads
to
acHn

47. 47
3.
ContracHon
=
power
stroke

48. 48
4.
Detachment
of
myosin
heads

49. Myosin heads hydrolyze
ATP and become
reoriented and
energized
Myosin heads bind to
actin, forming cross-
bridges
As myosin heads bind
ATP, the cross-bridges
detach from actin
Myosin cross-bridges
rotate toward center of
sarcomere (power stroke)
ADP
ADP
ADP
P
P
ATP
ATP
Key:
= Ca2+
Contraction cycle continues
if ATP is available and Ca2+
level in sarcoplasm is high
1
2
3
4

50. 50

51. 51
ContracHon

52. 52
RelaxaHon

53. 53
Length-­‐
Tension
RelaHonship
Tension
=
force
of
contracQon
OpQmal
sarcomere
length
Overstretched
Understretched

54. 54
Muscle
Metabolism
CreaHne
phosphate
Anaerobic
glycolysis
Aerobic
cellular
respiraHon

55. 55
CreaHne
Phosphate
Made
from
excess
ATP
in
resQng
muscle
15
sec
=
maximum
contracQon
Short,
intense
bursts
of
energy

56. 56
Anaerobic
Glycolysis
Makes
ATP
from
glucose
breakdown
during
glycolysis
If
no
O2:
Pyruvic
acid
à
lacQc
acid
à
blood
2
min
=
maximum
contracQon

57. 57
Aerobic
Cellular
RespiraHon
Makes
ATP
from
glucose
breakdown
in
mitochondria
If
O2:
Pyruvic
acid
à
mitochondria
à
ATP
Several
minutes
to
hours
=
maximum
contracQon

58. 58
Muscle
FaHgue
Feeling
Qred
&
wanQng
to
stop
exercise
=
central
faHgue
Low
Ach
&
Ca+2
Low
creaQne
phosphate
Low
O2
or
glycogen
Oxygen
debt
(recovery
oxygen
uptake)
Build-­‐up
of
lacQc
acid

59. 59
Motor
Units
One
motor
neuron
+
10-­‐2000
muscle
fibers
(150
fibers
avg)
All
fibers
contract
in
unison
Strength
of
contracQon
depends
on:
the
size
of
a
motor
unit
&
the
#
of
fibers
ac4vated
at
a
give
4me

60. 60

61. 61
Control
of
Muscle
Tension
Twitch
contracHon
Brief
=
20-­‐200
msec
All
muscle
fibers
in
motor
unit
contract
in
response
to
AP

62. Parts
of
a
Twitch
ContracHon
Latent
Period
ContracHon
Period
RelaxaHon
Period
Refractory
Period
62

63. 63

64. 64
Refractory
Period

65. 65
Frequency
of
SHmulaHon
Wave
summaHon
Unfused
(Incomplete)
tetanus
Fused
(Complete)
tetanus

66. Myograms
Forceofcontraction
(a) Single twitch (b) Wave summation (c) Unfused tetanus (d) Fused tetanus
Time (msec)
Action
potential

67. 67
Wave
SummaHon

68. 68
Unfused
(Incomplete)
Tetanus

69. 69
Fused
(Complete)
Tetanus

70. 70
Why
does
summaHon
&
tetanus
occur?
Ca+2
remains
in
sarcoplasm
ElasQc
components
(tendons,
CT)
remain
taut
Myotonic
goats!

71. 71
Motor
Unit
Recruitment
Large
motor
units
à
High
tension
(Strength)
Small
motor
units
à
Low
tension
(Precision)
Motor
units
in
whole
muscle
fire
asynchronously
Why?

72. 72
Muscle
Tone
Involuntary
contracQon
&
relaxaQon
of
small
#
of
motor
units
Alternate
in
constantly
shiing
pa4ern
No
movement
produced
(but
muscles
kept
firm)
FuncQons:
posture,
blood
pressure

73. 73
Isotonic
ContracHon
Generates
movement
Concentric:
flexion
(muscle
shortens)
Eccentric:
extension
(muscle
lengthens)

74. 74
Isometric
ContracHon
No
movement
Maintains
posture
Maintains
objects
in
fixed
posiQon

75. 75
VariaHons
in
Skeletal
Muscle
Fibers
Differ
in
amount
of
myoglobin,
mitochondria,
capillaries
Red
muscle
(darker)
White
muscle
(lighter)
Range
of
contracQon
speeds
&
faQgue
resistance

76. 76
3
Types
of
Skeletal
Muscle
Fibers
Slow
OxidaHve
(SO)
Fast
OxidaHve
GlycolyHc
(FOG)
Fast
GlycolyHc
(FG)

77. Transverse
secHon
of
three
types
of
skeletal
muscle
fibers
Slow oxidative fiber
Fast glycolytic fiber
Fast oxidative–
glycolytic fiber
LM 440x

78. 78
Slow
OxidaHve
(SO)
Fibers
Smallest,
weakest,
slowest
(slow-­‐twitch)
Red
muscle:
lots
of
mito,
myo,
&
blood
Aerobic
cellular
respiraQon
à
ATP

79. 79
Slow
OxidaHve
(SO)
Fibers
Sustained
contracQons
High
faQgue
resistance
Maintains
posture,
yoga
poses
Aerobic
endurance
acQviQes
(marathon
running)

80. 80
Fast
OxidaHve-­‐
GlycolyHc
(FOG)
Fibers
Large
diameter
&
strength
Fast-­‐twitch
Red
muscle:
lots
of
mito,
myo,
&
blood

81. 81
Fast
OxidaHve-­‐
GlycolyHc
(FOG)
Fibers
Aerobic
&
anaerobic
respiraQon
à
ATP
(store
glycogen)
Moderate
faQgue
resistance
Walking,
sprinQng

82. 82
Fast
GlycolyHc
(FG)
Fibers
Strongest,
fast
twitch
fibers
High
glycogen
storage
White
muscle:
less
mito,
myo,
blood

83. 83
Fast
GlycolyHc
(FG)
Fibers
Anaerobic
cellular
respiraQon
à
ATP
Low
faQgue
resistance
Rapid,
intense,
brief
contracQons:
weight
liing

84. 84
Cardiac
Muscle
Tissue
Striated,
branching,
shorter
fibers
of
heart
Intercalated
discs
with
gap
juncHons
One
central
nucleus
per
fiber

85. 85

86. 86
Cardiac
Muscle
Tissue
Same
acQn
&
myosin
arrangement
as
skeletal
muscle
Autorhythmic
Longer
contracQons
(longer
Ca+2
delivery)

87. 87
Smooth
Muscle
Tissue
Small,
single,
nonstriated,
tapered,
involuntary
fibers
No
T
tubules
&
li4le
SR
Contains
acQn
&
myosin,
but
no
sarcomeres
Dense
bodies

88. Autonomic
neurons
Nucleus
Muscle fibers
(a) Visceral (single-unit)
smooth muscle tissue
(b) Multiunit smooth
muscle tissue