biol 121 chp 10: muscular tissue
DESCRIPTION
This is a lecture presentation for my BIOL 121 Anatomy and Physiology I students on Chapter 10: Muscular Tissue (Principles of Anatomy and Physiology, 14th Ed. by Tortora and Derrickson). Rob Swatski, Associate Professor of Biology, Harrisburg Area Community College - York Campus, York, PA. Email: [email protected] Please visit my website for more anatomy and biology learning resources: http://robswatski.virb.com/TRANSCRIPT
1
Muscular Tissue
BIOL 121: A&P I
Chapter 10
Rob Swatski Associate Professor of Biology
HACC – York Campus
Text
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Myology
MoHlity
ContracHon
RelaxaHon
Chemical energy à Mechanical
energy
3
Muscle Tissue
Skeletal muscle
Cardiac muscle
Smooth muscle
4
Skeletal Muscle A4ached to bone, skin,
fascia
Striated & voluntary
Parallel fibers
5
Cardiac Muscle
Heart muscle
Striated, involuntary, autorhythmic
Branching fibers
6
Smooth Muscle
In walls of viscera
Nonstriated & involuntary
Tapered individual
cells
7
FuncHons of Muscle Tissue
Movement Stability Storing and TransporHng Substances
Thermogenesis
8
ProperHes of Muscle Tissue
Excitability Extensibility ContracHlity ElasHcity
9
Skeletal Muscle Whole muscle
= organ
MulQnucleated muscle cell =
fiber
Fascicle
Muscle belly à Tendon à
Bone
10
ConnecHve Tissue
Components of Muscle
Epimysium
Perimysium
Endomysium
Perimysium around fascicle
Satellite cell
Mitochondrion
Endomysium
Myofibril
Muscle fiber
Sarcolemma
Sarcoplasm
Nucleus
OrganizaHon of a fascicle
12
Tendons
Extensions of CT
A4ach muscle to bone or to other muscle
Dense regular CT
Aponeurosis
13
Nerve & Blood Supply of Muscle
Nerve, artery, 1-‐2 veins per muscle
Motor neuron supplies several
fibers
Neuromuscular juncHon (NMJ)
14
15
Structure of Muscle Fibers
Sarcolemma
Transverse (T) tubules
Sarcoplasm: glycogen & myoglobin
Mitochondria
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
Myofibrils
Create striaHons
Surrounded by sarcoplasmic reHculum (SR)
Thick & thin contracHle filaments
18
19
Sarcomeres
Organized contracQle units
Separated by z-‐discs
Thick & thin filaments overlap
20
21
Sarcomere Structure
M-‐line
H-‐zone
A-‐band
I-‐band
Z-‐disc
22
23
24
25
Myofibril Proteins ContracHle proteins
Regulatory proteins
Structural proteins
26
ContracHle Proteins
AcHn
Myosin
Myosin-binding site (covered by tropomyosin)
PorHon of a thin filament
Actin Troponin Tropomyosin
28
29
30
31
Regulatory Proteins
Troponin
Tropomyosin
32
Structural Proteins
Nebulin: alignment
TiHn: extensibility & elasQcity
Myomesin: anchorage
Dystrophin: transmits tension
33
Sarcolemma Sarcoplasmic reticulum (SR)
Transverse tubule
Terminal cistern of SR
Sarcoplasm
Membrane protein
Nucleus Z
disc
Dystrophin
Thin filament Thick filament
Sarcomere
SimplisHc representaHon of a muscle fiber
Myofibril
= Ca2+
Key:
= Ca2+ release channels
= Ca2+ active transport pumps
Glycogen granules Myoglobin Mitochondrion
Z disc
35
Sliding Filament Mechanism of ContracHon
36
NMJ
Axon terminal of motor neuron
SynapHc end bulb
Motor end plate
Synapse
SynapHc cleW
Neuromuscular juncHon
Axon collateral of somatic motor neuron
Axon terminal
Synaptic end bulb
Neuromuscular junction (NMJ)
Sarcolemma
Myofibril in muscle fiber
Muscle fiber
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
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
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
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
6 7
8
9
42
Muscle ContracHon
Muscle acHon potenHal à
sarcolemma & T-‐tubules
SR à Ca+2 into sarcoplasm
Ca+2 binds to troponin
43
Muscle ContracHon
Tropomyosin swivels open
Exposes myosin-‐binding sites (on
acQn)
ContracHon Cycle begins
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
1. ATP hydrolysis
46
2. Binding of myosin heads to acHn
47
3. ContracHon = power stroke
48
4. Detachment of myosin heads
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
51
ContracHon
52
RelaxaHon
53
Length-‐Tension
RelaHonship
Tension = force of contracQon
OpQmal sarcomere length
Overstretched
Understretched
54
Muscle Metabolism
CreaHne phosphate
Anaerobic glycolysis
Aerobic cellular respiraHon
55
CreaHne Phosphate
Made from excess ATP in resQng muscle
15 sec = maximum contracQon
Short, intense bursts of energy
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
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
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
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
61
Control of Muscle Tension
Twitch contracHon
Brief = 20-‐200 msec
All muscle fibers in motor unit contract in
response to AP
Parts of a Twitch ContracHon
Latent Period
ContracHon Period
RelaxaHon Period
Refractory Period
62
63
64
Refractory Period
65
Frequency of
SHmulaHon
Wave summaHon
Unfused (Incomplete)
tetanus
Fused (Complete) tetanus
Myograms
Forc
e of
con
tract
ion
(a) Single twitch (b) Wave summation (c) Unfused tetanus (d) Fused tetanus Time (msec)
Action potential
67
Wave SummaHon
68
Unfused (Incomplete)
Tetanus
69
Fused (Complete)
Tetanus
70
Why does summaHon & tetanus occur?
Ca+2 remains in sarcoplasm
ElasQc components (tendons, CT) remain taut
Myotonic goats!
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
Muscle Tone
Involuntary contracQon &
relaxaQon of small # of motor units
Alternate in constantly shi\ing
pa4ern
No movement produced (but
muscles kept firm)
FuncQons: posture, blood pressure
73
Isotonic ContracHon
Generates movement
Concentric: flexion (muscle shortens)
Eccentric: extension (muscle lengthens)
74
Isometric ContracHon
No movement
Maintains posture
Maintains objects in fixed posiQon
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
3 Types of Skeletal Muscle Fibers
Slow OxidaHve (SO)
Fast OxidaHve GlycolyHc (FOG)
Fast GlycolyHc (FG)
Transverse secHon of three types of skeletal muscle fibers
Slow oxidative fiber
Fast glycolytic fiber
Fast oxidative– glycolytic fiber
LM 440x
78
Slow OxidaHve (SO) Fibers
Smallest, weakest, slowest (slow-‐twitch)
Red muscle: lots of mito, myo, &
blood
Aerobic cellular respiraQon à ATP
79
Slow OxidaHve (SO)
Fibers
Sustained contracQons
High faQgue resistance
Maintains posture, yoga poses
Aerobic endurance acQviQes (marathon
running)
80
Fast OxidaHve-‐GlycolyHc
(FOG) Fibers
Large diameter & strength
Fast-‐twitch
Red muscle: lots of mito, myo, & blood
81
Fast OxidaHve-‐GlycolyHc
(FOG) Fibers Aerobic & anaerobic
respiraQon à ATP (store glycogen)
Moderate faQgue
resistance
Walking, sprinQng
82
Fast GlycolyHc (FG) Fibers
Strongest, fast twitch fibers
High glycogen storage
White muscle: less mito, myo, blood
83
Fast GlycolyHc (FG) Fibers
Anaerobic cellular
respiraQon à ATP
Low faQgue resistance
Rapid, intense, brief
contracQons: weight li\ing
84
Cardiac Muscle Tissue
Striated, branching,
shorter fibers of heart
Intercalated discs with gap juncHons
One central nucleus per fiber
85
86
Cardiac Muscle Tissue Same acQn &
myosin arrangement as skeletal muscle
Autorhythmic
Longer contracQons (longer Ca+2 delivery)
87
Smooth Muscle Tissue Small, single, nonstriated, tapered,
involuntary fibers
No T tubules & li4le SR
Contains acQn & myosin, but no sarcomeres
Dense bodies
Autonomic neurons
Nucleus
Muscle fibers
(a) Visceral (single-unit) smooth muscle tissue
(b) Multiunit smooth muscle tissue