Muscles
Skeletal
Cardiac
Smooth
15-Mar-16
Muscles
1
Muscles
 Specialized
tissue
 Convert chemical energy into
mechanical energy
 The energy obtained from nutrients

Enable the muscles to contract
 Move
different skeletal bones around joints
 Cardiac muscle to pump blood
 Smooth muscle to contract eg- GIT
15-Mar-16
Muscles
2
Types of Muscles
 There
are three types of muscles
 Smooth
 Skeletal
(striated)
 Cardiac (which is also striated)
15-Mar-16
Muscles
3
Types of Muscles
Skeletal Muscle
Syncytial
smooth Muscle
15-Mar-16
Cardiac Muscle
Multiunit smooth
Muscle
Muscles
4
Skeletal Muscles
 Structure
 Muscle
cell (muscle fiber)
Long cylindrical multinucleated cell
 Lie parallel to each other

 Force
of action is directed along the fiber’s
long axis
Length varies from few mm to 30 cm or
more
 Width is about 0.15 mm

15-Mar-16
Muscles
5
Skeletal Muscles
Endomysium


Muscle fiber

Perimysium

Muscle fibers
15-Mar-16
Level of organization
Fine layer of
connective tissue
(endomysium)
Muscles
Wraps each muscle
fiber
It separates it from
neighboring fiber
6
Skeletal Muscles
Endomysium
Muscle fiber


Perimysium
Another layer:
perimysium
Surround a bundle of
up to 150 muscle
fibers

Muscle fibers

A fascia

15-Mar-16
Muscles
Fascicules
Fibrous connective
tissue surround the
entire muscle
7
Skeletal Muscles
 Beneath
 The
the endomysium lie
sarcolema
 Thin
elastic membrane
 Enclose the fiber’s cellular contents
 Contain the plasma membrane
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Muscles
8
Skeletal Muscles
 Plasma

Conduct electrochemical wave of
depolarization
 Over

15-Mar-16
membrane
the surface of fiber
Insulates one fibre from another during
depolarization
Muscles
9
Epimysium
(Connective tissue
sheath)
Fascicules within sheath
of perimyesium
Bundles of fibers.
Muscles fibers are
enclosed by own sheath
of endomyesium
Sarcoplasmic reticulum
15-Mar-16
Muscles
From H.Taher Sherief;
Physiology Book(CD)
10
Skeletal Muscles
 Within
the muscle fiber
Aqueous protoplasm (sarcoplasm) which
contains
 Enzymes, fat, glycogen particles
 Nuclei (about 250 per mm length)

 Genes,
15-Mar-16
mitochondria, organelles
Muscles
11
Sarcoplasmic Reticulum
Nucleus
Sarcoplasmic
reticulum
Terminal cisterna
(lateral sacs)
Myofibrils
Sarcolemma

Longitudinal
network of tubular
channels and
vesicles

Z disc
sarcoplasmic
reticulum
(SR)
Allows the wave of
depolarization
 To spread from
outer surface to
inner environment
Z-disc
Triad
15-Mar-16
Muscles
12
Sarcoplasmic Reticulum
Nucleus
Sarcoplasmic
reticulum
Myofibrils
 Through
tubules

Terminal cisterna
(lateral sacs)
Sarcolemma

Z disc
sarcoplasmic
reticulum
(SR)
15-Mar-16
Muscles
To initiate
muscle
contraction
Contain Ca++ pump
in their membrane

Z-disc
Triad
the T
Pump Ca++ from
sarcoplasm into
vesicles
13
Skeletal Muscles
 Chemical
composition
75% water
 20% proteins
 5% minerals & nutrients

 Salts,
high energy phosphates, urea, lactate
 Na+, Ca++, Mg++, Cl- phosphorous,
 Fat, carbohydrate, AA
15-Mar-16
Muscles
14
Skeletal Muscles
Ultra-structure
 A single multinucleated muscle fibre
contain



Smaller functional units
Lie parallel to long axis


Myofibrils contain even smaller units

•
•
•
15-Mar-16
Myofibrils
•
Myofilaments
Actin
Troponin
Tropomyosin
myosin
Muscles
15
Ultra-structure
MYOFIBRILS ARE MADE OF
REPEATING ASSEMBLIES OF
THICK AND THIN FILAMENTS
15-Mar-16
Muscles
16
Epimysium
(Connective tissue
sheath)
Fascicules within sheath
of perimyesium
Bundles of fibers.
Muscles fibers are
enclosed by own sheath
of endomyesium
Sarcoplasmic reticulum
Actin
15-Mar-16
Muscles
From H.Taher ;
Physiology Book(CD)
17
Myosin Filament

Light
chains

Myosin
globular
head
Made up of 4 protein
chains
2 myosin molecules


Double helix
Tail segment

Tail, Heavy
Meromysin (HMM)
Light
Meromysin
Heavy meromysin
(HMM)
Light meromysin
Myosin
globular
head
LMM
HMM
15-Mar-16
Muscles
18
Myosin Filament


Light
chains


Myosin
globular
head
Tail, Heavy
Meromysin (HMM)
Globular head
4 light chains

Light
Meromysin
Cross-bridge formation
ATPase
2 associated with each
myosin molecule
globular heads
Myosin
globular
head
LMM
HMM
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Muscles
19
Myosin Filament
15-Mar-16
Muscles
20
Actin Filaments

Actin filament
Made up of

Tropomyosin
Troponin
2 strands of actin
molecules
twisted together
 Double helix

Can exists as


15-Mar-16
Muscles
Globular proteins
Fibrilar proteins
21
Actin Filaments
Actin filament

Troponin complex


15-Mar-16
Tropomyosin

Tropomyosin
Troponin
Muscles
Attaches tropomyosin
to actin
Covers active sites on
actin
22
Other Muscle Proteins
 Others
include
 -actinin distributed along Z band
 -actinin found in actin filament
 M protein
 C protein

15-Mar-16
Muscles
23
Muscle Contraction

Pure myosin and actin



Combine to form
Actomyosin
Sliding filament theory of muscle
contraction
15-Mar-16
Muscles
24
Cross bridge Z - line
Z - line
Sarcomere showing the
region of overlap
between thick and thin
filaments
RELAXED
Sarcomere shortening in
response to crossbridge
formation
Increase in the degree of overlap
CONTRATING
FULLY
CONTRACTED
From: Physiology textbook CD
by Hassen T. Sherief
15-Mar-16
Muscles
25
Mechanism of Muscle
Contraction
Active sites
Inhibitor
Actin filament


At rest
Interaction between
actin and myosin

15-Mar-16
Muscles
Prevented by troponin
tropomyosin complex
26
Mechanism of Muscle
Contraction
Active sites
Inhibitor

Actin filament
Ca++
In the presence of
Ca++


Leads to
conformational
change of
tropomyosin

15-Mar-16
Muscles
Ca++ bind to troponin C
Uncovering of active
sites
27
Mechanism of Muscle
Contraction
Active sites
Inhibitor
Actin filament


Myosin bind to actin
Bending of globular
head


15-Mar-16
Muscles
While still attached to
actin
Moves the actin
molecule
28
Mechanism of Muscle
Contraction
Active sites
Inhibitor

Actin filament
The bending of
globular head


ATP bind on myosin
head

15-Mar-16
Muscles
Exposes ATP binding
site
Detachment from actin
29
Mechanism of Muscle
Contraction
Active sites
Inhibitor

Actin filament

ATP is hydrolyzed to
ADP and energy
ADP, energy



15-Mar-16
Muscles
Incorporated into
myosin head
Straightening of bent
head to 900
Ready to attach to
next active sight
30
Mechanism of Muscle
Contraction
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Muscles
31
15-Mar-16
Muscles
32
Excitation Contraction
Coupling
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Muscles
33
15-Mar-16
Muscles
34
Excitation Contraction
Coupling
AP
T-tubule

AP
Arrival of AP on
motor end plate


Sarcoplasmic ret
Ca++
Ca++
AP along sarcolema

Voltage
gated
channels
Mg++
Ca++
NMJ transmission
Spread through

Ca++/Mg++
ATPase
T-tubules
Ca++
Ca++
Ca++
15-Mar-16
Muscles
35
Excitation Contraction
Coupling
AP

T-tubule
AP
Opening of voltage
gated

Sarcoplasmic ret
Voltage
gated
channels

Ca++
Ca++
Mg++
Ca++

Ca++
Ca++
Sarcoplasmic reticulum
Into sarcoplasm

Ca++
15-Mar-16
Ca++ move from

Ca++/Mg++
ATPase
Ca++ channels
Muscles
 Ca++ concentration
36
Actin Filaments

Actin filament
Ca++ bind to troponin C


Tropomyosin
Troponin
Active site

Actin and myosin


15-Mar-16
Muscles
Conformational change
of tropomyosin
Uncovering of active
sites
Crossbridge formation
Muscle contraction
37
Excitation Contraction
Coupling
AP
T-tubule


AP
Sarcoplasmic ret
Ca++
Ca++
Voltage
gated
channels
Mg++
Ca++
Ca++
Relaxation occur
Ca++/Mg++
ATPase
Active pumping of
Ca++ into
sarcoplasmic
reticulum

Ca++/Mg++ ATPases
Ca++
Ca++
15-Mar-16
Muscles
38
Actin Filaments

Actin filament
There is a

Tropomyosin
Troponin

Active site

15-Mar-16
Muscles
↓ in the Concentration
of Ca++ in the
cytoplasm
Closure of active sites
relaxation
39
Excitation Contraction coupling
15-Mar-16
Muscles
40
15-Mar-16
Muscles
41
Length – Tension
Relationship
15-Mar-16
Muscles
42
Length – Tension relationship
During muscle contraction the isometric
force exerted by the muscle
 Depend on the



Actual length of the muscle fibers
The force developed

Related to degree of overlap between

15-Mar-16
Actin and myosin
Muscles
43
15-Mar-16
Muscles
44
Cross-bridges

Mechanical link


The interaction
between



Muscles
Myosin head and
Actin filament
Cause the head to

15-Mar-16
Between thick and thin
filament
Tilt towards the arm
45
Cross-bridges

This drags the actin
filament



This is the power
stroke
The number of cross
bridges determine

15-Mar-16
Muscles
Towards centre of the
sarcomere
Force produced by
muscle fibre
46
Cross-bridges

Each of the crossbridge


The greater the
number of crossbridges


15-Mar-16
Muscles
Operate independently
of the others
Attaching to actin
The greater the force
of contraction
47
Cross bridge Z - line
Z - line
Sarcomere showing the
region of overlap
between thick and thin
filaments
RELAXED
Sarcomere shortening in
response to crossbridge
formation
Increase in the degree of overlap
CONTRATING
FULLY
CONTRACTED
From: Physiology textbook CD
by Hassen T. Sherief
15-Mar-16
Muscles
48
15-Mar-16
Muscles
49
Smooth Muscles
15-Mar-16
Muscles
50
Smooth Muscles

Responsible for contractility

Hollow organs

Blood vessels, GIT, urinary bladder, uterus
Structure differ from that of skeletal
muscle
 Can develop isometric force per cross
sectional area



Equal to or greater than that of skeletal muscle
Speed of contraction

15-Mar-16
A fraction of that of skeletal muscle
Muscles
51
Smooth Muscles
 Does not show cross
 Under microscope
striation
 It
is also known as INVOLUNTARY
muscle because



15-Mar-16
Its function is not under our voluntary will
Its activities arises spontaneously
Or through the autonomic nervous system
Muscles
52
Smooth Muscles
Smooth muscle from different tissue differ
 In structure



Organization in sheets, bundles
In property

15-Mar-16
Response to different types of stimuli,
innervations
Muscles
53
Smooth Muscles

But in general
individual cells

Are long and
spindle shaped



About 50 to 500 μm
long
Are 5 to 10 μm wide
Have one nucleus
per cell
Guyton Textbook of
Physiology
15-Mar-16
Muscles
54
Smooth Muscles

Are surrounded by a
cell membrane



Exhibit invagination
(surface vesicles,
caveoli)
Have myosin and
actin
Contain
sarcoplasmic
reticulum
Guyton Textbook of
Physiology
15-Mar-16
Muscles
55
Multi-Unit Type

Multi-unit smooth
muscle



www.uic.edu/classes/phyb/phyb516/
smoothmusclesleu3.htm
15-Mar-16
Muscles
Composed of individual
muscle fibres
Each with its own
nerve inervation
Can function
independently
56
Multi-Unit Type

Each muscle fibre is



www.uic.edu/classes/phyb/phyb516/
smoothmusclesleu3.htm
15-Mar-16
Muscles
Discrete and operates
independently
There is no
spontaneous
contraction
Activity controlled by
the autonomic
nervous system
57
Multi-Unit Type

The axon terminal


Found in the


www.uic.edu/classes/phyb/phyb516/
smoothmusclesleu3.htm
15-Mar-16
Muscles
Makes several synaptic
contacts on the
membrane
Iris, ciliary body
Around hair follicles
58
Unitary (Single unit) Type



Unitary (single unit),
visceral smooth
muscle
Individual cells join
together to form a
sheet of cells
When one cell is
excited

Then all contract as a
single unit
Guyton Textbook of
Physiology
15-Mar-16
Muscles
59
Unitary (Single unit) Type

Found in the walls of
viscera


Digestive system,
urinary bladder, ureters
Blood vessels
Guyton Textbook of
Physiology
15-Mar-16
Muscles
60
Unitary (Single unit) Type


Cells are aggregated
together into sheets or
bundles
The cell membranes
adhere to each other at
several points



Tight and gap junctions
Where ions can flow freely
from one fibre to next
Force generated in one
muscle fibre can be
transmitted into the next
Guyton Textbook of
Physiology
15-Mar-16
Muscles
61
The Contractile Process in Smooth
Muscles:

Smooth muscles



Guyton Textbook of
Physiology
Contain both myosin
and actin
Not arranged in
orderly way as in
skeletal muscles
Do not have troponin
and tropomyosin
 Instead there is


15-Mar-16
Muscles
Caldesmon
Calponin
62
The Contractile Process in Smooth
Muscles:
 The
actin
filaments

Are attached to
dense bodies
 Contraction
is
achieved by the

Guyton Textbook of
Physiology
15-Mar-16
Muscles
Sliding action of
filaments like in
skeletal muscles
63
Molecular Basis for Contraction


Initiated by calcium
as it is in skeletal
muscles
Smooth muscle

www.uic.edu/classes/phyb/phyb516/
smoothmusclesleu3.htm
15-Mar-16
Muscles
Has poorly developed
sarcoplasmic reticulum
64
Molecular Basis for Contraction

Stimulation by
nerves, or stretching

Causes membrane
depolarization



www.uic.edu/classes/phyb/phyb516/
smoothmusclesleu3.htm
15-Mar-16
Muscles
Opening voltage
gated calcium ion
channels
Influx of calcium ions
from the extra cellular
fluid
Electromechanical
coupling
65
Molecular Basis for Contraction

Stimulation by
hormones, drugs

Causes activation
of receptors

www.uic.edu/classes/phyb/phyb516/
smoothmusclesleu3.htm
15-Mar-16
Muscles
Release of Ca++
ions from
sarcoplasmic
reticulum
66
Molecular Basis for Contraction


Calcium ions bind to
calmodulin
Myosin light chain
kinase (MLCK) is
activated



www.uic.edu/classes/phyb/phyb516/
smoothmusclesleu3.htm
15-Mar-16
Muscles
Activated MLCK Catalyses
the phosphorylation of
the myosin head
Actin then bind with
myosin
Producing muscle
contraction
67
Cessation of Contraction
Myosin is de-phosphorylated by a
phosphatase
 However, the cross bridges remain
attached to actin


This produces sustained contraction


Latch mechanism (phenomenon)
Relaxation of smooth muscle occurs

15-Mar-16
When there is dissociation of calciumcalmodulin complex
Muscles
68
Control of Smooth Muscle
Contraction
•Low levels of Ca++
•Caldesmon blocks
actin binding sites
•Muscle RELAXED
•High Ca++ levels
•Ca++ Calmodulin complex
•Removes
caldesmon and
Caldesmon
bound to Ca++calmodulin
complex
•Activates myosin
light chain kinase
(MLCK)
•Which
phosphorylates
myosin
•Promoting cycling
From: Physiology textbook CD
by Hassen T. Sherief
15-Mar-16
Muscles
69