The muscle are biological motors which convert chemical energy into force and mechanical work. This biological machinery is composed of proteins – which is actomyosin and the fuel is ATP. With the use of muscles we are able to act on our environment.

2.  Importance of muscular movement
 Muscles are biological machines.
 Functional characteristics of muscles.
 Muscle organization-skeletal , plain and cardiac muscles –
comparison
 Skeletal muscle-structure, fibrillar system, contractile
proteins
 Energy sources of muscle –ATP, CP and glucose.
 Cori’s lactic acid cycle.
 Events of muscle stimulation.
 Molecular events of muscle contraction and relaxation.
 Theories of muscle contraction
 Summary

3.  Movement is the basic property of
living systems.
 Animals move by contracting muscles.
 Muscle contraction is one of the key
processes of animal life.
 Movement of muscle is the prerequisite
for vital activities like
digestion, reproduction, excretion and
circulation.

4.  Gives shape and structure to the body.
Enables animals to maintain erect
Skeletal muscle

posture.
 Brings about movement
 Helps the animal to secure food and
shelter and escape from danger.
 Helps to communicate its wishes.
 Assist breathing movements
 Aids hearing and vision.
Smooth muscle
 Helps digestion, excretion, reproduction
and circulation.
 Propels digested food, body
fluids, glandular secretions and waste
products.
 Pumps blood to all parts of the body.

5. The function of
Muscles are muscle is to convert The chemical energy
biological machines chemical energy into is obtained from
made up of proteins. mechanical work ATP and CP
and force.

6. Excitability • the ability to receive and respond to stimuli.
Conductivity • The ability to receive a stimulus and transmit a
wave of excitation (electrochemical activity)
Contractility • the ability to shorten forcibly when stimulated.
Extensibility • the ability to be stretched or extended.
Elasticity • The ability to bounce back to original length

7. Plain
muscle
Quick
Slow Smooth Acting
muscle Un-striped/ Muscle muscle
Non-
striated
muscle
Fast Striped /
Skeletal
moving Striated
Visceral In- muscle
voluntary
muscle muscle
muscle muscle
Voluntary
muscle

8.  Elongated spindle shaped
muscle fibers with
thickened central belly and
two pointed terminals.
 The cytoplasm is granular
without any cross
striations.
 A rod like nucleus is placed
in the center.
 Myofibrils are arranged in
longitudinal axis.
 Found alimentary
canal, respiratory
tract, uterus, urinary
bladder, arteries and veins.

9.  Branched and form a net
work.
 The two adjacent muscle
cells form tight junctions in
the form of intercalated
discs.
 Exhibit faint transverse
striations.
 Innervated by autonomic
nerve fibers.
 Nucleus is round or oval in
shape.
 Fewer myofibrils with
greater amount of
sarcoplasm for more
storage of glycogen.
 Sarcolemma is indistinct.

10.  Complex, elongated, cylindr
ical and fast moving
muscles.
 Each fiber is multinucleated
with transverse and
longitudinal striations.
 The cytoplasm is composed
of myofibrils with many
myofilaments.
 Large number tubules run
through sarcoplasm and
form sarcoplasmic
reticulum.
 The sarcosomes or
mitochondria supply ATP to
the myofibrils..

11. parameters striped muscle Plain muscle Heart muscle
Occurrence Associated with Present in the visceral Present in the heart
Skeletal system organs
Shape long Cylindrical Spindle shaped Short cylindrical
Striations Longitudinal and Only longitudinal Faint Longitudinal and
transverse stripes stripes transverse stripes
Nucleus multinucleated Single centrally placed Single centrally placed
Sarcolemma Well defined and tough Not well defined Not well defined
Branching No branching No branching branched
Nerve supply somatic autonomic autonomic
Rhythmicity Not present present present
Contractility Fast Slow Medium fast
Tetanus possible Partially possible Not possible

12.  Muscle displays dark or A
bands or anisotropic
bands and light or I bands
or isotropic bands.
 Each A band has a less
denser region called H
band or Hensen’s line.
 In each I band, there is a
dense cross line called Z
band.
 The area between two
adjacent Z lines is called a
sarcomere.

13.  The myofilaments
consists of thick
myosin filaments and
thin actin filaments
and are arranged in
an overlapping manner.
 The myosin filaments
bear thick knob like
projections called cross
bridges.
 The sarcoplasmic
reticulum is made up
of longitudinal system
of canals between
myofilaments.
 There is also T system
of canals.

14. Water
• Muscle contains about 75-80% of water.
• Water provides a good medium for inorganic and organic compounds.
• Water reduces friction and dehydration of muscles.
Proteins
• Muscle consists 3 types of proteins:- structural proteins, contractile proteins and
enzymatic proteins
Minerals
• Calcium ions of sarcoplasm initiates muscle contraction.
• Magesium ions are important for muscle contraction.
• sodium and Potassium ions set the action potential.
Organic compounds
• Muscle is a storehouse of glycogen and oxidation of glycogen provides energy.
• The activity of muscle is proportional to the amount of phospholipids.
• ATP is the primary source of energy for muscle contraction.

15. Structural •Collagen provides toughness
•Elastin offers elasticity to
proteins muscles
•Myosin, actin, tropomyosin, and
Contractile troponin.
•Myosin constitutes 35% and actin
proteins 15% of total proteins.
Enzymatic •Adenosine triphosphatase
•Creatine phosphatase
proteins •Lactic dehydrogenase

16. Myosin – prime contractile element of muscle.
Have triple helical structure.
Molecular weight is 420,000.
Hydrolysis of myosin with enzyme trypsin yields
two fractions – heavy meromyosin (HMM) and
light meromyosin (LMM).
Hmm acts as an enzyme ATPase for splitting of
ATP into ADP and Pi.
Hydrolysis of HMM with papain yields sub-
fragment 1 and sub-fragment 2.

17.  Non-contractile and elastic in nature.
 Made up of spherical molecules (G-
actin). Molecular weight =60,000.
 G-actin polymerizes into double
stranded helices called fibrous or F-
actin.
 G-actin +ATP -F-actin +ADP +Pi.

18.  1 mole of actin +3 mole of myosin -
actomyosin (super- precipitation).
 Actomyosin +ATP—ca++, mg++actin
+myosin +ADP

19.  Non-contractile, fibrous protein.
 It plays important role in in sensitizing
actin and myosin molecules to calcium
ions.
 This sensitivity is important in order to
switch contraction on or off.
Tropomyosin
invertebrates
A
Tropomyosin
Tropomyosin
vertebrates
B

20.  Troponin occurs at intervals on the
actin filament.
 Troponin takes up ca++ ions from the
sarcoplasm to initiate muscle
contraction.
 In muscle troponin and tropomyosin
combines to form troponin-
tropomyosin system.

21. Molecular Molecular
Energy Events of
events of events of
muscle
Sources muscle muscle
stimulation
contraction relaxation

22. • Immediate
Creatine
Phosphate • Phosphagen
system
• Short term
Anaerobic
glycolysis • Lactic acid
system
• Long term
Aerobic • Glucose, fatty
glycolysis acids, Amino
acids

23. Creatine
phosphate
CP
Adenosine
triphosphate Glucose
ATP
Chemical
Energy
sources

24.  ATP is the immediate source of energy for
muscle contraction.
 The break down of phosphate bond of ATP
releases maximum energy.
Anaerobic glycolysis:
Glucose - 2 moles of lactic acid +8ATPs.
Aerobic glycolysis coupled with Kreb‘s cycle:
Glucose --6 CO2 + 6H2O +38 ATPs.

25.  Forms a reservoir of high energy
phosphate in the muscle
 Cannot be used as a direct source of
energy.
 Used for regeneration of ATP from ADP.
Creatine phosphatase
 Creatine phosphate----------creatine
+ phosphoric acid
 Phosphoric acid +ADP ------- ATP

26.  Glucose is stored in the muscle in the form of
glycogen.
 Muscle glycogen is converted into glucose by
glycogenolysis.
 Glucose is oxidized by glycolysis.
 C6H12O6 + 6O2--------6CO2 +6H2O +38 ATP

28. Muscle
Anaerobic
glycogenesis glycogen glycolysis
Blood Blood
glucose Lactic acid
Glycogenolysis
Liver Enzymatic
glycogen transformation

29.  The oxidation of lactic acid to carbon dioxide
produces energy for the reconversion of ADP to
ATP.
 The lactic acid produced in the muscle
contraction passes into blood stream and is
transported to the liver.
 Within the liver, lactic acid is converted to liver
glycogen and then to blood glucose.
 The conversion of lactic acid to glycogen requires
oxygen.
 Muscle glycogen comes only from the glucose of
the blood.

30. ATP acts as a central agent
responsible for
The actin-
The synthesis of
myosin The synthesis of
phosphocreatine
interaction to glycogen from
from creatine
cause muscle lactic acid
and phosphate.
shortening

31. 1. Conduction of nerve impulse from CNS to
neuromuscular junction.
2. Depolarization of sarcolemma – influx of Na+
ions & efflux of k+ ions.
3. Release of Ca2+ ions from sarcoplasmic
reticulum.
4. Diffusion of Ca2+ ions to actin filament.

32.  Binding Ca2+ ions to troponin.
 Troponin – Ca2+ complex removes tropomyosin
blockage of actin sites.
 Heads of myosin – ATP complex form Cross-
bridges to actin filament.
 Hydrolysis of ATP induces conformational
changes in the heads of myosin.
 1 mole of Actin + 3 moles of myosin 
Actomyosin

33.  Ca2+ ions sequestered from actin filament by
sacroplasmic reticulum.
 Ca2+ returns to sacroplasmic reticulum.
 Ca2+ released from troponin – Ca2+ complex.
 Troponin permits tropomyosin return to blocking
position.
 Myosin-action cross-bridges break.
 ATP – myosin Complex reformed in heads of
thick filament.

34.  Heat production -liberation of heat is always
associated with muscle contraction.
 Electricity generation -small amount of electrical
energy is released.
 Volume changes –negligible changes in volume
occur.
 Change in optical properties -changes in the
birefringence and transparency occur at the
muscle fiber.
 Sound production -muscle sound noted during
contraction.

35.  This theory was evolved independently and more or
less simultaneously by A.F Huxley and H.E. Huxley
around 1950s.
 According to this theory, the force of contraction is
developed by the cross bridges in the overlap region.
 The active shortening is caused by the movement of
the cross bridges, which causes one filament to slide
over the other.
 During muscle contraction, the actin filaments alone
show movement.
 But the myosin filaments remain static.
 The mechanical movement utilizes the energy
derived from the break down of ATP molecules.

36.  In the resting state, the cross bridges are in
slanting position due to negative charges in both
the basal and tips of cross bridges due to the
concentration of magnesium ions.
 After the stimulation of muscle, the release of
calcium ions change the electrical character
which cause mutual repulsion and shortening of
the cross bridges.
 The attachment of cross bridges on the actin
filaments cause sliding of actin filaments while
myosin filaments remain static.

37.  According to this scheme, there are flexible
hinges on myosin: one between S1 heads and
the long rods and the second between S2 and
the LMM at the trypsin reaction site.
 When the head piece(S1 )binds to the exposed
site on actin it is thought to rotate.
 This type of rotation occurs simultaneously at
numerous locations of actin – myosin filaments
which cause shortening of the muscle.
 The energy for this process derived from the
hydrolysis of ATP.

38.  The muscle are biological motors which
convert chemical energy into force and
mechanical work.
 This biological machinery is composed
of proteins – which is actomyosin and
the fuel is ATP.
 With the use of muscles we are able
to act on our environment.

39.  Dr.B.Victor is a highly experienced
professor, recently retired(2008) from the
reputed educational institution- St. Xavier’ s
College, Palayamkottai, India-627001.
 He was the dean of sciences, IQAC
coordinator and assistant controller of
examinations.
 He has more than 32 years of teaching and
research experience
 He has published 5 research articles in
international journals and 32 in reputed
Indian journals and guided 12 PhDs.
 Send your comments to :
bonfiliusvictor@gmail.com