Muscular system Physiology

bsu unversity russia

1. The Muscular System
LECTURE

2. (b)2. Cardiac muscle ©3. Smooth muscle
1. Skeletal muscle
Three Types of Muscular Tissue

3. Location Function Appearance Control
Skeletal
skeleton
movement,
heat, posture
Striated,, multi-
nucleated (eccentric),
fibers parallel
Voluntary
(can be
controlled by
will)
Cardiac
heart
pump blood
continuously
Striated,one central
nucleus
Involuntary
(cannot be
controlled by
will)
Smooth muscle
G.I. tract,
uterus, eye,
blood vessels
Peristalsis,
blood pressure,
pupil size,
erects hairs
no striations,one
central nucleus
involuntary
There Are Three Types of Muscular Tissue

4. Slide 4of 16
Which type of muscle are
the following?
1.
2.
3.

5. Characteristics of Muscles
All muscles have 4 common characteristics
–Excitability–ability to respond to a stimulus
(i.e: nerve impulse)
–Contractibility–muscle fibers that are
stimulated by nerves contract (become
shorter) and causes movement
–Extensibility–ability to be stretched
–Elasticity–allows the muscle to return to its
original shape after it has been stretched

6. Sources of heat/energy
When muscles work, they produce heat that
our body needs to function properly
Major source of this energy is ATP
When the muscle is stimulated, ATP is
released, thus producing heat

7. Skeletal Muscle

8. Skeletal muscle is the only organ of the
muscular system
Muscular system made up of over 600
different muscles
Skeletal muscle is composed of skeletal muscle
tissue and also contains nervous tissue, blood
vessels and connective tissue
Half of the body’s weight is muscle tissue
–Skeletal muscle = 40% in males, 32% in females
–Cardiac muscle = 10%

10. Characteristics of Skeletal Muscle Tissue
1.Long, thin contractile fibers (cells)
2.Striated –have visible banding
3.Under voluntary control
4.Attached to the bones of the skeleton by tendons
5.Cells are surrounded and bundled by connective tissue
= great force, but tires easily
6.Allow for movement, facial expressions, breathing,
swallowing, writing, talking and singing, posture, heat
production, joint stability

11. Function of Skeletal muscles
Attach to bones to provide voluntary
movement
–Tendons: strong, tough connective cords
–Fascia: tough, sheet-like membrane
Produce heat and energy for the body
Help maintain posture
Protect internal organs

12. Connective Tissue Wrappings of
Skeletal Muscle
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Epimysium –covers whole
organ (entire skeletal muscle)
Perimysium-covers the
fascicles
Epimysium –covers
individual cells
Figure 6.1

13. Skeletal Muscle Attachments
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Epimysium blends into a connective
tissue attachment
Tendon –cord-like structure
Sites of muscle attachment
Bones
Cartilages
Connective tissue coverings

14. A muscle, a fasciculus, and a fiber all visualized
Organization of Skeletal Muscle Tissue

15. Organization of a fasciculus
Organization of Muscle Tissue (Fascicle)
Skeletalmusclefibers(cells)arearrangedintobundles
calledfascicles
Fasciclesareboundbyconnectivetissue

16. Organization of Muscle Tissue (Muscle Fiber)
A single muscle cell is a muscle fiber.
Muscle fiber are made up of:
Sarcolemma(muscle cell membrane)
Sarcoplasma(muscle cell cytoplasm)
Myofibrils(myofibrils are made up of thick and thin
filaments)
Nucleus
Mitochondrion
Sarcoplasmic reticulum

17. Organization of Muscle Tissue (Myofibril)
Myofibrils are striated
–Striations due to arrangement of thick and thin
filaments
Seen as alternating areas of light and dark bands
The length of each myofibril is divided into
repeating units called sarcomeres
–A sarcomereis the functional unit of skeletal
muscle

18. Sarcomere Arrangement

19. Sarcomere Structure
Sarcomere exists from Z-line to Z-line
A-Band is dark middle band
I-Band –ends of A-Band, thin filaments only
Z-disk is in the middle of the I-Band
M-line is in the middle of the A-Band
Simplified sarcomere scheme

20. Thick Filament Structure
Composed of many myosinmolecules
–Each myosin molecule has a tail region and 2
globular heads (crossbridges)
Head
Tail

21. Thin Filament Structure
Composed of 3 proteins:
1. Actin protein
2 strands of globular actin molecules twisted into a helix. Actin
filaments have binding sites for myosin cross bridges
2. Tropomyosinprotein spirals around actin helix.
3.Troponin protein (3 subunits) is attached to actin and holds
tropomyosinin place.
Call this the troponin-tropomyosincomplex.
Troponin complex Tropomyosin Actin

22. Specialized Organelles of Skeletal Muscle
Sarcoplasmic Reticulum (SR) –a type of ER
–-Surrounds each myofibril, running parallel to it
–-Stores calcium, when stimulated, calcium
diffuses into sarcoplasm
Transverse Tubules (TT)
–-Extends into sarcoplasm as invaginations
continuous with sarcolemma
T tubules run between cisternae of SR
–-Filled with extracellular fluid
–-Cisternae of SR and TT form a triad near where
thick and thin filaments overlap

23. Relationship of the sarcoplasmic reticulum and T
tubules to myofibrils of skeletal muscle
Myofibril
Myofibrils
Triad
Tubules of
sarcoplasmic
reticulum
Sarcolemma
Sarcolemma
Mitochondrion
I band I bandA band
H zone Z discZ disc
Part of a skeletal
muscle fiber (cell)
T tubule
Terminal cisterna
of the sarcoplasmic
reticulum
M
line

24. Skeletal Muscle
Contraction

25. Nerve Stimulus to Muscles
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Skeletal
muscles must
be stimulated
by a nerve to
contract (motor
neuron)
Motor unit
One neuron
Muscle cells
stimulated by
that neuron
Figure 6.4a

26. Slide
6.15a
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
NJ is
association site
of nerve and
muscle
Figure 6.5b
Neuromuscular junctions (NJ)

27. Neuromuscular Junction

28. Sliding Filament Theory
A sarcomere is the functional unit of
skeletal muscle
When a skeletal muscle contracts,
sarcomeres shorten
This is described by the sliding filament
theory

29. Sliding Filament Theory
Sarcomeres shorten because thick and
thin filaments slide past one another
Thin filaments move towards the center of
the sarcomere from both ends

30. Sarcomere Relaxed

31. Sarcomere Partially Contracted

32. Sarcomere Completely
Contracted

33. A band stays the same
I band gets smaller
H zone gets smaller
Sarcomere shortens

34. NEURO-MASCULAR
COUPLING

35. Sarcoplas
mic
Reticulum

36. Sequence of events
1.An action potential arrives at the end of
a motor neurone, at the neuromuscular
junction.
2.This causes the release of the
neurotransmitter acetylcholine.
3This initiates an action potential in the
muscle cell membrane (Sarcolemma).
4.This action potential is carried quickly
into the large muscle cell by invaginations
in the cell membrane called T-tubules.

37. Sequence of events
5.The action potential causes the
sarcoplasmic reticulum to release its store
of calcium into the myofibrils.
6. Ca
2+
causes tropomoysin to be displaced
uncovering myosin binding sites on actin.
7.Myosin cross bridges can now attach
and the cross bridge cycle can take place.
8. Relaxation is the reverse of these steps.

38. CROSS BRIDGE CYCLE

39. CROSS BRIDGE CYCLE

40. CROSS BRIDGE CYCLE

41. STEPS OF CROSS BRIDGE CYCLE
Step 1: Binding of myosin to actin.
ADP and Pi are bound to ATPase site of myosin head. Creates high
affinity for actin and the myosin head binds to thin filament.
Step 2: Power Stroke.
Myosin head pivots and pulls thin filament toward the M-line.
Step 3: Unbinding of Myosin and Actin.
ATP enters the ATPase site on myosin head triggering a
conformational change, decreasing myosin's affinity for actin and
detaching myosin from actin.
Step 4: Cocking of the Myosin Head.
ATP is split by hydrolysis releasing energy which is captured by the
myosin molecule and it returns to its high-energy conformation. ADP
and Pi remain bound to ATPase site.

42. Muscle Relaxation Mechanism
1. Acetylcholinesterasepresent in the NMJ destroys
ACh(preventing continual stimulation)
2. Calcium ions are transported from the
sarcoplasmback into the SR
3. Linkages between myosin and actinare broken
–Requires ATP binding
THEN: The muscle fiber relaxes

44. Energy for Contraction
Muscle cells require huge amounts of
ATP energy to power contraction
The cells have only a very small store
of ATP
Three pathways supply ATP to power
muscle contraction

45. ATP Supply for Contraction
Pathway 1
DEPHOSPHORYLATION
CREATINE PHOSPHATE
Pathway 2
AEROBIC RESPIRATION
Pathway 3
GLYCOLYSIS ALONE
creatine
oxygen
glucose from bloodstream and
from glycogen breakdown in cells
ADP + P
i
Relaxation
Contraction

46. Energy for Contraction
ATP initially supplied from cellular
respiration
If ATP is abundant, is converted to creatine
phosphateand stored in skeletal muscles
When ATP is low, creatinephosphate
supplies phosphate to ADP making ATP
CP & ATP stores only good for about a 10
second maximal contraction
ATP must then come from cellular
respiration or glycolysis

47. •*All muscles do work by contracting, or
becoming shorter and thicker.
How Muscles Work
•*Many skeletal muscles work in pairs.
•*Then, the other muscle in the pair contracts to move the
b*One muscle in the pair contracts to
move the bone in one direction.
•one back.
*Then,theothermuscleinthepair
contractstomovetheboneback.

48. Muscle Pairs
Biceps contracted
Biceps relaxed
Triceps relaxed
Triceps contracted

49. Smooth Muscle Characteristics
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Has no striations
Spindle-shaped
cells
Single nucleus
Involuntary –no
conscious control
Found mainly in
the walls of hollow
(intestines,
bladder, stomach,
uterus, blood
vessels)
Slow, sustained
and tireless
Figure 6.2a

50. Cardiac Muscle Characteristics
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Striated and
branched
Usually has a
single nucleus
Joined to another
muscle cell at an
intercalated disc
Involuntary
Found only in the
heart
Steady pace!
Figure 6.2b

51. Special muscles
Sphincter (dilator) muscles are openings
between
–the esophagus and stomach
–The stomach and small intestines
–Walls of the anus, urethra and mouth
Open and close to control passage of
substances

52. Parts of the Muscular System
Latissimus Dorsi
•Deltoid
•Trapezius
•Extensors
•Triceps
•Gluteals
•Hamstring
•Achille’s
Tendon
•Soleus
•Gastrocnemius

53. The Muscular System
•Major Pectoral
•Biceps
•Flexors
•Sartorius
•Quadriceps
•Abdominals

54. Problems of The Muscular
System
Pulled or Torn Muscle
–Treatment: Medical
Help
Strain: Soreness due
to overwork
–Treatment: Rest, ice
or heat

55. Problems of The Muscular System
Tendonitis: Stretched
or torn tendon.
–Treatment: Rest and
ice to possible surgery
Cramp: Muscle unable
to relax; feels tight
and sore
–Treatment: Message /
Drink fluids

56. Problems of The Muscular System
Muscular Dystrophy:
Weakening of the
skeletal muscles,
eventually inability to
walk or stand.
–Treatment: No Cure

57. The Skeletal / Muscular System
Test Questions
Latissimus Dorsi
Deltoid
Trapezius
Extensors
Triceps
Gluteals
Hamstring
Achille’s Tendon
Soleus
Gastrocnemius
Major Pectoral
Biceps
Flexors
Sartorius
Quadriceps
Abdominals

58. QUESTIONS
Types of muscle tissue.
Characteristics of muscles.
Characteristics and functions of skeletal muscle tissue.
Structure of Skeletal muscle.
Skeletal muscle fiber.
Myofibrilsstructure.
Componentsofsarcomere.
Sliding Filament Theory.
Excitation-contraction coupling in skeletal muscle.
Cross-bridge cycle in skeletal muscle.
Skeletal Muscle Energy Metabolism.
Frequency-Tension Relation. Tetanus.
Characteristics smoothmuscle.
Characteristics cardiac muscle.