1. Chapter 9 Muscular System

2. Functions of a Muscle Tissue
Movement:
Skeletal - locomotion , vision, facial expression.
Cardiac – blood pumping
Smooth – food digestion
Posture - (skeletal)
Joint Stability - (skeletal)
Heat Generation - (skeletal)

3. Chapter 9 Muscular System
Three Types of Muscle Tissues
Skeletal Muscle
usually attached to bones
voluntary- under conscious control
striated
Cardiac Muscle
wall of heart
involuntary - not under conscious control
striated
Smooth Muscle
walls of most viscera, blood vessels, skin
involuntary - not under conscious control
not striated
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4. Structure of a Skeletal Muscle
organs of the muscular system
skeletal muscle tissue
nervous tissue
blood
Connective tissues and muscle tissue:
1.fascia – covers the muscle
2.tendon – attaches the muscle
3.aponeuroses – muscle to muscle
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5. Functional Characteristics of Muscle
Excitability – receive and respond to stimuli
Contractility – shorten forcibly and when stimulated
Extensibility – stretched or extended
Elasticity – bounce back to original length

6. Structure of a Skeletal Muscle
Coverings of a muscle
1. Epimysium - outter
2. Perimysium - middle
3. Endomysium - inner
Organization of Muscle
muscle
fascicles
muscle fibers
myofibrils
thick and thin filaments
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7. Structure of a Skeletal Muscle
Coverings of a muscle
1. Epimysium – connective tissue surrounding the entire muscle
2. Perimysium – connective tissue surrounding a fascicle
3. Endomysium – thin connective tissue surrounding each muscle cell
Organization of Muscle
muscle
fascicles – bundle of muscle cells
muscle fibers – a muscle cell
myofibrils – a long, filamentous organelle found within muscle cells that has a banded appearance
thick and thin filaments (myofilament)- actin &myosin filaments
sarcomere – contractile unit of muscle
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8. Skeletal Muscle Fiber sarcolemma - sacroplasm sarcoplasmic reticulum
transverse tubule
triad
cisterna of sarcoplasmic reticulum
myofibril
actin filaments
myosin filaments
sarcomere
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9. Skeletal Muscle Fiber
sarcolemma – Plasma membrane surrounding each muscle fiber
sarcoplasm – specialized cytoplasm
sarcoplasmic reticulum – network of tubes and sacs
transverse tubule – tubular organelles that run across fibers, right angles
triad
cisternae of sarcoplasmic reticulum
transverse tubule
myofibril – consists of the many, bundled myofilaments
actin filaments – thin filaments
myosin filaments – thick filaments
sarcomere – basic contractile unit of muscle

10. Acting and Myosin Filaments
Actin and Myosin

11. Sarcomere
I band
A band
H zone
Z line
M line
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12. Sarcomere Structure
A sarcomere is defined as the segment between two neighboring Z lines .  
Z-line- the disc in between the I bands. Appears as a series of dark lines.
I-band is the zone of thin filaments that is not superimposed by thick filaments.
A-band contains the entire length of a single thick filament.
H-band is the zone of the thick filaments that is not superimposed by the thin filaments.
Finally, inside the H-zone is a thin M-line formed of cross-connecting elements of the cytoskeleton.
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13. Sliding Filament Theory
When sarcomeres shorten, actin and myosin filaments slide past one another
VIDEO#1
VIDEO #2
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14. Skeletal Muscle Contraction?
How does a muscle contract?

15. Sequence of a Muscle Contraction Neuromuscular Junction
Brain
Spinal Cord
Nerve
(Action potential)
Motor Unit
Neuromuscular Junction
(Calcium is released)
Acetylcholine
(Neurotransmitter)
Contraction

16. Motor Unit single motor neuron (a single nerve)
one motor neuron and many skeletal muscle fibers
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17. Neuromuscular Junction
site where a motor nerve fiber and a skeletal muscle fiber meet
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18. Muscle Contraction
Action potential causes the release of Ca at the NMJ.
a neurotransmitter releases a chemical substance from the motor end fiber, causing stimulation of the muscle fiber
That substance is called acetylcholine (ACh)
ACh causes the muscle fibers to become stimulated and contract (shorten).
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19. Relaxation of a Muscle
acetylcholinesterase – an enzyme that breaks down acetylcholine. NMJ
muscle impulse stops
calcium moves back into sarcoplasmic reticulum
myosin and actin action prevented
muscle fiber relaxes Cd
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20. Sequence of a Muscle Contraction Neuromuscular Junction
Brain
Spinal Cord
Nerve
(Action potential)
Motor Unit
Neuromuscular Junction
(Calcium is released)
Acetylcholine
(Neurotransmitter)
Contraction

21. Recruitment of Motor Units
Recruitment - increase in the number of motor units activated
whole muscle composed of many motor units
as intensity of stimulation or contraction increases, recruitment of motor units continues until all motor units are activated = all or none principle
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22. Question ????
We now know how a muscle contracts and relaxes, so is energy needed for that to happen? NO or
YES ?

23. How is energy that is stored in carbohydrates released?
Cellular Respiration
Oxygen
Glucose
H2O + CO2
Useable Energy is Adenosine triphosphate (ATP)

24. Adenosine triphosphate (ATP)
It serves as a source of energy for many metabolic processes.
ATP releases energy when it is broken down into ADP by hydrolysis during cell metabolism.

25. ENERGY
The energy used to power the interaction between actin and myosin filaments comes from ATP (useable chemical energy) produced by cellular respiration. ATP stored in skeletal muscle last only about six seconds. ATP must be regenerated continuously if contraction is to continue

26. Two Energy Sources for Contraction
1) Creatine phosphate (ADP) 2) Cellular respiration
creatine phosphate – stores energy that quickly converts unusable energy (ADP) to usable energy (ATP) 6 Seconds!!
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27. Cellular Respiration (CR)
THREE SERIES OF REACTIONS in CR
Glycolysis
Citric acid cycle
Electron transport chain
Produces
carbon dioxide
water
ATP (chemical energy)
heat
Two Types of Reactions
Anaerobic Respiration (without O2) - produce little ATP
Aerobic Respiration (requires O2) - produce most ATP
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28. Anaerobic Reaction (Glycolysis)
Recall that glycolysis results in pyruvate acid. If O2 is not present, pyruvate can be fermented into LACTIC ACID.
Lactic Acid
It is a waste product of pyruvate acid.
Occurs in many muscle cells.
Accumulation causes muscle soreness and fatigue.

29. Oxygen Supply and Cellular Respiration
Anaerobic Phase
Steps are called glycolysis.
occur in the cytoplasm
no oxygen
produces pyruvic acid
and produces lactic acid
little ATP
Aerobic Phase
Steps are called citric acid cycle and electron transport chain.
occur in the mitochondrion
oxygen
produces most ATP / CO2/ H2O
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31. Summary of Cellular Respiration
Total ATP Production 2 ATP – Glycolysis 2 ATP – Citrus Acid Cycle 34 ATP – Electron Transport Chain 38 ATP – Total energy released from one molecule of glucose.

32. Oxygen Debt
Oxygen debt – amount of oxygen needed by liver to convert lactic acid to glucose
oxygen not available
glycolysis continues
pyruvic acid converted to lactic acid
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33. What happens to the lactic acid once it has accumulated?
The liver filters the blood and rids the body of toxins. Lactic acid is a toxin.
liver converts lactic acid to glucose

34. Muscle Fatigue
Muscle fatigue- is a state of physiological inability to contract
commonly caused from
decreased blood flow
ion imbalances
accumulation of lactic acid
Cramp – sustained, involuntary contraction
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35. Muscle Cramp Muscle Cramp
The exact cause of muscle cramps is still unknown, but the theories most commonly cited include:
Altered neuromuscular control
Dehydration
Electrolyte depletion
Poor conditioning
Muscle fatigue
Doing a new activity

36. Muscle Tone Muscle tone – continuous state of partial contraction
Even when a muscle appears to be at rest, a certain amount of sustained contraction is occurring in its fibers.
Atrophy – a wasting away or decrease in size of an organ or tissue.
Hypertrophy – Enlargement of an organ or tissue.
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37. Two Types of Isotonic Contractions
Types of Contractions
Two Types
1. Isometric – muscle contracts but does not change length
2. Isotonic – muscle contracts and changes length
Two Types of Isotonic Contractions
1. Eccentric – (negative) lengthening contraction
2. Concentric – (positive) shortening contraction
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38. Types of Contractions

39. Smooth and Cardiac Muscle

40. Smooth Muscle Fibers Compared to skeletal muscle fibers shorter
single nucleus
elongated with tapering ends
myofilaments randomly organized
no striations
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41. Two Types of Smooth Muscle
Multiunit Smooth Muscle
irises of eye
walls of blood vessels
contractions are rapid and vigorous
similar to skeletal muscle tissue
Visceral Smooth Muscle
Location - walls of most hollow organs (intestine)
contractions are slow and sustained
exhibit rhythmicity – pattern of repeated contractions
exhibit peristalsis – wave-like motion that helps substances through passageways.
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42. Smooth Muscle Contraction
Resembles skeletal muscle contraction
interaction between actin and myosin
both use calcium and ATP
both depend on impulses
Different from skeletal muscle contraction
hormones affect smooth muscle
stretching can trigger smooth muscle contraction
smooth muscle slower to contract and relax
smooth muscle more resistant to fatigue
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43. Cardiac Muscle Anatomy only in the heart
striated uninuclear cells join end-to-end forming a network
arrangement of actin and myosin are not as organized as skeletal muscle
Physiology
self-exciting tissue (Pacemaker)
rhythmic contractions
involuntary, all or nothing contractions
Pumps blood to:
1. lungs for oxygenation
2. body for distribution of O2 and nutrients
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