Chapter 10: Muscular Tissue - Anatomy and...

Copyright 2009, John Wiley & Sons, Inc.

Chapter 10: Muscular Tissue


Muscular TissueChapter 10 Overview of Muscular Tissue Skeletal Muscle Tissue Contraction and Relaxation of Skeletal Muscle Fibers Muscle Metabolism Control of Muscle Tension Types of Skeletal Muscle Fibers Exercise and Skeletal Muscle Tissue Cardiac Muscle Tissue Smooth Muscle Tissue Regeneration of Muscle Tissue Development of Muscle Aging and Muscular Tissue


Overview of Muscular Tissue Types of Muscular Tissue

The three types of muscular tissue Skeletal Cardiac Smooth

Skeletal Muscle Tissue So named because most skeletal muscles move bones Skeletal muscle tissue is striated:

Alternating light and dark bands (striations) as seen when examined with a microscope

Skeletal muscle tissue works mainly in a voluntary manner Its activity can be consciously controlled

Most skeletal muscles also are controlled subconsciously to some extent Ex: the diaphragm alternately contracts and relaxes without

conscious control


Overview of Muscular Tissue Cardiac Muscle Tissue

Found only in the walls of the heart Striated like skeletal muscle Action is involuntary

Contraction and relaxation of the heart is not consciously controlled

Contraction of the heart is initiated by a node of tissue called the “pacemaker”

Smooth Muscle Tissue Located in the walls of hollow internal structures

Blood vessels, airways, and many organs Lacks the striations of skeletal and cardiac muscle

tissue Usually involuntary


Overview of Muscular Tissue


Overview of Muscular Tissue Functions of Muscular Tissue Producing Body Movements Walking and running

Stabilizing Body Positions Posture

Moving Substances Within the Body Heart muscle pumping blood Moving substances in the digestive tract

Generating heat Contracting muscle produces heat Shivering increases heat production


Overview of Muscular Tissue Properties of Muscular Tissue Properties that enable muscle to function

and contribute to homeostasis Excitability Ability to respond to stimuli

Contractility Ability to contract forcefully when stimulated

Extensibility Ability to stretch without being damaged

Elasticity Ability to return to an original length


Skeletal Muscle Tissue Connective Tissue Components

Fascia Dense sheet or broad band of irregular connective tissue that

surrounds muscles Epimysium

The outermost layer Separates 10-100 muscle fibers into bundles called fascicles

Perimysium Surrounds numerous bundles of fascicles

Endomysium Separates individual muscle fibers from one another

Tendon Cord that attach a muscle to a bone

Aponeurosis Broad, flattened tendon


Skeletal Muscle Tissue


Skeletal Muscle Tissue Nerve and Blood Supply Neurons that stimulate skeletal muscle

to contract are somatic motor neurons The axon of a somatic motor neuron

typically branches many times Each branch extending to a different

skeletal muscle fiber Each muscle fiber is in close contact

with one or more capillaries


Skeletal Muscle Tissue Microscopic Anatomy The number of skeletal muscle fibers is

set before you are born Most of these cells last a lifetime

Muscle growth occurs by hypertrophy An enlargement of existing muscle fibers

Testosterone and human growth hormone stimulate hypertrophy

Satellite cells retain the capacity to regenerate damaged muscle fibers


Skeletal Muscle Tissue Sarcolemma

The plasma membrane of a muscle cell Transverse (T tubules)

Tunnel in from the plasma membrane Muscle action potentials travel through the T tubules

Sarcoplasm, the cytoplasm of a muscle fiber Sarcoplasm includes glycogen used for synthesis of

ATP and a red-colored protein called myoglobin which binds oxygen molecules

Myoglobin releases oxygen when it is needed for ATP production


Skeletal Muscle Tissue Myofibrils

Thread like structures which have a contractile function

Sarcoplasmic reticulum (SR) Membranous sacs which encircles each myofibril Stores calcium ions (Ca++) Release of Ca++ triggers muscle contraction

Filaments Function in the contractile process Two types of filaments (Thick and Thin) There are two thin filaments for every thick filament

Sarcomeres Compartments of arranged filaments Basic functional unit of a myofibril


Skeletal Muscle Tissue Z discs

Separate one sarcomere from the next Thick and thin filaments overlap one another

A band Darker middle part of the sarcomere Thick and thin filaments overlap

I band Lighter, contains thin filaments but no thick filaments Z discs passes through the center of each I band

H zone Center of each A band which contains thick but no thin filaments

M line Supporting proteins that hold the thick filaments together in the H

zone


Skeletal Muscle Tissue


Contraction and Relaxation of Skeletal Muscle


Skeletal Muscle Tissue Muscle Proteins Myofibrils are built from three kinds of

proteins 1) Contractile proteins Generate force during contraction

2) Regulatory proteins Switch the contraction process on and off

3) Structural proteins Align the thick and thin filaments properly Provide elasticity and extensibility Link the myofibrils to the sarcolemma


Skeletal Muscle Tissue Contractile Proteins

Myosin Thick filaments Functions as a motor protein which can achieve motion Convert ATP to energy of motion Projections of each myosin molecule protrude outward (myosin

head) Actin

Thin filaments Actin molecules provide a site where a myosin head can attach Tropomyosin and troponin are also part of the thin filament In relaxed muscle Myosin is blocked from binding to actin Strands of tropomyosin cover the myosin-binding sites Calcium ion binding to troponin moves tropomyosin away from

myosin-binding sites Allows muscle contraction to begin as myosin binds to actin


Skeletal Muscle Tissue Structural Proteins Titin

Stabilize the position of myosin accounts for much of the elasticity and extensibility of

myofibrils Dystrophin

Links thin filaments to the sarcolemma



The Sliding Filament Mechanism Myosin heads attach to and “walk” along

the thin filaments at both ends of a sarcomere

Progressively pulling the thin filaments toward the center of the sarcomere

Z discs come closer together and the sarcomere shortens

Leading to shortening of the entire muscle


Contraction and Relaxation of Skeletal Muscle The Contraction Cycle

The onset of contraction begins with the SR releasing calcium ions into the muscle cell

Where they bind to actin opening the myosin binding sites


Contraction and Relaxation of Skeletal Muscle The contraction cycle consists of 4 steps 1) ATP hydrolysis

Hydrolysis of ATP reorients and energizes the myosin head 2) Formation of cross-bridges

Myosin head attaches to the myosin-binding site on actin 3) Power stroke

During the power stroke the crossbridge rotates, sliding the filaments

4) Detachment of myosin from actin As the next ATP binds to the myosin head, the myosin

head detaches from actin The contraction cycle repeats as long as ATP is available

and the Ca++ level is sufficiently high Continuing cycles applies the force that shortens the

sarcomere

1 Myosin headshydrolyze ATP andbecome reorientedand energized ADPP

= Ca2+Key:

Contraction cycle continues ifATP is available and Ca2+ level inthe sarcoplasm is high

1 Myosin headshydrolyze ATP andbecome reorientedand energized

Myosin headsbind to actin,formingcrossbridges

ADP

ADP

P

P

= Ca2+Key:

2




Myosin crossbridgesrotate toward center of thesarcomere (power stroke)


ADP

ADP

ADP

P

P

= Ca2+Key:

2

3



Myosin crossbridgesrotate toward center of thesarcomere (power stroke)

As myosin headsbind ATP, thecrossbridges detachfrom actin


ADP

ADP

ADP

ATP

P

P

= Ca2+Key:

ATP

2

3

4


Contraction and Relaxation of Skeletal Muscle Excitation–Contraction Coupling

An increase in Ca++ concentration in the muscle starts contraction

A decrease in Ca++ stops it Action potentials causes Ca++ to be released from the

SR into the muscle cell Ca++ moves tropomyosin away from the myosin-

binding sites on actin allowing cross-bridges to form The muscle cell membrane contains Ca++ pumps to

return Ca++ back to the SR quickly Decreasing calcium ion levels

As the Ca++ level in the cell drops, myosin-binding sites are covered and the muscle relaxes


Contraction and Relaxation of Skeletal Muscle Length–Tension Relationship The forcefulness of muscle contraction

depends on the length of the sarcomeres

When a muscle fiber is stretched there is less overlap between the thick and thin filaments and tension (forcefulness) is diminished

When a muscle fiber is shortened the filaments are compressed and fewer myosin heads make contact with thin filaments and tension is diminished


Contraction and Relaxation of Skeletal Muscle The Neuromuscular Junction

Motor neurons have a threadlike axon that extends from the brain or spinal cord to a group of muscle fibers

Neuromuscular junction (NMJ) Action potentials arise at the interface of the motor neuron and muscle

fiber Synapse

Where communication occurs between a somatic motor neuron and a muscle fiber

Synaptic cleft Gap that separates the two cells

Neurotransmitter Chemical released by the initial cell communicating with the second cell

Synaptic vesicles Sacs suspended within the synaptic end bulb containing molecules of

the neurotransmitter acetylcholine (Ach) Motor end plate

The region of the muscle cell membrane opposite the synaptic end bulbs Contain acetylcholine receptors


Contraction and Relaxation of Skeletal Muscle Nerve impulses elicit a muscle action potential in

the following way 1) Release of acetylcholine

Nerve impulse arriving at the synaptic end bulbs causes many synaptic vesicles to release ACh into the synaptic cleft

2) Activation of ACh receptors Binding of ACh to the receptor on the motor end plate opens an ion

channel Allows flow of Na+ to the inside of the muscle cell

3) Production of muscle action potential The inflow of Na+ makes the inside of the muscle fiber more

positively charged triggering a muscle action potential The muscle action potential then propagates to the SR to release its

stored Ca++

4) Termination of ACh activity Ach effects last only briefly because it is rapidly broken down by

acetylcholinesterase (AChE)

1

Axon terminal

Axon terminal

Axon collateral ofsomatic motor neuron

Sarcolemma

Myofibril

ACh is releasedfrom synaptic vesicle

Junctional fold

Synaptic vesiclecontainingacetylcholine(ACh)

Sarcolemma

Synaptic cleft(space)

Motor end plate


(a) Neuromuscular junction

(b) Enlarged view of theneuromuscular junction

(c) Binding of acetylcholine to ACh receptors in the motor end plate

Synapticend bulb

Synapticend bulbNeuromuscularjunction (NMJ)

Synaptic end bulb

Motor end plate

Nerve impulse

11

Axon terminal

Axon terminal


Sarcolemma

Myofibril


ACh binds to Achreceptor

Junctional fold


Sarcolemma


Motor end plate





Synapticend bulb


Synaptic end bulb

Motor end plate

Nerve impulse

Na+

1

22

1

Axon terminal

Axon terminal


Sarcolemma

Myofibril



Junctional fold


Sarcolemma


Motor end plate





Synapticend bulb


Synaptic end bulb

Motor end plate

Nerve impulse

Muscle action potential is produced

Na+

1

2

3

2

1

Axon terminal

Axon terminal


Sarcolemma

Myofibril



Junctional fold


Sarcolemma


Motor end plate





Synapticend bulb


Synaptic end bulb

Motor end plate

Nerve impulse

Muscle action potential is produced

ACh is broken down

Na+

1

2

4

3

2

Nerve impulse arrives ataxon terminal of motorneuron and triggers releaseof acetylcholine (ACh).

Synaptic vesiclefilled with ACh

ACh receptor

Muscle action potential

Nerveimpulse

1

ACh diffuses acrosssynaptic cleft, bindsto its receptors in themotor end plate, andtriggers a muscle action potential (AP).



ACh receptor


Nerveimpulse

1

2 ACh diffuses acrosssynaptic cleft, bindsto its receptors in themotor end plate, andtriggers a muscle action potential (AP).



ACh receptor Acetylcholinesterase insynaptic cleft destroysACh so another muscleaction potential does notarise unless more ACh isreleased from motor neuron.


Nerveimpulse

1

2

3

ACh diffuses acrosssynaptic cleft, bindsto its receptors in themotor end plate, andtriggers a muscle action potential (AP).



ACh receptor Acetylcholinesterase insynaptic cleft destroysACh so another muscleaction potential does notarise unless more ACh isreleased from motor neuron. Ca2+


Nerveimpulse

SR

Muscle AP travelling alongtransverse tubule opens Ca2+release channels in thesarcoplasmic reticulum (SR)membrane, which allowscalcium ions to flood into thesarcoplasm.

1

2

3

4

Transverse tubuleACh diffuses acrosssynaptic cleft, bindsto its receptors in themotor end plate, andtriggers a muscle action potential (AP).





Nerveimpulse

SR

Ca2+ binds to troponin onthe thin filament, exposingthe binding sites for myosin.


1

2

3

4

5






Nerveimpulse

SR

Contraction: power strokesuse ATP; myosin heads bindto actin, swivel, and release;thin filaments are pulled towardcenter of sarcomere.



Elevated Ca2+

1

2

3

4

5

6






Nerveimpulse

SR


Ca2+ activetransport pumps

Ca2+ release channels inSR close and Ca2+ activetransport pumps use ATPto restore low level of Ca2+ in sarcoplasm.



Elevated Ca2+

1

2

3

4

5

67






Nerveimpulse

SR


Troponin–tropomyosincomplex slides back into position where it blocks the myosinbinding sites on actin.





Elevated Ca2+

1

2

3

4

5

67

8






Nerveimpulse

SR


Troponin–tropomyosincomplex slides back into position where it blocks the myosinbinding sites on actin.

Muscle relaxes.





Elevated Ca2+

1

2

3

4

9

5

67

8

Transverse tubule


Contraction and Relaxation of Skeletal Muscle Botulinum toxin Blocks release of ACh from synaptic vesicles May be found in improperly canned foods

A tiny amount can cause death by paralyzing respiratory muscles

Used as a medicine (Botox®) Strabismus (crossed eyes) Blepharospasm (uncontrollable blinking) Spasms of the vocal cords that interfere with speech Cosmetic treatment to relax muscles that cause facial wrinkles Alleviate chronic back pain due to muscle spasms in the

lumbar region


Contraction and Relaxation of Skeletal Muscle Curare

A plant poison used by South American Indians on arrows and blowgun darts

Causes muscle paralysis by blocking ACh receptors inhibiting Na+ ion channels

Derivatives of curare are used during surgery to relax skeletal muscles

Anticholinesterase Slow actions of acetylcholinesterase and removal of

ACh Can strengthen weak muscle contractions

Ex: Neostigmine Treatment for myasthenia gravis Antidote for curare poisoning Terminate the effects of curare after surgery


Muscle MetabolismProduction of ATP in Muscle FibersA huge amount of ATP is needed to: Power the contraction cycle Pump Ca++ into the SR

The ATP inside muscle fibers will power contraction for only a few seconds

ATP must be produced by the muscle fiber after reserves are used up

Muscle fibers have three ways to produce ATP 1) From creatine phosphate 2) By anaerobic cellular respiration 3) By aerobic cellular respiration


Muscle Metabolism


Muscle MetabolismCreatine PhosphateExcess ATP is used to synthesize creatine

phosphate Energy-rich molecule

Creatine phosphate transfers its high energy phosphate group to ADP regenerating new ATP

Creatine phosphate and ATP provide enough energy for contraction for about 15 seconds


Muscle Metabolism Anaerobic Respiration Series of ATP producing reactions that do not require

oxygen Glucose is used to generate ATP when the supply of

creatine phosphate is depleted Glucose is derived from the blood and from glycogen

stored in muscle fibers Glycolysis breaks down glucose into molecules of pyruvic

acid and produces two molecules of ATP If sufficient oxygen is present, pyruvic acid formed by

glycolysis enters aerobic respiration pathways producing a large amount of ATP

If oxygen levels are low, anaerobic reactions convert pyruvic acid to lactic acid which is carried away by the blood

Anaerobic respiration can provide enough energy for about 30 to 40 seconds of muscle activity


Muscle Metabolism Aerobic Respiration Activity that lasts longer than half a minute depends on aerobic

respiration Pyruvic acid entering the mitochondria is completely oxidized

generating ATP carbon dioxide Water Heat

Each molecule of glucose yields about 36 molecules of ATP Muscle tissue has two sources of oxygen 1) Oxygen from hemoglobin in the blood 2) Oxygen released by myoglobin in the muscle cell

Myoglobin and hemoglobin are oxygen-binding proteins Aerobic respiration supplies ATP for prolonged activity Aerobic respiration provides more than 90% of the needed ATP

in activities lasting more than 10 minutes


Muscle MetabolismMuscle FatigueInability of muscle to maintain force of

contraction after prolonged activityFactors that contribute to muscle fatigueInadequate release of calcium ions from the

SRDepletion of creatine phosphateInsufficient oxygenDepletion of glycogen and other nutrientsBuildup of lactic acid and ADPFailure of the motor neuron to release enough

acetylcholine


Muscle MetabolismOxygen Consumption After ExerciseAfter exercise, heavy breathing continues and

oxygen consumption remains above the resting level

Oxygen debt The added oxygen that is taken into the body after

exerciseThis added oxygen is used to restore muscle

cells to the resting level in three ways 1) to convert lactic acid into glycogen 2) to synthesize creatine phosphate and ATP 3) to replace the oxygen removed from myoglobin


Control of Muscle Tension The tension or force of muscle cell

contraction varies

Maximum Tension (force) is dependent on The rate at which nerve impulses arrive The amount of stretch before contraction The nutrient and oxygen availability The size of the motor unit


Control of Muscle Tension Motor Units

Consists of a motor neuron and the muscle fibers it stimulates The axon of a motor neuron branches out forming neuromuscular

junctions with different muscle fibers A motor neuron makes contact with about 150 muscle fibers Control of precise movements consist of many small motor units

Muscles that control voice production have 2 - 3 muscle fibers per motor unit

Muscles controlling eye movements have 10 - 20 muscle fibers per motor unit

Muscles in the arm and the leg have 2000 - 3000 muscle fibers per motor unit

The total strength of a contraction depends on the size of the motor units and the number that are activated


Control of Muscle Tension


Control of Muscle Tension Twitch Contraction The brief contraction of the muscle fibers in a

motor unit in response to an action potential Twitches last from 20 to 200 msec L Latent period (2 msec) A brief delay between the stimulus and muscular

contraction The action potential sweeps over the sarcolemma

and Ca++ is released from the SR Contraction period (10–100 msec) Ca++ binds to troponin Myosin-binding sites on actin are exposed Cross-bridges form


Control of Muscle Tension Relaxation period (10–100 msec) Ca++ is transported into the SR Myosin-binding sites are covered by tropomyosin Myosin heads detach from actin

Muscle fibers that move the eyes have contraction periods lasting 10 msec

Muscle fibers that move the legs have contraction periods lasting 100 msec

Refractory period When a muscle fiber contracts, it temporarily cannot

respond to another action potential Skeletal muscle has a refractory period of 5 milliseconds Cardiac muscle has a refractory period of 300 milliseconds


Control of Muscle Tension Muscle Tone A small amount of tension in the muscle due

to weak contractions of motor units Small groups of motor units are alternatively

active and inactive in a constantly shifting pattern to sustain muscle tone

Muscle tone keeps skeletal muscles firm Keep the head from slumping forward on the

chest


Control of Muscle Tension Types of Contractions Isotonic contraction The tension developed remains constant while the

muscle changes its length Used for body movements and for moving objects Picking a book up off a table

Isometric contraction The tension generated is not enough for the object

to be moved and the muscle does not change its length

Holding a book steady using an outstretched arm


Types of Skeletal Muscle Fibers Muscle fibers vary in their content of

myoglobin Red muscle fibers Have a high myoglobin content Appear darker (dark meat in chicken legs and

thighs) Contain more mitochondria Supplied by more blood capillaries

White muscle fibers Have a low content of myoglobin Appear lighter (white meat in chicken breasts)


Types of Skeletal Muscle Fibers Muscle fibers contract at different speeds, and

vary in how quickly they fatigue Muscle fibers are classified into three main types

1) Slow oxidative fibers 2) Fast oxidative-glycolytic fibers 3) Fast glycolytic fibers


Types of Skeletal Muscle Fibers Slow Oxidative Fibers (SO fibers)

Smallest in diameter Least powerful type of muscle fibers Appear dark red (more myoglobin) Generate ATP mainly by aerobic cellular respiration Have a slow speed of contraction

Twitch contractions last from 100 to 200 msec Very resistant to fatigue Capable of prolonged, sustained contractions for

many hours Adapted for maintaining posture and for aerobic,

endurance-type activities such as running a marathon


Types of Skeletal Muscle Fibers Fast Oxidative–Glycolytic Fibers (FOG fibers)

Intermediate in diameter between the other two types of fibers

Contain large amounts of myoglobin and many blood capillaries

Have a dark red appearance Generate considerable ATP by aerobic cellular

respiration Moderately high resistance to fatigue Generate some ATP by anaerobic glycolysis Speed of contraction faster

Twitch contractions last less than 100 msec Contribute to activities such as walking and sprinting


Types of Skeletal Muscle Fibers Fast Glycolytic Fibers (FG fibers)

Largest in diameter Generate the most powerful contractions Have low myoglobin content Relatively few blood capillaries Few mitochondria Appear white in color Generate ATP mainly by glycolysis Fibers contract strongly and quickly Fatigue quickly Adapted for intense anaerobic movements of short

duration Weight lifting or throwing a ball


Types of Skeletal Muscle Fibers


Types of Skeletal Muscle Fibers Distribution and Recruitment of

Different Types of Fibers Most muscles are a mixture of all three types

of muscle fibers Proportions vary, depending on the action of

the muscle, the person ’s training regimen, and genetic factors Postural muscles of the neck, back, and legs have

a high proportion of SO fibers Muscles of the shoulders and arms have a high

proportion of FG fibers Leg muscles have large numbers of both SO and

FOG fibers


Exercise and Skeletal Muscle Tissue Ratios of fast glycolytic and slow oxidative

fibers are genetically determined Individuals with a higher proportion of FG

fibers Excel in intense activity (weight lifting, sprinting)

Individuals with higher percentages of SO fibers Excel in endurance activities (long-distance

running)


Exercise and Skeletal Muscle Tissue Various types of exercises can induce

changes in muscle fibers Aerobic exercise transforms some FG fibers

into FOG fibers Endurance exercises do not increase muscle mass

Exercises that require short bursts of strength produce an increase in the size of FG fibers Muscle enlargement (hypertrophy) due to increased

synthesis of thick and thin filaments


Cardiac Muscle Tissue Principal tissue in the heart wall

Intercalated discs connect the ends of cardiac muscle fibers to one another Allow muscle action potentials to spread from one cardiac muscle

fiber to another Cardiac muscle tissue contracts when stimulated by its own

autorhythmic muscle fibers Continuous, rhythmic activity is a major physiological difference

between cardiac and skeletal muscle tissue Contractions lasts longer than a skeletal muscle twitch Have the same arrangement of actin and myosin as skeletal

muscle fibers Mitochondria are large and numerous Depends on aerobic respiration to generate ATP

Requires a constant supply of oxygen Able to use lactic acid produced by skeletal muscle fibers to make

ATP


Smooth Muscle Tissue Usually activated involuntarily Action potentials are spread through the fibers

by gap junctions Fibers are stimulated by certain

neurotransmitter, hormone, or autorhythmic signals

Found in the Walls of arteries and veins Walls of hollow organs Walls of airways to the lungs Muscles that attach to hair follicles Muscles that adjust pupil diameter Muscles that adjust focus of the lens in the eye


Smooth Muscle Tissue Microscopic Anatomy of Smooth

Muscle Contains both thick filaments and thin

filaments Not arranged in orderly sarcomeres

No regular pattern of overlap thus not striated Contain only a small amount of stored Ca++ Filaments attach to dense bodies and stretch

from one dense body to another Dense bodies

Function in the same way as Z discs During contraction the filaments pull on the dense bodies

causing a shortening of the muscle fiber


Smooth Muscle Tissue


Smooth Muscle Tissue Physiology of Smooth Muscle

Contraction lasts longer than skeletal muscle contraction

Contractions are initiated by Ca++ flow primarily from the interstitial fluid

Ca++ move slowly out of the muscle fiber delaying relaxation

Able to sustain long-term muscle tone Prolonged presence of Ca++ in the cell provides for a state of

continued partial contraction Important in the:

Gastrointestinal tract where a steady pressure is maintained on the contents of the tract

In the walls of blood vessels which maintain a steady pressure on blood


Smooth Muscle Tissue Physiology of Smooth Muscle Most smooth muscle fibers contract or relax in

response to: Action potentials from the autonomic nervous

system Pupil constriction due to increased light energy

In response to stretching Food in digestive tract stretches intestinal walls initiating

peristalsis Hormones

Epinephrine causes relaxation of smooth muscle in the air-ways and in some blood vessel walls

Changes in pH, oxygen and carbon dioxide levels


Smooth Muscle Tissue


Regeneration of Muscular Tissue Hyperplasia

An increase in the number of fibers Skeletal muscle has limited regenerative abilities

Growth of skeletal muscle after birth is due mainly to hypertrophy

Satellite cells divide slowly and fuse with existing fibers Assist in muscle growth Repair of damaged fibers

Cardiac muscle can undergo hypertrophy in response to increased workload Many athletes have enlarged hearts

Smooth muscle in the uterus retain their capacity for division


Development of Muscle Muscles of the body are derived from mesoderm As the mesoderm develops it becomes arranged on

either side of the developing spinal cord Columns of mesoderm undergo segmentation into

structures called somites The cells of a somite differentiate into three regions:

1) Myotome Forms the skeletal muscles of the head, neck, and limbs

2) Dermatome Forms the connective tissues, including the dermis of the skin

3) Sclerotome Gives rise to the vertebrae

Cardiac muscle and smooth muscle develop from migrating mesoderm cells


Development of Muscle


Aging and Muscular Tissue Aging

Brings a progressive loss of skeletal muscle mass A decrease in maximal strength A slowing of muscle reflexes A loss of flexibility

With aging, the relative number of slow oxidative fibers appears to increase

Aerobic activities and strength training can slow the decline in muscular performance


End of Chapter 10

Copyright 2009 John Wiley & Sons, Inc.All rights reserved. Reproduction or translation of this work beyond that permitted in section 117 of the 1976 United States Copyright Act without express permission of the copyright owner is unlawful. Request for further information should be addressed to the Permission Department, John Wiley & Sons, Inc. The purchaser may make back-up copies for his/her own use only and not for distribution or resale. The Publishers assumes no responsibility for errors, omissions, or damages caused by the use of theses programs or from the use of the information herein.

�Chapter 10: �Muscular Tissue�Muscular Tissue�Chapter 10Overview of Muscular TissueOverview of Muscular TissueOverview of Muscular TissueOverview of Muscular TissueOverview of Muscular TissueSkeletal Muscle TissueSkeletal Muscle TissueSkeletal Muscle TissueSkeletal Muscle TissueSkeletal Muscle TissueSkeletal Muscle TissueSkeletal Muscle TissueSkeletal Muscle TissueContraction and Relaxation of Skeletal MuscleSkeletal Muscle TissueSkeletal Muscle TissueSkeletal Muscle TissueContraction and Relaxation of Skeletal MuscleContraction and Relaxation of Skeletal MuscleContraction and Relaxation of Skeletal MuscleContraction and Relaxation of Skeletal MuscleContraction and Relaxation of Skeletal MuscleContraction and Relaxation of Skeletal MuscleContraction and Relaxation of Skeletal MuscleContraction and Relaxation of Skeletal MuscleSlide Number 28Contraction and Relaxation of Skeletal MuscleContraction and Relaxation of Skeletal MuscleContraction and Relaxation of Skeletal MuscleContraction and Relaxation of Skeletal MuscleContraction and Relaxation of Skeletal MuscleContraction and Relaxation of Skeletal MuscleContraction and Relaxation of Skeletal MuscleSlide Number 36Contraction and Relaxation of Skeletal MuscleSlide Number 38Contraction and Relaxation of Skeletal MuscleContraction and Relaxation of Skeletal MuscleMuscle MetabolismMuscle MetabolismMuscle MetabolismMuscle MetabolismMuscle MetabolismMuscle MetabolismMuscle MetabolismControl of Muscle TensionControl of Muscle TensionControl of Muscle TensionControl of Muscle TensionControl of Muscle TensionControl of Muscle TensionControl of Muscle TensionControl of Muscle TensionControl of Muscle TensionControl of Muscle TensionTypes of Skeletal Muscle FibersTypes of Skeletal Muscle FibersTypes of Skeletal Muscle FibersTypes of Skeletal Muscle FibersTypes of Skeletal Muscle FibersTypes of Skeletal Muscle FibersTypes of Skeletal Muscle FibersExercise and Skeletal Muscle TissueExercise and Skeletal Muscle TissueCardiac Muscle TissueSmooth Muscle TissueSmooth Muscle TissueSmooth Muscle TissueSmooth Muscle TissueSmooth Muscle TissueSmooth Muscle TissueRegeneration of Muscular TissueDevelopment of MuscleDevelopment of MuscleAging and Muscular TissueEnd of Chapter 10

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