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By

Khairun Nisa, dr

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TYPES OF THE MUSCLE

1. Skeletal Muscle

2. Smooth Muscle

3. Cardiac Muscle

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THE MUSCLE

Muscles are the contraction specialists of the body

Skeletal muscleattaches to the skeleton. Contraction of

skeletal muscle moves bones to which they attached,

allowing the body to perform a variety of motor activities

Skeletal muscles that support homeostasis include thoseimportant in acquiring, chewing, and swallowing food and

those essential for breathing. Skeletal muscle contraction

is also used move the body away from harm. Heat

generating muscle contractions are important in

temperature regulation.

Skeletal muscle are also used for non homeostatic

activities, such as dancing ar operating a computer

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THE MUSCLE

Smooth muscleis found in the wall of hollow

organs and tubes. Controoled contraction of

smooth muscle regulates movement of blood

through blood vessels, food through the digestive

tract, air through respiratory airway, urine to

exterior

Cardiac muscleis found only in heart, contraction

pums life-sustaining blood throughout the body

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SKELETAL MUSCLE

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THE MUSCLE

Skeletal muscle contr ibute to homeostasis by

playing a major role in the procurement of

food, breathing, heat generation for

maintenance of body temperature, andmovement away from harm (raflexes)

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Functions of the Muscular System

1. Body Movement

Most skeletal muscles are attached to bones are responsible for most

body movement including walking, running, or manipulating objects

with hands

2. Maintenance of posture

Skeletal muscle constantly maintain tone, which keeps sitting or

standing erect

3. Respiration

Muscles of the thorax are responsible for the movements necessary

for respiration

4. Production of body heat

When skeletal muscles contract, heat is given off as by-product for

maintaining body temperature

Functions ..

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5. Communication Skeletal muscles are involved in all aspects of communication, such

as speaking, writing, typing, gesturing, and facial expression

6. Constriction of organs and vessels

The contraction of smooth muscles within the walls of internal organsand vessels causes constriction of those structures. This constriction can

help propel and mix food and water in the digestive tract, propel

secretions from organs, and regulate blood flow though the vessels

7. Heart beat The contraction of cardiac muscle causes the heart to beat, propelling

blood to all part of the body

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Properties of muscle

1. Contractility The contractility is the ability of muscle to shorten or to lengthen with

a force

2. Excitability

Excitability is the capacity of muscle to respond to a stimulus

3. Extensibility

Extensibility means that muscle can stretched to its normal resting

length and beyond to a limited degree

4. Elasticity

Elasticity is the ability of muscle to recoil to its original resting length

after it has been stretched

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Types and comparison of muscle types

Features Skeletal muscle Smooth muscle Cardiac muscle

Location Attached to bones Walls of hollow

organs, blood

vessels, eyes,

glands, and skin

Heart

Striation Yes No Yes

Control Voluntary and

involuntary

(reflex)

Involuntary Involuntary

Function Body movement To move the

content of visceral

organs

Pump blood

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Muscle parts

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Physiology of Skeletal Muscle Fibers

1. Membrane potential

Plasma membrane are polarized, there is tendency of K+ to diffuse

out of the celldifference charges

2. Ion channels

Ligand gated and voltage gated channels responsible for

producing action potentials

3. Action potentials

Diffusing Na

+

and K+

across membrane produce action potentials

4. .

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4. Neuromuscular junction

Acetylcholine released from the presynaptic terminal changes

membrane permeability of postsynaptic membrane

5. Excitationcontraction coupling

Ca

2+

ions released from the reticulum sarcoplasm cause actin filamentslides over the myosin

6. Cross bridge movement

ATP is hydrolized and causes angular movement of the cross bridge

7. Muscle relaxation

Ca2+ ions diffuse away from troponin and are transported into the

reticulum sarcoplasm cause muscle to relax

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Neuromuscular Junction

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Breakdown of ATP and

Cross-bridge Movement

During Muscle Contraction

1. Ca2+binds to troponin, active site on

actin exposed

2. The myosin molecules attach to actin

3. Energy stored in the head of myosin

is used to move the head of myosin

4. ATP binds the myosin head

releases of actin from myosin

5. ATP is broken down to ADP and P,

which remain bound to the myosin

head (energized myosin)

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Cross-br idge cycle1. ATP split by miosin ATPase; ADP and P remain attached to

myosin; energy stored in cross bridge

2. Ca2+ released on excitation; removes inhibitory influence from

acting, anabling it to bind with cross bridge

3. Power stroke of cross bridge triggered on contact between

myosin and actin; P and ADP released

4. Linkage between actin and myosin broken as fresh molecule ofATP binds to myosin cross bridge; cross bridge assumes

original conformation; ATP hydrolyze

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Steps of excitation-contraction coupling and relaxation

1.Acetylcholin released from the terminal of a motor neuron initiates an action

potential in the muscle cell that is propagated over the entire surface of the

muscle cell membrane2. The suface electric activity is carried into the central portions of the muscle fiber

by the T tubules

3. Spread of the action potential down the T tubules triggers the release of stored

Ca2+ from the adjacent alteral sacs of the sarcoplasmic reticulum

4. Released Ca2+ binds with troponin and changes its shape so hat the troponin-

tropomyosin complex is physically pull aside, uncovering actins cross-bridge

binding site

5. Exposed actin sites bind with myosin cross bridge, which have previously been

energized by splitting of ATP into ADP + Pi + energy by the myosin ATPase

site on the cross bridge

6. Binding of actin and myosin at a cross bridges causes the cross bridge to bend,

producing a power stroke that pulls the thin filament inward. Inward sliding of

all the filaments surounding a thick filament shortens sarcomere (cause muscle

contraction)

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Steps of excitation-contraction coupling and relaxation

7. Pi is released from the cross bridge during the power stroke; ADP is released

after the power stroke is complete

8. Attachment of a new molecule of ATP permits detachment of he cross bridge,which returns to its original conformation

9. Splitting of the fresh ATP molecule by myosin ATP ase energizes the cross

bridge once again

10. If Ca2+ is still present so that the troponin-tropomyosin complex remains pulled

aside, the coss bridge go through another cycle of binding and bending, pulling

the thin filament in even further

11. When there is no longer a local action potential and Ca2+ has been actively

returned to its storage site in the sarcoplasmic reticulums lateral scs, the

troponin-tropmyosin complex slips back into its blocking position, actin and

myosin no longer bind at the cross bridge, and the thin filaments passively slide

back to their resting position as relaxation takes place.

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Physiology of Skeletal Muscle

1. Muscle twitch A muscle twitch is the contraction of a single fiber or a whole muscle

is response to a stimulus

A muscle twitch has lag, contraction, and relaxation phases

2. Stimulus strength and muscle contraction

For a given condition, a muscle fiber or motor unit contracts with a

consistent force in response to each action potential, which is called

the allnone law of skeletal muscle contraction

For a whole muscle, a stimulus of increasing magnitude results ingraded contractions of increased force as more motor units are

recruited (multiple motor unit summation)

3.

Physiology .

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3. Stimulus frequency and muscle contraction

A stimulus of increasing frequency increases the force of contraction

(multiplewave summation)

Incomplete tetanus is partial relaxation between contraction, and

complete tetanus is no relaxation between contractions

The force contraction of a whole muscle increases with increased

frequency of stimulation because of an increasing concentration of

Ca2+ around the myofibrils and because of complete stretching of

muscle elastic elements

Trepe is a n increase in force of contraction during the first few

contraction of a rested muscle

Twitch contraction .

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Lag

phaseContraction phase Relaxation phase

Phases of a Muscle Contraction

Tens

ion

Stimulus

applied

Multiple motor unit summation .

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Motor Unit

One nerve fiber supplies a number of muscle fibers

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Subthreshold stimulus

(no motor unit respond)

Threshold

stimulus (one

motor unit

responds)

Submaximal stimuli

(increasing numbers of

motor units respond)

Supramaximal stimuli (all motor units respond)

Multiple Motor Unit Summation

Multiplewave summation ..

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1

2

3

45

MultipleWave Summation

Multiplewave summation caused by stimuli of increased frequency (1 5):

complete relaxation between stimuli (1), incomplete tetanuspartial relaxation

between stimuli (24), and complete tetanusno relaxation between stimuli (5)

Trepe ..

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Stimuli of constant strength

Trepe

When a rested muscle is stimulated repeatedly with maximal stimuli at afrequency that allows complete relaxation between stimuli, the second

contraction produces a slightly greater tension than the first, and the third

contraction produces a greater tension than the second. After a few

contractions, the tension produced by all contraction is equal

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Type of Muscle Contraction

1. Isometric contractionscause a change in muscle tension but no change in

muscle length.

2. Isotonic contractions cause a change in muscle length but no change in

muscle tension.

3. Concentric contractionscause muscles to shorten and tension to increase

(auxotonic contraction).

4. Eccentric contractionscause muscles to increase the length and the tension

to gradually decrease (lengthening contraction)

5. Muscle toneis maintenance of a steady tension for long periods.

6. Asynchronous contractionsof motor units produce smooth, steady musclecontraction

1 2 3

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1 2 3

Isotonic Isometric Auxotonic

Shortening contraction

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4 5

Concentric Eccentric

Shortening contraction Lengthening contraction

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Fatigue

1. Fatigue is the decreased ability to do work and the reduced efficiency of

performance that normally follows a period of activity.

2. Fatigue develop at three possible sites: the nervous system, the muscle,

and neuromuscular junction

3. Psychologic fatigue, the most common type, involves the CNS. The

muscles are capable of functioning, but the individual perceives thatadditional muscular work is not possible. This fatigue depends on the

emotional state.

4. Muscular fatigue results from ATP depletion

5. Synaptic fatigue occur in the neuromuscular junction caused by depletionof acetylcholine. This type is very rare.

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Physiologic Contracture and Rigor Mortis1. Physiologic contracture (inability of muscles to contract or to

relax) result from inadequate amounts of ATP. ATP depletion

causes the Ca2+ accumulates within the sarcoplasm, the

myosin cross bridge cannot release from the actin.

2. Rigor mortis (stiff muscles after death). ATP production stops

shortly after death ATP depletion. Ca2+ also leaks from

the sarcoplasmic reticulum after cell death. Then cross

bridges are unable to release and re-form in a cyclic fashionto produce contraction

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Energy Sources

1. Energy for muscle contraction comes from ATP

2. Creatine phosphate is produced during resting condition by using energyfrom aerobic respiration. Creatine Phosphate + ADP creatine + ATP.

ATP from this source provides energy for a short time (8 10 seconds)

during intense exercise.

3. Anaerobic respiration synthesizes ATP and is used to provide energy for a

short time (up to 3 minutes) during intense exercise. Anaerobicrespiration produces ATP less efficiently but more rapidly than aerobic

respiration. Lactic acid level increase because of anaerobic respiration.

4. Although more slowly, aerobic respiration produces ATP more efficiently.

Aerobic respiration produces energy for muscle contractions under resting

condition or during exercises such as longdistance running.

5. Oxygen debt is the difference between the amount of oxygen needed for

aerobic respiration during muscle activity and the amount that actually

was used. (After intense exercise, the rate of aerobic metabolism remains

elevated for a time).

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Type of muscle fiber

1. Slowtwitch, or Highoxidative, muscle fibers.

Split ATP slowly and have a well-developed blood supply, many

mitochondria, and myoglobin

2. Fasttwitch, or Lowoxidative, muscle fibers. Split ATP

Splits ATP rapidly

Fatigable fast twitch fibers have large amount of glycogen, a poor

blood supply, fewer mitochondria. And little myoglobin

Fatigue resistant fast twitch fibers have a well-developed blood

supply, more mitochondria, and more myoglobin

Characteristic of Skeletal Muscle Fiber Types

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Characteristic of Skeletal Muscle Fiber Types

Characteristics Slow-twitch high-

oxidative (Type I)

Fast-twitch Low-

oxidative (Type IIa)

Low-oxidative

(Type IIx)

Fiber diameter Smallest Intermediate Largest

Myoglobin content High Intermediate Low

Mitochondria Many Intermediate Few

Capillaries Many Intermediate Few

Metabolism High aerobic capacity Intermediate aerobiccapacity Low aerobiccapacity

Fatigue Resistant Resistant Fast

Rate of ATP

breakdown by

ATPase in myosin

Slow Fast Fast

Location where

fibers are

numerous

Generally postural

muscles and more in

lower than upper limbs

Can predominates in

lower limbs (sprinters)

Upper limbs (more

in upper than lower

limbs, more in legs

Functions Endurance activities

and posture

Endurance activities in

endurance trainedmuscles

Rapid, intense

movements of shortduration

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Distribution of Fasttwitch and Slowtwitch muscle

1. Sprinter have a greater percentage of fast twitch muscle

fibers

2. Good longdistance runner have a higher percentage of slow

twitch muscle fibers in their legs

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Effects of Exercise

1. Muscle increase (hypertrophy) or decrease (atrophy) in size

because of a change in the size of muscle fibers2. Anaerobic exercise develops fatigable fast twitch fibers.

Aerobic exercise develops slow twitch fibers and changes

fatigable fast twitch fiber into fatigue resistant fast

twitch fibers

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Effect of Aging on Skeletal Muscle

1. Aging skeletal muscle is associated with reduced muscle

mass, increased response time, and increased time that muscletakes to contract in response to nervous stimuli

2. Muscle fibers decrease in number, motor units decrease in

number, and recovery time increases.

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Heat production

1. Heat is produced as by-product of chemical reactions in

muscles

2. Shivering produces heat to maintain body temperature

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SMOOTH MUSCLE

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SMOOTH MUSCLE

1. Smooth muscle cells are spindle-shaped with a single nucleus.They have actin myofilaments and myosin myofilaments but

are not striated

2. The sarcoplasmic reticulum is poorly developed, and

caveolae may function as a T tubule system

3. .

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3. Ca2+

enters the cell to initiate contraction; calmodulin binds toCa2+and activates an enzyme that transfer a phosphate group

from ATP to myosin. When phosphate groups are attached to

myosin, cross-bridges form

4. Relaxation results when myosin phosphatase removes aphosphate group from the myosin molecule

- If phosphate while the cross-bridges are attached,

relaxation occurs very slowly, and this is referred to as the

catch phase

- If phosphate is removed while the cross-bridges are not

attached, relaxation occurs rapidly

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Types of Smooth Muscle

1. Visceral smooth muscle fibers contract slowly, have gap

junction (and thus function as a single unit), and can beautorhythmic

2. Multiunit smooth muscle fibers contract rapidly in response

to stimulation by neuron and function independently

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Electrical Properties of Smooth muscle

1. Spontaneous contractions results from Na+and Ca2+leakage

into cells, Na+and Ca2+movement into the cell is involved in

depolarization

2. The autonomic nervous system and hormones can inhibit or

stimulate action potentials (and thus contraction). Hormones

can also stimulate or inhibit contractions without affecting

membrane potentials

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Functional Properties of Smooth Muscle1. Smooth muscle can contract autorhythmically in response to

stretch or when stimulated by autonomic nervous system or

hormones.

2. Smooth muscle maintain a steady tension for long periods

3. The force of smooth muscle contraction remain nearly

constant, despite changes in muscle length

4. Smooth muscle does not develop an oxygen debt

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Regulation of Smooth Muscle

1. Smooth muscle is innervated by the autonomic nervous

system and is involuntary

2. Hormones are important in regulating smooth muscle. Somehormones can increase the Ca2+permeability of some smooth

muscle membrane and, therefore, cause contraction without a

change in the resting membrane potential.

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CARDIAC MUSCLE

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CARDIAC MUSCLE

Cardiac muscle fibers are striated, have a single nucleus, are

connected by intercalated disks (thus function as a single unit),

and are capable of autorhythmicity

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Assignment

1. List the function of skeletal, smooth, and cardiac muscles and explain how

each is accomplished.

2. Define contractility, excitability, and elasticity of muscle tissue.

3. Compare the structure, function, location, and control of the three major

muscle tissue types.

4. Define skeletal muscle fibers. Do the number of muscle fibers increases

significantly after birth?

5. Name the connective tissue structures that surround muscle fibers, muscle

fasciculi, and whole muscles. Define sarcolemma and fascia.

6. What are motor neuron? How do the axons of motor neurons and blood

vessels extend to muscle fibers?

7. Define sarcoplasm, myofibril, and myofilament.

8. How do G actin, tropomyosin, and troponin combine to form an actin

myofilament? Name the three subunits of troponin.

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9. Describe the structure of myosin molecules and how they combine to form

a myosin myofilament.

10. List three important properties of the myosin head. What is a cross-bridge?

11. How are Z disks, actin myofilaments, myosin myofilament, and M lines

arranged to form a sarcomere? Describe how this arrangement produces

the I band, A band, and h zone.

12. Why do the I band and H zones shorten during muscle contraction, but the

length of the A band is unchanged?

13. How does shortening of sarcomeres explain muscle contraction?

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