chapter 4. muscular_system je.pptx

8/14/2019 Chapter 4. Muscular_System je.pptx

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dr. Calvina Theresia

dr. Michael Je

Muscular System


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Introduction

OVERVIEW OF MUSCLE TISSUES

A. Muscle Types Skeletal

SmoothCardiac

B. Similarities1. All muscle cells are elongated = muscle fibers

2. Muscle contraction depends on two kinds of myofilaments(actinand myosin)

3. The cell membrane of a muscle cell is called "sarcolemma",

while the cytoplasm of a muscle cell is called "sarcoplasm

4. The smooth Endoplasmic reticulum (ER) in muscle tissue isreferred to as the sarcoplasmic reticulum.


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The endoplasmic reticulum(ER) is a eukaryotic organelle.

ER contains:

Rough endoplasmic reticulasynthesize proteins

Smooth endoplasmic reticulasynthesize lipids and

steroids, metabolize carbohydrates and steroids, and

regulate calcium concentration, drug detoxification,

and attachment of receptors on cell membrane proteins. Sarcoplasmic reticulasolely regulate calcium levels.


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1Nucleus 2Nuclear pore 3Rough endoplasmic

reticulum (RER) 4Smooth endoplasmic reticulum

(SER) 5Ribosomeon the rough ER 6Proteinsthat are

transported 7Transport vesicle 8Golgi

apparatus 9Cis face of the Golgi apparatus 10Trans

face of the Golgi apparatus 11Cisternae of the Golgi

apparatus
http://en.wikipedia.org/wiki/Cell_nucleushttp://en.wikipedia.org/wiki/Nuclear_porehttp://en.wikipedia.org/wiki/Ribosomehttp://en.wikipedia.org/wiki/Proteinhttp://en.wikipedia.org/wiki/Vesicle_(biology)http://en.wikipedia.org/wiki/Golgi_apparatushttp://en.wikipedia.org/wiki/Golgi_apparatushttp://en.wikipedia.org/wiki/Golgi_apparatushttp://en.wikipedia.org/wiki/Golgi_apparatushttp://en.wikipedia.org/wiki/Vesicle_(biology)http://en.wikipedia.org/wiki/Proteinhttp://en.wikipedia.org/wiki/Ribosomehttp://en.wikipedia.org/wiki/Nuclear_porehttp://en.wikipedia.org/wiki/Cell_nucleus


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C. Skeletal Muscle Characteristics

1. long, thin and multi-nucleated fibers2. striations

3. voluntary control

4. arranged into packages called muscles thatattach to and cover the bony skeleton.

5. contracts rapidly & vigorously, but tiredeasily; may exert greatforce.


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Introduction


D. Cardiac Muscle Characteristics:

1. network of branched fibers connected by gap junctions (intercalated

disks);

2. only in heart;

3. striations;

4. involuntary control;5. contracts at rhythmic, steady rate set by "pacemaker".

E. Smooth Muscle Characteristics:

1. lacks striations;

2. walls of hollow visceral organs and blood vessels;

3. involuntary control;

4. contractions are slow & sustained.


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Introduction


F. Functions:

1. Movement= locomotion & manipulation, vision,facial expression (skeletal), blood pumping (cardiac),food digesting, urination (smooth)

2. Posture Maintenance(skeletal)

3. Joint Stability (skeletal)4. Heat Generation(skeletal)


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G. Functional Characteristics of Muscle:

1. Excitability = the ability to receive andrespond to stimuli

2. Contractility = the ability to shorten

forcibly when stimulated3. Extensibility = the ability to bestretched or extended

4. Elasticity = the ability to bounce backto original length


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Structure of a Skeletal Muscle

Skeletal Muscle

Organ of the muscular systemSkeletal muscle tissue

Nervous tissue

Blood

Connective tissues

FasciaTendons

Aponeuroses


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Structure of a Skeletal Muscle:

A. Each skeletal muscle is coved by a

very tough fibrous layer of CTcalled deep fascia

- the deep fascia may extend past

the length of the muscle (tendon

or aponeurosis), and attach thatmuscle to a bone, cartilage or

muscle

B. The epimysiumis found deep to the

fascia and closely surrounds the

skeletal muscle


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Structure of a Skeletal MuscleStructure of a Skeletal Muscle:

F. Recall that skeletal muscle tissuepossesses striations

- Striations are caused by thearrangement of thick and thinfilaments within the myofibrils


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Structure of a Skeletal MuscleStructure of a Skeletal Muscle:

G. Striations are caused by the arrangement ofthick and thin filaments within the

myofibrils:

1. I-Band= light area = actin filamentsonly

2. A-Band= dark area = overlapping ofthick and thin filaments

3. H zone= slightly lighter central regionof A band = myosinfilaments only

4. M line= center of sarcomere=

consists of proteins that help holdmyosinin place

5. titin= protein that anchors the myosinfilaments to the Z line


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Skeletal Muscle Fibers

2. Thick filaments= protein myosin

a. rod-like tail(axis) that terminates

in two globularheads orcrossbridges

b. Cross bridges interact with activesites on thin filaments;

Skeletal Muscle Fibers

3. Thin filaments= protein actin

a. coiled helical structure

(resembles twistedstrands of pearls):

b. Tropomyosin= rod-shaped protein spiraling

around actin backbone tostabilize it;

c. Troponin= complexof polypeptides:

- one binds to actin

- one that binds totropomyosin

- one that binds tocalcium ions


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Skeletal Muscle Contraction

Motor unit:

Single motor neuron

All muscle fiberscontrolled by motor

neuron

As few as four fibers

As many as 1000s of

muscle fibers


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Skeletal Muscle ContractionSkeletal Muscle Contraction:

1. Neuromuscular Junction Stimulationof Skeletal Muscle Cell:

a. Neuromuscular Junction (NMJ)the site where a motor nervefiber and a skeletal muscle fibermeet; (also called a synapse orsynaptic cleft)

b. In order for a skeletal muscle tocontract, its fibers must first

be stimulated by a motor neuron


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c. Motor End Plate= the specificpart of a skeletal muscle fiber's

sarcolemma directly beneaththe NMJ.

d. Neurotransmitter= chemicalsubstance released from amotor end fiber, causing

stimulation of the sarcolemmaof muscle fiber; acetylcholine(ACh)

e. Synaptic cleftsmall spacebetween neuron and muscle


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Skeletal Muscle Contraction:

4.Release of Calcium from SR

Muscle impulses cause SR to

release calcium ions into cytosol

Calcium binds to troponinto

change its shape

The position of tropomyosinis

altered

Binding sites on actin are nowexposed

Actin and myosin molecules bind

via myosin cross-bridges


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19

Animation:

Action Potentials

and Muscle Contraction

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SKELETAL MUSCLE

5. Cross-Bridge Cycling


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SKELETAL MUSCLE



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SKELETAL MUSCLE



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Skeletal Muscle Contaction


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SKELETAL MUSCLE

6. Changes in muscle during contraction:

- The distance between the Z-lines of the sarcomeres decreases;- The I-Bands (light bands) and H zone narrows;

- The A-Bands move closer together, but do not diminish in length.


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SKELETAL MUSCLE

7. Sliding Filament Theory:a. most popular theory concerning muscle contraction

b. first proposed by Hugh Huxley in 1954

c. states that muscle contraction involves the sliding movementof the thin filaments (actin) past the thick filaments(myosin)

d. Sliding continues until the overlapping between the thin &thick filaments is complete


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8. Relaxation:

a. Acetylcholinesterase is an enzyme present in the NMJ;

b. It immediately destroys acetylcholine, so the motor end-plate is no l

longer stimulated (i.e. it cannot cause continuous muscle contraction).

c. Calcium ions are transported from sarcoplasm back into sarcoplasmic

reticulum by active transport

d. Linkages between actin and myosin are broken. e. The muscle fiber relaxes.


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9. Energy Sources for Contraction:

a. Introduction: The energy used to power the interaction between actinand myosin comes from ATP.

b. ATP stored in skeletal muscle lasts only about six seconds.

- ATPmust be regenerated continuously if contraction is to

continue.

- There are three pathways in which ATP is regenerated:

1. Coupled Reaction with Creatine Phosphate(CP)

2. Anaerobic Cellular Respiration

3. Aerobic Cellular Respiration


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9. Energy Sources for Contraction:

c. Coupled Reaction with Creatine Phosphate(CP)- CP + ADP creatine + ATP

- Muscle stores a lot of CP,

- This coupling reaction allows for about 10 seconds worth ofATP.

Sk l l M l C i


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Skeletal Muscle Contraction:9. Energy Sources for Contraction:

d. Oxygen Supply andCellular

Respiration:a. Anaerobic Respiration

- Steps are calledglycolysis

- Steps occur in thecytoplasm of the cell

- Results in production ofpyruvic acidand 2 ATP

b. Aerobic Respiration- Steps are called citric acid

cycle and electron

transport chain- Oxygen is required- Steps occur in the

mitochondrion of the cell.- Results in CO2, water

and 36ATP

Sk l l M l C i


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Oxygen debtamount of oxygen needed by liver cells to use

the accumulated lactic acid to produce glucose

Oxygen not available

Glycolysis continues

Pyruvic acid converted to

lactic acid

Liver converts lactic acid to

glucose

Sk l t l M l C t ti


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Muscle fatigue

Inability to contract muscle

Commonly caused from: Decreased blood flow

Ion imbalances across the sarcolemma

Accumulation of lactic acid

Crampsustained, involuntary muscle contractionPhysiological vs. psychological fatigue

Heat production

By-product of cellular respiration Muscle cells are major source of body heat

Blood transports heat throughout body core

M l R


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Muscular ResponsesMUSCULAR RESPONSES

1. Threshold Stimulus

a. The minimal strengthof stimulation requiredto cause contraction.

2. Recording a Muscle Contraction

a. A myogramis a

recording of a musclecontraction

b. The delay betweenstimulation andcontraction is calledthe latent period

c. A muscle fiber mustreturn to its restingstate, this is called therefractory period

M l R


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Muscular Responses

MUSCULAR RESPONSES

3. All-or-Nothing Response

- If a muscle fiber is brought to threshold or above, it responds with acomplete contraction.

- If the stimulus is sub-threshold, the muscle fiber will not respond.

M l R


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Muscular Responses

MUSCULAR RESPONSES

5. Three factors determine the strength of a whole muscle contraction:

1. the frequency at which individual muscle fibers are stimulated

2. the number of motor units (how many muscle fibers are involved)

3. the initial length of the muscle

Muscular Responses


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Muscular Responses

MUSCULAR RESPONSES





Muscular Responses


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Muscular Responses

Recruitment - increase in the number of motorunits activated

Whole muscle composed of many motor units

As intensity of stimulation increases, recruitmentof motor units continues until all motor units are

activated

Smaller motor units (smaller diameter axons)recruited first

Larger motor units (larger diameter axons)

recruited later

Muscular Responses


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Muscular Responses

MUSCULAR RESPONSES





Muscular Responses


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Muscular Responses

Isotonicmuscle contracts and

changes length

Eccentriclengthening contraction

Concentricshortening contraction

Isometricmuscle contracts but does

not change length

Muscular Responses


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Muscular Responses

Hypertrophy= increase in size of exercised muscles

Atrophy= decrease in size of unused muscles


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THANK YOU

QUESTIONS


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QUESTIONS

1. How many type of muscle in human body and

how to differentiate it?2. What is sarcoplasm and sarcolemma?

3. Muscle contraction depends on two kinds of

myofilaments, what is it?

4. What is thick filament and thin filament??

5. What neurotransmitter is needed for contractions

and how it breakdown??


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6. How many pathways to produce ATP? And

explains?7. How many ATP is produced by aerobic

respiration?

8. What is Threshold Stimulus?

9. What is the different between isometric and

isotonic?

10.What is atrophy and hypertrophy???

Smooth Muscle


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Smooth Muscle

Smooth Muscle

Compared to skeletal muscle fibers, smooth muscle fibers are:

Shorter Single, centrally located nucleus

Elongated with tapering ends

Myofilaments randomly organized

Lack striations Lack transverse tubules

Sarcoplasmic reticula (SR) not well developed

Smooth Muscle


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Smooth Muscle

Visceral Smooth Muscle

Single-unit smooth muscle

Sheets of muscle fibersFibers held together by gap

junctions

Exhibit rhythmicity

Exhibit peristalsis

Walls of most hollow organs

Slow sustained contraction

Multi-unit Smooth Muscle

Less organized

Function as separate units

Fibers function separately

Iris of eye

Walls of blood vessels

Can have rapid and vigorous

contraction

Smooth Muscle


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Smooth Muscle

Resembles skeletal muscle contraction in that:Interaction between actin and myosin

Both use calcium and ATPBoth are triggered by membrane impulses

Different from skeletal muscle contraction in that:Smooth muscle lacks troponin

Smooth muscle uses calmodulinTwo neurotransmitters affect smooth muscle

Acetlycholine(Ach) and norepinephrine(NE)

Hormones affect smooth muscle (oxytocin)

Stretching can trigger smooth muscle contraction

Smooth muscle slower to contract and relax

Smooth muscle more resistant to fatigueSmooth muscle can change length without changing tautness

Cardiac Muscle


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Cardiac MuscleCARDIAC MUSCLE(Will be studied in greater detail in Chapter 15)

A. Location:

1. Only in heart.

B. Anatomy:

1. Striated uninuclearcells joined end-to-end forming a network.

a. Cell junctions are called intercalated discs

- gap junctions

2. Arrangement of actin and myosin not as organized as skeletal muscle.

3. Contains sarcoplasmic reticula, transverse tubules, and numerousmitochondria:

a. Sarcoplasmic reticulum is less developed than SR in skeletal muscleand stores much less calcium.

C. Physiology

1. Self-exciting tissue (i.e. Pacemaker);

2. Rhythmic contractions (60-100 beats/minute);3. Involuntary, all-or-nothing contractions

a. Function as a syncytium (all-or-nothing)

4. Pumps blood to:

a. Lungs for oxygenation;

b. Body for distribution of oxygen and nutrients.

Cardiac Muscle


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Cardiac Muscle

Cardiac Muscle


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Cardiac Muscle

Skeletal Muscle Actions


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Skeletal muscles generate a great variety of body

movements.

The action of each muscle mostly depends upon the kind

of joint it is associated with and the way the muscle is

attached on either side of that joint.



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SKELETAL MUSCLE ACTIONS

A. Introduction: Skeletal muscles generate a great variety of body movements.

The action of a muscle primarily depends upon the joint associated with it and

the manner in which the muscle is attached on either side of that joint.

B. Origin and Insertion:Recall that skeletal muscles are usually attached to a

fixed body part and a movable body part

1. The originof a muscle is its immovable (anchored) end.

2. The insertionof a muscle is the movable end of a muscle.

**When a muscle contracts and shortens, its insertion is pulled toward its origin.



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Review of Skeletal Muscle Actions:

1. Flexion= decreasing the angle between 2 bones;

a. Dorsiflexion = decreasing the angle between the foot and shin;b. Plantar flexion = pointing toes;

2. Extension= increasing the angle between 2 bones;

3. Abduction= moving a body part away from the midline;

4. Adduction= moving a body part toward the midline;

5. Circumduction = movement in a circular (cone-shaped) motion;6. Rotation= turning movement of a bone about its long axis; (i.e.atlas/axis);

7. Supination= thumbs up;

8. Pronation= thumbs down;

9. Inversion= sole of foot in;

10. Eversion= sole of foot out;

11. Elevation= lifting a body part; (i.e. shoulder shrug);

12. Depression= returning a body part to pre-elevated position.



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Interactions of Skeletal Muscles

1. Prime Mover (agonist)= the primary muscle responsible for a movement.

The biceps brachii in flexing the arm at the elbow,

2. Antagonist(s)= the muscle(s) in opposition to the action of the primemover. The antagonist relaxes (or stretches) during the prime movement.

The triceps brachii is the antagonist of the biceps brachii whenwe flex the arm at the elbow.

3. Synergist(s)= muscles that assist the prime mover.

The brachialis helps the biceps brachii during elbow flexion.

4. Fixators= muscle groups that stabilize the origin of the prime mover (i.e.

hold it in place) so that the prime mover can act more efficiently. The scapula is the origin for many arm muscles, but it must be

held in place by fixator muscles in order to function in this way.

a. serratus anterior

b. pectoralis minor


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THANK YOU

chapter 4. muscular_system je.pptx

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