nerve activates contraction -...

Chapter 6

The Muscular System

Introduction to Muscular System

Tissue Types

Naming of Skeletal Muscles

Day 1

The Muscular System

Muscles are responsible for body movement

Three muscle types

Smooth muscle Cardiac muscle Skeletal muscle

Characteristics of Muscles

Skeletal and smooth muscle cells are elongated

(muscle cell muscle fiber)

Contraction and shortening of muscles is due to the

movement of microfilaments

Characteristics of Skeletal Muscles

Location: attached to bones or skin (facial muscles)

Single, long cells

Cylindrical

Multinucleated

Striated

Voluntary – nervous system

Connective tissue wraps fibers

and includes:

Endomysium

Perimysium

Epimysium

Characteristics of Smooth Muscles

Location: Walls of hollow visceral organs (except heart)

Single cells

Spindle shaped

Non-striated

Involuntary

Nervous system

Hormones

Chemicals

Connective tissue

Endomysium

Characteristics of Smooth Muscles

Location: Walls of the heart

Branching chain of cells

Intercalated disks

Striated

Involuntary

Nervous system

Hormones

Chemicals

Connective tissue

Endomysium attached to fibrous skeleton of heart

Connective Tissue Wrappings of Skeletal Muscle

Cells are surrounded and bundled by connective

tissue

Endomysium—encloses a single muscle fiber

Perimysium—wraps around a fascicle (bundle) of

muscle fibers

Epimysium—covers the entire skeletal muscle

Fascia—on the outside of the epimysium

© 2015 Pearson

Figure 6.1 Connective tissue wrappings of skeletal muscle.

Blood vessel

Perimysium

Muscle

fiber

(cell)

Fascicle

(wrapped by

perimysium)

Endomysium

(between

fibers)

Tendon

Bone

Epimysium

(wraps entire

muscle)

Skeletal Muscle Attachments

Epimysium blends into a connective tissue

attachment

Tendons—cordlike structures

Mostly collagen fibers

Often cross a joint because of their toughness and

small size

Aponeuroses—sheetlike structures

Attach muscles indirectly to bones, cartilages, or

connective tissue coverings

© 2015 Pearson

Skeletal Muscle Attachments

Sites of muscle attachment

Bones

Cartilages

Connective tissue coverings

© 2015 Pearson

Figure 6.2a Arrangement of smooth and cardiac muscle cells.

Mucosa

Circular layer

of smooth muscle

(longitudinal

view of cells)

Submucosa

(a)

Longitudinallayer ofsmooth muscle(cross-sectionalview of cells)

© 2015 Pearson Education, Inc.

Figure 6.2b Arrangement of smooth and cardiac muscle cells.

Cardiacmusclebundles

(b)

Skeletal Muscle Functions

Produce movement

Maintain posture

Stabilize joints

Generate heat

© 2015 Pearson

Naming Skeletal Muscles

By direction of muscle fibers

Example: rectus (straight)

By relative size of the muscle

Example: maximus (largest)

By location of the muscle

Example: temporalis (temporal bone)

By number of origins

Example: triceps (three heads)

© 2015 Pearson

Naming Skeletal Muscles

By location of the muscle’s origin and insertion

Example: sterno (on the sternum)

By shape of the muscle

Example: deltoid (triangular)

By action of the muscle

Example: flexor and extensor (flexes or extends bone)

(a)

(b)

(c)

(e)

(f)

(g)

(a) Circular

(orbicularis oris)

(b) Converent

(pectoralis major)

(c) Fusiform

(biceps brachii)

(d) Parallel

(sartorius)

(e) Multipennate

(deltoid)

(g) Unipennate

(extensor digitorum

longus)

(f) Bipennate

(rectus

femoris)

(d)

Cranial

aponeurosis

Frontalis

Orbicularis

oculi

Zygomaticus

Buccinator

Orbicularis

oris

Platysma

Masseter

ADD:

Sternocleidomastoid

Occipitalis

Temporalis

Cranial

aponeurosis

Microscopic Skeletal Anatomy

Sliding Filament Theory

Day 2

Blood vessel

Perimysium

Muscle

fiber

(cell)

Fascicle

(wrapped by

perimysium)

Endomysium

(between

fibers)

Tendon

Bone

Epimysium

(wraps entire

muscle)

How many fascicles are inside this muscle?

Organization of a Muscle

Organization of a FascicleHow many muscle cells are shown in this fascicle?

Inside the Muscle Cell

(skeletal muscle fiber)

Myofibrils

• Long, striated

organelle

Mitochondria

Sarcolemma

Cell plasma

membrane

Sarcolemma

Myofibril

NucleusDark

(A) band

Light

(I) band

Microscopic Anatomy of Muscle Fiber (Cell)

Sarcolemma—specialized plasma membrane

Myofibrils—long organelles inside muscle cell

Dark (A) bands

Light (I) bands

Myofilaments (protein)

Inside the Myofibril (organelle)

Sarcomere – Contractile Muscle Unit

Myofilaments produce banding (striped) pattern

Thick filaments myosin filaments

Thin filaments actin filaments

Muscle Myofilaments Banding Pattern


Z discZ disc H zone

Thin (actin)

myofilament

Thick (myosin)

myofilament

I band A band M lineI band

Sarcomere

Muscle Myofilaments Banding Pattern


Figure 6.3c Anatomy of a skeletal muscle fiber (cell).

Thin (actin)

myofilament

Thick (myosin)

myofilament

Sarcomere (segment of a myofibril)

Z discM line

Z disc

Sarcomere

(c)


Myosin Actin

Z

I

Z

I

H

A

(a) Relaxed sarcomere

A

Z

I

Z

I

(b) Fully contracted sarcomere

Muscle Contraction: The Sliding Filament Theory

A&P Flix™: The Cross Bridge Cycle

https://www.youtube.com/watch?v=7O_ZHyPeIIA

https://www.youtube.com/watch?v=7O_ZHyPeIIA

Clavicle

Deltoid

Sternum

Pectoralis

major

Biceps

brachii

Brachialis

Brachio-

radialis

Figure 6.17b Muscles of the anterior trunk, shoulder, and arm.

Pectoralis

major

Rectus

abdominis

Transversus

abdominis

Internal

oblique

External

oblique

Aponeurosis

Skeletal Muscle Activity

and the Neuromuscular Junction

Day 3

Occipital bone

Spine of scapulaDeltoid (cut)

Humerus

Occipital bone

Spine of scapulaDeltoid (cut)

Triceps brachii

Latissimus dorsi

Humerus

Deltoid

Trapezius

Sternocleidomastoid

Characteristics of Skeletal Muscle Fiber

Irritability (responsiveness)

ability to receive and respond to a stimulus

Contractility

ability to shorten when an adequate stimulus is received

Extensibility

ability of muscle cells to be stretched

Elasticity

ability to recoil and resume resting length after stretching

Contraction of Skeletal Muscle


Skeletal Muscle Contraction

• https://www.youtube.com/watch?v=hr1M4SaF1D4

https://www.youtube.com/watch?v=hr1M4SaF1D4


Muscle fiber contraction is “all or none”

Within a skeletal muscle, not all fibers may be

stimulated during the same interval

Different combinations of muscle fiber contractions

may give differing responses

Graded responses—different degrees of skeletal

muscle shortening

Graded Responses Can Be Produced By…

Changing the frequency of muscle stimulation

Changing the number of cells stimulated at one time

Types of Graded Responses

Twitch• Single, brief contraction

• Not a normal function

(Stimuli)

Ten

sio

n (

g)

(Stimuli)

Te

ns

ion

(g

)

Summing of contractions• One contraction immediately

followed by another

• Stimulations are frequent, the

muscle does not completely

return to a resting state

• Effects are “summed” (added)

Incomplete and Complete Tetanus Responses

Unfused (incomplete) tetanus

Some relaxation between contractions

Nerve stimuli arrive at an even faster rate than during summing of contractions

Fused (complete) tetanus

No relaxation before the following contractions

Frequency of stimulations does not allow for relaxation between contractions

Results in a smooth and sustained muscle contraction

(Stimuli)

Ten

sio

n (

g)

(Stimuli)Te

nsio

n (

g)

Muscle Response to Strong Stimuli

Muscle force depends upon

number of fibers stimulated

Contraction of more fibers

= greater muscle tension

Muscles continue to

contract unless they run

out of energy (ATP)

Energy for Muscle Contraction

ATP

Immediate source of energy

Stored in muscle fibers in small amounts

Stored ATP is used up quickly

Once ATP is used up, other pathways produce ATP

1. Make ATP using creatine phosphate (fastest)

2. Aerobic cellular respiration (slow, requires O2)

3. Anaerobic glycolysis and lactic acid formation

(fast, inefficient, lactic acid builds up)

Muscles Contract ONLY When Calcium is Present


https://www.youtube.com/watch?v=0kFmbrRJq4w

https://www.youtube.com/watch?v=0kFmbrRJq4w

What Causes Calcium to Flood into Myofibrils?

Nerve Impulse

Opens a channel

Calcium is stored in the

sarcoplasmic reticulum

Irritability (responsiveness) at the Neuromuscular Junction

The Nerve Stimulus and Action Potential

Skeletal muscles are stimulated by a nerve cell

Motor unit—one motor neuron (nerve cell) and all

the skeletal muscle cells stimulated by that neuron

The Nerve Stimulus and Action Potential

Neuromuscular junction

Site of axon terminal of the

motor neuron and sarcolemma

Neurotransmitter

Chemical released by nerve

Stimulates next cell

Acetylcholine (ACh) is the

neurotransmitter that stimulates

skeletal muscle

Synaptic cleft

Gap between nerve and muscle

Nerve and muscle do not touch

A&P Flix™: Events at the Neuromuscular Junction

https://www.youtube.com/watch?v=CLS84OoHJnQ


The Neuromuscular Junction

Day 4

Which leg muscles flex and extend the leg at the hip?

Which leg muscles abduct and adduct the leg at the hip?

Tibia

Iliac crest

Qu

ad

ric

ep

s

5thlumbar vertebra

Patella

Tibia

Iliac crest

Qu

ad

ric

ep

s

5thlumbar vertebra

Patella

Sartorius

Rectus femoris

Vastus lateralis

Vastus medialis

Adductorgroup

Psoas majorFibularis longus

Tibialis anteriorSoleus

Transmission of Nerve Impulse

Name muscle fiber structures

Sarcolemma

Sarcoplasmic reticulum

T tubule

Myofibril

Myofilaments

Actin

Myosin

Sarcomere

Neuromuscular Junction and the

Story of Muscle Contraction

Day 5

Upper Body Muscles – Anterior and Posterior(no word bank)

Online Resources to Learn MusclesWiley Anatomy Drill and PracticeYour eText - click and drag

1. Go to this website.

Find it from my website or by googling:

wiley anatomy drill interface

2. Select Muscular System

3. Select Illustrated Anatomy

4. Start here.

Complete Level 1 and

Level 2 for each of the

4 Overview pages.


Name muscle fiber structures

Sarcolemma

Sarcoplasmic reticulum

T tubule

Myofibril

Myofilaments

Actin

Myosin

Sarcomere

A&P Flix™: Events at the Neuromuscular Junction



Events of the Neuromuscular Junction part 2

https://www.youtube.com/watch?v=IOkn1ldFO60

https://www.youtube.com/watch?v=IOkn1ldFO60

Contraction of Skeletal Muscle Nerve impulse arrives (action potential)

Ach released

Binds to receptors

Opens Na+ channels

Generates action potential in sarcolemma

Action potential travels to T-tubules

Opens Ca2+ channels

Ca2+ flood myofibril organelles

Myofilament proteins interact

Actin/Myosin

Sliding filament theory

Muscle contraction

Muscle shortens

Creates tension

Your Turn:

The Story of

Muscle Contraction

Project

Contraction of Skeletal Muscle Nerve impulse arrives (action potential)

Ach released

Binds to receptors

Opens Na+ channels

Generates action potential in sarcolemma

Action potential travels to T-tubules

Opens Ca2+ channels

Ca2+ flood myofibril organelles

Myofilament proteins interact

Actin/Myosin

Sliding filament theory

Muscle contraction

Muscle shortens

Creates tension

Transmission of Nerve ImpulseWhen nerve impulse reaches the axon terminal

1. Ca2+ channels open, Ca2+

enters axon terminal

2. Ca2+ entry causes synaptic vesicles to release acetylcholine (ACh)

3. ACh diffuses across the synaptic cleft and attaches to receptors on the sarcolemma

4. Action potential is generated

5. Acetylcholinesterase (AChE) breaks down acetylcholine into acetic acid and choline

AChE ends muscle contraction

6. Cell returns to its resting state

START HERE

Iliotibial tract

Hamstring group

Gluteus medius

Gluteus maximus

Adductor

magnus

Iliotibial tract

Biceps femoris

Semitendinosus

Semimembranosus

Hamstring group

Gastrocnemius

(a)

Calcaneal

(Achilles)

tendon

Gastrocnemius

Soleus

Calcaneal

(Achilles)

tendon

Muscle Movement

Muscle Fatigue

Day 6

Muscle Fatigue and Oxygen Deficit

If muscle activity is strenuous and prolonged,

muscle fatigue occurs because:

Ionic imbalances occur

Lactic acid accumulates in the muscle

Energy (ATP) supply decreases

After exercise, the oxygen deficit is repaid by rapid,

deep breathing

Your Turn:

The Story of

Muscle Contraction

Project

Muscle Movement & Exercise

Developmental Aspects

Day 7

Types of Muscle Contractions

Isotonic contractions

Myofilaments are able to slide past each other during

contractions

The muscle shortens, and movement occurs

Example: bending the knee; rotating the arm

Isometric contractions

Tension in the muscles increases

The muscle is unable to shorten or produce

movement

Example: pushing against a wall with bent elbows

Muscle Tone

Muscle tone keeps muscles healthy and ready to

react

Result of a staggered series of nerve impulses

delivered to different cells within the muscle

If the nerve supply is destroyed, the muscle loses

tone, becomes paralyzed, and atrophies

© 2015 Pearson

Effect of Exercise on Muscles

Exercise increases muscle size, strength, and

endurance

Aerobic (endurance) exercise (biking, jogging)

results in stronger, more flexible muscles with

greater resistance to fatigue

Makes body metabolism more efficient

Improves digestion, coordination

Resistance (isometric) exercise (weight lifting)

increases muscle size and strength

© 2015 Pearson


Figure 6.11 The effects of aerobic training versus strength training.

(a) (b)


Table 6.2 The Five Golden Rules of Skeletal Muscle Activity.

Leg Muscles (Posterior)

Table 6.4 Superior Posterior Muscles of the Body (Some Forearm Muscles Also Shown) (See Figure 6.23) (3 of 3).

Leg Muscles (no word bank)

Review

Anatomy – Skeletal Muscles

Physiology – Muscle Contraction,

Neuromuscular Junction,

Movement

Day 8

nerve activates contraction -...

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