the muscular system...control of muscle contraction table 7-1 summary of contraction process control...

Essentials of Anatomy & Physiology, 4th Edition

Martini / Bartholomew

PowerPoint® Lecture Outlines

prepared by Alan Magid, Duke University

The Muscular

System 7

Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Slides 1 to 110

Overview of Muscular System

Types of Muscle Tissue

• Under voluntary control

• Skeletal muscles

• The muscular system

• Under involuntary control

• Cardiac muscle

• Heart wall

• Smooth muscle

• Visceral organs


Overview of Muscular System

• Skeletal muscles attach to bones

directly or indirectly

• Perform five functions

• Produce movement of skeleton

• Maintain posture and body position

• Support soft tissues

• Guard entrances and exits

• Maintain body temperature


Anatomy of Skeletal Muscles

Gross Anatomy

• Connective tissue organization

• Epimysium

• Fibrous covering of whole muscle

• Perimysium

• Fibrous covering of fascicle

• Endomysium

• Fibrous covering of a single cell (a

muscle fiber)

• Tendons (or aponeurosis)



The Organization of a Skeletal Muscle

Figure 7-1


Microanatomy of a Muscle Fiber

• Sarcolemma

• Muscle cell membrane

• Sarcoplasm

• Muscle cell cytoplasm

• Sarcoplasmic reticulum (SR)

• Like smooth ER

• Transverse tubules (T tubules)

• Myofibrils (contraction organelle)

• Sarcomeres



Sarcomere—Repeating structural unit

of the myofibril

• Components of a sarcomere

• Myofilaments

• Thin filaments (mostly actin)

• Thick filaments (mostly myosin)

• Z lines at each end

• Anchor for thin filaments



The Organization of a Single Muscle Fiber

Figure 7-2(a)


The Organization of a

Single Muscle Fiber

Figure 7-2(b)


The Organization of a Single Muscle Fiber

Figure 7-2(cde) Anatomy of Skeletal Muscles PLAY

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Changes in the

Appearance of

a Sarcomere

During

Contraction of

a Skeletal

Muscle Fiber

Figure 7-3 (1 of 2)


Changes in the

Appearance of

a Sarcomere

During

Contraction of

a Skeletal

Muscle Fiber

Figure 7-3 (2 of 2)

Control of Muscle Contraction

Steps in Neuromuscular Transmission

• Motor neuron action potential

• Acetylcholine (ACh) release and

binding

• Action potential in sarcolemma

• T tubule action potential

• Calcium release from SR



The Neuromuscular Junction

• Synaptic terminal (nerve)

• Acetylcholine release

• Synaptic cleft (gap)

• Motor end plate (muscle)

• Acetylcholine receptors

• Acetylcholine binding

• Acetylcholinesterase (AChE)

• Acetylcholine removal



The Structure and Function of the

Neuromuscular Junction

Figure 7-4(a)

Figure 7-4(b-c)

1 of 5 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Synaptic cleft

Vesicles in the synaptic terminal fuse

with the neuronal membrane and dump

their contents into the synaptic cleft.

The binding of ACh to the receptors

increases the membrane permeability to

sodium ions. Sodium ions then rush

into the cell.

An action potential spreads across the

surface of the sarcolemma. While this

occurs, AChE removes the ACh.

Appearance of an action potential in the sarcolemma

ACh binding at the motor and plate

Release of acetylcholine

Arrival of an action potential at the synaptic terminal

Sarcolemma of motor end plate

Arriving action potential

Vesicles

ACh

AChE molecules

ACh receptor site

Action potential

Synaptic terminal

Axon

Sarcolemma

Muscle fiber

Action potential

Na+

Na+

Na+

Figure 7-4(b-c)


Synaptic cleft




Vesicles

ACh

AChE molecules

ACh receptor site

Action potential

Synaptic terminal

Axon

Sarcolemma

Muscle fiber

Figure 7-4(b-c)


Synaptic cleft








Vesicles

ACh

AChE molecules

ACh receptor site

Action potential

Synaptic terminal

Axon

Sarcolemma

Muscle fiber

Figure 7-4(b-c)


Synaptic cleft







into the cell.






Vesicles

ACh

AChE molecules

ACh receptor site

Action potential

Synaptic terminal

Axon

Sarcolemma

Muscle fiber

Na+

Na+

Na+

Figure 7-4(b-c)


Synaptic cleft







into the cell.

An action potential spreads across the

surface of the sarcolemma. While this

occurs, AChE removes the ACh.

Appearance of an action potential in the sarcolemma






Vesicles

ACh

AChE molecules

ACh receptor site

Action potential

Synaptic terminal

Axon

Sarcolemma

Muscle fiber

Action potential

Na+

Na+

Na+


The Contraction Process

• Actin active sites and myosin cross-bridges

interact

• Thin filaments slide past thick filaments

• Cross-bridges undergo a cycle of movement

• Attach, pivot, detach, return

• Troponin-tropomyosin control interaction

• Prevent interaction at rest



Figure 7-5

1 of 7

Resting sarcomere

Myosin head

Myosin reactivation

Active-site exposure

Cross bridge detachment

Cross-bridge formation

Pivoting of myosin head

Troponin

Actin Tropomyosin

ADP

P +

ADP

P +

ADP

P +

Active site

Sarcoplasm

Ca2+

Ca2+

ADP

P +

ADP

+ P

Ca2+

ADP

+ P

Ca2+

Ca2+

ADP + P

Ca2+

ADP + P

Ca2+

ATP

ATP

Ca2+

Ca2+

Ca2+

ADP

P +

+ P

ADP


Figure 7-5

2 of 7

Resting sarcomere

Myosin head

Troponin

Actin Tropomyosin

ADP

P +

ADP

P +


Figure 7-5

3 of 7

Resting sarcomere

Myosin head


Troponin

Actin Tropomyosin

ADP

P +

ADP

P +

ADP

P +

Active site

Sarcoplasm

Ca2+

Ca2+

ADP

P +


Figure 7-5

4 of 7

Resting sarcomere

Myosin head

Active-site exposure Cross-bridge formation

Troponin

Actin Tropomyosin

ADP

P +

ADP

P +

ADP

P +

Active site

Sarcoplasm

Ca2+

Ca2+

ADP

P +

ADP

+ P

Ca2+

ADP

+ P

Ca2+


Figure 7-5

5 of 7

Resting sarcomere

Myosin head

Active-site exposure Cross-bridge formation


Troponin

Actin Tropomyosin

ADP

P +

ADP

P +

ADP

P +

Active site

Sarcoplasm

Ca2+

Ca2+

ADP

P +

ADP

+ P

Ca2+

ADP

+ P

Ca2+

Ca2+

ADP + P

Ca2+

ADP + P


Figure 7-5

6 of 7

Resting sarcomere

Myosin head





Troponin

Actin Tropomyosin

ADP

P +

ADP

P +

ADP

P +

Active site

Sarcoplasm

Ca2+

Ca2+

ADP

P +

ADP

+ P

Ca2+

ADP

+ P

Ca2+

Ca2+

ADP + P

Ca2+

ADP + P

Ca2+

ATP

ATP

Ca2+

Control of Muscle Fiber Contraction PLAY


Figure 7-5

7 of 7

Resting sarcomere

Myosin head

Myosin reactivation





Troponin

Actin Tropomyosin

ADP

P +

ADP

P +

ADP

P +

Active site

Sarcoplasm

Ca2+

Ca2+

ADP

P +

ADP

+ P

Ca2+

ADP

+ P

Ca2+

Ca2+

ADP + P

Ca2+

ADP + P

Ca2+

ATP

ATP

Ca2+

Ca2+

Ca2+

ADP

P +

+ P

ADP

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Table 7-1

Summary of Contraction Process


Key Note

Skeletal muscle fibers shorten as thin

filaments interact with thick filaments and

sliding occurs. The trigger for contraction

is the calcium ions released by the SR

when the muscle fiber is stimulated by its

motor neuron. Contraction is an active

process; relaxation and the return to

resting length is entirely passive.


Muscle Mechanics

Some Basic Muscle Definitions

• Muscle tension—The pulling force on the

tendons that muscle cells generate when

contracting

• Muscle twitch—A brief contraction-relaxation

response to a single action potential


Muscle Mechanics

The Twitch and Development of Tension

Figure 7-6

Muscle Mechanics

The Frequency of Muscle Fiber Stimulation

• Summation—Addition of twitch tension when

a stimulus is applied before tension has

completely relaxed

• Incomplete tetanus—Tension peaks and

falls repeatedly and builds up beyond twitch

tension

• Complete tetanus—Tension is steady (no

relaxation phase) and largest if stimuli arrive

at very high rates


Muscle Mechanics

The Effects of Repeated Stimulations

Figure 7-7

Muscle Mechanics

Motor Units

• Motor Unit —A motor neuron and all

the muscle cells it controls

• Recruitment—To increase muscle

tension by activating more motor units

• Small motor units provide finer control

• Motor units are intermixed in the

muscle to pull evenly on the tendon


Muscle Mechanics

Motor Units

Figure 7-8

Muscle Mechanics

Key Note

All voluntary (intentional) movements

involve the sustained, sub-tetanic

contractions of skeletal muscle fibers

organized into distinct motor units. The

force generated can be increased by

increasing the frequency of action

potentials or by recruiting additional

motor units.


Muscle Mechanics

• Muscle tone—Tension in a “resting” muscle produced by a low level of spontaneous motor neuron activity. Distinct from resting tension produced by passive stretching.

• Function of muscle tone

• Stabilizes bones, joints

• Prevents atrophy (muscle wasting )


Muscle Mechanics

Types of Contractions

• Isotonic contraction

The tension (load) on a muscle stays

constant (iso = same, tonic = tension)

during a movement. (Example: lifting a

baby)

• Isometric contraction

The length of a muscle stays constant

(iso = same, metric = length) during a

“contraction” (Example: holding a baby

at arms length)


Muscle Mechanics

Muscle Elongation

• Muscle contracts actively

• Muscles can only pull

• Muscles never push

• Muscle elongates passively

• Elastic forces

• Contraction of opposing

muscles

• Effects of gravity


Energetics of Muscle Contraction

ATP and Creatine Phosphate Reserves

• Muscle contraction consumes much ATP

• ATP transfers energy directly to cycling

cross-bridges and calcium pumping

• CP stores energy and regenerates ATP

• CP transfers its energy to ADP

• Creatine phosphokinase (CPK) catalyzes

• ADP (2 “P”s) becomes ATP(3 “P”s)

• CP levels greatly exceed ATP levels



ATP Generation

• Light activity

• Aerobic metabolism of fatty acids

• Storage of glucose as glycogen

• Moderate activity

• Breakdown of glycogen to glucose

• Glycolysis of glucose

• Peak activity

• Anerobic breakdown of glucose

• Production of lactic acid



Muscle Metabolism

Figure 7-9(a)


Muscle Metabolism

Figure 7-9(b)


Muscle Metabolism

Figure 7-9(c)


Muscle Fatigue—When a muscle

loses ability to contract due to a low

pH (lactic acid buildup), low ATP

levels, or other problems

Recovery Period—Time after muscle

activity that it takes to restore pre-

exertion conditions

Oxygen Debt—Amount of excess

oxygen used during the recovery

period Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings


Key Note

Skeletal muscles at rest metabolize

fatty acids and store glycogen. During

light activity, muscles can generate

ATP through the aerobic breakdown of

carbohydrates, lipids, or amino acids.

At peak levels of activity, most of the

energy is provided by anaerobic

reactions that generate lactic acid.


Muscle Performance

Two Types of Skeletal Muscle Fibers

• Fast fibers

Large diameter, abundant myofibrils, ample

glycogen, scant mitochondria. Produce

powerful, brief contractions

• Slow fibers

Smaller diameter, rich capillary supply, many

mitochondria, much myoglobin. Produce

slow, steady contractions


Muscle Performance

Physical Conditioning

• Anaerobic endurance

Time over which a muscle can contract

effectively under anerobic conditions.

• Hypertrophy

Increase in muscle bulk. Can result from

anerobic training.

• Aerobic endurance

Time over which a muscle can contract

supported by mitochondria. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Muscle Performance

Key Note

What you don’t use, you lose. When

motor units are inactive for days or

weeks, muscle fibers break down their

contractile proteins and grow smaller

and weaker. If inactive for long periods,

muscle fibers may be replaced by

fibrous tissue.


Cardiac and Smooth Muscle

Cardiac Muscle Tissue

• Small cells

• Single nucleus/cell

• Aerobic metabolism

• Intercalated discs

• Long contraction time

• Self-exciting (automaticity)

• No tetanic contraction



Smooth Muscle Tissue

• Nonstriated cells (no sarcomeres)

• Calcium control of contraction

different from striated muscle

• Wide range of operating lengths

• Involuntary muscle

• Under hormonal or local control

• Pacesetter cells

• Motor neurons often unneeded



Figure 7-10(a)

Cardiac

Muscle

Tissue


Figure 7-10(b)

Smooth Muscle Tissue


Table 7-2

Anatomy of the Muscular System

An Overview

of the Major

Skeletal

Muscles

Figure 7-11(a)


An Overview

of the Major

Skeletal

Muscles

Figure 7-11(b)


Origins, Insertions, and Actions

• Origin

Muscle attachment that remains fixed

• Insertion

Muscle attachment that moves

• Action

What joint movement a muscle produces



Primary Action Categories

• Prime mover (agonist)

• Main muscle in an action

• Synergist

• Helper muscle in an action

• Antagonist

• Opposed muscle to an action



Muscle Terminology

• Names of muscles provide clues to

location, orientation, or action

• Axial musculature—Muscles with origins

on the axial skeleton that position and

move head, spine, rib cage

• Appendicular musculature—Muscles that

stabilize or move appendicular

components



The Axial Muscles

• Four groups of axial muscles

• Head and neck

• Spine

• Trunk

• Pelvic floor



Selected Muscles of the Head

• Frontalis

• Orbicularis oris

• Buccinator

• Masseter

• Temporalis

• Pterygoids



Selected Muscles of the Neck

• Platysma

• Digastric

• Mylohyoid

• Stylohyoid

• Sternocleidmastoid



Muscles of the Head and Neck

Figure 7-12(a)


Muscles of the

Head and

Neck

Figure 7-12(b)


Muscles of the Head and Neck

Figure 7-12(c)


Muscles of the Anterior Neck

Figure 7-13


Selected Muscles of the Spine

• Splenius capitis

• Semispinalis capitis

• Erector spinae groups

• Spinalis

• Longissimus

• Iliocostalis



Muscles of

the Spine

Figure 7-14


Axial Muscles of the Trunk

• Thoracic region

• External intercostals

• Internal intercostals

• Diaphragm

• Abdominal region

• Rectus abdominis

• External oblique

• Internal oblique

• Transversus abdominis



Figure 7-15(a)

Oblique and Rectus

Muscles and the

Diaphragm


Oblique and Rectus Muscles and

the Diaphragm

Figure 7-15(b)


Oblique and Rectus Muscles and

the Diaphragm

Figure 7-15(c)


Muscles of the Pelvic Floor (Perineum)

• Sheets of muscle

• From sacrum and coccyx

• To pubis and ischium

• Pelvic organ support

• Control of material passing through

urethra and anus



Muscles of the Perineum—Female

Figure 7-16(a)


Muscles of the Perineum—Male

Figure 7-16(b)


The Appendicular Muscles

• Two functionally distinct groups

• Muscles of the shoulder and

upper limbs

• Muscles of the pelvic girdle

and lower limbs



Selected Shoulder Muscles

• Trapezius

• Rhomboid

• Levator scapulae

• Serratus anterior

• Pectoralis minor



Muscles of the Shoulder

Figure 7-17(a)


Muscles of the Shoulder

Figure 7-17(b)


Muscles the Move the Arm

• Deltoid

• Supraspinatus

• Subscapularis

• Teres major

• Infraspinatus

• Teres minor

• Pectoralis major

• Latissiumus dorsi



Muscles that Move the Arm

Figure 7-18(a)


Muscles that Move the Arm

Figure 7-18(b)


Muscles That Move the Forearm

• Biceps brachii

• Triceps brachii

• Brachialis

• Brachioradialis

• Pronators

• Supinator



Muscles That Move the Wrist

• Wrist flexors

• Flexor carpi ulnaris

• Flexor carpi radialis

• Palmaris longus

• Wrist extensors

• Extensor carpi radialis

• Extensor carpi ulnaris



Muscles That Move the Forearm and Wrist

Figure 7-19


Muscle of the Pelvis and Lower Limbs

• Three functional groups

• Thigh movement

• Leg movement

• Ankle, foot, and toe movement



Muscles That Move the Thigh

• Gluteal muscles

• Thigh adductors

• Adductor magnus

• Adductor brevis

• Adductor longus

• Pectineus

• Gracilis

• Thigh flexors

• Iliopsoas (psoas major + iliacus)



Muscles That Move the Thigh

Figure 7-20(a)


Muscles That Move

the Thigh

Figure 7-20(b)


Flexors of the Knee

• Biceps femoris

• Semimembranosus

• Semitendinosus

• Sartorius

• Popliteus

• Synergist muscle unlocks knee



Extensors of the Knee

• Quadriceps femoris group

• Rectus femoris

• Vastus lateralis

• Vastus intermedius

• Vastus medialis



Figure 7-21

Muscles That Move the Leg


Muscles That Move the Foot

• Plantar flexion

• Gastrocnemius

• Soleus

• Eversion and plantar flexion

• Fibularis (peroneus)

• Dorsiflexion

• Tibialis anterior



Muscles That Move the Foot and Toes

Figure 7-22(a)


Figure 7-22(b)

Muscles That Move

the Foot and Toes


Figure 7-22(c)

Muscles That Move

the Foot and Toes


Figure 7-22(d)

Muscles That

Move the Foot

and Toes

Aging and the Muscular System

Age-Related Reductions

• Muscle size

• Muscle elasticity

• Muscle strength

• Exercise tolerance

• Injury recovery ability


The Muscular System

in Perspective

FIGURE 7-23

Functional Relationships Between

the Muscular System and Other Systems

Figure 7-23


Figure 7-23

2 of 11

• Removes excess body heat;

synthesizes vitamin D3 for

calcium and phosphate

absorption; protects underlying

muscles

• Skeletal muscles pulling on

skin of face produce facial

expressions


The Integumentary System

Figure 7-23


The Skeletal System

• Maintains normal calcium and phosphate levels in body fluids; supports skeletal muscles; provides sites of attachment

• Provides movement and support; stresses exerted by tendons maintain bone mass; stabilizes bones and joints

Figure 7-23

4 of 11

The Nervous System

• Controls skeletal muscle contractions; adjusts activities of respiratory and cardiovascular systems during periods of muscular activity

• Muscle spindles monitor body position; facial muscles express emotion; muscles of the larynx, tongue, lips and cheeks permit speech


Figure 7-23

5 of 11

The Endocrine System

• Hormones adjust muscle

metabolism and growth;

parathyroid hormone and

calcitonin regulate calcium

and phosphate ion

concentrations

• Skeletal muscles provide

protection for some endocrine

organs


Figure 7-23

6 of 11

The Cardiovascular System

• Delivers oxygen and

nutrients; removes carbon

dioxide, lactic acid, and heat

• Skeletal muscle contractions

assist in moving blood

through veins; protects deep

blood vessels


Figure 7-23

7 of 11

The Lymphatic System

• Defends skeletal muscles

against infection and assists

in tissue repairs after injury

• Protects superficial lymph

nodes and the lymphatic

vessels in the

abdominopelvic cavity


Figure 7-23

8 of 11

The Respiratory System

• Provides oxygen and eliminates carbon dioxide

• Muscles generate carbon dioxide; control entrances to respiratory tract, fill and empty lungs, control airflow through larynx, and produce sounds


Figure 7-23

9 of 11

The Digestive System


• Provides nutrients; liver

regulates blood glucose and

fatty acid levels and removes

lactic acid from circulation

• Protects and supports soft

tissues in abdominal cavity;

controls entrances to and

exits from digestive tract

Figure 7-23

10 of 11

The Urinary System

• Removes waste products of

protein metabolism; assists in

regulation of calcium and

phosphate concentrations

• External sphincter controls

urination by constricting

urethra


Figure 7-23

11 of 11

The Reproductive System

• Reproductive hormones

accelerate skeletal muscle

growth

• Contractions of skeletal

muscles eject semen from

male reproductive tract;

muscle contractions during

sex act produce pleasurable

sensations
