Muscular System Chapter Overview

© 2013 Pearson Education, Inc.
PowerPoint®
Lecture Slides
prepared by
Meg Flemming
Austin Community College
C H A P T E R
The
Muscular
System
7

Chapter 7 Learning Outcomes
• 7-1
• Specify the functions of skeletal muscle tissue.
• 7-2
• Describe the organization of muscle at the tissue level.
• 7-3
• Identify the structural components of a sarcomere.
• 7-4
• Explain the key steps involved in the contraction of a skeletal
muscle fiber beginning at the neuromuscular junction.
• 7-5
• Compare the different types of muscle contractions.

• 7-6
• Describe the mechanisms by which muscles obtain the energy to
power contractions.
• 7-7
• Relate the types of muscle fibers to muscle performance, and
distinguish between aerobic and anaerobic endurance.
• 7-8
• Contrast the structures and functions of skeletal, cardiac, and
smooth muscle tissues.
• 7-9
• Explain how the name of a muscle can help identify its location,
appearance, or function.

• 7-10
• Identify the main axial muscles of the body together with their
origins, insertions, and actions.
• 7-11
• Identify the main appendicular muscles of the body together with
their origins, insertions, and actions.
• 7-12
• Describe the effects of aging on muscle tissue.
• 7-13
• Discuss the functional relationships between the muscular system
and other organ systems.

Five Skeletal Muscle Functions (7-1)
1. Produce movement of the skeleton
• By pulling on tendons that then move bones
2. Maintain posture and body position
3. Support soft tissues
• With the muscles of the abdominal wall and the pelvic floor
4. Guard entrances and exits
• In the form of sphincters
5. Maintain body temperature
• When contraction occurs, energy is used and converted to
heat

Checkpoint (7-1)
1. Identify the five primary functions of skeletal
muscle.

Organization of Skeletal Muscle Tissue (7-2)
• Skeletal muscles
• Are organs that contain:
• Connective tissue
• Blood vessels
• Nerves
• Skeletal muscle tissue
• Single skeletal muscle cells
• Also called skeletal muscle fibers

Three Layers of Connective Tissue (7-2)
1. Epimysium
• Covers the entire muscle
2. Perimysium
• Divides the muscle into bundles called fascicles
• Blood vessels and nerves are contained in the
perimysium
3. Endomysium
• Covers each muscle fiber and ties fibers together
• Contains capillaries and nerve tissue

Tendons (7-2)
• Where the ends of all three layers of connective
tissue come together
• And attach the muscle to a bone
• Aponeurosis
• A broad sheet of collagen fibers that connects muscles to
each other
• Similar to tendons, but do not connect to a bone

Blood Vessels and Nerves (7-2)
• Extensive network of blood vessels in skeletal
muscle
• Provides high amounts of nutrients and oxygen
• To skeletal muscles which have high metabolic needs

Control of Skeletal Muscle (7-2)
• Mostly under voluntary control
• Must be stimulated by the central nervous system
• Axons
• Push through the epimysium
• Branch through the perimysium
• And enter the endomysium
• To control individual muscle fibers

Figure 7-1 The Organization of Skeletal Muscles.
Skeletal Muscle (organ)
Epimysium Perimysium Endomysium Nerve
Muscle
fascicle
Muscle
fibers
Blood
vessels
Muscle Fascicle (bundle of fibers)
Perimysium
Muscle fiber
Endomysium
Epimysium
Blood vessels
and nerves
Endomysium
Perimysium
Tendon
Muscle Fiber (cell)
Capillary Myofibril Endomysium
Sarcoplasm
Mitochondrion
Stem cell
Sarcolemma
Nucleus
Axon of neuron

Checkpoint (7-2)
2. Describe the connective tissue layers associated
with a skeletal muscle.
3. How would severing the tendon attached to a
muscle affect the muscle's ability to move a body
part?

Features of Skeletal Muscle Fibers (7-3)
• Are specifically organized to produce contraction
and have specific names for general cell
structures
• Can be very long and are multinucleated
• Composed of highly organized structures, giving
them a striped or striated appearance

The Sarcolemma and Transverse Tubules (7-3)
• The sarcolemma
• Specific name of muscle fiber plasma membrane
• Has openings across the surface that lead into a network of
transverse tubules, or T tubules
• T tubules allow for electrical stimuli to reach deep into each
fiber
• The sarcoplasm
• Specific name for muscle fiber cytoplasm

Myofibrils in Muscle Fiber (7-3)
• Hundreds to thousands in each fiber
• Are encircled by T tubules and are as long as the
entire muscle fiber
• Are bundles of thick and thin myofilaments
• Actin molecules are found in thin filaments
• Myosin molecules are found in thick filaments
• Are the contractile proteins that shorten and are
responsible for contraction

The Sarcoplasmic Reticulum (7-3)
• Or SR
• Specialized smooth endoplasmic reticulum
• Expanded end that is next to the T tubule is the
terminal cisternae
• Contain high concentrations of calcium ions
• Triad
• A combination of two terminal cisternae and one T tubule

Sarcomeres (7-3)
• Smallest functional unit of skeletal muscle fiber
• Formed by repeating myofilament arrangements
• Each myofibril has about 10,000 sarcomeres
• Thick and thin filament arrangements are what
produce the striated appearance of the fiber
• Overlapping filaments define lines and bands

Sarcomere Lines (7-3)
• Z lines
• Thin filaments at both ends of the sarcomere
• Another protein connects the Z lines to the thick filament to
maintain alignment
• M line
• Made of connections between the thick filaments

Sarcomere Bands (7-3)
• A band
• Contains the thick filaments
• I band
• Contains the thin filaments, including the Z line

Figure 7-2 The Organization of a Skeletal Muscle Fiber.
T tubules
Terminal
cisterna
Sarcoplasmic
reticulum Triad Sarcolemma
Mitochondria
Thick
filament
MyofilamentsThin
filament
MYOFIBRIL
The structure of a skeletal
muscle fiber.
SARCOMERE
Z line
Zone of overlap
M line
Myofibril
I band H band
A band
Zone of overlap
The organization of a sarcomere, part of a single myofibril.
Z line M line Z line
A stretched out
sarcomere.
Z line and thin
filaments
Active site
Z line
Actin molecules
Thick filaments
M line
ACTIN
STRAND
Troponin Tropomyosin
Thin filament
MYOSIN MOLECULE
Myosin tail
Myosin
head
Hinge
The structure of a thick filament.
The structure of a thin filament.

Figure 7-2a The Organization of a Skeletal Muscle Fiber.
T tubules
Terminal
cisterna
Sarcoplasmic
reticulum Triad Sarcolemma
Mitochondria
Thick
filament
MyofilamentsThin
filament
MYOFIBRIL
The structure of a skeletal
muscle fiber.

Figure 7-2b The Organization of a Skeletal Muscle Fiber.
Z line Zone of overlap
M line
Myofibril
I band H band Zone of overlap
A band
SARCOMERE
The organization of a sarcomere, part of a single myofibril.

Figure 7-2c The Organization of a Skeletal Muscle Fiber.
Z line M line Z line
A stretched out
sarcomere.
Z line and thin
filaments
Z line
Thick filaments
M line

Figure 7-2d The Organization of a Skeletal Muscle Fiber.
Active site Actin molecules
ACTIN
STRAND
Troponin Tropomyosin
Thin filament
The structure of a thin filament.

Figure 7-2e The Organization of a Skeletal Muscle Fiber.
MYOSIN MOLECULE
Myosin tail
Myosin
head
Hinge
The structure of a thick filament.

Thin and Thick Filaments (7-3)
• Actin
• A thin twisted protein, with specific active sites for myosin to
bind to
• At rest, active sites are covered by strands of tropomyosin,
held in position by troponin
• Myosin
• A thick filament with tail and globular head that attaches to
actin active sites during contraction

Steps of Contraction (7-3)
1. Calcium released from SR
2. Calcium binds to troponin
3. Change of troponin shape causes tropomyosin to
move away from active sites
4. Myosin heads bind to active site, creating cross-
bridges, rotate and cause actin to slide over
myosin

Sliding Filament Theory (7-3)
• Based on observed changes in sarcomere
• I bands get smaller
• Z lines move closer together
• H bands decrease
• A bands don't change, indicating that the thin filaments are
sliding toward the center

Figure 7-3 Changes in the Appearance of a Sarcomere during Contraction of a Skeletal Muscle Fiber.
I band A band
Z line H band Z line
A relaxed sarcomere showing
locations of the A band, Z lines,
and I band.
I band
During a contraction, the A band stays the
same width, but the Z lines move closer
together and the I band gets smaller.
Z line H band Z line
A band

Checkpoint (7-3)
4. Describe the basic structure of a sarcomere.
5. Why do skeletal muscle fibers appear striated
when viewed through a light microscope?
6. Where would you expect the greatest
concentration of calcium ions to be in a resting
skeletal muscle fiber?

The Neuromuscular Junction (7-4)
• Where a motor neuron communicates with a
skeletal muscle fiber
• Axon terminal of the neuron
• An enlarged end that contains vesicles of the
neurotransmitter
• Acetylcholine (ACh)
• The neurotransmitter that will cross the synaptic cleft

The Neuromuscular Junction (7-4)
• ACh binds to the receptor on the motor end plate
• Cleft and the motor end plate contain
acetylcholinesterase (AChE)
• Which breaks down ACh
• Neurons stimulate sarcolemma by generating an
action potential
• An electrical impulse

The cytoplasm of the axon
terminal contains vesicles
filled with molecules of ace-
tylcholine, or ACh. Acetylcho-
line is a neurotransmitter, a
chemical released by a
neuron to change the perme-
ability or other properties of
another cell’s plasma mem-
brane. The synaptic cleft and
the motor end plate contain
molecules of the enzyme
acetylcholinesterase (AChE),
which breaks down ACh.
Vesicles ACh
Synaptic cleft
Motor
end plate
AChE
Slide 1Figure 7-4 Skeletal Muscle Innervation.

The stimulus for ACh
release is the arrival of an
electrical impulse, or
action potential, at the
axon terminal. The action
potential arrives at the
NMJ after traveling along
the length of the axon.
Arriving action
potential

When the action
potential reaches the
neuron’s axon terminal,
permeability changes in
the membrane trigger the
exocytosis of ACh into the
synaptic cleft. Exocytosis
occurs as vesicles fuse
with the neuron’s plasma
membrane.
Motor
end plate

ACh molecules diffuse
across the synaptic cleft
and bind to ACh receptors
on the surface of the motor
end plate. ACh binding
alters the membrane’s
permeability to sodium
ions. Because the extracell-
ular fluid contains a high
concentration of sodium
ions, and sodium ion
concentration inside the cell
is very low, sodium ions
rush into the sarcoplasm.
ACh receptor site

The sudden inrush of
sodium ions results in
the generation
of an action potential
in the sarcolemma.
AChE quickly breaks
down the ACh on the
motor end plate and in
the synaptic cleft, thus
inactivating the ACh
receptor sites.
Action
potential
AChE

The Contraction Cycle (7-4)
• Involves the triads
• Action potential travels over the sarcolemma,
down into the T tubules
• Causes release of calcium from the SR
• Calcium binds to troponin and the contraction
cycle starts

Contraction Cycle
Begins
Myosin head
Troponin
ActinTropomyosin
Figure 7-5 The Contraction Cycle Slide 1

Active-Site Exposure
Sarcoplasm
Active
site

Cross-Bridge Formation

Myosin Head Pivoting

Cross-Bridge
Detachment

Myosin Reactivation

Table 7-1 Steps Involved in Skeletal Muscle Contraction and Relaxation

Checkpoint (7-4)
7. Describe the neuromuscular junction.
8. How would a drug that blocks acetylcholine
release affect muscle contraction?
9. What would you expect to happen to a resting
skeletal muscle if the sarcolemma suddenly
became very permeable to calcium ions?

Contraction Produces Tension (7-5)
• As sarcomeres contract, so does the entire muscle
fiber
• As fibers contract, tension is created by tendons
pulling on bones
• Movement will occur only if the tension is greater
than the resistance
• Compression is a force that pushes objects
• Muscle cells create only tension, not compression

• Individual fibers
• Are either contracted or relaxed
• "On" or "off"
• Tension is a product of the number of cross-bridges a fiber
contains
• Variation in tension can occur based on:
• The amount of overlap of the myofilaments
• The frequency of stimulation
• The more frequent the stimulus, the more Ca2+
builds up,
resulting in greater contractions

• Whole skeletal muscle organ
• Contracts with varying tensions based on:
• Frequency of muscle fiber stimulation
• Number of fibers activated

A Muscle Twitch (7-5)
• A single stimulus-contraction-relaxation cycle in a
muscle fiber or whole muscle
• Represented by a myogram

Three Phases of a Muscle Twitch (7-5)
1. Latent period
• Starts at the point of stimulus and includes the action
potential, release of Ca2+
, and the activation of
troponin/tropomyosin
2. Contraction phase
• Is the development of tension because of the cross-bridge
cycle
3. Relaxation phase
• Occurs when tension decreases due to the re-storage of
Ca2+
and covering of actin active sites

Figure 7-6 The Twitch and Development of Tension.
Maximum tension
development
Tension
Stimulus
Time (msec) 0 5 10 20 30 40
Resting
phase
Latent
period
Contraction
phase
Relaxation
phase

Summation and Tetanus (7-5)
• Summation
• Occurs with repeated, frequent stimuli that trigger a response
before full relaxation has occurred
• Incomplete tetanus
• Near peak tension with little relaxation
• Complete tetanus
• Stimuli are so frequent that relaxation does not occur
ANIMATION Frog Wave SummationPLAYPLAY

Figure 7-7 Effects of Repeated Stimulations.
= Stimulus Maximum tension
(in tetanus)
Time Time Time
Summation. Summation
of twitches occurs when
successive stimuli arrive
before the relaxation phase
has been completed.
Incomplete tetanus.
Incomplete tetanus occurs
if the stimulus frequency
increases further. Tension
production rises to a peak,
and the periods of
relaxation are very brief.
Complete tetanus.
During complete tetanus,
the stimulus frequency is
so high that the relaxation
phase is eliminated;
tension plateaus at
maximal levels.
Tension

Varying Numbers of Fibers Activated (7-5)
• Allows for smooth contraction and a lot of control
• Most motor neurons control a number of fibers
through multiple, branching axon terminals

Motor Unit (7-5)
• A single motor neuron and all the muscle fibers it
innervates
• Motor units are dispersed throughout the muscle
• Fine control movements
• Use motor units with very few fibers per neuron
• Gross movements
• Motor units have a high fiber-to-neuron ratio

Recruitment (7-5)
• A mechanism for increasing tension to create
more movement
• A graded addition of more and more motor units to
produce adequate tension

Figure 7-8 Motor Units.
Axons of
motor neurons
SPINAL CORD
Motor
nerve
Muscle fibers
Motor unit 1
Motor unit 2
Motor unit 3
KEY

Muscle Tone and Atrophy (7-5)
• Muscle tone
• Some muscles at rest will still have a little tension
• Primary function is stabilization of joints and posture
• Atrophy
• Occurs in a muscle that is not regularly stimulated
• Muscle becomes small and weak
• Can be observed after a cast comes off a fracture

Types of Contraction (7-5)
• Isotonic contraction
• When the length of the muscle changes, but the tension
remains the same until relaxation
• For example, lifting a book
• Isometric contraction
• When the whole muscle length stays the same, the tension
produced does not exceed the load
• For example, pushing against a wall

Elongation of Muscle after Contraction (7-5)
• No active mechanism for returning a muscle to a
pre-contracted, elongated state
• Passively uses a combination of:
• Gravity
• Elastic forces
• Opposing muscle movement

Checkpoint (7-5)
10. What factors are responsible for the amount of
tension a skeletal muscle develops?
11. A motor unit from a skeletal muscle contains
1500 muscle fibers. Would this muscle be
involved in fine, delicate movements or in
powerful, gross movements? Explain.
12. Can a skeletal muscle contract without
shortening? Explain.

ATP and CP Reserves (7-6)
• At rest, muscle cells generate ATP, some of which
will be held in reserve
• Some is used to transfer high energy to creatine
forming creatine phosphate (CP)

ATP and CP Reserves (7-6)
• During contraction each cross-bridge breaks down
ATP into ADP and a phosphate group
• CP is then used to recharge ATP
• The enzyme creatine phosphokinase (CPK or
CK) regulates this reaction
• It lasts for about 15 seconds
• ATP must then be generated in a different way

Aerobic Metabolism (7-6)
• Occurs in the mitochondria
• Using ADP, oxygen, phosphate ions, and organic substrates
from carbohydrates, lipids, or proteins
• Substrates go through the citric acid cycle
• A series of chemical reactions that result in energy to make
ATP, water, and carbon dioxide
• Oxygen supply decides ATP aerobic production

Glycolysis (7-6)
• Breaks glucose down to pyruvate in the cytoplasm
of the cell
• If pyruvate can go through the citric acid cycle with
oxygen, it is very efficient
• Forming about 34 ATP
• With insufficient oxygen, pyruvate yields only 2
ATP
• Pyruvate is converted to lactic acid
• Potentially causing a pH problem in cells

Figure 7-9 Muscle Metabolism.
Fatty acids G Blood vessels
Glucose Glycogen
Mitochondria
Creatine
Resting: Fatty acids are catabolized; the ATP produced
is used to build energy reserves of ATP, CP, and glycogen.
Fatty acids
Glucose Glycogen
Pyruvate
2
2
34
34
To myofibrils to support
muscle contraction
Moderate activity: Glucose and fatty acids are catabolized;
the ATP produced is used to power contraction.
Lactate
Glucose Glycogen
Pyruvate
Creatine
2
2
muscle contraction
Peak activity: Most ATP is produced through glycolysis,
with lactate and hydrogen ions as by-products. Mitochondrial
activity (not shown) now provides only about one-third of
the ATP consumed.
Lactate

Figure 7-9a Muscle Metabolism.
Fatty acids Blood vessels
Glucose
G
Glycogen
Mitochondria
Creatine
Resting: Fatty acids are catabolized; the ATP produced
is used to build energy reserves of ATP, CP, and glycogen.

Figure 7-9b Muscle Metabolism.
Fatty acids
Glucose Glycogen
Pyruvate
2
34
muscle contraction
34
2
Moderate activity: Glucose and fatty acids are catabolized;
the ATP produced is used to power contraction.

Peak activity: Most ATP is produced through glycolysis,
with lactate and hydrogen ions as by-products. Mitochondrial
activity (not shown) now provides only about one-third of
the ATP consumed.
Lactate
Glucose Glycogen
Pyruvate
Lactate
Creatine
muscle contraction
2
2
Figure 7-9c Muscle Metabolism.

Muscle Fatigue (7-6)
• Caused by depletion of energy reserves or a
lowering of pH
• Muscle will no longer contract even if stimulated
• Endurance athletes, using aerobic metabolism,
can draw on stored glycogen and lipids
• Sprinters, functioning anaerobically, deplete CP
and ATP rapidly, and build up lactic acid
ANIMATION Frog FatiguePLAYPLAY

The Recovery Period (7-6)
• Requires "repaying" the oxygen debt by continuing to
breathe faster
• Even after the end of exercise, and recycling lactic acid
• Heat production occurs during exercise
• Raising the body temperature
• Blood vessels in skin will dilate; sweat covers the skin and
evaporates
• Promoting heat loss

Checkpoint (7-6)
13. How do muscle cells continuously synthesize
ATP?
14. What is muscle fatigue?
15. Define oxygen debt.

Muscle Performance (7-7)
• Measured in force
• The maximum amount of tension produced by a muscle or
muscle group
• Measured in endurance
• The amount of time a particular activity can be performed
• Two keys to performance
1. Types of fibers in muscle
2. Physical conditioning or training

Fast Fibers (7-7)
• The majority of muscle fibers in the body
• Large in diameter
• Large glycogen reserves
• Few mitochondria
• Rely on glycolysis
• Are rapidly fatigued

Slow Fibers (7-7)
• About half the diameter of, and three times slower
than, fast fibers
• Are fatigue resistant because of three factors
1. Oxygen supply is greater due to more perfusion
2. Myoglobin stores oxygen in the fibers
3. Oxygen use is efficient due to large numbers of mitochondria

Percentages of Muscle Types Vary (7-7)
• Fast fibers appear pale and are called white
muscles
• Extensive vasculature and myoglobin in slow
fibers cause them to appear reddish and are
called red muscles
• Human muscles are a mixture of fiber types and
appear pink

Muscle Conditioning and Performance (7-7)
• Physical conditioning and training
• Can increase power and endurance
• Anaerobic endurance
• Is increased by brief, intense workouts
• Hypertrophy of muscles results
• Aerobic endurance
• Is increased by sustained, low levels of activity

Checkpoint (7-7)
16. Why would a sprinter experience muscle fatigue
before a marathon runner would?
17. Which activity would be more likely to create an
oxygen debt in an individual who regularly
exercises: swimming laps or lifting weights?
18. Which type of muscle fibers would you expect
to predominate in the large leg muscles of
someone who excels at endurance activities
such as cycling or long-distance running?

Cardiac Muscle Tissue (7-8)
• Found only in heart
• Cardiac muscle cells
• Relatively small with usually only one central nucleus
• Striated and branched
• Intercalated discs, which connect cells to other cells
• Communicate through gap junctions, allowing all the fibers to
work together

Cardiac Pacemaker Cells (7-8)
• Exhibit automaticity
• Make up only 1 percent of myocardium
• Establish rate of contraction

Cardiac Contractile Cells (7-8)
• 99 percent of myocardium
• Contract for longer period than skeletal muscle
fibers
• Unique sarcolemmas make tetanus impossible
• Are permeable to calcium
• Rely on aerobic metabolism

Smooth Muscle Tissue (7-8)
• Found in the walls of most organs, in the form of
sheets, bundles, or sheaths
• Lacks myofibrils, sarcomeres, or striations
• Smooth muscle cells
• Also smaller than skeletal fibers
• Spindle-shaped and have a single nucleus

• Thick filaments are scattered throughout
sarcoplasm
• Thin filaments are anchored to the sarcolemma
• Causing contraction to be like a twisting corkscrew
• Cells are bound together
• Resulting in forces being transmitted throughout the tissue

• Different from other muscle types
• Calcium ions from the extracellular fluid are needed to trigger
a contraction mechanism that is different from other muscle
tissues
• Function involuntarily
• Can respond to hormones or pacesetter cells

Figure 7-10 Cardiac and Smooth Muscle Tissues.
A light micrograph of cardiac muscle tissue.
Intercalated
discs
Cardiac
muscle cell
Circular
muscle layer
Longitudinal
muscle layer
Many visceral organs contain several layers of smooth
muscle tissue oriented in different directions. Here, a
single sectional view shows smooth muscle cells in
both longitudinal (L) and transverse (T) sections.
Cardiac muscle tissue
Smooth muscle tissue
LM x 575
LM x 100
L
T

Table 7-2 A Comparison of Skeletal, Cardiac, and Smooth Muscle Tissues

Checkpoint (7-8)
19. How do intercalated discs enhance the
functioning of cardiac muscle tissue?
20. Extracellular calcium ions are important for the
contraction of what type(s) of muscle tissue?
21. Why can smooth muscle contract over a wider
range of resting lengths than skeletal muscle?

Skeletal Muscle System Names (7-9)
• Based on:
• Action
• What they do
• Origin
• The end that stays stationary
• Insertion
• The end that moves

Actions (7-9)
• Described as relative to the bone that is moved
• Example, "flexion of the forearm"
• Described as the joint that is involved
• Example, "flexion at the elbow"

Primary Actions of Muscles (7-9)
• Prime mover, or agonist
• The muscle that is chiefly responsible for producing a
movement
• Antagonist
• A muscle that opposes another muscle
• Synergist
• A muscle that helps the prime mover
• Example, flexion of the elbow
• The biceps brachii is the prime mover, the triceps brachii is
the antagonist, and the brachialis is the synergist

Table 7-3 Muscle Terminology (1 of 2)

Table 7-3 Muscle Terminology (2 of 2)

Muscle Terminology (7-9)
• Combining the various terms in Table 7-3,
anatomists name the muscles using:
• Location, direction of fibers, number of origins, and/or
function
• Muscles are organized into two groups
1. Axial muscles (mostly stabilizers)
2. Appendicular muscles (stabilizers or movers of the limbs)

Figure 7-11a An Overview of the Major Skeletal Muscles.
Frontalis
Temporalis
Masseter
Sternocleidomastoid
Trapezius
Clavicle
Deltoid
Pectoralis major
Biceps brachii
Triceps brachii
Brachialis
Pronator teres
Palmaris longus
Flexor carpi radialis
Flexor digitorum
Tensor fasciae
latae
Vastus lateralis
Rectus femoris
Patella
Tibia
Tibialis anterior
Extensor digitorum
Sternum
Latissimus dorsi
Serratus anterior
External oblique
Rectus abdominis
Extensor carpi radialis
Brachioradialis
Flexor carpi ulnaris
Gluteus
medius
Iliopsoas
Adductor longus
Gracilis
Sartorius
Vastus medialis
Fibularis
Gastrocnemius
Soleus
Anterior view

Figure 7-11b An Overview of the Major Skeletal Muscles.
Sternocleidomastoid
Trapezius
Deltoid
Infraspinatus
Teres minor
Latissimus dorsi
Brachioradialis
Extensor carpi
radialis
Occipitalis
Triceps brachii
Rhomboid major
Flexor carpi ulnaris
External oblique
Extensor digitorum
Extensor carpi ulnaris
Gluteus medius
Gluteus maximus
Adductor magnus
Semimembranosus
Gracilis
Sartorius
Tensor fasciae
latae
Semitendinosus
Biceps femoris
Gastrocnemius
Soleus
Calcaneal
tendon
Calcaneus
Teres major
Posterior view

Checkpoint (7-9)
22. Identify the kinds of descriptive information used
to name skeletal muscles.
23. Which muscle is the antagonist of the biceps
brachii?
24. What does the name flexor carpi radialis longus
tell you about this muscle?

Axial Muscles (7-10)
• Muscles of the head and neck
• Muscles of the spine
• Muscles of the trunk
• Muscles of the pelvic floor

Muscles of the Head and Neck (7-10)
• Orbicularis oris
• Constricts the mouth opening
• Buccinator
• Compresses check to blow forcefully
• Masseter
• Prime mover for chewing
• Temporalis and pterygoid
• Synergists for chewing
• Digastric
• Depresses the mandible
• Sternocleidomastoid
• Rotates head or flexes neck

Muscles of the Head and Neck (7-10)
• Epicranium, or scalp, contains a two-part muscle, the occipitofrontalis
1. Anterior frontalis
2. Posterior occipitalis
• Connected by epicranial aponeurosis
• Platysma
• Covers ventral neck extending from the base of the neck to the mandible
• Mylohyoid
• Supports the tongue
• Stylohyoid
1. Connects hyoid to styloid process

Figure 7-12 Muscles of the Head and Neck.
Epicranial
aponeurosis
(tendinous sheet)
Frontalis
Orbicularis
oculi
Zygomaticus
Orbicularis oris
Depressor
anguli oris
Temporalis
Occipitalis
Buccinator
Masseter
Sternocleidomastoid
Lateral pterygoid
Medial pterygoid
Mandible
Platysma
Zygomaticus
Orbicularis oris
Platysma
Sternocleidomastoid
Platysma
(cut and reflected)
Epicranial
aponeurosis
(tendinous sheet)
Frontalis
Temporalis
Orbicularis
oculi
Masseter
Buccinator
Depressor
anguli oris
Trapezius
Lateral view
Lateral view, pterygoid
muscles exposed Anterior view

Figure 7-13 Muscles of the Anterior Neck.
Mylohyoid
Stylohyoid
Hyoid bone
Cartilages
of larynx
Sternothyroid
Sternohyoid
Sternocleidomastoid
Cut heads of
sternocleidomastoid
Clavicle
Sternocleidomastoid
(cut)
Digastric
Mylohyoid
Mandible
Sternum

Table 7-4 Muscles of the Head and Neck (1 of 2)

Table 7-4 Muscles of the Head and Neck (2 of 2)

Muscles of the Spine (7-10)
• Splenius capitis and semispinalis capitis
• Work together to either extend the head or tilt the head
• Erector spinae
• Are spinal extensors and include spinalis, longissimus, and
iliocostalis
• Quadratus lumborum
• Flex the spinal column and depress the ribs

Figure 7-14 Muscles of the Spine.
Semispinalis capitis
Splenius capitis
Iliocostalis
Erector
spinae
muscles
Longissimus
Spinalis
Quadratus
lumborum

Table 7-5 Muscles of the Spine

Axial Muscles of the Trunk (7-10)
• External and internal intercostals
• Elevate and depress ribs, respectively
• Diaphragm
• Muscle used for inhalation of breath
• External and internal obliques, and the
transversus abdominis
• Compress abdomen, can flex spine
• Rectus abdominis
• Depresses ribs, flexes spine

Figure 7-15 Oblique and Rectus Muscles and the Diaphragm.
Central tendon
of diaphragm
Rectus
abdominis
Xiphoid
process
External
oblique
Inferior
vena cava
T10
Erector spinae group
Spinal cord
Aorta
Diaphragm
Serratus
anterior
Esophagus
Internal
intercostal
External
intercostal
Superior view at the level
of the diaphragm
Serratus
anterior
Internal intercostal
External intercostal
External oblique
(cut)
Internal oblique
Rectus abdominis
Anterior view
Linea alba
(midline band
of dense
connective
tissue)
Aponeurosis
External
oblique
Rectus abdominis
External
oblique
Transversus
abdominis
Internal
oblique
Horizontal section view at
the level of the umbilicus
Quadratus
lumborum
Linea alba
L3

Table 7-6 Axial Muscles of the Trunk

Muscles of the Pelvic Floor (7-10)
• Form the perineum and support the organs of the
pelvic cavity
• Flex the coccyx
• Control materials moving through the anus and
urethra with sphincters

Figure 7-16 Muscles of the Pelvic Floor.
Superficial Dissections Deep Dissections
Urethra
Ischiocavernosus
External urethral sphincter
Bulbospongiosus
Central tendon of perineum
Vagina
Transverse
perineus
Levator ani
External anal sphincter
Gluteus maximus
Female
Testis
No differences between
deep musculature in
male and female
Urethra (connecting
segment removed)
Ischiocavernosus
Bulbospongiosus
Transverse
perineus
Anus
Gluteus maximus
External urethral sphincter
Central tendon of perineum
Levator ani
External anal sphincter
Male
Anus

Table 7-7 Muscles of the Pelvic Floor

Checkpoint (7-10)
25. If you were contracting and relaxing your
masseter muscle, what would you probably be
doing?
26. Which facial muscle would you expect to be well
developed in a trumpet player?
27. Damage to the external intercostal muscles
would interfere with what important process?
28. If someone were to hit you in your rectus
abdominis, how would your body position
change?

Appendicular Muscles (7-11)
• Muscles that position the pectoral girdle
• Muscles that move the arm, forearm, and wrist
• Muscles that move the hand and fingers
• Muscles of the pelvic girdle
• Muscles that move the thigh and leg
• Muscles that move the foot and toes

Muscles That Position Pectoral Girdle (7-11)
• Trapezius
• Diamond-shaped muscle, has many actions depending on the
region
• Rhomboid
• Adducts and rotates scapula laterally
• Levator scapulae
• Adducts and elevates scapula
• Serratus anterior
• Abducts and rotates scapula
• Pectoralis minor and subclavius
• Depress and abduct shoulder

Figure 7-17 Muscles That Position the Pectoral Girdle.
Superficial Dissection Deep Dissection
Muscles That Position
the Pectoral Girdle
Trapezius
Levator scapulae
Rhomboid muscles
Serratus anterior
Triceps
brachii
Posterior view
Trapezius Levator scapulae
Subclavius
Pectoralis minor
Pectoralis major
(cut and reflected)
Internal intercostals
External intercostals
Pectoralis minor
(cut)
Serratus anterior
Biceps brachii
Anterior view
the Pectoral Girdle
the Pectoral Girdle
the Pectoral Girdle
Scapula
T12 vertebra

Table 7-8 Muscles That Position the Pectoral Girdle

Muscles That Move the Arm (7-11)
• Deltoid
• Abducts arm, supraspinatus assists
• Subscapularis, teres major, infraspinatus, and
teres minor
• Form the rotator cuff
• Pectoralis major
• Flexes the arm at the shoulder
• Latissimus dorsi
• Extends the arm at the shoulder
A&P FLIX™ Rotator cuff muscles: An overview (b)PLAYPLAY
A&P FLIX™ Rotator cuff muscles: An overview (a)PLAYPLAY

Figure 7-18 Muscles That Move the Arm.
Anterior view
Sternum
Clavicle Ribs (cut)
Muscles That
Move the Arm
Subscapularis
Coracobrachialis
Teres major
Biceps brachii
Vertebra T12
Deltoid
Latissimus dorsi
Supraspinatus
Infraspinatus
Teres minor
Teres major
Triceps brachii
Pectoralis major
Muscles That
Move the Arm
Muscles That
Move the Arm
Supraspinatus
Deltoid
Muscles That
Move the Arm
Posterior view
Vertebra T1

Table 7-9 Muscles That Move the Arm

Muscles That Move the Forearm and Wrist
(7-11)
• Biceps brachii
• Flexes the elbow and supinates forearm
• Triceps brachii
• Extends elbow
• Brachialis and brachioradialis
• Flex elbow
• Flexor carpi ulnaris, flexor carpi radialis, and palmaris
longus
• Flex wrist
• Extensor carpi radialis and extensor carpi ulnaris
• Extend wrist
• Pronators and supinators
• Rotate radius

Muscles That Move the Hand (7-11)
• Extensor digitorum
• Extends fingers
• Flexor digitorum
• Flexes fingers
• Abductor pollicis
• Abducts thumb
• Extensor pollicis
• Extends thumb
A&P FLIX™ The elbow joint and forearm: An overviewPLAYPLAY

Figure 7-19 Muscles That Move the Forearm and Wrist.
Triceps brachii
Brachioradialis
Extensor
carpi radialis
Extensor
carpi ulnaris
Extensor
digitorum
Abductor
pollicis
Extensor
pollicis
Extensor
retinaculum
Flexor
digitorum
superficialis
Flexor
retinaculum Pronator
quadratus
Flexor carpi
ulnaris
Palmaris longus
Humerus
Coracobrachialis
Biceps brachii
Pronator teres
Flexor
carpi
ulnaris
Ulna
Brachioradialis
Brachialis
Flexor carpi
radialis
Supinator
Pronator
teres
Ulna
Radius
Posterior view of
right upper limb
Anterior view of
right upper limb
Anterior view of the
muscles of pronation
and supination when
the limb is supinated

Table 7-10 Muscles That Move the Forearm, Wrist, and Hand (1 of 2)

Table 7-10 Muscles That Move the Forearm, Wrist, and Hand (2 of 2)

Checkpoint (7-11)
29. Which muscle do you use to shrug your
shoulders?
30. Sometimes baseball pitchers suffer rotator cuff
injuries. Which muscles are involved in this type
of injury?
31. Injury to the flexor carpi ulnaris would impair
which two movements?

Muscles That Move the Thigh (7-11)
• Gluteal group
• Includes gluteus maximus, the largest and most posterior;
is a hip extensor
• Adductors
• Include the adductor magnus, adductor brevis, adductor
longus, the pectineus, and the gracilis
• Largest hip flexor is the iliopsoas
• Made up of the psoas major and the iliacus
A&P FLIX™ Anterior muscles that cross the hip jointPLAYPLAY

Figure 7-20 Muscles That Move the Thigh.
Iliac crest
Gluteus
medius (cut)
Gluteus
maximus
(cut)
Sacrum
Gluteal Group
Gluteus maximus
Gluteus medius
Gluteus minimus
Tensor fasciae
latae
Iliotibial tract
Vastus lateralis
Biceps femoris
Semimembranosus
Plantaris
Head of fibula
Patella
Patellar
ligamentLateral
view
Iliopsoas Group
Psoas major
Iliacus
Pectineus
Adductor brevis
Adductor longus
Adductor magnus
Gracilis
Sartorius
Rectus
femoris
Gluteal region, posterior
view
Adductor Group
Anterior view of the
iliopsoas muscle and
the adductor group
5L

Table 7-11 Muscles That Move the Thigh (1 of 3)

Muscles That Move the Leg (7-11)
• Knee flexors are the hamstrings
• Biceps femoris, semimembranosus, semitendinosus, and
the sartorius
• Knee extensors are the quadriceps femoris
• Which include the rectus femoris and the three vastus
muscles
• Popliteus muscle
• Unlocks the knee joint

Figure 7-21 Muscles That Move the Leg.
Iliac crest
Gluteus medius
Tensor fasciae
latae
Gluteus maximus
Adductor magnus
Gracilis
Iliotibial tract
Flexors of the Knee
Biceps femoris
Semitendinosus
Semimembranosus
Sartorius
Popliteus
Iliacus
Psoas major Iliopsoas
Tensor fasciae
latae
Pectineus
Adductor longus
Gracilis
Sartorius
Extensors of the Knee
(Quadriceps muscles)
Rectus femoris
Vastus lateralis
Vastus medialis
Vastus intermedius
(deep to above muscles)
Quadriceps tendon
Patella
Patellar ligament
Hip and thigh, posterior view Quadriceps and thigh muscles, anterior view

Table 7-12 Muscles That Move the Leg

Muscles That Move the Foot and Toes (7-11)
• The gastrocnemius of the calf is assisted by the
underlying soleus
• They share a common calcaneal tendon, and are both
plantar flexors
• Fibularis muscles
• Produce eversion and plantar flexion
• Tibialis
• Cause inversion of the foot
• Tibialis anterior is largest and produces dorsiflexion

Figure 7-22a Muscles That Move the Foot and Toes.
Ankle Extensors
Plantaris
Gastrocnemius
Soleus
Gastrocnemius
(cut and removed)
Popliteus
Tendon of flexor
hallucis longus
Calcaneal
tendon
Calcaneus
Head of fibula
Ankle Extensors
(Deep)
Tibialis posterior
Fibularis longus
Fibularis brevis
Digital Flexors
Flexor digitorum
longus
Flexor hallucis
longus
Tendon of flexor digitorum
longus
Tendons of fibularis
muscles
Posterior views

Iliotibial tract
Head of fibula
Ankle Extensors
Ankle Flexors
Gastrocnemius
Fibularis longus
Soleus
Fibularis brevis
Tibialis anterior
Extensor digitorum
longus
Tendon of extensor
hallucis longus
Calcaneal tendon
Retinacula
Lateral view
Digital Extensors
Figure 7-22b Muscles That Move the Foot and Toes.

Figure 7-22c Muscles That Move the Foot and Toes.
Patella
Patellar
ligament
Medial surface
of tibial shaft
Ankle Extensors
Gastrocnemius
Soleus
Tibialis posterior
Calcaneal tendon
Retinacula
Tendon of
tibialis anterior
Medial view
Ankle Flexors
Tibialis anterior
Tendon of extensor
hallucis longus
Digital Extensors

Table 7-13 Muscles That Move the Foot and Toes (1 of 2)

Table 7-13 Muscles That Move the Foot and Toes (2 of 2)

Checkpoint (7-11)
32. You often hear of athletes suffering a "pulled
hamstring." To what does this phrase refer?
33. How would you expect a torn calcaneal tendon
to affect movement of the foot?

Four Effects of Aging on Skeletal Muscle (7-12)
1. Muscle fibers become smaller in diameter
2. Muscles become less elastic and more fibrous
3. Tolerance for exercise decreases due to a
decrease in thermoregulation
4. Ability to recover from injury is decreased

Checkpoint (7-12)
34. Describe general age-related effects on skeletal
muscle tissue.

Exercise Engages Multiple Systems (7-13)
• Cardiovascular system
• Increases heart rate and speeds up delivery of oxygen
• Respiratory system
• Increases rate and depth of respiration
• Integumentary system
• Dilation of blood vessels and sweating combine to increase
cooling
• Nervous and endocrine systems
• Control of heart rate, respiratory rate, and release of stored
energy

Figure 7-23
SYSTEM INTEGRATORBody System Muscular System Muscular System Body System
Integumentary
Skeletal
Removes excess body heat;
synthesizes vitamin D3 for calcium
and phosphate absorption; protects
underlying muscles
Provides mineral reserve for maintaining
normal calcium and phosphate levels in
body fluids; supports skeletal muscles;
provides sites of attachment
Skeletal muscles pulling on skin of
face produce facial expressions
Integumentary
(Page138)
Provides movement and support;
stresses exerted by tendons maintain
bone mass; stabilizes bones and
joints
Skeletal
(Page188)
The MUSCULAR System
The muscular system performs five
primary functions for the human
body. It produces skeletal
movement, helps maintain
posture and body position,
supports soft tissues, guards
entrances and exits to the body,
and helps maintain body
temperature.
Nervous
(Page302)
Endocrine
(Page376)
Cardiovascular
(Page467)
Lymphatic
(Page500)
Respiratory
(Page532)
Digestive
(Page572)
Urinary
(Page637)
Reproductive
(Page671)

Checkpoint (7-13)
35. What major function does the muscular system
perform for the body as a whole?
36. Identify the physiological effects of exercise on
the cardiovascular, respiratory, and
integumentary systems, and indicate the
relationship between these physiological effects
and the nervous and endocrine systems.

Muscular System Chapter Overview

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Muscular System Chapter Overview