Download CHAPTER 9: THE MUSCULAR SYSTEM

UNIT 2 - CHAPTER 9: MUSCULAR SYSTEM
LEARNING OUTCOMES:
9.1
Introduction
1.
9.2
9.3
9.4
9.5
List various outcomes of muscle actions.
Structure of a Skeletal Muscle
2.
Describe the structure of a skeletal muscle.
3.
Name the major parts of a skeletal muscle fiber and describe the functions of each.
Skeletal Muscle Contraction
4.
Describe the neural control of skeletal muscle contraction.
5.
Identify the major events of skeletal muscle fiber contraction.
6.
List the energy sources for the skeletal muscle fiber contraction.
7.
Describe oxygen debt.
8.
Describe how a muscle may become fatigued.
Muscular Responses
9.
Distinguish between a twitch and sustained contraction.
10.
Explain how various types of muscular contractions produce body movements and
help maintain posture.
11.
Distinguish between fast and slow twitch muscle fibers.
Smooth Muscles
12.
Distinguish between the structures and functions of multiunit smooth muscle and
visceral smooth muscle.
13.
Compare the contraction mechanisms of skeletal and smooth muscle fibers.
9-1
UNIT 2 - CHAPTER 9: MUSCULAR SYSTEM
LEARNING OUTCOMES:
9.6
Cardiac Muscle
14.
9.7
Skeletal Muscle Actions
15.
9.8
Explain how the attachments, locations, and interactions of skeletal muscles make
possible certain movements.
Major Skeletal Muscles
16.
9.9
Compare the contraction mechanisms of skeletal and cardiac muscle fibers.
Identify and locate the skeletal muscles of each body region and describe the
action(s) of each muscle.
Life-Span Changes
17.
Describe aging-related changes in the muscular system.
18.
Discuss how exercise can help maintain a healthy muscular system as the body
ages.
9-2
UNIT 2 - CHAPTER 9: MUSCULAR SYSTEM
9.1
INTRODUCTION
A.
All body movements require muscles.
B.
Muscles are organs composed of specialized cells that use the chemical energy
stored in nutrients to exert a pulling force on structures to which they are attached.
C.
Muscle actions also:
1.
provide muscle tone
2.
propel body fluids and food
3.
generate the heartbeat
4.
distribute heat
Three Muscle Types (Review Chapter 5, Muscle Tissues)
1.
Skeletal
2.
Smooth
3.
Cardiac
*
See Table 9.2, page 310: Characteristics of Muscles Tissues.
D.
E.
9.2
This chapter focuses primarily on skeletal muscle.
STRUCTURE OF SKELETAL MUSCLE
Each skeletal muscle is an organ made up of skeletal muscle fibers, connective tissue
coverings, blood vessels, and nerve fibers.
A.
Connective Tissue (CT) Coverings: See Fig 9.2, page 294 & Fig 9.3, page 295.
1.
Each muscle fiber (cell) is wrapped in a thin, delicate layer of CT called
endomysium.
2.
Many muscle fibers are bundled together into groups called fascicles.
See Fig 9.3, page 295.
a.
Each fascicle is wrapped in a second layer of CT made of collagen
called perimysium.
3.
Many fascicles are bundled together to form a skeletal muscle.
a.
Each skeletal muscle is covered by a third layer of dense, fibrous
CT called epimysium.
4.
Each skeletal muscle is then covered by a fourth, very tough fibrous layer
of CT called deep fascia.
a.
The deep fascia may extend past the length of the muscle (tendon
or aponeurosis), and attach that muscle to a bone, cartilage or
muscle.
b.
See Fig 9.1, page 293 to compare these two extensions.
9-3
UNIT 2 - CHAPTER 9: MUSCULAR SYSTEM
9.2
STRUCTURE OF SKELETAL MUSCLE
B.
Skeletal Muscle Fibers
Recall from Chapter 5 that skeletal muscle fibers possess striations:
1.
A muscle fiber is a long, thin cell.
a.
2.
Thick filaments = protein myosin. See Fig 9.6, page 296.
a.
b.
3.
Each muscle fiber is composed of myofibrils.
o
Each myofibril is composed of two types of protein
filaments (cytoskeletal elements):
1.
Thick filaments composed of the protein myosin.
2.
Thin filaments primarily composed of the protein
actin.
o
Striations are caused by the arrangement of thick and thin
filaments within the myofibrils:
See Fig 9.5, page 296.
1.
A-Band = dark area = overlapping of thick and thin
filaments.
2.
I-Band = light area = thin filaments alone.
o
The length of each myofibril is divided into sarcomeres:
1.
Sarcomeres meet one another at an area called the
Z-line.
o
See Fig 9.4, page 296.
rod-like tail (axis) that terminates in two globular heads (or cross
bridges).
The myosin heads (cross bridges) interact with active sites on thin
filaments making linkages between the thick and thin filament.
Thin filaments = protein actin. See Fig 9.6, page 296.
a.
b.
c.
d.
coiled helical structure (resembles twisted strands of pearls)
Tropomyosin = rod-shaped protein spiraling around actin
backbone to stabilize it.
Troponin = complex of polypeptides:
o
one binds to actin
o
one binds to tropomyosin
o
one binds to calcium ions
Both tropomyosin and troponin help control actin's interaction with
myosin during contraction.
9-4
UNIT 2 - CHAPTER 9: MUSCULAR SYSTEM
9.2
STRUCTURE OF SKELETAL MUSCLE
B.
Skeletal Muscle Fibers
4.
Within the sarcoplasm of a muscle fiber, there are two specialized
membranous organelles: See Fig 9.7, page 297.
a.
b.
Sarcoplasmic reticulum (SR)
o
network of membranous channels that surrounds each
myofibril and runs parallel to it
o
same as endoplasmic reticulum in other cells
o
SR has high concentrations of calcium ions compared to the
sarcoplasm (maintained by active transport calcium pump).
o
When stimulated by muscle impulse, membranes become
more permeable to calcium ions and calcium diffuses out of
SR and into sarcoplasm.
Transverse tubules (TT)
○
set of membranous channels that extend into the
sarcoplasm as invaginations continuous with muscle cell
membrane (sarcolemma)
○
TTs are filled with extracellular fluid and extend deep into
the muscle cell.
○
Each TT runs between two enlarged portions of SR called
cisternae.
 These structures form a triad near the region where
actin and myosin overlap.
c.
SR and TT are involved in activating the muscle contraction
mechanism (discussed in greater detail later).
d.
Because one TT is associated with two SR they are termed the
triad.
9-5
UNIT 2 - CHAPTER 9: MUSCULAR SYSTEM
9.3
SKELETAL MUSCLE CONTRACTION
A.
Neuromuscular Junction (NMJ) Stimulation of Skeletal Muscle Cell
1.
2.
B.
NMJ = the site where a motor nerve ending (fiber) and a skeletal muscle
fiber meet (also called a synapse or synaptic cleft).
a.
In order for a skeletal muscle to contract, its fibers must first be
stimulated by a motor neuron.
b.
See Figure 9.8, page 298.
Other important features:
a.
Motor neuron = the nerve cell that stimulates the muscle cell.
b.
Neurotransmitter = chemical substance released from a motor
ending (fiber), causing stimulation of the sarcolemma of muscle
fiber; acetylcholine (ACh).
c.
Motor Unit = one motor neuron and many skeletal muscle fibers.
See Fig 9.17, page 306.
d.
Motor End Plate = the specific part of a skeletal muscle fiber's
sarcolemma directly beneath the NMJ.
Stimulus for Contraction
See Table 9.1, page 302.
1.
2.
3.
4.
Introduction: The function of skeletal muscle is to move bones of the
skeleton under voluntary control. Contraction of a skeletal muscle fiber is
a complex interaction of several cellular and chemical constituents. The
final result is a movement whereby actin and myosin filaments slide past
one another. Accordingly, the muscle fiber shortens and pulls on its
attachments.
The process begins when a motor impulse is initiated by the brain. It
travels down the spinal cord, into a motor neuron, which branches into
many motor nerve fibers/endings.
a.
Each motor nerve fiber extends to the motor end-plate of a skeletal
muscle fiber forming a neuromuscular junction (NMJ).
b.
When the motor impulse reaches the end of the motor nerve
fiber/ending, the membrane is depolarized (-70mV to -55mV).
o
Calcium ions rush into motor nerve fiber, and
o
neurotransmitter (Acetylcholine) is released into the NMJ
(via exocytosis).
Acetylcholine diffuses across the NMJ & stimulates/depolarizes the motor
end-plate (sarcolemma) of a skeletal muscle fiber from -100mV to
–70mV.
The muscle impulse begins and travels over the surface of the skeletal
muscle fiber and deep into the muscle fiber by means of the TTs.
9-6
UNIT 2 - CHAPTER 9: MUSCULAR SYSTEM
9.3
SKELETAL MUSCLE CONTRACTION
C.
Excitation Contraction Coupling
1.
2.
3.
4.
5.
D.
The muscle impulse reaches the sarcoplasmic reticulum, which releases
calcium ions into the sarcoplasm of the muscle fiber.
Calcium binds to troponin, moving tropomyosin and exposing myosin
binding sites on actin filament.
Linkages (cross-bridges) form between actin and myosin.
Actin filaments are pulled inward by myosin cross-bridges.
The muscle fiber shortens as contraction occurs.
The Sliding Filament Model of Muscle Contraction
1.
2.
3.
5.
a most popular theory concerning muscle contraction
first proposed by Hugh Huxley in 1954
states that muscle contraction involves the sliding movement of the thin
filaments (actin) past the thick filaments (myosin)
sliding continues until the overlapping between the thin and thick
filaments is complete.
Remember that in a relaxed muscle cell, overlapping of thick and thin
filaments is only slight (i.e. striations).
Changes in muscle during contraction: See Fig 9.10, page 301.
6.
a.
The distance between the Z-lines of the sarcomeres decreases.
b.
The I-Bands (light bands) shorten and disappear.
c.
The A-Bands move closer together, but do not diminish in length.
The Role of Calcium in Contraction Mechanism:
4.
*
a.
In a resting muscle cell (i.e. in the absence of calcium ions):

Tropomyosin blocks or inhibits the myosin binding sites on
actin.

See Fig 9.9(1), page 300.
b.
When calcium ions (Ca2+) are present:

Ca2+ binds to troponin causing a conformational change in
the troponin-complex, which causes:
1.
tropomyosin to move
2.
which "opens" or exposes the myosin binding sites
on actin
3.
This results in interaction between the active sites
on actin and the heads (or cross bridges) of myosin.

See Fig 9.9(2), page 300.
9-7
UNIT 2 - CHAPTER 9: MUSCULAR SYSTEM
9.3
SKELETAL MUSCLE CONTRACTION
E.
Cross-Bridge Cycling
See Fig 9.9, page 300.
When calcium ions are present, the myosin binding sites on actin are exposed:
1.
Cross-bridge attaches.
a.
ATP breakdown provides energy to “cock” myosin head.
b.
“Cocked” myosin attaches to exposed actin binding site.
2.
Cross-bridge (myosin head) springs from cocked position and pulls on
actin filament.
3.
Cross bridges break.
a.
ATP binds to cross-bridge (but is not yet broken down)
b.
Myosin heads are released from actin.
*
As long as calcium ions and ATP are present, this step-wise walking
continues until the muscle fiber is fully contracted.
F.
Relaxation
1.
2.
3.
4.
5.
G.
See right side of Table 9.1, page 302.
Acetylcholinesterase is an enzyme present in the NMJ.
It immediately destroys acetylcholine, so the motor end-plate is no longer
stimulated (i.e. so it cannot cause continuous muscle contraction).
Calcium ions are transported from sarcoplasm back into sarcoplasmic
reticulum.
Linkages between actin and myosin are broken.
The muscle fiber relaxes.
Energy Sources for Contraction
1.
2.
3.
Introduction: The energy used to power the interaction between
actin and myosin comes from ATP.
ATP stored in skeletal muscle lasts only about six seconds.
a.
ATP must be regenerated continuously if contraction is to
continue.
b.
There are three pathways in which ATP is regenerated:
○
Coupled Reaction with Creatine Phosphate (CP)
○
Anaerobic Cellular Respiration
○
Aerobic Cellular Respiration
Coupled Reaction with Creatine Phosphate (CP)
See Fig 9.11, page 302.
o
o
o
CP + ADP ↔ creatine + ATP
Muscle stores a lot of CP.
This coupling reaction allows for about 10 seconds worth
of ATP.
9-8
UNIT 2 - CHAPTER 9: MUSCULAR SYSTEM
9.3
SKELETAL MUSCLE CONTRACTION
H.
Oxygen Supply and Cellular Respiration: See Fig 9.12, page 303.
Review from Chapter 4.
1.
2.
I.
Oxygen Debt:
1.
J.
See Fig 9.13, page 303.
The oxygen debt is the amount of oxygen necessary to support
a.
the conversion of lactic acid (see below) to glucose.
b.
the resynthesis of ATP and CP.
c.
the return of tissue and blood O2 levels back to pre-exercise levels.
Muscle Fatigue
1.
2.
3.
K.
Anaerobic Respiration
a.
Steps are called glycolysis.
b.
Steps occur in the cytoplasm of the cell.
c.
results in production of pyruvic acid and 2 ATP.
Aerobic Respiration
a.
Steps are called citric acid cycle and electron transport chain.
b.
Oxygen is required.
c.
Steps occur in the mitochondrion of the cell.
d.
results in CO2, water and 36 ATP.
*
See box on page 304, which illustrates how a runner utilizes the
sources discussed above.
Muscle fatigue is a state of physiological inability to contract.
If no oxygen is available in muscle cells to complete aerobic respiration,
pyruvic acid is converted to lactic acid, which in animals causes muscle
fatigue and soreness. See Fig 9.13, page 303 and text on page 304.
results from a relative deficit of ATP and/or accumulation of lactic acid
(which decreases pH).
Heat Production
1.
Almost half of the energy released during muscle contraction is lost to
heat, which helps maintain our body temperature at 37o C.
a.
Excessive heat is lost through many negative feedback mechanisms
(discussed in chapter 1) including sweating, dilation of superficial
blood vessels, increased breathing rate, and increased heart rate.
9-9
UNIT 2 - CHAPTER 9: MUSCULAR SYSTEM
9.4
MUSCULAR RESPONSES
A.
Threshold Stimulus
1.
2.
B.
Recording a Muscle Contraction: See Fig 9.14, page 305.
1.
2.
3.
4.
5.
6
7.
C.
is the minimal strength of stimulation required to cause contraction.
A skeletal muscle fiber’s resting membrane potential must be depolarized
from –100mV to –70mV, before an impulse begins. Therefore the
threshold stimulus is +30mV.
A myogram is a recording of a muscle contraction.
A twitch is a single contraction that lasts a fraction of a second, followed
by relaxation. See Fig 9.16a, page 306.
The delay between stimulation and contraction is called the latent period.
The force a muscle fiber can generate depends on the length to which it is
stretched when stimulated. See Fig 9.15, page 305.
A muscle fiber must return to its resting state (-100mV) before it can be
stimulated again. This is called the refractory period.
All-or-None Response
a.
If a muscle fiber is brought to threshold or above, it responds with
a complete twitch.
b.
If the stimulus is subthreshold, the muscle fiber will not respond.
Staircase Effect (treppe):
a.
Most muscle fiber contraction is “all-or-none”.
b.
However a muscle fiber that has been inactive can be subjected to a
series of stimuli and:

The fiber undergoes a series of twitches with relaxation
between.

The strength of each successive contraction increases
slightly.

This phenomenon is small and brief and involves excess
calcium in the sarcoplasm and muscle warming.
Summation: See Fig 9.16b, page 306.
1.
When several stimuli are delivered in succession to a muscle fiber, it
cannot completely relax between contractions.
2.
The individual twitches begin to combine and the muscle contraction
becomes sustained.
a.
In a sustained contraction, the force of individual twitches
combines in a process called summation. Also See 9.4 E below.
b.
When the resulting sustained contraction lacks even slight
relaxation, it is called tetanic contraction.
Fig 9.16c, page 306.
9-10
UNIT 2 - CHAPTER 9: MUSCULAR SYSTEM
9.4
MUSCULAR RESPONSES
D.
Recruitment of Motor Units
1.
2.
3.
4.
Recall that a motor unit is a motor neuron and the many skeletal muscle
fibers it stimulates. See Fig 9.17, page 306.
Because the motor neuron branches into several motor nerve endings, it
can stimulate many skeletal muscles fibers at the same time, which then
contract simultaneously.
a. The number of muscle fibers in a motor unit varies from ten-hundreds.
Because a whole muscle is composed of many motor units, controlled by
many different motor neurons, simultaneous contraction of all units does
not necessarily occur.
As the intensity of stimulation increases, recruitment of motor units
increases, until all contract simultaneously.
E.
Sustained Contractions
1.
Even when a muscle is at rest, a certain amount of sustained contraction is
occurring in its fibers. This is called muscle tone.
a.
Muscle tone is very important in maintaining posture.
F.
Types of Contractions: See Fig 9.18, page 307.
1.
Isotonic contractions
a.
The muscle shortens and its attachment(s) move(s).
2.
Isometric contraction,
a.
The muscle becomes taut, but the attachment(s) do not move;
tensing a muscle.
3.
Most muscular movements involve both isotonic and isometric
contractions.
4.
See Clinical Application 9.2, page 308: Use and Disuse of Skeletal
Muscles.
G.
Fast- and Slow-Twitch Muscle Fibers
1.
Muscle fibers vary in contraction speed (i.e. slow or fast twitch).
2.
Slow-Twitch Fibers are also called red fibers.
a.
They contain oxygen carrying pigment, myoglobin, receive a rich
blood supply, and contain many mitochondria.
b.
can generate ATP fast enough to keep up with breakdown
c.
These fibers contract for long periods without fatiguing.
3.
Fast-twitch fibers are also called white fibers.
a.
They contain less myoglobin, blood, and fewer mitochondria.
b.
contain extensive sarcoplasmic reticulum to store and reabsorb
calcium.
c.
These fibers contract rapidly, but fatigue easily due to lactic acid
accumulation.
b. See box on page 308 re: dark and white meat.
9-11
UNIT 2 - CHAPTER 9: MUSCULAR SYSTEM
9.5
SMOOTH MUSCLES:
A.
Introduction: The contraction mechanism of smooth muscle is similar to that of
skeletal muscle in that interaction occurs between actin and myosin. However the
transverse tubules and sarcoplasmic reticula are greatly reduced, and troponin is
absent.
B.
Smooth Muscle Fibers - Two types: See pages 308-309 in text.
1.
Multiunit smooth muscle
a.
b.
2.
Visceral smooth muscle
a.
b.
c.
d.
C.
location:
o
irises of eyes
o
walls of blood vessels
Contraction is rapid and vigorous (similar to skeletal muscle
tissue).
Location = the walls of hollow organs.
Contraction is slow and sustained.
o
Rhythmicity = pattern of repeated contractions.
o
Peristalsis = wave-like motion that helps push substances
through passageways.
Structure:
o
random arrangement of actin and myosin filaments
o
Two layers of muscle surround the passageway.
1.
inner circular layer
2.
outer longitudinal layer
See Fig 5.29, page 172.
Smooth Muscle Contraction:
1. A protein, calmodulin binds to calcium ions (no troponin), and activates the
contraction mechanism.
2. Most calcium diffuses into smooth muscle cells from the extracellular fluid
(reduced SR).
3. Norepinephrine and acetylcholine are smooth muscle neurotransmitters.
4. Contraction is slow and sustained.
9-12
UNIT 2 - CHAPTER 9: MUSCULAR SYSTEM
9.6
CARDIAC MUSCLE:
A.
Location:
1.
B.
C.
*
See text pages 309-310, Fig 9.19, page 310 and Fig 5.30,
page 173. Will be studied in greater detail in Chapter 15.
only in heart
Anatomy:
1.
Striated uninuclear cells joined end-to-end forming a network
a.
Cell junctions are called intercalated discs.
o
gap junctions
o
See Fig 5.1, page 153.
2.
Arrangement of actin and myosin is not as organized as in skeletal muscle.
3.
contains sarcoplasmic reticula, transverse tubules, and numerous
mitochondria:
a.
Sarcoplasmic reticulum is less developed than SR in skeletal
muscle and stores much less calcium.
*
See box on page 309 re: Calcium channel blockers.
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.
See Table 9.2, page 310: Characteristics of Muscles Tissues.
9-13
UNIT 2 - CHAPTER 9: MUSCULAR SYSTEM
9.7
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.
Body Movement
1.
Skeletal muscles are attached to bones by tendons.
a.
serve as levers to move bones
b.
See Fig 9.20 page 311 for examples of levers.
c.
See Fig 9.21 page 312 for examples of how muscles pull on bones.
C.
Origin and Insertion: See Fig 9.22, page 312.
Recall that skeletal muscles are usually attached to a fixed body part and a
moveable body part:
1.
2.
*
D.
The origin of a muscle is its immovable (anchored) end.
The insertion of a muscle is the movable end of a muscle.
When a muscle contracts and shortens, its insertion is pulled toward its
origin.
Review of Skeletal Muscle Actions (from Chapter 8)
1.
Flexion = decreasing the angle between 2 bones (i.e. head toward chest).
2.
Extension = increasing the angle between 2 bones (i.e. straightening the
knee).
3.
Hyperextension = increasing the angle greater than at anatomical position
(i.e. bending the head back).
4.
Dorsiflexion = bringing toes toward shin.
5.
Plantar flexion = pointing one's toe (flexion toward the sole).
6.
Abduction = moving a limb away from the midline (i.e. raising arm or
thigh laterally).
7.
Adduction = moving a limb toward the midline.
8.
Rotation = turning movement of a bone along its longitudinal axis.
9.
Circumduction = moving a limb in a circular (cone-shaped) manner.
10.
Supination = thumbs up.
11.
Pronation = thumb down.
12.
Eversion = sole outward.
13.
Inversion = sole inward.
14.
Protraction = moving a part forward (i.e. chin thrust forward).
15.
Retraction = moving a part backward (i.e. pulling the head back).
16.
Elevation = raising a part (i.e. shoulder shrug).
17.
Depression = lowering a part (i.e. depressing the mandible).
9-14
UNIT 2 - CHAPTER 9: MUSCULAR SYSTEM
9.7
SKELETAL MUSCLE ACTIONS
E.
Interactions of Skeletal Muscles
1.
2.
3.
4.
9.8
See page 313.
Prime Mover (agonist) = the primary muscle responsible for a movement.
o
The biceps brachii is the prime mover in flexing the arm at the
Elbow.
Synergist(s) = muscles that assist the prime mover.
○
The brachialis helps the biceps brachii during elbow flexion.
Antagonist(s) = the muscle(s) in opposition to the action of the prime
mover. The antagonist relaxes (or stretches) during the prime movement.
o
The triceps brachii is the antagonist of the biceps brachii during
elbow flexion.
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.
o
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
MAJOR SKELETAL MUSCLES
NAMING OF SKELETAL MUSCLES
CHARACTERISTIC
Direction of fascicles
relative to midline
Location (i.e. the bone or
body part that a muscle
covers)
Relative Size
Number of Origins (Heads)
Shape
Location of Origin and/or
Insertion
Action of Muscle
EXAMPLES
rectus = parallel
transverse = perpendicular
oblique = at 45o angle
frontal bone
tibia
EXAMPLES IN HUMANS
Rectus abdominis
Transversus abdominis
External Oblique
Frontalis
Tibialis Anterior
maximus = largest
longus = longest
brevis = shortest
biceps = 2 origins
triceps = 3 origins
deltoid = triangle
trapezius = trapezoid
serratus = saw-toothed
orbicularis = circular
origin = sternum
insertion = mastoid process
Gluteus maximus
Palmaris longus
Peroneus longus
Biceps brachii
Triceps brachii
Deltoid
Trapezius
Serratus anterior
Orbicularis oris
Sternocleidomastoid
flexion
extension
adduction
Flexor carpi radialis
Extensor digitorum
Adductor longus
9-15
UNIT 2 - CHAPTER 9: MUSCULAR SYSTEM
9.8
MAJOR SKELETAL MUSCLES (Keyed at the end of this outline)
ONLY A REPRESENTATIVE SAMPLE OF SKELETAL MUSCLES DISCUSSED
IN CHAPTER 9 ARE INCLUDED IN THIS OUTLINE.
Use the figures and tables on pages 314-340 to complete the following information.
If a muscle is starred (*), please include its origin and insertion. Also see Human
and Cadaver Reference Plates Fifty-Five – Seventy-Five, pages 348-359.
A.
Muscles of Facial Expression:
See Fig 9.25 and Table 9.3 on page 315.
NAME OF MUSCLE
LOCATION/
DESCRIPTION
ACTION
Epicranius
Frontalis
Occipitalis
Orbicularis oris
Zygomaticus (*)
Major
Minor
Buccinator
Platysma
Orbicularis oculi
B.
Muscles of Mastication: See Fig 9.25 on page 315 and Table 9.4 on page 316.
NAME OF MUSCLE
LOCATION/
DESCRIPTION
ACTION
Masseter(*)
Temporalis
9-16
UNIT 2 - CHAPTER 9: MUSCULAR SYSTEM
9.8
MAJOR SKELETAL MUSCLES
ONLY A REPRESENTATIVE SAMPLE OF SKELETAL MUSCLES DISCUSSED
IN CHAPTER 9 ARE INCLUDED IN THIS OUTLINE.
C.
Muscles that Move the Head and Vertebral Column:
See Fig 9.25 on page 315, Fig 9.26, page 317, and Table 9.5 on page 318.
NAME OF MUSCLE
LOCATION/
DESCRIPTION
ACTION
Sternocleidomastoid (*)
Erector Spinae
D.
Muscles that Move (or fixate) the Pectoral Girdle:
See Fig 9.27 on page 319, Fig 9.28 on page 320, and Table 9.6 on page 321.
NAME OF MUSCLE
LOCATION/
DESCRIPTION
ACTION
Trapezius (*)
Pectoralis minor
Serratus anterior
E.
Muscles that Move the Arm (Humerus):
See Fig 9.27, page 319, Fig 9.28, page 320, and Table 9.7, page 322.
NAME OF MUSCLE
LOCATION/
DESCRIPTION
ACTION
Pectoralis major (*)
Latissimus dorsi
Deltoid
9-17
UNIT 2 - CHAPTER 9: MUSCULAR SYSTEM
9.8
MAJOR SKELETAL MUSCLES
ONLY A REPRESENTATIVE SAMPLE OF SKELETAL MUSCLES DISCUSSED
IN CHAPTER 9 ARE INCLUDED IN THIS OUTLINE.
F.
Muscles that Move the Forearm (radius & ulna):
See Fig 9.30, page 322, Fig 9.31, page 323, and Table 9.8, page 324.
NAME OF MUSCLE
LOCATION/
DESCRIPTION
ACTION
Biceps Brachii (*)
Brachialis
Brachioradialis
Triceps brachii
G.
Muscles that Move the Hand
See Fig 9.32, page 325, Fig 9.33, page 326, and Table 9.9, page 327.
NAME OF MUSCLE
LOCATION/
DESCRIPTION
ACTION
Flexor carpi radialis
Flexor carpi ulnaris
Palmaris longus
Extensor digitorum
9-18
9.8
UNIT 2 - CHAPTER 9: MUSCULAR SYSTEM
MAJOR SKELETAL MUSCLES
ONLY A REPRESENTATIVE SAMPLE OF SKELETAL MUSCLES DISCUSSED
IN CHAPTER 9 ARE INCLUDED IN THIS OUTLINE.
H.
Muscles of the Abdominal Wall:
See Fig 9.35, page 329, and Table 9.10, page 330.
NAME OF MUSCLE
LOCATION/
DESCRIPTION
ACTION
Rectus abdominis (*)
External Oblique
Internal Oblique
Transversus abdominis
I.
Muscles of the Pelvic Outlet
See Fig 9.36 page 330 and Table 9.11 page 331.
NAME OF MUSCLE
LOCATION/
DESCRIPTION
ACTION
Levator ani
Coccygeus
Superficial transversus perinea
Bulbospongiosus
Ischiocavernosus
Sphincter urethrae
9-19
9.8
UNIT 2 - CHAPTER 9: MUSCULAR SYSTEM
MAJOR SKELETAL MUSCLES
ONLY A REPRESENTATIVE SAMPLE OF SKELETAL MUSCLES DISCUSSED
IN CHAPTER 9 ARE INCLUDED IN THIS OUTLINE.
J.
Muscles that Move the Thigh (Femur):
See Fig 9.37, page 332, Fig 9.38, page 333, and Table 9.12, page 335.
NAME OF MUSCLE
LOCATION/
DESCRIPTION
ACTION
Gluteus Maximus (*)
Gluteus Medius
Adductor Longus
Gracilis
*
See box on page 331 re: Gluteal Gait.
K.
Muscles that Move the Leg (Tibia & Fibula):
See Fig 9.37, page 322, Fig 9.39, page 334, and Table 9.13, page 336.
NAME OF MUSCLE
LOCATION/
DESCRIPTION
ACTION
Rectus femoris
Vastus lateralis
Vastus medialis
Vastus intermedius
Sartorius (*)
Biceps femoris
Semitendinosus
Semimembranosus
9-20
UNIT 2 - CHAPTER 9: MUSCULAR SYSTEM
9.8
MAJOR SKELETAL MUSCLES
ONLY A REPRESENTATIVE SAMPLE OF SKELETAL MUSCLES DISCUSSED
IN CHAPTER 9 ARE INCLUDED IN THIS OUTLINE.
L.
Muscles that Move the Foot
See Fig 9.41, page 337, Fig 9.42, page 338, Fig 9.43, page 339, and
Table 9.14, page 340.
NAME OF MUSCLE
LOCATION/
DESCRIPTION
ACTION
Tibialis anterior
Fibularis longus
Gastrocnemius (*)
Soleus
*
*
Note the location of the Calcaneal Tendon in Fig 9.43, page 339.
See box on page 340 re: Torn Achilles (Calcaneal) Tendon
9.9
LIFE-SPAN CHANGES
A.
B.
C.
Supplies of ATP, myoglobin, and creatine phosphate in muscle fibers begin to
decline in one’s forties.
Half of one’s muscle mass has been replaced by connective and adipose tissue by
age 80, and reflexes are reduced.
Exercise is the best way to maintain muscle function. Both strength training and
aerobic exercise, with stretching before and after, is recommended. A side
benefit of regular exercising, especially among older individuals is fewer bouts of
depression.
9-21
UNIT 2 - CHAPTER 9: MUSCULAR SYSTEM
OTHER INTERESTING TOPICS:
A.
B.
C.
D.
E.
F.
G.
H.
I.
J.
K.
L.
M.
N.
O.
The Muscular Movements Behind “Texting”. See Introduction on page 293.
Tendinitis and Tenosynovitis, See box on page 294.
Compartment Syndrome. See box on page 294.
Muscle Strain. See box on page 297.
Dystrophin in skeletal muscle. See box on page 297.
Poliomyelitis. See box on page 298.
Myasthenia Gravis. See Clinical Application 9.1, page 299.
Botulism and Botox. See box on page 299.
Rigor Mortis. See box on page 301.
TMJ Syndrome. See Clinical Application 9.3, page 316.
Triangle of Auscultation. See box on page 332.
Parkinson Disease. See box on page 327.
Gluteal Gait. See box on page 331.
Pulled Hamstring. See box on page 334.
Myositis Ossificans. See box on page 336.
INNERCONNECTIONS of the Muscular System - see page 342.
CHAPTER SUMMARY – see pages 341, 343-345.
CHAPTER ASSESSMENTS – see pages 345-347.
INTEGRATIVE ASSESSMENTS/CRITICAL THINKING – see page 347.
9-22
UNIT 2 - CHAPTER 9: MUSCULAR SYSTEM
SKELETAL MUSCLE SUMMARY TABLES
A.
Muscles of Facial Expression
NAME OF MUSCLE
LOCATION/
DESCRIPTION
Covers cranium
Epicranius
Frontalis
Occipitalis
ACTION
elevates eyebrow
over forehead
over occipital
Orbicularis oris
circular muscle around the
mouth
closes lips
(“kissing muscle”)
Zygomaticus Major and
Minor (*)
Origin: zygomatic bone
Insertion: corners of
orbicularis oris
muscle that connects
zygomatic arch to corner of
mouth
elevates corners of mouth
(“smiling muscle”)
Buccinator
hollow of cheek
compresses cheeks
“trumpeter’s muscle”
Platysma
lower border of mandible
“pouting muscle”
Orbicularis oculi
circular muscle around eye
closes eye
B.
Muscles of Mastication
NAME OF MUSCLE
LOCATION/
DESCRIPTION
ACTION
Masseter(*)
Origin: Zygomatic Arch
Insertion: Lateral Mandible
over lateral mandible
elevates mandible
Temporalis
convergent muscle over
temporal bone
elevates mandible
9-23
UNIT 2 - CHAPTER 9: MUSCULAR SYSTEM
SKELETAL MUSCLE SUMMARY TABLES
C.
Muscles that Move the Head and Vertebral Column:
NAME OF MUSCLE
LOCATION/
DESCRIPTION
Sternocleidomastoid(*)
Origin: sternoclavicular
region
Insertion: mastoid process
of temporal
Major neck muscle
flexion of head toward chest
(as synergists)
rotation/abduction of head
(as antagonists)
Erector Spinae
Group of midline dorsum
muscles
Maintain posture
D.
ACTION
Muscles that Move the Pectoral Girdle
NAME OF MUSCLE
LOCATION/
DESCRIPTION
ACTION
Trapezius (*)
Origin: occipital bone &
spines of C7-T12
Insertion: clavicle, spine and
acromion process of scapulae
Trapezoid shaped muscle in
posterior neck and upper
back
elevates pectoral girdle
(“shoulder shrug”)
Pectoralis minor
Muscle deep to Pectoralis
major
scapula fixator
Serratus anterior
Saw-toothed lateral thoracic
muscle
scapula fixator
E.
Muscles that Move the Arm (Humerus)
NAME OF MUSCLE
LOCATION/
DESCRIPTION
ACTION
Pectoralis major (*)
Origin: clavicle, sternum, &
costal cartilages of ribs 1-6
Insertion: between tubercles
of humerus
Large, convergent chest
muscle
flexes arm medially (pull
arms forward and together)
Latissimus dorsi
Large, back muscle
adduction of humerus
Deltoid
Triangular shaped shoulder
muscle
abduction of humerus
9-24
UNIT 2 - CHAPTER 9: MUSCULAR SYSTEM
SKELETAL MUSCLE SUMMARY TABLES
F.
Muscles that Move the Forearm (radius & ulna)
NAME OF MUSCLE
LOCATION/
DESCRIPTION
ACTION
Biceps Brachii (*)
Origin: Coracoid process
Insertion: Radial tuberosity
fusiform, parallel, anterior
upper arm muscle (two
origins)
flexion of arm at elbow
(prime mover)
Brachialis
muscle beneath biceps
brachii
flexion of arm at elbow
(synergist)
Brachioradialis
lateral muscle between upper
and forearm
flexion of arm at elbow
(synergist)
Triceps brachii
posterior upper arm muscle
(three heads)
extension of arm at elbow
G.
Muscles that Move the Hand
NAME OF MUSCLE
LOCATION/
DESCRIPTION
ACTION
Flexor carpi
Radialis
anterior, lateral forearm
muscle
flexion of wrist
Flexor carpi
Ulnaris
anterior, medial forearm
muscle
flexion of wrist
Palmaris longus
anterior forearm muscle
located between two above
flexion of wrist
Extensor digitorum
posterior forearm muscle
extension of wrist/fingers
9-25
UNIT 2 - CHAPTER 9: MUSCULAR SYSTEM
SKELETAL MUSCLE SUMMARY TABLES
H.
Muscles of the Abdominal Wall
NAME OF MUSCLE
LOCATION/
DESCRIPTION
ACTION
Rectus abdominis (*)
Origin: pubic crest &
symphysis
Insertion: xiphoid process &
costal cartilages of 5-7th ribs
strap like muscle from costal
cartilages to ilium
tenses abdominal wall
External Oblique
superficial/lateral oblique
abdominal muscle
tenses abdominal wall
Internal Oblique
deep oblique abdominal
muscle
tenses abdominal wall
Transversus abdominis
deep abdominal muscle that
runs perpendicular to rectus
abdominis
tenses abdominal wall
I.
Muscles of the Pelvic Outlet
NAME OF MUSCLE
LOCATION/
DESCRIPTION
ACTION
Levator ani
Thin sheet surrounding anus,
urethra and vagina
Supports viscera and aids
sphincters
Coccygeus
Fan shaped, posterior to
levator ani
Same as above
Superficial transversus
perinea
Band of muscle anterior to
levator ani
Supports viscera
Bulbospongiosus
Surrounds base of penis or
vagina
Male – assists ejaculation
Female – constricts vaginal
orifice
Ischiocavernosus
Band of muscle lateral to
bulbospongiosus
Same as above
Sphincter urethrae
Surround urethra
Opens and closes urethral
orifice
9-26
UNIT 2 - CHAPTER 9: MUSCULAR SYSTEM
SKELETAL MUSCLE SUMMARY TABLES
J.
Muscles that Move the Thigh (Femur)
NAME OF MUSCLE
LOCATION/
DESCRIPTION
ACTION
Gluteus Maximus (*)
Origin: dorsal ilium,
sacrum, coccyx
Insertion: posterior femur
buttocks, largest muscle in
body
extension of hip at thigh (as
in walking or climbing
stairs)
Gluteus Medius
lateral hip muscle
abduction of femur
Adductor Longus
medial thigh muscle
adduction of femur
Gracilis
medial thigh muscle
adduction of femur
K.
Muscles that Move the Tibia & Fibula
NAME OF MUSCLE
LOCATION/
DESCRIPTION
ACTION
Rectus femoris
anterior thigh quadriceps
extension of leg at knee
Vastus lateralis
lateral anterior thigh
quadriceps
extension of leg at knee
Vastus Medialis
medial anterior thigh
quadriceps
extension of leg at knee
Vastus intermedius
deep anterior thigh
quadriceps
extension of leg at knee
Sartorius (*)
Origin: iliac spine
Insertion: medial tibia
parallel strap-like muscle
that crosses thigh
flexion of knee forward
Biceps femoris
posterior thigh hamstring
flexion of leg at knee
Semitendinosus
posterior thigh hamstring
flexion of leg at knee
Semimembranosus
posterior thigh hamstring
flexion of leg at knee
9-27
UNIT 2 - CHAPTER 9: MUSCULAR SYSTEM
SKELETAL MUSCLE SUMMARY TABLES
L.
Muscles that Move the Foot
NAME OF MUSCLE
LOCATION/
DESCRIPTION
ACTION
Tibialis anterior
anterior to tibia
dorsiflexion
Peroneus longus
lateral to fibula
eversion
Gastrocnemius (*)
Origin: condyles of femur
Insertion: calcaneus
posterior lower leg (i.e. calf
muscle) two origins
plantar flexion (prime
mover)
Soleus
deep to gastrocnemius
plantar flexion (synergist)
9-28