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Chapter 8
Muscular System
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Interesting muscle facts:
 There
are over 600 individual muscles
in the human body
 Muscle weight is half your body
weight
 The face has 60 muscles, 20 for
smiling and 40 for frowning!
 Smallest muscle is stapedius in inner
ear
 Largest is the gluteus maximus
 Longest is the sartorius of the thigh
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 In
today’s lesson we will review
the three kinds of muscle tissue
and describe the structure of a
skeletal muscle
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 Introduction:

Muscles are organs that use chemical
energy to contract
 What is chemical energy?
 What does it mean to contract?

The three types of muscle in the body
are:
 skeletal
 smooth
 cardiac muscle
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3 Types of Muscle Tissue
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•
•
•
•
•
•
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 Smooth Muscles
Smooth Muscle Fibers
elongated cells with tapered ends (spindle
shaped)
One nucleus per cell
involuntary
lack striations and transverse tubules
undeveloped sarcoplasmic reticulum
Found in walls of hollow organs
 Cardiac Muscle
• branching, striated cells
• One nucleus per cell
• Striated
• Connected by intercalated discs
•Transmits muscle impulse from cell
to cell
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•Skeletal Muscle



Long, multinucleate cylinders
Striated
Voluntary
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 Structure
(8.2)
of a Skeletal Muscle
muscle is an organ made of several
tissues:
1. skeletal muscle tissue
2. connective tissues
3. nervous tissue
4. blood vessels/blood
 Each
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Vocabulary:
Connective tissue coverings/muscle organization:
1.
Fascia
2.
Epimysium
3.
Perimysium
4.
Endomysium
5.
Muscle fiber
6.
Myofibrils
7.
Filaments
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Fascia
Epimysium
Perimysium
Muscle Fiber
Endomysium
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Analogy
Pretend you are going to play a joke on someone
and give them a gift of 100 pencils. The pencils
will represent muscle fibers.
First you wrap each individual pencil in tissue paper
(This would be endomysium.)
Then you take about 10 pencils in a bundle (a
fascicle) and wrap them in paper (perimysium).
After that you take all the bundles and wrap them in
gift wrap (epimysium).
But you are going to mail this gift, so you also have
to wrap
8 - 18 it in brown paper representing the
(fascia).
Review:
How many types of muscle tissue are there?
 What are they called?
 Where are they found?
 What are their distinguishing features?

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 Today’s
lesson will learn how a
skeletal muscle fibers differs
from a composite cell.
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Vocabulary:
Skeletal muscle Fibers:
8.
Fiber
9.
Sarcolemma
10. Sarcoplasm
11. Myofibril
12. Myosin
13. Actin
14. Striations
15. sarcomere
16. sarcoplasmic reticulum
17. transverse tubule
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Skeletal Muscle Fibers—very
differentiated cells!
Each muscle fiber is a single, long, cylindrical,
multinucleate cell that contains:
sarcolemma
sarcoplasm
many mitochondria (why?)
sarcoplasmic reticulum
transverse tubules
myofibrils (organelle)
separated into sarcomeres
containing actin and myosin
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overlapping to cause striations
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CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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Sarcomere
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 In
today’s lesson you will
learn the steps involved in
skeletal muscle contraction
at the cellular level
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Quick Review….
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New Vocabulary
18.
19.
20.
21.
22.
23.
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neuromuscular junction
motor end plate
synaptic vessicles
neurotransmitter
acetycholine
motor unit

Motor Units
A motor neuron and the muscle fibers it controls
make up a motor unit

Muscle fibers of the motor unit contract all at once

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
Lets watch an animation of how motor
units work…..
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Neuromuscular Junction

The site where the motor neuron and muscle
fiber meet is the neuromuscular junction

The muscle fiber membrane forms a motor end
plate in which the sarcolemma is tightly folded

The cytoplasm of the motor neuron contains
numerous mitochondria and synaptic vesicles storing
the neurotransmitter acetylcholine.
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Skeletal Muscle Contraction
1.
2.
3.
Acetylcholine released from motor neuron binds to
receptors on muscle fiber
Muscle impulse travels down tranverse tubules to
sarcoplasmic reticulum
Sarcoplasmic reticulum releases Ca++ into
sarcoplasm
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4.
High Ca++ levels allow actin and myosin to
bind to each other
(regulatory proteins are removed from actin)
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5. When actin and myosin bind, myosin pulls
actin toward the center of the sarcomere,
shortening it.
6. This binding and pulling requires ATP.
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Mechanism of Muscle contraction
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
Lets watch an animation of the
mechanism of muscle contraction…

Tomorrow we will act this out live!
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Rigor mortis
Several hours after death, skeletal
muscles contract
 This is a result of the release of Ca++
ions from the sarcoplasmic reticulum
and lack of ATP required to relax the
muscles
 They will relax as they decompose
 Can be used to estimate the time of
death

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Exit pass….
Put the following steps of muscle contraction in the
correct order:
A.
B.
C.
D.
E.
Actin and myosin bind
A muscle impulse travels down the t-tubule
Acetylcholine binds to a receptor on the motor
end plate
Myosin pulls actin toward the center of the
sarcomere
Calcium is released from the SR
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
In today’s lesson you will learn about
how muscles get the energy they need
to contract and what happens when
they do not get it.
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New Vocabulary:
24. Glycolysis
25. Citric acid cycle
26. Electron transport chain
27. Aerobic respiration
28. Lactic acid
29. Oxygen deficiency
30. Fatigue
31. Myoglobin
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ATP Production in the muscle cell
Glycolysis
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Oxygen Deficiency

During rest or moderate activity,
there is enough oxygen to support
aerobic respiration/muscle contraction

Oxygen deficiency may develop
during strenuous exercise with lactic
acid accumulating
Lactic acid diffuses out of
muscle cells and is carried in
the bloodstream to the liver.

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Muscle Fatigue

When a muscle loses its ability to
contract during strenuous exercise,
it is referred to as fatigue

Muscle fatigue usually arises from
the accumulation of lactic acid in the
muscle
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In
this lesson you will
learn the major superficial
skeletal muscles of the
body.
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Vocabulary
32.
33.
34.
35.
36.
Origin
Insertion
Prime mover
Synergist
Antagonist
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 Skeletal Muscle Actions

Muscles are connected to bones at origins and
insertions

Origins are ends that do not involve
movement

insertions usually span a joint that moves
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Interaction of Skeletal Muscles
prime mover is the muscle responsible for the
movement
Synergists are helper muscles
antagonists are opposing muscles
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 Major Skeletal Muscles
Muscles are named according to any
of the following criteria: size, shape,
location, action, number of
attachments, or direction of its
fibers.
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Muscles to know…
 You
will be responsible for knowing
the names of the anterior and
posterior superficial muscles in
Figures 8.15 and 8.16 on pages
184-185.
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
Muscles of the head and neck
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Muscles of Facial Expression
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1.
Muscles of facial expression
attach to underlying bones
and overlying connective
tissue of skin
2.
Major muscles include the
epicranius, orbicularis oculi,
orbicularis oris, buccinator,
and zygomatigus.
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Muscles of Mastication
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1.
Chewing movements include
up and down as well as sideto-side grinding motions of
muscles attached to the skull
and lower jaw.
2.
Chewing muscles include
masseter and temporalis.
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Muscles that Move the Head
1. Paired muscles in the neck and back
flex, extend, and turn the head.
2. Major muscles include
sternocleidomastoid, splenius
capitis, and semispinalis capitis.
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
Muscles of the pectoral girdle and arm
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Muscles that Move the Pectoral
Girdle
1. The chest and shoulder muscles
move the scapula.
2. Major muscles include the
trapezius, rhomboideus major,
levator scapulae, serratus anterior,
and pectoralis minor.
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Muscles that Move the Arm
1.
Muscles connect the arm to the
pectoral girdle, ribs, and vertebral
column, making the arm freely
movable.
2.
Flexors include the
coracobrachialis and pectoralis
major.
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3.
4.
5.
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Extensors include the teres major
and latissimus dorsi.
Abductors include the
supraspinatus and the deltoid.
Rotators are the subscapularis,
infraspinatus, and teres minor.
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Muscles that Move the Forearm
1.These muscles arise from the humerus or
pectoral girdle and connect to the ulna and
radius.
2.Flexors are the biceps brachii, the brachialis,
and the brachioradialis.
3.An extensor is the triceps brachii muscle.
4.Rotators include the supinator, pronator teres,
and pronator quadratus.
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Muscles that Move the Wrist, Hand, and
Fingers
1.
Movements of the hand are caused
by muscles originating from the
distal humerus, and the radius and
ulna.
2.
Flexors include the flexor carpi
radialis, flexor carpi ulnaris, palmaris
longus, and flexor digitorum
profundus.
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3.
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Extensors include the extensor carpi
radialis longus, extensor carpi
radialis brevis, extensor carpi
ulnaris, and extensor digitorum.

Muscles of the abdomen
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Muscles of the Abdominal Wall
1.
This group of muscles connects the
rib cage and vertebral column to the
pelvic girdle.
a.
A band of tough connective
tissue, the linea alba,
extending from the xiphoid
process to the symphysis
pubis, serves as an
attachment for certain
abdominal wall muscles.
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2.
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These four muscles include:
external oblique, internal oblique,
transverse abdominis, and rectus
abdominis.

Muscles of the pelvic girdle and leg
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Muscles that Move the Thigh
1.
The muscles that move the thigh
are attached to the femur and to
the pelvic girdle.
2.
Anterior group includes the
psoas major and iliacus.
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3.
Posterior group is made up of the
gluteus maximus, gluteus medius, gluteus
minimus, and tensor fasciae latae.
4.
Thigh adductors include the adductor
longus, adductor magnus, and gracilis.
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Muscles that Move the Leg
1.
This group connects the tibia or
fibula to the femur or pelvic girdle.
2.
Flexors are the biceps femoris,
semitendinosus semimembranosus,
and sartorius.
3.
An extensor is the quadriceps
femoris group made up of four
parts: rectus femoris, vastus
lateralis, vastus medialis, and vastus
intermedius.
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Muscles that Move the Ankle, Foot, and
Toes
1. Muscles that move the foot are
attached to the femur, fibula, or
tibia, and move the foot upward,
downward, or in a turning
motion.
2. Dorsal flexors include the tibialis
anterior, peroneus tertius, and
extensor digitorum longus.
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3.
4.
5.
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Plantar flexors are the
gastrocnemius soleus, and flexor
digitorum longus.
An invertor is the tibialis posterior.
An evertor is the peroneus longus.
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