Ch07 lecture ppt_a (1)

Seeley’s
ESSENTIALS OF
Anatomy &
Physiology
Tenth Edition
Cinnamon Vanputte
Jennifer Regan
Andrew Russo
See separate PowerPoint slides for all figures and tables
pre-inserted into PowerPoint without notes.
© 2019 McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom. No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.

© 2019 McGraw-Hill Education
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Chapter 7
Muscular System
Lecture Outline

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Types of Muscles
Skeletal
attached to bones
striated
voluntarily controlled
Cardiac
located in the heart
striated
involuntarily controlled

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Types of Muscles
Smooth
Located in blood vessels, hollow
organs
Non-striated
involuntarily controlled

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Comparison of Skeletal, Cardiac, and Smooth Muscles
Characteristics Skeletal Cardiac Smooth
Body location Attached to bones
or, for some facial
muscles to skin
Walls of the heart Mostly in walls
of hollow
visceral organs
Cell shape and
appearance
Single, very long,
cylindrical, multi-
nucleate cells with
very obvious
striations
Branching chains of
cells; uninucleate,
striations;
intercalated discs
Single, fusiform,
uninucleate, no
striations
Connective tissue
components
Epimysium,
perimysium, and
endomysium
Endomysium
attached to the
fibrous skeleton of
the heart
Endomysium
Regulation of
contraction
Voluntary, via
nervous system
control
Involuntary; the
heart has pacemaker;
nervous system
control; hormone
Involuntary;
nervous system
controls;
hormones,
chemicals

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Characteristics Skeletal Cardiac Smooth
Speed of
Contraction
Slow to fast slow Very slow
Rhythmic
contraction
No Yes Yes, in some

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The Muscular System
Functions
 Movement
 Maintain posture
 Respiration
 Production of body heat
 Communication
 Heart beat
 Contraction of organs and
vessels
Figure 7.1

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Properties of Muscles
Contractility
 the ability of muscle to shorten forcefully,
or contract
Excitability
 the capacity of muscle to respond to a
stimulus

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Properties of Muscles
Extensibility
 ability to be stretched beyond it normal
resting length and still be able to contract
Elasticity
 ability of the muscle to recoil to its original
resting length after it has been stretched

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Skeletal Muscle Structure1
 Skeletal muscle, or striated muscle, with its
associated connective tissue, constitutes
approximately 40% of body weight.
 Skeletal muscle is so named because they are
attached to the skeletal system.
 Some skeletal muscles attach to the skin or
connective tissue sheets.

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Skeletal Muscle Structure2
 Skeletal muscle is also called striated muscle
because transverse bands, or striations.

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Connective Tissue Coverings
 Epimysium a connective tissue sheath that
surround each skeletal muscle
 A skeletal muscle is subdivided into groups of
muscle cells, termed fascicles.
 Perimysium -surround the fascicle.
 Endomysium - surround each skeletal muscle
cell (fiber)

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Muscle Fiber Structure1
 a single cylindrical cell, with several nuclei
located at its periphery.
 It range in length 1 cm to 30 cm and are
generally 0.15 mm in diameter.
 Skeletal muscle fibers contain several nuclei
that are located at the periphery of the fiber.
 The sarcolemma (cell membrane) has many
tubelike inward folds, called transverse
tubules, or T tubules.

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 T tubules occur at regular intervals along the
muscle fiber and extend into the center of the
muscle fiber.
 The T tubules are associated with enlarged
portions of the smooth endoplasmic reticulum
called the sarcoplasmic reticulum.
 The enlarged portions are called terminal
cisternae.
 T tubules connect the sarcolemma to the terminal
cisternae to form a muscle triad.

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 Sarcoplasm it the cytoplasm of a muscle fiber
which contains many bundles of protein
filaments.
 Myofibrils are bundles of protein filaments.
 Myofibrils consist of the myofilaments, actin
and myosin.

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Figure 8.1

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Structure of Skeletal Muscle
Figure 7.2

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Sarcomere1
 the basic structural and functional unit of a
skeletal muscle capable of contracting.
 Z Disks - form a network of protein fibers
that serve as an anchor for actin
myofilaments and separate one sarcomere
from the next.
 A sarcomere extends from one Z disk to the
next Z disk.

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The Sarcomere2
 The organization of actin and myosin
myofilaments gives skeletal muscle its
striated appearance and gives it the ability
to contract.
 The myofilaments slide past each other,
causing the sarcomeres to shorten.
 Each sarcomere consists of two light-staining
bands separated by a dark-staining band.

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Figure 8.2c

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The Sarcomere3
 I bands -light bands, consist only of actin
myofilaments that extends toward the
center of the sarcomere to the ends of the
myosin myofilaments.
 A bands -dark staining bands that extend the
length of the myosin myofilaments.
 Actin and myosin myofilaments overlap for
some distance on both ends of the A band
that causes the contraction.


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Figure 8.2c

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The Sarcomere4
 Actin myofilaments are made up of three
components: Actin, Troponin, and Tropomyosin.
 Troponin -molecules have binding sites for Ca2
+
 Tropomyosin - filaments block the myosin
myofilament binding sites on the actin
myofilaments.
 Myosin myofilaments, or thick myofilaments,
resemble bundles of tiny golf clubs.
 Myosin heads have ATP binding sites, ATPase and
attachment spots for actin.

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Figure 8.3a

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Figure 8.3b

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Sliding Filament Mechanism
During contraction myosin heads bind actin
sites
Pull and slide actin molecules (and Z-discs)
toward H-zone
I-bands and H-zones narrow
Sliding generates force and shortens
sarcomeres.

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Figure 8.4

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Skeletal Muscle Fiber
Figure 7.3

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Excitability of Muscle Fibers
 Muscle cells (fibers) have a resting membrane
potential, but can also perform action
potentials.
Resting Membrane Potential
 the inside of the membrane is negatively charged and
the outside of the membrane is positively charged.
Action potentials
 due to the membrane having gated channels.

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Resting Membrane Potential1
The resting membrane potential exists because of:
 The concentration of K+ being higher on the inside of
the cell membrane and the concentration of Na+ being
higher on the outside
 The presence of many negatively charged molecules,
such as proteins, inside the cell that are too large to
exit the cell
 The presence of leak protein channels in the
membrane that are more permeable to K+ than it is to
Na+

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 Na+ tends to diffuse into the cell and K+ tends
to diffuse out.
 In order to maintain the resting membrane
potential, the sodium-potassium pump
recreates the Na+ and K+ ion gradient by
pumping Na+ out of the cell and K+ into the
cell.

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Figure 7.4 (1)

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Action Potential1
 Resting membrane potential must be changed
to an action potential.
 Changes in the resting membrane potential
occur when gated cell membrane channels
open.
 In a skeletal muscle fiber, a nerve impulse
triggers gated Na+ channels to open and Na+
diffuses into the cell down its concentration
gradient and toward the negative charges
inside the cell.

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Action Potential2
 The entry of Na+ causes the inside of the cell
membrane to become more positive than when
the cell is at resting membrane potential.
 This increase in positive charge inside the cell
membrane is called DEPOLARIZATION.
 If the depolarization changes the membrane
potential to a value called threshold, an action
potential is triggered.
 An action potential is a rapid change in charge
across the cell membrane.

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Action Potential3
 Depolarization during the action potential is
when the inside of the cell membrane becomes
more positively charged than the outside of the
cell membrane.
 Near the end of depolarization, the positive
charge causes gated Na+ channels to close and
gated K+ channels to open.
 Opening of gated K+ channels starts
repolarization of the cell membrane.

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Action Potential4
 Repolarization is due to the exit of K+ from
the cell.
 The outward diffusion of K+ returns the cell
to its resting membrane conditions and the
action potential ends.
 In a muscle fiber, an action potential results
in muscle contraction.

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Depolarization
 change in charges
inside becomes more + and outside more –
 Na+ channels open
Figure 7.4 (2)

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Repolarization
 Na+ channels close
 change back to resting potential
Figure 7.4 (3)

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Ion Channels and Action Potentials
Figure 7.4

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Nerve Supply & Muscle Fiber
Stimulation1
 Motor neuron - a nerve cell stimulates muscle
cells.
 Neuromuscular junction-a synapse where a the
fiber of a nerve connects with a muscle fiber.
 Synapse refers to the cell-to-cell junction
between a nerve cell and either another nerve
cell or an effector cell.
 Motor unit -a group of muscle fibers that a
motor neuron stimulates.

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Nerve Supply2
 Presynaptic terminal is the end of a neuron cell
axon fiber.
 Synaptic cleft is the space between the
presynaptic terminal and postsynaptic
membrane.
 Postsynaptic membrane is the muscle fiber
membrane (sarcolemma).
 Synaptic vesicle is a vesicle in the presynaptic
terminal that stores and releases
neurotransmitter chemicals.

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Nerve Supply3
 Neurotransmitters - are chemicals that
stimulate or inhibit postsynaptic cells.
 Acetylcholine - the neurotransmitter that
stimulates skeletal muscles.
 Acetylcholinesterase- an enzyme that breaks
down the acetylcholine to prevent
overstimulation of muscle fiber.

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Neuromuscular Junction
Figure 7.5
(b) ©Ed Reschke/Photolibrary/Getty Images

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Muscle Contraction1
1. An action potential travels down motor
neuron to presynaptic terminal causing Ca2+
channels to open.
2. Ca2+ causes synaptic vesicles to release
acetylcholine into synaptic cleft.
3. Acetylcholine binds to receptor sites on Na+
channels, Na+ channels open, and Na+ rushes
into postsynaptic terminal (depolarization).

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Function of the
Neuromuscular Junction
Figure 7.6

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Muscle Contraction2
4. Na+ causes sarcolemma and t-tubules to
increase the permeability of sarcoplasmic
reticulum which releases stored calcium.
5. Ca2+ binds to troponin which is attached to
actin.
6. Ca2+ binding to troponin causes tropomyosin
to move exposing attachment sites for myosin.
7. Myosin heads bind to actin.

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Muscle Contraction3
8. ATP is released from myosin heads and
heads bend toward center of sarcomere.
9. Bending forces actin to slide over myosin.
10. Acetylcholinesterase (enzyme breaks down
acetylcholine) is released, Na+ channels
close, and muscle contraction stops.

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Skeletal Muscle Excitation1
Figure 7.8 (1)

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Figure 7.8 (2,3)

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Figure 7.8 (4)

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Figure 7.8 (5,6)

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Figure 7.8 (6,7,8)

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Figure 7.8 (9)

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Muscle Twitch1
 is a single contraction of a muscle fiber in
response to a stimulus.
 has three phases: latent phase, contraction
phase, and relaxation phase.

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Muscle Twitch1
Latent phase
 the time between the application of a stimulus
and the beginning of contraction.
Contraction phase
 the time during which the muscle contracts and
the
Relaxation phase
 is the time during which the muscle relaxes.

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Muscle Twitch2
Figure 7.10

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Summation and Recruitment
Summation- the individual muscles contract
more forcefully.
Tetanus is a sustained contraction that occurs
when the frequency of stimulation is so rapid
that no relaxation occurs.
Recruitment is the stimulation of several motor
units which increases the total number of muscle
fibers contracting.

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Multiple-Wave Summation
Figure 7.11

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Skeletal Muscle Fiber Types1
Slow twitch fibers
• contract slowly
• fatigue slowly
• have a considerable amount of myoglobin
• use aerobic respiration
• are dark in color
• used by long distance runners

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Skeletal Muscle Fiber Types2
Fast twitch fibers
• contract quickly
• fatigue quickly
• use anaerobic respiration
• energy from glycogen
• light color
• used by sprinters

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Energy Requirements
for Muscle Contractions
1. Aerobic production of ATP during most
exercise and normal conditions.
2. Anaerobic production of ATP during
intensive short-term work
3. Conversion of a molecule called creatine
phosphate to ATP
4. Conversion of two ADP to one ATP and one
AMP (adenosine monophosphate) during
heavy exercise

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ATP Production in Resting & Exercise
Muscle
REST
 1. ATP is produced by aerobic respiration
 2. Small amounts of ATP are used by muscle
contractions that maintain muscle tone
 3. Excess ATP is used to produced creatine
phosphate

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EXERCISE
4. As exercise begins, ATP already in the muscle cells is
used first, but during moderate exercise, aerobic
respiration provides most of the ATP necessary for
muscle contraction.
5. During times of extreme exercise, anaerobic
respiration provides small amount of ATP that can
sustain muscle contraction for brief periods.
6. Energy store in creatine phosphate can also be used
to produce ATP.
7. Throughout the time of exercise, ATP from all of
these sources (4-6) provides energy for active muscle
contraction.

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Muscle Fatigue1
 is a temporary state of reduced work
capacity.
 Without fatigue, muscle fibers would be
worked to the point of structural damage to
them and their supportive tissues.

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Mechanisms of Fatigue
 Acidosis and ATP depletion due to increased ATP
consumption or a decreased ATP production
 Oxidative stress- buildup of excess reactive oxygen
species (ROS; free radicals)
 Local inflammatory reactions

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Types of Contractions1
Isometric contraction
 has an increase in muscle tension, but no
change in length.
Isotonic contraction
 has a change in muscle length with no
change in tension.

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Types of Contractions2
Concentric contractions
 are isotonic contractions in which muscle
tension increases as the muscle shortens.
Eccentric contractions
 are isotonic contractions in which tension is
maintained in a muscle, but the opposing
resistance causes the muscle to lengthen.

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ISOTONIC EXERCISE
 There is a change in
muscle length, no
change in tension.
ISOMETRIC EXERCISE
 increase in muscle
tension, but no change
in length.

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Muscle Tone
 is the constant tension produced by body
muscles over long periods of time.
 responsible for keeping the back and legs
straight, the head in an upright position, and the
abdomen from bulging.
Disturbance in muscle tone
 Atrophy
 Flaccidity

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Smooth Muscle
 are non-striated small, spindle-shaped muscle
cells, usually with one nucleus per cell.
 Contain less actin and the myofilaments are
not organized into sarcomeres.
 The cells comprise organs controlled
involuntarily, except the heart.
 Neurotransmitter substances, hormones, and
other substances can stimulate smooth
muscle.

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Cardiac Muscle1
 are long, striated, and branching, with usually
only one nucleus per cell.
 is striated as a result of the sarcomere
arrangement
 contraction is autorhythmic.

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Cardiac Muscle
 muscle cells are connected to one another by
specialized structures that include
desmosomes and gap junctions called
intercalated disks.
 Cardiac muscle cells function as a single unit
in that action potential in one cardiac muscle
cell can stimulate action potentials in adjacent
cells causing to contract all together.

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Arrangement of Fascicles
Circular
 arranged in concentric rings or in circle
around the opening.
 Acts as sphincters to open and close the
opening
 Ex: orbicularis oris, orbicularis oculi

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Convergent
 fascicles converge toward a single
insertion tendon
 such muscle is triangular or fan-shaped.
 Ex: pectoralis major and minor

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Parallel
 the length of the fascicles run parallel to
one another to the long axis of the
muscle.
 Ex: trapezium, quadrate, rhomboidal

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Pennate
 Fascicles originate from a tendon that
runs the length of the entire muscle.
 Unipennate - fascicles on only one side of
the tendon. (Palmar interosseus)
 Bipennate- fascicles on both sides of the
tendon. (Rectus femoris)
 Multipennate- fascicles arranged at many
places around the central tendon (deltoid)

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Fusiform
 fascicles lie parallel to long axis of
muscle
 Ex: biceps brachii, triceps brachii

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Skeletal Muscles1
Figure 7.14a

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Skeletal Muscles2
Figure 7.14b

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Skeletal Muscle Anatomy
Tendon - connects skeletal muscle to bone.
Aponeuroses- are broad, sheetlike tendons.
Retinaculum- is a band of connective tissue
that holds down the tendons at each wrist and
ankle.
Origin – the most stationary, fixed, end of a
muscle.
Insertion -is the end of the muscle attached to
the bone undergoing the greatest movement.

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Skeletal Muscle Anatomy2
Belly
 the part of the muscle between the origin and
the insertion
Agonists
 a single or group of muscles working together.
Antagonists
 a muscle or group of muscles that oppose
muscle actions.

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Synergist
 members of a group of muscles working
together to produced movement
 Brachii and brachialis
 Deltoid, biceps brachii, and pectoralis major

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Muscle Attachment
Figure 7.13

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Prime Mover
 one muscle plays the major role to
accomplish the desired movement.
 Ex: Brachialis is the prime mover in flexing the
elbow
FIXATORS
 Are muscles that hold one bone in place
 stabilize origin of prime mover
 Scapular muscles acts as a fixator to hold the
scapula in place.

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Nomenclature1
Muscles are named according to:
1. Location – a pectoralis muscle is located in
the chest.
2. Size – the size could be large or small, short or
long.
3. Shape - the shape could be triangular,
quadrate, rectangular, or round.
4. Orientation of fascicles – fascicles could run
straight (rectus) or at an angle (oblique).

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Nomenclature2
5. Origin and insertion. The sternocleidomastoid
has its origin on the sternum and clavicle and
its insertion on the mastoid process of the
temporal bone.
6. Number of heads. A biceps muscle has two
heads (origins), and a triceps muscle has
three heads (origins).
7. Function. Abductors and adductors are the
muscles that cause abduction and adduction
movements.

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Figure 8-13a

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Figure 8-13b

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Muscles of the Head and Neck
 Facial muscles,
 Mastication or chewing tongue
 Swallowing muscles
 Eyes muscles
 head and neck muscles

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Figure 8.14

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Facial Muscles
BUCCINATOR
 Wall of the cheeks
 flattens the cheek (as in whistling or blowing
a trumpet)
 “Kissing Muscle or Trumpeter’s muscle
 Compresses cheek to hold food teeth

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Depressor anguli oris
 Lower corners of mouth/depresses the corner
of mouth
Levator Labii superioris
 Elevates one side of the upper lip
OccipitoFrontalis
 Moves scalp, raises eyebrows, and to wrinkle
your forehead

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Orbicularis oris
 closes the mouth and protrudes the lips,
 the “kissing” muscle
Orbicularis oculi
 close the eyes, squint, blink, and wink.
Zygomaticus
 the “smiling” muscle
 elevate the upper lip and corner of the
mouth.

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Muscles of Facial Expression
and Mastication
Figure 7.16
©McGraw-Hill Education/ Christine Eckel

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CHEWING MUSCLES
1. Masseter - closes the jaw by elevating and
pushing the mandible anteriorly
2. Temporalis -elevates and draws mandible
posteriorly.
3. Ptergoid
1. Lateral- pushes the mandible anteriorly and
depresses mandible, close the jaw
2. Medial- pushes the mandible anteriorly and
elevates mandible; closes the jaw

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Tongue and Swallowing Muscles
Tongue Muscles
 Intrinsic- change the shape of the tongue
 Extrinsic- moves the tongue
Hyoid Muscles
Suprahyoid (geniohyoid, stylohyoid, hyoglossus)
 elevates or stabilized hyoid
Infrahyoid- depresses or stabilizes hyoid

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Tongue and Swallowing Muscles
Figure 7.17

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Deep Neck Muscles
1. Neck Flexors
 originate on the anterior side of the vertebra
which flex the head and neck
2. Neck Extensor
 originate on the posterior side of the vertebra
that extend the head and neck

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Sternocleidomastoid
 Individually rotate the head; together it flex
the neck
Platysma
 pull the corners of the mouth inferiorly
Trapezius
 Extends and laterally flexes the neck

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Figure 8-13b

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Figure 8.14

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Trunk Muscles
 Vertebral column,
 Thorax,
 Abdominal wall and
 Pelvic floor.

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Trunk Muscles
Muscles of the Vertebral Column
Erector Spinae
 Extends vertebral column & maintain
posture.
 Divides in 3 column; Iliocostalis,
longissimus, Spinalis.

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Deep Neck and Back Muscles
Figure 7.18

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Deep Back Muscles
 Located between spinous and transverse
processes adjacent to vertebra
 Responsible for movement of vertebral
column including extension, lateral flexion
and rotation
 torn or stretched od these muscles cause
sprain and strain.

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Thoracic Muscles
Scalenes- elevates the ribs, during
inspiration
External intercostals- elevate ribs for
inspiration
Internal intercostals- depress ribs during
forced expiration
Diaphragm- moves during quiet breathing

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Muscles of the Thorax
Figure 7.19

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Abdominal Wall Muscles1
Rectus abdominis
 center of abdomen
 compresses abdomen
External abdominal oblique
 sides of abdomen

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Abdominal Wall Muscles2
Internal abdominal oblique
Transverse abdominis

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Muscles of the Anterior Abdominal Wall
Figure 7.20

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Pelvic Floor Muscles1
 Levator ani
Perineum Muscles
 Ischiocavernosus
 Bulbospongiosus
 Deep transverse perineal
 Superficial transverse perineal

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Pelvic Floor Muscles2
Figure 7.21

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Muscles Acting on the Scapula
Trapezius
 shoulders and upper back
 extends neck and head
 Elevates, depress, retracts, rotates, and fixes scapula
Pectoralis minor
 Located in the chest
 Depresses scapula or elevates ribs

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2
Serratus anterior
• between ribs (1-9)
• Rotates and protracts scapula; elevates ribs
Levator scapulae
 elevates., retracts, and rotates scapula
 Laterally flexes the neck

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Muscles Acting on the Scapula
Major and Minor Rhomboids
 Retracts, rotates, and fixes scapula

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Muscles of the Humerus that Act on the
Forearm
Deltoid Muscle
 Flexes and extend shoulder; abducts and
medially and laterally rotates the arm
Triceps brachii
 3 heads, extends elbow, extend shoulders, adducts
the arm
Biceps brachii
 “flexing muscle”, flexes elbow and shoulder

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126

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Upper Limb Muscles2
Brachialis
 flexes elbow
Latissimus dorsi
 lower back
 extends shoulder, adducts and medially rotates the
forearm

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Forearm Muscles
Anterior Forearm Muscles
1. Palmaris longus- tightens skin of palm
2. Flexor carpi radialis- flex and abducts wrist
3. Flexor carpi ulnaris- flexes and adducts wrist
4. Flexor digitorum profundus-flex fingers & wrist
5. Flexor digitorum superficialis- flex fingers &
wrist
6. Pronator (Quadratus, Teres)- pronates forearm

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Muscles of the Forearm
Figure 7.24

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Posterior Forearm Muscle
Brachioradialis- flexes the elbow
Extensor carpi radialis brevis- extends &
abducts wrist
Extensor carpi radialis longus- extends &
abducts wrist
Extensor carpi ulnaris- extends & adducts wrist
Extensor digitorum- extends fingers and wrist
Supinator-supinates forearm

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Retinaculum
 covers the flexors and extensor tendons and
holds them in place around the wrist
Intrinsic Hand Muscles
 nineteen muscles which are located within
the hand
Interossei Muscles
 located in the metacarpal bones responsible
for abduction and adduction of fingers

134
Muscles of the Forearm
Figure 7.24

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Muscles of Hips and Thighs
Iliopsoas
 Anterior muscle that flexes hip
Gluteus Maximus
 buttocks
 extends hip, abducts and laterally rotates
the thigh
 Not ideal for IM injection

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Gluteus Medius
 abducts and medially rotates the thigh
 steadies pelvis during walking
 Ideal site of IM injection
Tensor Fasciae Latae
 A thick band of fascia on the lateral side
of the thigh
 It helps steady the femur on the tibia
when standing

137

138

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Muscles of the Upper Leg1
Quadriceps femoris is comprised of 4 thigh muscles:
1. Rectus femoris:
 front of thigh
 extends knee and flexes hip
2. Vastus lateralis:
 extends knee
3. Vastus medialis:
 extends knee
4. Vastus intermedius:
 extends knee

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141
Sartorius
longest muscle in the body
tailor’s” muscle
 it flexed the hip and knee and rotates the
thigh laterally for sitting cross legged.

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Medial Compartment
Adductor Longus
 flexes the hip; adducts and laterally rotates
the thigh
Adductor Magnus
 extends the hip; adducts and laterally rotates
the thigh
Gracilis
adducts thigh and flexes knee

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Figure 8.23b

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Muscles of the Upper Leg2
Hamstring Muscles
back of thigh
flexes knee, rotates leg, extends hip

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HAMSTRINGS MUSCLES
Biceps femoris
 flexes the knee, extend the hip, laterally rotates the
leg
Semimembranosus
 flex knee and extend the hip, medially rotates the
leg
Semitendinosus
 flex knee and extend the hip, medially rotates
the leg

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Adductor Muscles
 adducts the thigh

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Figure 8.23b

150
Muscles of the Hip and Thigh
Figure 7.26

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Muscles Causing Movement at the
Ankle and Foot
Anterior Compartment
Extensor digitorum longus
 extends the four lateral toes; dorsiflexes and
everts foot
Extensor hallucis longus
 extend great toes; dorsiflex and inverts foot

152
Figure 7.8ef

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Figure 7.8g

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Muscles Causing Movement at the
Ankle and Foot
Anterior Compartment
Tibialis anterior
 dorsiflexes and inverts the foot
Fibularis/Peroneus tertius
 dorsiflexflexes and everts the foot

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Muscles of Lower Leg
Posterior Compartment
Gastrocnemius
 calf
 plantarflexes the foot; flexes the leg
 “toe dancer’s” muscle
Soleus
 attaches to ankle
 Plantar flexes the foot

156
Figure 7.8g

158
Lateral Compartment Muscles
Fibularis/Peroneus (longus, brevis,)
 Plantar flexes and everts the foot

159
Effects of Aging In Muscles
 Reduction in muscle mass
 Slower response time for muscle contraction
 Reduced stamina
 Increased Recovery time

160
Diseases and Disorders of Muscular
System
Cramps
 painful spastic contraction of muscle due to
build up of lactic acid
Fibromyalgia
 chronic widespread pain in muscles with no
known cause

161
Hypertrophy
 enlargement of a muscle due to increased
myofibrils due to increased muscle used
Atrophy
 decreased in muscle size due to
decreased myofibrils because of disuse
muscle as in paralysis
Tendinitis
 inflammation of a tendon or its attachment
joint due to overuse of a muscle

162
Muscular dystrophy
 a group of inherited muscle-destroying
disease that affect muscle group.
 The most common & serious form is
Duchenne’s muscular dystrophy.

163
Duchenne Muscular Dystrophy
 results from abnormal gene on the X
chromosome
 The gene is carried by female but DMD
common on males
 DMD gene is responsible for producing a
protein called DYSTROPIN

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DMD
 part of the gene is missing and the protein in
produces is nonfunctional resulting to
progressive muscular weakness and muscular
contractures.

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SYMPTOMS
 Muscular weakness
 Muscle atrophy
 Contractures

166
Nervous
 Mental retardation
Cardiovascualr
 Affects cardiac muscles leading heart failure
Respiratory
 Weakness of the respiratory muscles leading
to respiratory failure

167
Digestive
 Affects smooth muscle and reduce the ability
of smooth muscle to contract
Urinary
 Reduced smooth muscle function
 Increase UTI

168
Skeletal
 Shortened inflexible muscles
 Kyphoscoliosis- sever curvature of the
vertebra laterally or anteriorly
 Wheelchair dependency

169
Duchenne Muscular Dystrophy

170
Treatment
 Physical therapy primarily involves exercise
 No effective treatment to prevent

171
Myasthenia Gravis
 characterized by drooping of the upper eyelid
difficulty of swallowing & talking and generalized
muscle weakness and fatigability.
 Death occurs as a result of the inability of the
respiratory muscle to function (respiratory failure).

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