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The Muscular System
Seminar 6
Teresa Thomas, RN, BSN, MBA
Types of Muscle Tissue
 Remember
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Skeletal
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◘
Smooth


◘
Striated
Voluntary
Striated
Involuntary
Cardiac
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
Nonstriated
Involuntary
these from Chapter 3?
Muscle Tissue
 Types of muscle tissue
◘ Skeletal muscle
 Striated or voluntary muscle
 Represents 40% to 50% of body weight
 Attached to bones
 Microscope reveals crosswise stripes or
striations
 Contractions can be voluntarily controlled
Muscle Tissue
 Types (cont’d)
◘ Cardiac muscle—composes bulk of heart



Cardiac muscle cells branch frequently
Characterized by unique dark bands called
intercalated disks
Interconnected nature of cardiac muscle cells allows
heart to contract efficiently as a unit
Muscle Tissue
 Types (cont’d)
◘ Smooth (Visceral)
 Nonstriated muscle or involuntary
‒ Lacks cross stripes or striation when seen under a
microscope; appears smooth
‒ Found in walls of hollow visceral structures, such as
digestive tract, blood vessels, and ureters
‒ Contractions not under voluntary control; movement
caused by contractions is involuntary
 Function—all muscle cells specialize in
contraction (shortening)
Structure of Skeletal Muscle
 Parts of a skeletal muscle:
◘ Origin—attachment to the bone that remains
relatively fixed when movement at the joint occurs
◘ Insertion—point of attachment to the bone that
moves when a muscle contracts
◘ Body—main part of the muscle
Structure of Skeletal Muscle (cont’d)
 Muscles attach to the bone by tendons—strong
cords of fibrous connective tissue
◘ Some tendons are enclosed in synovial-lined
tubes and lubricated by synovial fluid
 Bursae—small synovial-lined sacs containing a
small amount of synovial fluid
Structure of Skeletal Muscle (cont’d)
Attachments of a Skeletal Muscle
Structure of Skeletal Muscle (cont’d)
 Microscopic structure
◘ Muscle tissue consists of specialized contractile
cells called fibers
◘ Each fiber contains two kinds of very fine,
threadlike structures:
 Thick myofilaments
 Thin myofilaments
Structure of Skeletal Muscle (cont’d)
 Sarcomere: basic functional (contractile) unit
◘ Separated from each other by dark bands called
Z lines
◘ Sliding filament model explains mechanism of
contraction
 Thick and thin myofilaments slide past each
other as a muscle contracts
Structure of a Sarcomere
Functions of Skeletal Muscle
 Three primary functions
◘ Posture (or muscle tone)
◘ Heat production
◘ Movement
◘ Now let’s talk about each…
Functions of Skeletal Muscle (cont’d.)
 Posture
◘ Tonic contraction: specialized muscle contraction
that enables us to maintain body position
 Only a few of a muscle’s fibers shorten at one
time
 Tonic contractions produce no movement
◘ Tonic contractions maintain muscle tone called
posture
Posture
Functions of Skeletal Muscle (cont’d.)
 Heat production
◘ Survival depends on the ability to maintain
constant body temperature
 Fever: An elevated body temperature; often
a sign of illness
 Hypothermia: A reduced body temperature
◘ Contraction of muscle fibers produces most of
the heat required to maintain normal body
temperature
Functions of Skeletal Muscle
 Movement
◘ Muscles produce movement
◘ As muscle contracts, it pulls the insertion bone
closer to the origin bone
◘ Movement occurs at the joint between the origin
and the insertion
MOVEMENTS – Muscle Contractions

Hand positions that result from rotation of the forearm
◘ Supination

results in a hand position with the palm turned to the
anterior position
Pronation
 occurs when the palm faces posteriorly
Foot Movements
◘ Dorsiflexion
◘
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◘
Plantar flexion

◘
the bottom of the foot is directed downward
Inversion

◘
results in elevation of the dorsum or top of the foot
inversion moves ankle to side so that sole faces inward
toward midline
Eversion

eversion turns ankle so that the sole faces out to the side
Types of Movements Produced by
Skeletal Muscle Contractions (cont’d.)
Examples of Body Movements
Types of Movements Produced by
Skeletal Muscle Contractions
• Flexion:
•
Decreases the angle between two bones at their joint
• Extension:
• Increases the angle between two bones at their joint
• Abduction:
• Movement of a part away from the midline of the body
• Adduction:
• Movement of a part toward the midline of the body
• Rotation:
• Movement around a longitudinal axis
Movement….
Types of Movements Produced by
Skeletal Muscle Contractions (cont’d.)
Muscles Involved….
Slide 21
Movement…..
Muscles Involved…..
Muscles Involved…..
Slide 24
Functions of Skeletal Muscle (cont’d.)
 Movement (cont’d)
◘Groups of muscles usually contract to produce a
single movement



Prime mover—contraction is mainly responsible for producing
a movement
Synergist—contractions help the prime mover produce a
movement
Antagonist—actions oppose the action of a prime mover in a
movement
Effects of Exercise on Skeletal Muscles
 Regular, properly practiced exercise improves muscle
tone and posture
 Results in more efficient heart and lung functioning
 Reduces fatigue
 Helps muscle tissue develop
 Helps maintain a healthy weight
• What is Hypertrophy?
• What is Atrophy?
Effects of Exercise on Skeletal Muscles (cont’d.)
 Effects of exercise on skeletal muscles
◘ Prolonged inactivity causes disuse, or atrophy
◘ Regular exercise increases muscle size, called
hypertrophy
Effects of Exercise on Skeletal Muscles (cont’d.)
 Strength training: Exercise involving contractions
of muscles against heavy resistance
◘Increases number of myofilaments in each
muscle fiber
◘Total mass of the muscle increases
◘Does not increase the number of muscle fibers
Effects of Exercise on Skeletal Muscles (cont’d.)
 Endurance training: Exercise that increases a
muscle’s ability to sustain moderate exercise over
long periods
◘Sometimes called aerobic training
◘Allows more efficient delivery of oxygen and
nutrients to a muscle via increased blood flow
◘Increases the number of blood vessels in a
muscle
◘Does not usually result in muscle hypertrophy
Muscle Fatigue
 Reduced strength of muscle contraction
 Caused by repeated muscle stimulation
◘ Repeated muscular contraction depletes cellular ATP store and
outstrips the ability of the blood supply to replenish oxygen and
nutrients
 Contraction in the absence of adequate oxygen produces lactic acid,
which contributes to muscle soreness
 Oxygen debt: The continued metabolic effort required to burn excess
lactic acid that may accumulate during prolonged periods of exercise
Types of Skeletal Muscle Contraction
 Twitch and tetanic contractions
◘ Twitch contractions: A quick, jerky response
to stimulus
 Single contraction of muscle fibers caused by
a single threshold stimulus
◘ Tetanic contractions—sustained, steady
muscular contractions
 Caused by a series of stimuli bombarding a
muscle in rapid succession
Types of Skeletal Muscle Contraction (cont’d.)
 Isotonic contractions
◘ Contraction of a muscle that produces movement
at a joint
◘ The muscle changes length, causing the insertion
end of the muscle to move relative to the point of
origin
◘ Most types of body movements such as walking
and running are isotonic contractions
Types of Skeletal Muscle Contraction (cont’d.)
 Isometric contractions
◘ Muscle contractions that do not produce
movement
 The muscle as a whole does not shorten
◘ No movement occurs during isometric
contractions, but tension within the muscle
increases
Types of Skeletal Muscle Contraction (cont’d.)
Motor Unit
 Stimulation of a muscle by a nerve impulse is
required to produce movement
◘ Motor neuron: Specialized nerve that
transmits an impulse to a muscle, causing
contraction
◘ Neuromuscular junction: Specialized point
of contact between a nerve ending and the
muscle fiber it innervates
◘ Motor unit: The combination of a motor
neuron with the muscle cell(s) it innervates
Muscle disorders

Take a look at these on your own…
◘
◘
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Strain—injury from overexertion or trauma
Cramps are painful muscle spasms (involuntary twitches)
Infections
Muscular dystrophy
Myasthenia gravis
Chapter 7
Let’s Review!
Review Question
Which is a function of muscle tissue?
A.
B.
C.
D.
Support
Heat Production
Movement
All of the above
Review Question
Which of these is not one of the three types of
muscle tissue?
A. Skeletal
B. Smooth
C. Cardiac
D. Connective
Review Question
Which of these is usually under
conscious control?
A.
B.
C.
Slide 40
Cardiac muscle
Smooth muscle
Skeletal muscle
Review Question
Calcium triggers the contraction of a
muscle fiber. Where in the muscle
fiber is this calcium stored?
D.
Nucleus
Calcium vesicles
Endoplasmic reticulum
Golgi apparatus
E.
Mitochondria
A.
B.
C.
Review Question
A person picks up a pencil, thus flexing the
elbow. Contraction of the biceps brachii
muscle during flexion is mainly
A.
B.
Slide 42
Isometric
Isotonic
Review Question
Contraction of the masseter muscle
causes what action?
A.
B.
C.
D.
E.
Slide 43
Flexion of the head and neck
Mouth closes
Mouth opens
Eye opens
Eye closes
Review Question
Plantar flexion
A.
B.
C.
D.
E.
Slide 44
Bends the elbow
Causes you to stand on your toes
Causes you to stand on your heels
Bends the wrist
Moves the leg out to the side of the body
KNOW ALL OF THESE!!
Know the Body Movements
 Rotation
 Adduction
and abduction
 Pronation and supination
 Dorsiflexion and plantarflexion
Skeletal Muscle Groups
 Give
examples of each:
◘
Muscle of head and neck
◘
Muscles that move the upper extremities
◘
Muscles of the trunk
◘
Muscles that move the lower extremities
Time for Q and A!
Final Project
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Don’t forget you should be working on your final project… It is due
at the end of Week 9 (no later than 11;59 p.m. on Tuesday).
Plan ahead and be sure that your PowerPoint meets the APA
requirements, content is thorough and proper grammar, spelling
and sentence structure rules are followed on the slides as well as
the speaker notes!
Citations are to be used within the speaker notes and slides.
Reference slide is required as well.
Questions ?