Download anatomy notes chapter 6 - muscular system

6
The Muscular System
PART A
PowerPoint® Lecture Slide Presentation by Jerry L. Cook, Sam Houston University
ESSENTIALS
OF HUMAN
ANATOMY
& PHYSIOLOGY
EIGHTH EDITION
ELAINE N. MARIEB
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The Muscular System
Function of Muscles:
 Produce movement
 Maintain posture
 Stabilize joints
 Generate heat
Three basic muscle types are found in the body
 Skeletal muscle
 Cardiac muscle
 Smooth muscle
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Characteristics of Muscles
 Muscle cells are elongated, and are called
muscle fibers (muscle cell = muscle fiber)
 Contraction of muscles is due to the
movement of microfilaments
 All muscles share some terminology
 Prefix myo refers to muscle
 Prefix mys refers to muscle
 Prefix sarco refers to flesh
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Skeletal Muscle Characteristics
Skeletal Muscle:
 Most are attached by tendons to bones
 Multinucleate – more than 1 nucleus
 Striated – have visible banding
 Voluntary – subject to conscious control
 Cells are surrounded and bundled by
connective tissue
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Connective Tissue Wrappings of Skeletal
Muscle
 Endomysium – around
single muscle fiber
 Perimysium – around a
fascicle (bundle) of
fibers
 Epimysium – covers
the entire skeletal
muscle
 Fascia – on the outside
of the epimysium
Figure 6.1
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Skeletal Muscle Attachments
 Muscles attach to bones by:
 Tendons – cord-like structure
 Aponeuroses – sheet-like structure
 Sites of muscle attachment
 Bones
 Cartilages
 Connective tissue coverings
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Smooth Muscle Characteristics
Smooth Muscle:
 Has no striations
 Spindle-shaped cells
 Single nucleus
 Involuntary – no
conscious control
 Found mainly in the
walls of hollow
organs
Figure 6.2a
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Cardiac Muscle Characteristics
Cardiac Muscle:
 Has striations
 Usually has a single
nucleus
 Joined to another
muscle cell at an
intercalated disc
 Involuntary
 Found only in the
heart
Figure 6.2b
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Microscopic Anatomy of Skeletal Muscle
 Sarcolemma – specialized plasma membrane
 Sarcoplasmic reticulum – specialized smooth
endoplasmic reticulum
 Sarcomere – contractile unit of a muscle fiber
Figure 6.3a
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Microscopic Anatomy of Skeletal Muscle
 Myofibril
 Bundles of myofilaments – actin & myosin
 Myofibrils are aligned to give distinct bands
 I band = light band
 A band = dark band
Figure 6.3b
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Microscopic Anatomy of Skeletal Muscle
 Organization of the sarcomere
 Thick filaments = myosin filaments
 Made of the protein myosin
 Thin filaments = actin filaments
 Composed of the protein actin
Figure 6.3c
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Microscopic Anatomy of Skeletal Muscle
 Myosin filaments have heads (extensions, or
cross bridges)
 At rest, there is a bare zone that lacks actin
filaments
 Sarcoplasmic
reticulum
(SR) – stores
calcium used in
contractions
- During contraction myosin & actin slide past
eachother
Figure 6.3d
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Nerve Stimulus to Muscles
 Irritability –receive
and respond to stimulus
 Contractility – shorten
when stimulated
 Skeletal muscles must
be stimulated by a
nerve to contract
 Motor unit
 One neuron
 Muscle cells
stimulated by that
neuron
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Figure 6.4a
Nerve Stimulus to Muscles
 Neuromuscular junctions – association site
of nerve and muscle (where they meet)
Figure 6.5b
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Nerve Stimulus to Muscles
 Synaptic cleft – gap
between nerve and
muscle
 Nerve and muscle
do not touch
 Area between
nerve and muscle
filled with
interstitial fluid
 Neurotransmitters
travel across space
Figure 6.5b
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Transmission of Nerve Impulse to Muscle
 Neurotransmitter acetylcholine – chemical
released by nerve upon arrival of impulse
 Acetylcholine attaches to receptors on the
sarcolemma of muscle
 Sarcolemma becomes permeable to sodium
(Na+)
 Sodium rushes into the cell and generates an
action potential (stimulus) for contraction
 Once started, muscle contraction cannot be
stopped
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The Sliding Filament Theory of Muscle
Contraction
 Activation by nerve
causes myosin heads
(crossbridges) to attach
to binding sites on actin
 Myosin heads then bind
to the next site actin
 This continued action
slides myosin along actin
 The result is that the
muscle is shortened
(contracted)
Figure 6.7
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The Sliding Filament Theory
Figure 6.8
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Contraction of a Skeletal Muscle
Skeletal Muscle Contraction:
 Muscle fiber contraction is “all or none”
 Within a skeletal muscle, not all fibers may
be stimulated during the same interval
 Different combinations of muscle fiber
contractions may give differing responses
 Graded responses – different degrees of
skeletal muscle shortening
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Types of Graded Responses
 Twitch
 Single, brief contraction
 Not a normal muscle function
Figure 6.9a–b
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Types of Graded Responses
 Tetanus (summing of contractions)
 One contraction is immediately followed
by another
 Contraction is
smooth and
sustained
Figure 6.9a–b
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Muscle Response to Strong Stimuli
 Muscle force depends upon the number of
fibers stimulated
 More fibers contracting results in greater
muscle tension
 Muscles can continue to contract unless they
run out of energy
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Energy for Muscle Contraction
Energy for Muscle Contraction:
 First, muscles used stored ATP for energy
 Bonds of ATP are broken to release energy
(lasts only few seconds)
 After this initial time, cells need to undergo
aerobic or anaerobic respiration to produce
energy for contraction
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Energy for Muscle Contraction
 Aerobic Respiration
 Occurs in the
mitochondria
 Glucose is broken
down to carbon
dioxide, water and ATP
(energy)
 This is a slower
reaction that requires
continuous oxygen
Figure 6.10b
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Energy for Muscle Contraction
 Anaerobic glycolysis
 Breaks down glucose
without oxygen
 Glucose is broken down
to pyruvic acid, then
lactic acid, to produce
some ATP
 Not as efficient as
aerobic respiration
Build up of lactic acid
Produces muscle fatigue
Figure 6.10c
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Types of Muscle Contractions
Types of Muscle Contractions
 Isotonic contractions
 Myofilaments are able to slide past each
other during contractions
 The muscle shortens
 Isometric contractions
 Tension in the muscles increases
 The muscle is unable to shorten
Different fibers contract at different times to
provide muscle tone
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Muscles and Body Movements
 Movement is attained due
to a muscle moving an
attached bone
 Muscles are attached to at
least two points
 Origin – attachment
to an immoveable
bone
 Insertion –
attachment to a
movable bone
Figure 6.12
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Effects of Exercise on Muscle
 Results of increased muscle use
 Increase in muscle size
 Increase in muscle strength
 Increase in muscle efficiency
 Muscle becomes more fatigue resistant
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Types of Ordinary Body Movements
Types of body movements due to muscles
 Flexion: brings bones closer together
 Extension: opposite of flex, increases
distance between bones
 Rotation: movement around longitudinal axis
(shaking head no)
 Abduction: moving limb away from body
 Adduction: opposite, move limb toward body
 Circumduction: proximal end is stationary
and distal end moves in a circle
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Body Movements
Figure 6.13a–c
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Body Movements
Figure 6.13d
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Special Movements
 Dorsifelxion: toes up, walking on heels
 Plantar flexion: toes down, walking on toes
 Inversion: turn sole medially (in toward body)
 Eversion: turn sole laterally (away from body)
 Supination: turn palm up (facing anteriorly)
 Pronation: turn palm down (facing
posteriorly)
 Opposition: ability to move thumb to touch
other fingers
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Types of Muscles
 Prime mover (Agonist) – muscle with the
major responsibility for a certain movement
 Antagonist – muscle that opposes or reverses
a prime mover
 Synergist – muscle that aids a prime mover
in a movement and helps prevent rotation
 Fixator – stabilizes the origin of a prime
mover
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Naming of Skeletal Muscles
 Direction of muscle fibers:
 Example: rectus (straight)
 Relative size of the muscle:
 Example: maximus (largest)
 Location of the muscle:
 Example: temporalis (temporal bone)
 Number of origins:
 Example: triceps (three heads)
 Shape of the muscle
 Example: deltoid (triangular)
 Action of the muscle
 Example: flexor and extensor
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Head and Neck Muscles
Figure 6.15
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Trunk Muscles
Figure 6.16
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Deep Trunk and Arm Muscles
Figure 6.17
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Muscles of the Pelvis, Hip, and Thigh
Figure 6.19c
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Muscles of the Lower Leg
Figure 6.20
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Superficial Muscles: Anterior
Figure 6.21
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Superficial Muscles: Posterior
Figure 6.22
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