Overview of Anatomy and Physiology Functions of the muscular
system Motion Maintenance of posture and Shape to body Production
of heat Support-blood vessels, nerves Protection-organs
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Muscular System Muscle fibers and tendons, innervated by nerves
Various size and shapes-relate to function Muscle fibers are
covered by connective tissue: Epimysium, Perimysium, and Endomysium
3 coverings join together to form a tendon which attaches the
muscle to bone Agonist pairs Action: contract or shorten
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Muscle Movement Voluntary Attached to bone Moved by person
Involuntary Within organs Not controlled by person
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Types of Muscle Smooth muscle Involuntary, wavelike motions Not
striated, one central nucleus per cell Makes walls of hollow body
organs Blood vessels Respiratory passages Relaxes slowly, can
sustain contraction
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Types of Muscle Cardiac muscle Involuntary, Makes wall of heart
Striated, one nucleus per cell, branching interconnections
Electrical stimulus is generated within (self- excitatory), but can
be modified by nervous stimuli and hormones
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Types of Muscle Skeletal muscle Voluntary control Heavily
striated Multiple nuclei per cell Contraction stimulated by nervous
system Contracts and relaxes rapidly Attached to bones Act in
groups to produce movement
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Muscle Groups Head & face Trunk Upper Extremeties Lower
Extremeties
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Figure 44-5 Anterior view of the body (
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Figure 44-6 Posterior view of the body
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Overview of Anatomy and Physiology Nerve and blood supply Blood
vessels provide a constant supply of oxygen and nutrition and nerve
cells/fibers supply a constant source of information
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Overview of Anatomy and Physiology Impulse from nerve cells
travels across the synaptic cleft, filled with tissue fluid, as
nerve and muscle cells do not directly touch each other.
Acetylcholine, a special chemical neurotransmitter, travels through
the fluid to stimulate the muscle fiber. Cholinesterase (enzyme)
breaks down the acetylcholine after it has transferred the message
and allows the muscle cell to relax.
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Muscle Stimulation Two properties of muscle needed for response
to a stimuli Excitability Contractility
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Muscle Contraction Muscle contraction Muscle stimuluswhen a
muscle cell is adequately stimulated, it will contract Muscle
toneskeletal muscles are in a constant state of readiness for
action Types of body movementsflexion, extension, abduction,
adduction, rotation, supination, pronation, dorsiflexion, and
plantar flexion
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Muscle Contraction Muscle stimulus All or none law Muscle Cell
Stimulated or Shocked Muscle Contracts Completely All or None?
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Think about muscle tone No Muscle Tone Paralyzed muscle
Flaccid(weak, soft, flabby, & lack normal tone) Limp
Atrophied(wasted) Cells no longer receive stimuli from nerves
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Muscle Excitability Muscles transmit electrical current along
cell membrane The spreading electrical current is called action
potential (calls muscle into action)
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Muscle Contractility Ability to change shape Shorten Get
thicker
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Role of Calcium Nerve stimulation releases calcium into cell to
cause contraction When stimulation stops, calcium is returned to
the endoplasmic reticulum, and the muscle relaxes
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Physiology Muscle Contraction Circulation- brings O 2, glucose,
nutrients to cells O 2 is stored in muscle cells as myoglobin
Glucose is stored in cells as glycogen for later breakdown into
glucose when needed (as in vigorous exercise) Glucose and O 2
oxidize/burn to produce ATP needed for contraction Lactic Acid
Waste product of cellular metabolism Causes muscle fatigue
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Oxygen Debt Glucose & O 2 from circulation used first, then
stored glucose & O 2 are used, both operate in an aerobic
process (with O 2 ) If cant breathe fast enough to provide O 2,
glucose is burned in an anaerobic process (without O 2 ) causing
lactic acid build up, muscle fatigue Exercising stops, breathing
continues until oxygen debt is paid
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Exercise Causes vasodilation, allowing increased nutrients to
be carried to muscles Temporary increases strengthen the heart
muscle and improve circulation Regular exercise increases
respiratory efficiency through enhanced gas exchange With athletic
training oxygen debt is delayed Bones & muscles get stronger,
decreased weight, blood pressure, & heart attacks
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Types of Movement
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Flexion Decreases angle between two adjoining bones Angle
decreased
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Extension Increases the angle between two adjoining bones If
the extension angle is more than 180 degrees - hyperextended
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Abduction Extremity away from the midline of the body
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Adduction Movement of extremity toward the axis of the
body
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Dorsiflexion Causes the top of the foot to elevate or tilt
upward
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Plantar Flexion Bottom of foot directed downward
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Supination and Pronation Hand and forearm moves palm upward or
downward