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Lecture 3

BIOM2000 Lecture 3: Unit 3 BIOM2000


Department
Biomedical Sciences
Course Code
BIOM 2000
Professor
N.Campbell
Lecture
3

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Physiology — Unit 3
Expectations:
Identify categories of muscle types
Compare + contrast skeletal, cardiac, smooth muscle
Describe micro anatomy of skeletal muscle
Differentiate between relaxed + contracted myofibril
Discuss events of neurotransmission
Describe sliding filament theory + role of calcium/ATP
Introduction:
Muscles — specialized tissues that carry out all body movements
Includes…
movement of axial (vertebral column)
appendicular skeleton (limbs, pectoral girdle + pelvic girdle)
movement of blood in cardiovascular system
respiratory movements
movements of gastrointestinal + reproductive tracts
Categories of Muscle Types:
Muscles — made up of elongated cells held together by connective tissue
Specialized cells respond to stimuli by contracting in length
3 basic types of muscles: skeletal, cardiac + smooth muscles

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Skeletal Muscle
Most skeletal muscles —> attached to bones (except facial muscles,
attached to skin)
Skeletal muscle cells referred to as muscle fibre
Nerve cell referred to as neuron
Skeletal muscle cells consist of fusion of cells w/ several nuclei
Fibres are long + have distinct striations
Regulation of skeletal muscles — under voluntary control and therefore
somatic nervous system
Speed of contraction — determined based on skeletal muscles fibres
Organization + connective tissue wrappings of skeletal muscle depicted in
figure below…tendons connect skeletal muscles to bones, each muscle
fibre is enclosed in connective tissue sheath called endomysium
Groups of sheathed fibres wrapped in fibrous perimysium to form bundle
called fascicle + many fascicles surrounded by tough epimysium

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Cardiac Muscle:
Cardiac muscle — made of bundles of cardiomyocytes that form the wall
of heart
Cardio = heart, myo = muscle, cyte = cell
Comprised of branching chains of cells that have 1 nucleus/cell
Similar to skeletal muscle —> it has distinct striations
Unlike skeletal muscle, cardiac muscle is involuntary — therefore under
control of pacemaker (located in heart) — contraction is rhythmic + slow
Smooth Muscle:
Smooth muscle forms sheets of muscle tissue in walls of hollow organs
such as blood vessels + gastrointestinal tract
Cells are fusiform in shape + have 1 nucleus/cell
not striated in appearance —> reason they are termed smooth muscle cells
involuntary + controlled by autonomic nervous system, hormones +
stretch stimuli
Smooth muscle contraction — usually rhythmic + slow
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