Muscle TissueMuscle Tissue

20072007

Muscle TissueMuscle Tissue Specialized for contractionsSpecialized for contractions Elongated cellsElongated cells Unique terms to describe Unique terms to describe

components of muscle cellscomponents of muscle cells Sarcolemma – muscle cell membranesSarcolemma – muscle cell membranes Sarcoplasm – cytoplasmSarcoplasm – cytoplasm Sarcoplasmic reticulum – endoplasmic Sarcoplasmic reticulum – endoplasmic

reticulum reticulum Muscle cell = muscle fiber (Muscle cell = muscle fiber (notnot like a CT like a CT

fiber)fiber)3 types of muscle: skeletal, cardiac, smooth

Organization of Skeletal Organization of Skeletal MuscleMuscle

Skeletal (striated, voluntary) Skeletal (striated, voluntary) MuscleMuscle

Long, cylindrical shaped cellsLong, cylindrical shaped cells Multinucleate cells Multinucleate cells Peripheral nucleiPeripheral nuclei Striated (striped) appearance seen in Striated (striped) appearance seen in

light microscope: A band, I band, Z line, light microscope: A band, I band, Z line, H band.H band.

Skeletal Muscle (longitudinal Skeletal Muscle (longitudinal section)section)

MyofibrilMyofibril – structural & functional subunit of muscle cells; consists of – structural & functional subunit of muscle cells; consists of myofilaments.myofilaments.

MyofilamentsMyofilaments – the contractile elements of skeletal muscle; consist – the contractile elements of skeletal muscle; consist of filamentous polymers of myosin (thick filaments) and actin (thin of filamentous polymers of myosin (thick filaments) and actin (thin

filaments). filaments).

Sarcomere – the basic contractile unit of skeletal Sarcomere – the basic contractile unit of skeletal muscle; muscle;

extends from Z-line to Z-lineextends from Z-line to Z-line

actin myosin

Motor end plateMotor end plate – the area of contact made by the endings of a – the area of contact made by the endings of a motor neuron onto a muscle fiber. motor neuron onto a muscle fiber.

Motor end plate - releases the neurotransmitter Motor end plate - releases the neurotransmitter acetylcholine.acetylcholine.

Neuromuscular JunctionNeuromuscular Junction

Skeletal Muscle (cross-section, Skeletal Muscle (cross-section, low power)low power)

Skeletal Muscle – High Skeletal Muscle – High PowerPower

Cardiac MuscleCardiac Muscle

- Striated- Striated- Single, large, oval, centrally located nucleusSingle, large, oval, centrally located nucleus- Branched cellsBranched cells- Intercalated disks = Intercalated disks = specialized end-to-end junctionsspecialized end-to-end junctions

Cardiac MuscleCardiac Muscle

Intercalated Disks - anchor myofibrils Intercalated Disks - anchor myofibrils and permit fast transmission of and permit fast transmission of

contractions;contractions;consist of 3 components: consist of 3 components:

Cardiac MuscleCardiac Muscle

Mitochondria in Cardiac Mitochondria in Cardiac MuscleMuscle

Purkinje Fibers - large, modified cardiac muscle Purkinje Fibers - large, modified cardiac muscle cells that electrical transmit impulses to cardiac cells that electrical transmit impulses to cardiac

muscle.muscle.

Smooth MuscleSmooth Muscle

Smooth MuscleSmooth Muscle

Most body tubes lined externally by Most body tubes lined externally by smooth muscle.smooth muscle.

Important in sphincters, peristalsis, Important in sphincters, peristalsis, blood pressure regulation.blood pressure regulation.

““involuntary muscle” – activated by involuntary muscle” – activated by autonomic nervous system and autonomic nervous system and hormones.hormones.

Smooth MuscleSmooth Muscle

Cells are fusiform in shape – round at center and tapered at ends.Cells are fusiform in shape – round at center and tapered at ends. A single nucleus, centrally located. A single nucleus, centrally located. When contracted, nuclei may have a corkscrew appearance.When contracted, nuclei may have a corkscrew appearance. No striations – actin & myosin present but not regularly arranged in a repeated No striations – actin & myosin present but not regularly arranged in a repeated pattern.pattern. Cells connected to each other by gap junctions that allow conduction of Cells connected to each other by gap junctions that allow conduction of impulses and contraction from one cell to another.impulses and contraction from one cell to another.

Smooth Muscle:Smooth Muscle:top: cross-section; bottom: longitudinal top: cross-section; bottom: longitudinal

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