Lecture 14: Muscle tissue Flashcards
Skeletal muscle characteristics
Multinucleated syncytium
Peripheral nuclei
Sarcomeric arrangment
Myofiber type 1 characteristics
Intense staining for oxidative enzymes
Rich in NADH transferase, myoglobin, mitochondira
Primarily utilize oxidative phosphorylation
Produce slow, continuous contractions
Referred to as dark/red fibers
Myofiber type 2 characteristics
Intermediate staining for oxidative enzymes
Utilize both aerobic and anaerobic respiration
Contract more rapidly than type 1
Resistance to fatigue
Myofiber type 3 characteristics
Light staining for oxidative enzymes Utilize primarily anaerobic respiration Rich in ATPase Contract very rapidly Fatigue quickly White/light fibers
Smooth muscle characteristics
Single mononucleated cells
No sarcomeric arrangement
Cells innervated via ANS
Gap junctions connect
Cardiac muscle characteristics
Mononucleated cells Central nuclei Branched cells Sarcomeric arrangement Intercalated discs Not directly innervated
Perimysium consists of
Fibroblasts and type I collagen
Myofiber is a
Muscle cell
Endomysium consists of
Basal lamina and reticular collagen fibers
Basal lamina characteristics
Secreted by muscle cells
Anchors muscle fibers to eachother
Helps distribute the force of contraction
“A” band consists of
Myosin/actin filaments
It is the length of the myosin filament
H band consists of
Only myosin filament
I band
Only actin filaments
Banded pattern origin
Filaments of the sarcomere are organized in such a way as to create a repeated banding pattern
Each myosin head has what regions
Actin binding region
ATP-binding region
Light-chain binding region
Two pairs of light chains on myosin head
Similar to calmodulin but have lost ability to bind calcium
Essential light chains contribute to stability of myosin head
Regulatory light chains maintain stability of myosin II and are sites for phosphate binding
F-actin
Polymer of G actin
Plus ends insert on Z disk
Tropomyosin
Each tropomyosin sits in the groove between two actin strands of an actin filament
Each tropomyosin spans 7 actin monomers
Troponin I
Inhibits binding between actin/myosin
Troponin C
Binds calcium ions
Troponin T
Binds to tropomyosin
T-tubules are located
At the A-I junction
aB-crystallin
Heat-shock protein that protects desmin from mechanical stress
Dystrophin
One of the proteins that links the a-actinin/desmin complex to cytoplasmic side of sarcolemma
Anchors actin to sarcolemma
Reinforces sarcolemma during contraction
Dystroglycan complex
Links dystrophin (intracellular) to laminin-2 (extracellular)
a-actinin
Attaches thin filaments to the Z-line
Nebulin
Extends from Z disc to actin filament
Serves as template to regulate length of actin filament
Titin
Extends from Z-disk to middle of H-band and connects ends of thick filaments to Z-line
Provides myosin with elasticity
Centers thick filaments in sarcomere
Desmin intermediate filaments
Framework of desmin filaments which surrounds the Z-line and extends into each sarcomere
Links myofibrils laterally and to the sarcomere
Plectin
Binds desmin filaments
Satellite cells
Attach to myotubes before basal lamina is laid down
Generally quiescent
Function as stem cells
Can become mitotic in times of stress
Give rise to myogenic precursor cells-replace damaged muscle by differentiating into skeletal muscle fibers
Neuromuscular spine components
Extrafusal fibers Intrafusal fibers--Nuclear bag/nuclear chain fibers. nuclear bag is sensory region Alpha motor neurons-to extrafusal fibers Gamma motor neurons-to intrafusal fibers Primary and secondary afferent fibers
T-tubule system in cardiac muscle tissue
Not as extensive as in skeletal muscle
Only interacts with one cisterna
Contents of intercalated discs
Macula adherentes
Fascia adherents (anchor actin filaments of sarcomeres)
Gap junction
ANP
Secreted by cardiac muscle cells in atria Regulate fluid electrolyte balance Relax vascular smooth muscle -reduces blood volume/pressure Release is stimulated by atrial stretch
Dense bodies in smooth muscle
Anchor actin filaments to eachother and cell membrane
Contain A-actinin
Interconnected by specific type of desmin
Communicate force of contraction to cytoskeleton and cell membrane
Found in cytoplasm and cell membrane
Smooth muscle cells do not have
T-tubule system or extensive SR
Smooth muscle cells dependent on
Extracellular calcium for contraction
-calcium transported by pinocytic vesicles
Caveolae/lipid rafts
Permanent depressions of cell membrane involved in fluid/electrolyte transport
Caveolin binds cholesterol in lipid rafts and initiates formation of caveolae
Vesicles formed and detach to participate in trafficking
Adrenergic and muscarinic receptors
Linked to G-proteins
Nicotinic cholinergic receptor
Cation channel
Smooth muscle sheet innervation
Smooth muscle sheets are mostly poorly innervated
Excitation is spread through gap junctions
