Ch.10 Muscle Tissue Flashcards
Two types of myofilaments
- Thin filament:
- F-actin-fibrous
- G-actin-globular - Thick filament:
made of Myosin II.
Striated muscle (3)
-exhibit cross-striations at the light microscope level
- skeletal: movement of axial and appendicular skeleton
- strong, quick, discontinuous voluntary contraction
- large, elongated multinuc fibers - Visceral striated: soft tissues, tongue, pharynx, esophagus
- weak, slow involuntary contraction
- fusiform cells - Cardiac: wall of heart and veins
- strong, quick, continuous involuntary
- irregular branched by intercalated disks
Smooth muscle
-don’t exhibit cross-striations becoz the myofilaments do not achieve the same degree of order in their arrangment
Skeletal muscle
-consists of striated muscle fibers held together by connective tissue
- myoblast fusion -> muscle fiber
- muscle cell = muscle fiber (multinucleated syncytium)
-nuclei found in cytoplasm beneath plasma membrane = sarcolemma
the connective tissue associated w/ the muscle fibers (3)
- endomysium: delicate layer that surrounds individual muscle fibers
- small-diameter caps and finest neuronal branches - perimysium: thicker layer that surrounds groups of fibers to form a bundle or fascicle, which is the functional unit of muscle fibers that work together for one specific function.
- large blood vessels and nerves - epimysium: (outside layer) sheath of dense conn tiss that surrounds a collections of fascicles that constitute a muscle
myoglobin
oxygen-binding protein that closely resembles hemoglobin and occurs in varying amounts in muscle fibers, providing muscle metabolic reactions
- myofibrils
- myofilaments
- structural and functional subunit of muscle fiber
- individual filamentous polymers of Myosin II and Actin. the actual contractile elements of striated muscle. bundles make up one myofibril, surrounded by smooth ER = Sarcoplasmic reticulum
- A band (anisotropic)
- I band (isotropic)
- (Thick filament) H line and M line
- (Thin filament w/ tropomyosin and troponin) Z line
- functional unit of myofibril is Sarcomere, from Z line to Z line
-When a muscle contracts, each sarcomere shortens and becomes thicker, but the myofilaments remain the same length.
- during contraction, the sarcomere and I-band shorten, while A-band remains the same length.
- H bands narrows and the thin filaments slide past.
Terminal Cisterna
-a regular ring-like channel at the junction between A and I bands, formed by sarcoplasmic reticulum.
transverse tubular system (T system)
- consists of numerous tubular invaginations of the plasma membrane; each one is called a T tubule.
- many T tubules penetrate all levels of the muscle fiber and are located between adjacent terminal cisternae at the A-I junctions
- Triad: the complex of T tubule and 2 adjacent terminal cisternae.
Cardiac muscle
- Intercalated disks: crossbands that represent specialized attachment sites between adj cells
- nucleas lies in the center of the cell
- Atrial natriuretic factor
- Brain natriuretic factor
-diuretic and inhibits contraction of vasc smooth muscle
- ”
- T tubules penetrate at level of Z line
- only one T tubule per sarcomere in cardiac muscle
- small terminal cisternae of the SER interact w/ the t tubules to form a diad at the Z line
Cardiac conducting cells
- specialized cardiac muscle cels to initiate heartbeat
- organized in nodes and highly specialized conducting fibers, that generate and rapidly transmit the contractile to various parts of the myocardium in a sequence.
- parasympathetic
- sympathetic
- slows down heartbeat, by decreasing frequency of impulses to the cardiac conducting cells
- accelerates heartbeat
*impulses don’t initiate contraction but only modify rate of intrinsic cardiac muscle contraction
