Anatomy Test 3Third organ system- muscular system- Composed of muscles- Blood vessels- Nerves 3 types of muscles tissue= 3 types of muscles as organs 3 Types of Muscle Tissue- Skeletal muscle tissue- Cardiac muscle tissue- Smooth muscle tissue Structural Differences- Skeletal - elongated cells called skeletal muscle fibers, striated, multinuclear, voluntary control- Cardiac - striated, highly branched cells that form intercalated discs, uninuclear, involuntary control - Smooth - spindle shaped cells, no obvious striation, uninuclear, involuntary controlSkeletal Muscle Tissue- Organized with connective tissue membrane’s to form skeletal muscle, the organ- Structural organization- each skeletal muscle fiber is covered by the endomysium - A bundle of endomysium covered skeletal muscle fibers wrapped in the perimysium forms a fascicle. - The arrangement of the fascicle in the skeletal muscle may be:o Parallelo Pennateo Convergent - A bundle of perimysium covered fascicle wrapped in the epimysium forms the organ called skeletal muscle- This skeletal muscle is infiltrated by blood vessels and axon terminals from motorneurons - Skeletal muscles attach to bones in the skeletal system hence, the name “skeletal muscle”- Skeletal muscles have 2 attachment siteso Origino Insertion - When the skeletal muscle contracts, it pulls the insertion towards the origin - The origin of a skeletal muscle is relatively stable when the skeletal muscle contracts Attachment of skeletal muscle (origin or insertion) may be- Direct attachment- Indirect attachment Direct Attachment - Epimysium of the skeletal muscles attaches directly to the surface of the bone. Anexample is the skeletal muscle attached to the cranial bones - Frontalis attaches directly to the frontal boneIndirect Attachment - Skeletal muscle attaches indirectly to the bone by tendon which extends from the epimysium covering the skeletal muscle - Most skeletal muscles in the human body use indirect attachment - Advantages of indirect attachment o Attachment by tendons occupy smaller surface area on the bone allowing for other skeletal muscles to attach to the same bone- for efficient attachment of skeletal muscles o Bones attached indirectly by skeletal muscles act as levers when the skeletal muscles contract to produce movements by the body o Tendons attaches skeletal muscle to the surface of bones protect skeletal muscle from direct contact when the bone surface (rough surface that can cause tearing/damage to skeletal muscle) Each muscle fiber contains - Myofibrils- rod like structures that run the entire length of the muscle fiber; 80% of the whole volume of the muscle fiber is occupied by the myofibrils- Myoglobin- a red pigment that binds and stores oxygen- Inclusions- glycosoes contain glycogen- Mitochondria- for aerobic respiration to produce energy- Sarcoplasm- cytoplasm of the muscle fiber- Sarcoplasmic reticulum (SR)- specialized smooth ER that stores/releases calcium into the sarcoplasm, the expanded ends of SR are called terminal cisternae- Sarcolemma- plasma membrane of muscle fiber- Transverse tubules (T-tubules)- involutions of the sarcolemma into the sarcoplasm Physiology of Skeletal Muscle Contraction - Explained at the cellular level- structure function of skeletal muscle cells which we call skeletal muscle fibers - Each skeletal muscle fiber o The plasma membrane is called a sarcolemma o In folding’s/ invaginations of the sarcolemma are called transverse tubuleso The cytoplasm of a skeletal muscle fiber is called sarcoplasm o The sarcoplasm contains several nuclei o Also present is all the cytoplasmic organelles such as mitochondria, smooth ER (called sarcoplasmic reticular- a specialized smooth Er that stores/ releases ionic calcium)o Also present is inclusions called glycosomes- store glycogen (polysaccharide/ storage form of glucose in animal cells)o Red pigment called myoglobin is present in the sarcoplasm o Myoglobin- binds/ releases oxygen to support aerobic respiration occurring in the mitochondria o Skeletal muscle fiber- transverse tubules are located between the 2 terminal cisternaeo Terminal cisternae are the extended ends of the sarcoplasmic reticularo Structure composed of terminal cisterm, T tubule, ksdjf =TRIADo Skeletal mucle fibers have rod like structures called myofibrils (80% of the volume of skeletal muscle fiber is occupied by myofibrilso Myofibris- run the entire length of the skeletal muscle fiberso Skeletal muscle fibers run the entire length of a skeletal muscle o Each myofibril is composed of thinner rod-like structures called myofilaments Thick filaments Thin filaments Skeletal Muscle fascicle skeletal muscle fibers myofibrils myofilaments Thick Filaments- Composed of proteins called myosin - Myosin has a rod-like tail that ends in 2 myosin globular heads - Each thick filament is composed of 300 molecules of myosin- The tails form the core of the thick filaments with the globular heads exposed- Myosin globular head has 2 binding siteso Binding site for actino Binding site for ATP- In addition, the myosin globular heads contain the enzyme ATPase - ATPase hydrolyzes ATP into ADP and an inorganic phosphate Thin Filaments- Composed of three different proteins o Structural proteins called actin o Regulatory proteins (troponin and tropomyosin) - Actin forms the structural framework of the thin filament - Actin has a binding site for the myosin globular head - Tropomyosin is a rod-like flexible protein that spiral around the actin and block myosin binding sites on actin when the skeletal muscle is relaxed - Troponin consists of 2 subuitso Troponin T (TnT)- binds to tropomyosino Inhibitor troponin TnI- binds to actin o Troponin C (TnC)- binds ionic calcium - Anchored by disc-like proteins called Z-discs (Z-lines) Myofibril- In a myofibril, the thick and thin filaments are arranged in an alternating pattern which explains the banded or striated appearance of skeletal muscle (same striations appear in cardiac muscle) - The distance between 2 successive Z discs in a myofibril is called a sarcomere - Sarcomeres are arranged end to end through the entire length of my myofibril - The myofibril runs the entire length of the skeletal muscle fibers and the skeletal muscle fibers run the entire length of the skeletal muscle Sarcomeres- The smallest contractile unit in a skeletal muscle hence, sarcomeres are the structural and functional unit of skeletal muscle - Skeletal muscle
View Full Document
Unlocking...