Lecture Exam 3 SLOs Flashcards
Describe the relationships of the structure and function of a tendon
~ extends from thick muscle and tapers into connective tissue attaching the muscle to the bone
Describe the relationship between the structure and function of the muscle body
~ bulk of muscle; thick for lots of muscle fibers and high contractility for force
Describe the relationship between the structure and function of the epimysium
~ surrounds the entire muscle; large thin sheet of CT protecting enclosed muscle
Describe the relationship between the structure and function of the fascicle
~ bundle of muscle fibers/cells; encloses muscle fibers, group multiple muscle fibers together for high contractility
Describe the relationship between the structure and function of the perimysium
~ CT surrounding the fascicle; ct is strong and endures stretching and shortening, fascicles contain muscle fibers with contractile organelles inside
Describe the relationship between the structure and function of the individual muscle fiber/cell.
~ elongated and cylindrical in shape, multinucleated to allow for transmission of signals along the entire length of the muscle
Describe the relationship between the structure and function of the endomysium
~ CT surrounding individual muscle fibers
Describe the relationship between the structure and function of the myofibrils
~ inside individual muscle fiber which is surrounded by endomysium, LOTS of them throughout the muscle body, run the entire length of the muscle to allow for unison contraction and shortening of the muscle upon pulling of myosin filaments on actin filaments
Where are the nuclei located in the muscle fibers?
~ get pushed to the periphery of the myocyte due to abundance of myofibrils within myofibers
Describe the importance of the sarcoplasmic reticulum
~ endoplasmic reticulum of muscle tissue; surrounds myofibrils like the foam netting surrounding delicate fruits, contains terminal cisternae (enlarged regions at the ends of the SR that make contact with T tubules, store Ca)
What is a triad?
~ terminal cisternae, T tubule (invagination of sarcolemma), terminal cisternae
Define sarcomere
~ functional unit of organization of myofibril and its overlapping arrangement of actin and myosin, hence the striated appearance of skeletal muscle
-from z line to z line
What is the A band? What does it do during muscle contraction?
~ entire length of myosin regardless of overlap with actin
~ remains the same
What is the I band? What does it do during muscle contraction?
~ length of only the thin actin filament, NO overlap with thick
~ shortens during contraction
What is the H zone? What do during muscle contraction?
~ length of only the thick myosin filament, NO overlap with thin filaments
~ shortens during muscle contraction
Why is the I band the lightest portion of the electro micrograph? Why is the A band the darkest? Why is the H zone darker than the I band?
~ thin filaments with no overlap with thick, more light can pass through them
~ A band is overlapping with thick and thin filaments, less light passes through
~ H zone is only thick filament, but thicker than I band so appears darker, less light passes
Contraction is also known as? Muscles always push or pull?
~shortening
~ PULL toward M line
Describe the formation of actin
~ G actin with myosin binding sites form F actin, then double helical actin strands (2 actin strands in double helix)
Describe the functions of troponin and tropomyosin
~ regulatory proteins; do not directly participate in muscle contraction
~ tropomyosin covers myosin binding sites on actin blocking contraction, troponin is attached to tropomyosin, Ca from SR binds to troponin, troponin undergoes a conformational change, causing tropomyosin to roll off myosin binding sites on actin so myosin can grab on and muscle contraction can proceed
Describe the relationship between the structure and function of myosin
~globular and fibrous portions
~ globular heads have actin binding sites and ATPase for the breakdown of ATP during muscle contraction
~ hundreds of myosin proteins, larger than actin
~ heads are staggered along the myosin allowing for continual force production
~ bare zone~ middle portion without any heads, typically associated with the H zone
Describe the function of titin fibers
~ anchors myosin, extends from z line (like a spring allows uncoil and recoil during contraction)
Describe the sequence of events that occurs in the cross-bridge cycle and relate this
sequence to the sliding filament model of muscle contraction
~ myosin heads grab onto myosin binding sites of actin and pull continually down the actin filament as the musxle fibers shorten
~ A band stays the same, H zone shortens, I band shortens
~ size of the protein doesn’t change but the overlap does, hence A band doesn’t change bc length of myosin regardless of overlap, but thin filaments get pulled closer to the M line, boundaries of sarcomere shorten
