Lecture 6-Molecular basis of contraction Flashcards
What are the three types of muscle?
-skeletal striated(voluntary) -cardiac, striated (involuntary) -smooth, unstriated (involuntary)
What is a muscle fibre?
-single muscle cell, multinucleate
What is a myofibril?
– componenent of the muscle cell, there are many myofibrils in one -90% volume of muscle fibre -cylindrical intracellular organelle -the more there is the greater the the contractile strength and tension -contractile element
What does a myofibril consist of?
-thick and thin filaments
What are thick filaments made of?
-protein myosin
What are thin filaments made of?
-protein actin
Why does skeletal muscle appear striated?
-alternating light and dark bands of actin and myosin = the myofilaments which slightly overlap
What is an A band?
-dark band in muscle -stack of thick filaments and a portion of thin filaments that overlap at both ends of the thick filament
What is the H zone?
-lighter area within the middle of the A band -where the thin filaments don’t reach
What is the I band?
-thin filaments that don’t project into the A band
What is a Z line?
-in the middle of the I band, dense vertical line -flat cytoskeletal disk(protein) connects thin filaments of two adjoining sarcomeres
What is a sarcomere?
- -the area between two Z lines -functional unit of skeletal muscle=smallest unit of a muscle fibre that can contract
What is a functional unit of an organ?
-the smallest unit that can perform the function of that organ
How does a muscle increase in size during growth?
-by adding new sarcomeres
What is a M line?
-proteins that hold the thick filaments together vertically in each stack -vertically down in the A band within the center of the H zone
What is a cross bridge?
-fine cross bridges between thick and thin filaments in the region where they overlap (within the A band)
What is myosin?+structure
-protein, has two subunits each shaped like a golfclub with two heads -the tails intertwined around each other, heads sticking out at one end -tails oriented towards the center of the filament and the heads out -the heads form the cross bridges between the thick and thin filaments
How many and which binding sites do the myosin heads have?
-each head has two binding sites = actin binding site =ATPase binding site
How is myosin linked to the Z line?
-elastic protein titin