Muscle Contraction Flashcards
what is the sliding filament theory?
-the basic principle of muscle contraction is that myosin and actin filaments slide past each other which therefore reduces the overall length of the sarcomere
what is the structure of the protein myosin?
-long fibrous molecule
-has small bulbous heads that stick out at intervals
what is the structure of actin which relates to the bulbous heads of myosin?
-actin is thinner and has small binding sites which the bulbous heads fit into
what are the binding sites like when the muscles are not contracting?
-the actin binding sites are blocked by another ancillary protein which prevents binding
what is the process of muscle contraction up until the myosin bulbous heads are bound with the binging sites on actin?
-an action potential stimulates the muscle fiber as it passes through the t tubules
-causes the calcium ion channels to open on the sarcoplasmic reticulum
-these ions move out of the reticulum down the concentration gradient to the sarcoplasm in muscle cells
-this causes the ancillary protein that normally cover the binding sites to be moved so then the myosin heads can bind to the sites to form bridges
what is the process of muscle contraction after the myosin heads are bound to the actin sites?
-once attached the heads change their angle and rotate to 45 degrees
-this causes the actin filaments to be pulled over the myosin filaments
-an ATP molecule attaches to each myosin head, energy is released through hydrolysis reaction which allows thew head to detach and return to its normal position
-this cycle of attachment of rotation and release repeats around 5 times every seconds
-cycle continues as long as the muscle fibers receives stimulation
what is the name given to the specialized endoplasmic reticulum of muscle cells? what is the name given to their cytoplasm?
-sarcoplasmic reticulum
-sarcoplasm
what happens to the sarcomere, the z band, the H zone and the I band during muscle contraction?
-sarcomere shortens
-z band becomes shorter as does the H zone and the I band
what happens the the A band during contraction of muscles?
-it stays the same length
what are two other types of muscle other than skeletal?
-smooth and cardiac
what is the appearance, distribution and control of skeletal muscle?
-banded multinucleate fibers
-it is attached to bone throughout the bone
-under voluntary control
what is the appearance, distribution and control of smooth muscle?
-uninucleate spindle shaped and are non banded
-line gut and blood vessels, also found in the iris and ciliary body
-involuntary, reflex
what is the appearance, distribution and control of cardiac muscle?
-banded but with inserted discs between cells, important in electrical conduction of the heart
-walls of the heart
-involuntary control and myogenic
