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outline 11

Comparative Physiology- Renner Lecture 11

another name for skeletal muscle fibers myofibrils
plasma membrane of skeletal muscles is called the _______________, the cytoplasm is the ____________________ and the endoplasmic reticulum is the ___________________ sarcolemma, sarcoplasm, sarcoplasmic reticulum
T/F most muscle fibers are the same length FALSE. muscle fibers vary in length
what is the usual diameter range for muscle fibers? few microns to 100 microns
shortest and longest muscle fiber examples shortest: insect flight wing, longest: giraffee
what has to happen to a muscle in order for it to function? what induces a fiber to function muscle fibers function by shortening to create tension in response to a stimulation from a motor neuron
what are muscles usually connected to? why? any exclusions? usually attached to one or more joints through cartelagenous structures called tendons, or aponeurosis which is just a sheet of connective tissue. Some exceptions to that are eye muscles, orifices (sphinctors), and upper esophagus
the repeated contractile units that form a myofibril are called __________________ sarcomeres
myofibrils are arranged in a __________________ and in a single myofibril the sarcomeres are arranged in a __________________ parallel, series
what separates sarcomeres from each other? z line forms the boundary of sarcomeres
given the structure of a sarcomere, what unit form the boundary, contains alpha actinin and contains the transverse tubule Z-line
given the structure of a sarcomere, what structure forms a gap between end of actin filaments? H zone
given the structure of a sarcomere, in what region does myosin not have a globular head? Pseudo H-zone, it is also the center of the H zone
given the structure of a sarcomere, what region has myosin heads in a parallel? A band
what does the A in A band stand for? what does that indicate? Means Anisotrophic, meaning it polarizes light-dark in color
what does alpha actinin do? anchors actin to the z line
given the structure of a sarcomere, what region contains actin filaments and shorten during contractions ? I band
what does the I in I band stand for? what does it mean? Isotrophic: does not polarize light. appears lighter in electron micrograph
given the structure of a sarcomere, what region contains enzymes? M line
what enzymes are found in the M line of a sarcomere? creatine, phosphatase, and myokinase
what is the role of enzymes in a sarcomere? produce energy when ATP is depleted during anaerobic conditions
each myosin is surrounded by ______________ actin filaments that are shared with surrounding myosins. so that each actin surrounds ____________ myosin filaments six, three
what forms cross bridges? projections that arise at regular intervals from myosin
what is the myosin filament composed of? two heavy chains that wind around each other at the end. an unwound portion that forms globular head associated with it are 2 lighter protein chains that have ATPase activity, actin binding site and flexible portion aka neck
the thick filament has approx ____________ myosin molecules 400
where are globular heads positioned in the thick filament of myosin? globular head protrude from the thick filament
functions of proteins associated with thick filament of myosin? 1. C protein- keeps thick myofilaments together 2. proteins at the M line- contain enzymes for energy, is binding point between myosin molecules
functions of proteins associated with thin filaments of myosin? 1. G and F actin- G: binding site for globular head, forms F actin (2 chain helix 2. tropomyosin- in groove of F actin, makes contact with 1 strand. 3. troponin- C site-Ca2+ binding site, I-inhibit head from binding actin, T- bind tropomyosin->troponin
tropomyosin is made up of __________polypeptide chains and troponin is made up of _______________ two, three
length of each strand of tropomyosin is enough to cover ___________ g actin subunits seven
C site on troponin can bind up to how many Ca2+ ions? four
function of troponin I? inhibits globular head from binding actin
function of troponin T? binds tropomyosin to troponin
what are the condition in a skeletal muscle fiber at rest? 1. Ca2+ concentrations are low 2. ATP concentrations are high 3. globular myosin head is oriented close to the filament
what happens following a stimulation of a motor neuron AP in skeletal muscle fiber? 1. Ach releases into synapse 2. Ach binds to nicotinic receptors stimulating end plate potential-local potential analogous to EPSP 3. if signal is sufficient to depolarize membrane of muscle to threshold, then muscle AP results
What happens in neuromuscular junctions to result in motor neuron AP? 1. open VgCa2+ channel in presynaptic terminal 2. Ca2+ influx stimulates vesicular docking & exocytosis 3. Ach releases into synapse 4. Ach binds to nicotinic receptors-> Increase Na+/K+ perm.->depolarize 5. endplate-> sum to threshold-->AP results
where does most docked Acetylcholine go? most is catabolized by Acetylcholinestrase, ~10% bind to nicotinic receptors
what happens as a result of muscle AP? 1.increase Ca sarcoplasm 2.Ca binds to C site troponin-conformational change->move tropomyosin 3.tropomyosin moves inward between F actins->F myosin binding site exposed 4.ATP on Myosin binds it to actin perpend 5. power stroke 6.ATP releases myosin head
what causes myosin head to bind to actin? ATP on myosin head is hydrolyzed, with presence of ATPase, that charges the myosin head allowing myosin to bind to actin-myosin binding site perpendicularly
What is the power stroke? movement of thin actin filament after being attached to myosin head. Myosin head tilts at approximately 45 degrees. The release of ADP and Pi from hydrolyzing ATP causes it.
how is actin released from myosin head? what happens if that doesn't happen? new ATP binds to myosin head causing it to detach from actin. If it doesn't happen, body goes stiff-> rigor mortis bc there is no ATP
the cycle of muscle contraction happens _______________ times per min. Each cycle is _____________msec with _____________nm of movement 50-100, 10, 10
rigor mortis is followed by ________________ putrefaction
Created by: rusulali97



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