Muscle flashcards
From Iusmphysiology
a fasiculus is a bundle of; muscle fibers (cells)
three layers of connective tissue in muscles and location; endomesium around a fasiculus, permesium around and in a whole muscle, and the epimesium around the whole muscle
three aspects of striation; parallel contractile apparatus, parallel myofibrils, parallel arrangement of myofibers (cells)
skeletal muscle is large, what's the diameter?; 90 microns
define "trained behavior"; reflex arcs that are somewhere between voluntary and involuntary and may have to be relearned after being bedridden
number and location of cardiac nuclei; 1 or 2, centrally located
which muscle cells have interacalated disks?; cardiac myocytes
name 2 fxns and 2 mechanical properties of intercalated disks; mechanical connection, chemical connection, desmosomes, gap junctions
this muscle tissue is under "myogenic control"; cardiac muscle
what difference between smooth muscle and skeletal / cardiac muscle cause smooth muscle to NOT have striation?; the disorganization of the proteins that attach the contractile apparatus to the cytoskeleton
smooth muscle: number, location, size of nucleus; single, centrally located, large (because of contraction and synthesis)
this type of muscle is found in all hollow organs except the heart; smooth muscle
size of smooth muscle cells (microns); 2 to 7 microns
does all smooth muscle have gap junctions?; no, only some
can smooth muscle undergo hypertrophy, hyperplasia, or both?; both
many myofibrils make up one; myofiber (muscle cell)
t tubules are invaginations of...; the sarcolemma
a sarcomere is defined as running form one...; z line to the next z line
what is happening at the z line?; the thin filaments are attaching to a common protein structure
the z line is the thin filamentas the ...; m line is the thick filaments
how many m lines in one sarcomere?; 1, in the center with thick filaments radiating outward toward the framing z lines
Describe the H line; the less dense area around the M line
define I bands, do they change with contraction?; the area of the sarcomere where thin and thick filaments do not overlap, change in length with contraction
define A bands, do they change with contraction?; the area of the sarcomere that contain thick filament (whether or not they over lap with thin filaments), does not change in length with contracton
around what point to I bands center?; z lines
name the changes in the sarcomere during contraction (ZHIAM); Z line distance shortens, H line shortens, I band shortens, A bands are unchanged, M line remains unchanged
actin forms what structure in thin filaments; double helix of 7 g-actins per half-turn
tropomyosin : actin and troponin : actin in thin filaments; 1:7
three subunits of troponin and their function; troponin I (inhibitory), troponin T (associates with tropomyosin), troponin C (binds Ca)
three proteins that make thin filaments and their functions; actin (binding site for myosin), troponin (, tropomyosin
myosin forms what structure in the thick filament; double helix
actin and myosin serve similar roles in what who sarcomere structures; thin and thick filaments
myosin has how many subunits? what are their structures like?; 6: 2 heavy chains (globular heads + tails) and 4 light chains
where on the myosin heavy chains do myosin light chains associate; the neck
which type of muscle is evolutionary oldest? what was it's original function?; smooth muscle, cardiovascular system regulation
the four light myosin chains fall into two categories (name, size, function); "essential", 17 kda, regulation and "regulatory", 20 kda, vestigial
mysoin fibers of thick filaments have polarity. why?; heavy chains arrange themselves with heads in one direction and tails in the other
what is the name of the currently accepted understanding of how the contractile apparatus works?; sliding filament theory
what are sarcoplasmic reticulum cisternae? where are they located?; they store Ca++, at the junction between T tubules and the sarcoplasmic reticulum
what are the two receptors and their locations at the T tubule-sarcoplasmic reticulum junction?; dihydropurine on the cell membrane and ryanidine on the cisternae
how does an AP go from tubule to Ca release; AP travels down the T tubule, causes change of conformation of dihydropurine foot which causes change of conformation of the ryanidine receptor which opens to let Ca into the cytoplasm
which subunit of the thin filament binds Ca? how many does it bind?; troponin, four
what causes tropomyosin to change locations on actin?; the conformational change of troponin when bound to Ca
why is skeletal muscle activation called a "dis-inhibition"?; because the myosin has ADP and Pi bound and is ready to bind to actin in the resting state it is just waiting for the inhibitory molecule (tropomyosin) to get out of the way
describe the cross-bridge cycle from when tropomyosin moves; myosin binds actin, Pi released, 45 degree movement, ADP released, 45 degree movement, ATP bound, actin released, myosin "relaxes" to cocked position, ATP burned....
where are ATP-dependent Ca pumps located?; on the cell membrane, in the "longitudinal zone" between T tubules
define motor unit summation; the recruitment of additional motor units to increase force
define mechanical-temporal summation; when APs come at such high frequency that the twitch before hasn't relaxed there is a summation that can generate work
There are three modes of muscle functioning (name, ATP state); incomplete tetany (enough ATP to allow for fluctuation between relaxation and contraction), muscle fatigue (reversible deficiency of ATP such that muscles can still relax), muscle contracture (depletion of ATP such that muscles cannot relax)
y axis of muscle transducer force-length curves; length, with shorter being upward on the plot.
define "passive length tension curve"; the plotting of length (x) versus tension (y) as a tissue is passively stretched (that is, no contraction is stimulated)
what structure interferes with force production when the sarcomere is very short?; the thick filaments bump in to one another
what is the optimal sarcomere length?; 2.5 microns
velocity is the slope of the length-tension curve. describe the position of the muscle when velocities are high; the muscle would be in very short or very long positions (as would the sarcomeres)
at what point is power maximized in muscle use; when the muscle is applying 1/3 it's maximum force
explain the sources of energy in muscle as hard work is continued; creatine phosphate (phosphate onto ADP), then glucose (via ETC), then glucose via glycolysis
what is oxygen debt?; our body's need for oxygen even after we stop hard exercise in order to put everything back to resting position (put the phosphate back onto creatine phospate, for example)
what difference in cardiac and skeletal muscle makes them good partners when hard exercise occurs?; skeletal muscle uses glucose and generates lactic acid while the heart burns lactic acid and lipids
smooth muscle contractile apparati attach to these two types of attachments; dense plaques (on the membrane) and dense bodies (in the cytoplasm)
IFs serve two functions in smooth muscle cell; provide a mesh against which the apparatus can push and pull and help restore cell to original shape
smooth muscle can be activated by four different types of stimuli; neurogenic stimuli, hormone / locally produced stimuli, membrane potential changes, mechanical stimuli, environmental changes (temp, pH, etc.)
explain what happens when a NT arrives at a smooth muscle receptor; PIP2 is split into IP3 and DAG, IP3 binds on the sarcoplasmic reticulum, Ca is released, AP occurs, Ca pumps on SR and sarcolemma are turned on, Ca concentration restored
explain how calcium activates contraction in smooth muscle; Ca binds to calmodulin, MLCK is actvated, MLC is phosed, myosin can bind to actin.
between smooth muscle and skeletal contraction, which is myosin-associated and which is actin-associated?; smooth muscle is myosin-associated because myosin is acted upon, whereas skeletal muscle is actin-associated because actin changes (tropomyosin moves)
how does smooth muscle conserve ATP?; by cycling MLCK on and off to take advantage of the lag time between MLCK being off and release of myosin heads from actin
which has a wider optimal range: smooth muscle or skeletal muscle?; smooth muscle
which retains integrity better when stretched?; smooth muscle
which muscle type has more actin filaments: smooth or skeletal? is more power produced?; smooth, twice as many, more power is not produced because of the small size of smooth muscle cells
three physiological reasons men are stronger than women. how much stronger?; more muscle mass, denser muscle mass, longer levers
which types of muscle undergo hypertrophy / hyperplasia?; all undergo hypertrophy, skeletal undergoes hyperplasia upon damage, smooth muscle can more readily undergo hyperplasia especially for damage
which types of muscles have motor end plates? how do the others work?; only skeletal has motor end plates, cardiac and smooth have autonomic innervation that releases NT directly onto the muscle cell
identify the control mode (neurogenic or myogenic) for each type of muscle; skeletal = neurogenic, smooth muscle = neurogenic or myogenic, cardiac muscle = myogenic with neurogenic modification
describe a cardiomyocyte (size, t tubule system, ER, cell structure (2)); 20-30 microns, t-tubule system that doesn't matter
explain the ion channels open during each of the 5 phases of the cardiac AP; 4 = membrane resting, 0 = Na channels open, 1 = K channels open, 2 = Ca channels open, 3 = K channels remain open.
during which phase(s) of the cardiac AP is the absolute refractory period found?; phases 1 and 2
during which phase(s) of the cardiac AP is the relative refractory period found?; phase 3
the initial sharp repolarization of in cardiac APs (phase number, channels responsible, ion direction); phase 1, K channels, K efflux
explain "supranormal excitability"; this refers to the time in phase 3 when the relative refractory period is decreasing such that Na channels can be triggered and when the membrane potential is still repolarizing and so it close to the threshold
what two factors cause the plateau of cardiac APs?; diffusion of Ca and extra long activation of Ca channels
pacemaker cells are leaky to what ion and tight against what ion?; leaky to Na (influxing), tight to K (effluxing)
three differences between pacemaker cardiac APs and normal cardiomyocyte APs; pacemakers have no plateau, have no phase 1 or 2, and phase 4 shows slow but steady gain of positive charge
two mechanisms that generate the "drift" of membrane potential in pacemaker cells; Na leaking into the cell, time-dependent decrease in K+ efflux
explain the 4 phases of the pacemaker AP; 4 = slow increase in potential, 0 = Na and Ca channels open, 2 = Na channels close, K channels open (K efflux matches Ca influx), 3 = K efflux
describe the path of a cardiac AP through the heart (6 entities); SA node, AV node, bundle of His, septum, perkinje fibers, ventricular myocytes
what NT is used at the effector junction of the sympathetic and parasympathetic divisions with the heart?; sympathetic = norepinephrine, parasympathetic = acetylcholine
list the types of muscle from widest to narrowest length of optimal function; smooth muscle, cardiac muscle, skeletal muscle
explain congestive heart failure in terms of cardiac muscle, stretch, and optimal length; as pressure increases, the heart muscle hypertrophies
explain the frank-starling law of the heart; the greater the volume of the blood put into the heart, the greater the volume pumped out. this is a function of cardiomyocyte stretching to optimal length because of the volume
rank the muscle types from slowest to fastest in velocity; smooth < cardiac < skeletal
rank the muscle types form least to most in force; smooth < cardiac < skeletal
name two diseases in which muscle velocity is affected and their mechanims; familial hypertrophic cardiomyopathies (genetic defects: myosin or troponin), thyrotoxic heart syndrome (hypothyroidism causes use of different myosin isoform that is less effective)
