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Physio Exam 4 skeletal muscle
Terms in this set (96)
what are the cells of skeletal muscle called?
what is the cell membrane of each skeletal muscle called?
what is the component of skeletal muscle cells that contract?
what are myofibrils composed of?
is myosin a thick or thin filament?
is actin a thick or thin filament?
thin filaments of myofibrils are composed of what three types of proteins?
actin, troppmyosin, and troponin
what is the protein of thin filaments that is rope like?
What is the piece of Troponin (Tn) that binds to 4 calcium?
what piece of troponin binds to tropomyosin?
when the muscle is relaxed, what protein of thin filaments covers the active sites of actin?
tropomyosin (TnI also helps cover the active sites)
what is the space between z discs called?
on a sarcomere, what is the space that only contains thick filament?
on a sarcomere, what is the space with only thin filament?
on a sarcomere, what is the area called that contains thick and thin filament, including the H band?
Duschenne disease is characterized by the lack of what cytoskeletal protein?
what is the cytoskeletal protein that is an actin-binding protein that anchors the entire myofibrillar array to the cell membrane?
what is the cytoskeletal protein that extends from the M lines to the z-discs. Part of this molecule passes through the thick filament, the rest of the molecule which is elastic or spring-like is anchored to the z disc? (AKA this protein attaches thick filament to the z-disc)
what cytoskeletal protein is associated with thin filaments. A single protein molecule extends from one end of the thin filament to the other?
what cytoskeletal protein anchors the thin filaments to the z-disc?
what two cytoskeletal proteins are involved with attaching thin filaments to the z-disc?
nebulin and alpha-actinin
what event occurs when the head of myosin attaches to actin?
What is the concentration of Ca2+ levels at rest?
cross bridges cannot occur when Ca levels are below what concentration?
The endoplasmic reticulum is well developed in skeletal muscle. In muscle cells it is the sarcoplasmic reticulum! What structure of muscle cells does the sarcoplasmic reticulum cover?
what structure, an extension of the sarcolemma inside the muscle cell, is wrapped by sarcoplasmic reticulum on each side which are the terminal cisterna?
what are the extensions of the sarcoplasmic reticulum that extend on either side of T-tubules, creating a triad?
in what structure of muscle cells, is there lots of Ca2+ stored?
sarcoplasmic reticulum (to release the Ca2+, the action potential must be brought to the T-tubule)
depolarization must come to T-tubule to release Ca2+. What is the voltage-gated Ca release channel on the T-tubule?
DHP (Dihydropyridine- named after the drug that inhibits it; NOTE: Ca influx into the cell through this channel is not required for excitation-contraction coupling)
depolarization must come to T-tubule to release Ca2+. What is the channel ON the terminal cisterna which are mechanically linked to DHP and make them open?
ryanodine receptors (SR calcium release channel)
where does action potential end in a muscle cell?
T-tubule (this changes DHP conformation which opens ryanodine receptors to release Ca2+)
regarding Ca2+ release by terminal cisterna: What is the Ca-ATPase pump that brings Ca2+ back into terminal cisterna and is the reason why there is very low Ca2+ inside the cell?
Calcium inside the terminal cisterna bind to what protein to keep the Ca2+ inside the cisterna until it is released?
True or False: shortening is required in order for contraction of muscle to occur.
False (can have isometric contraction)
In sliding theory, what filaments slides over which?
thin filament slides over thick filament
what is the shortest length that can be achieved in sliding theory?
length of thick filament
what end of actin filament (negative or positive) is near the z-disc?
what end of actin filament (negative or positive is near the center of the sarcomere?
in terms of nucleotide attachment, what is attached when the head of mysoin attaches to actin closer to positive side (power stroke!!)
ADP (ADP is bound, this step happens after Pi gets detached from myosin head)
during slide theory, about how far does the myosin head move when doing a power stroke?
in sliding theory, what gets released from myosin head which results in the head pivoting toward the negative end of actin, thus pulling the thin filament toward the center?
when does rigor occur?
when myosin head attaches to actin active site
what results when there is no ATP availabile and mysoin heads cannot detach from actin?
Can ATP cause relaxation?
no (ATO can only remove one head from actin, does not cause relaxation. Only way to relax muscle is to use calcium pump to remove calcium)
what is the only way to cause skeletal muscle relaxation?
use calcium pump to remove calcium (starts working as soon as Ca2+ is released)
why is relaxation of skeletal muscle also an active event?
you have to spend ATP to make calcium pump work to remove calcium
what is the resting membrane potential for muscle fiber?
what is the period of time in which the cell membrane is depolarizing but Ca2+ is not released yet to create contraction?
latent period (time between the stimulus and the contraction)
what is the idea called of one contraction and one relaxation of skeletal muscle?
what occurs when all the actin and myosin are recruited inside the muscle cell and maximum tension is reached and has small periods of relaxation?
what occurs when all the actin and myosin are recruited inside the muscle cell and maximum tension is reached and has no periods of relaxation?
what term describes the length of muscle before it goes into contraction?
what occurs when preload is held constant?
isometric contraction (doesnt shorten during contraction)
what contraction occurs when there is contraction but no shortening?
what contraction occurs when afterload is kept constant?
what term is described as the 'load' or resistance the muscle needs to overcome?
The lengths of sarcomeres are fixed. approx. how long?
2-2.5 micro meters
what type of tension of sarcomeres is produced during stretching of the muscle?
sarcomeres: when does maximum tension occur?
sarcomeres: what is the combination of active tension plus passive tension called?
regarding force-velocity relationship: when is Vmax achieved? (aka fastest speed in which shortening can occur)
when there is no resistance/load
what is maximum oxygen uptake (VO2 max) also called?
aerobic capacity (VO2 max)
what determines whether a given exercise is light, moderate or heavy for a given person?
VO2 max (maximum rate of oxygen consumption) and lactate threshold
what is the high end of VO2 max, can be this for athletes?
what is the unit for maximum rate of oxygen consumption?
what is lactate threshold also called?
at about what percent of VO2 maximum does lactic acid start accumulating?
what type of exercise occurs above the lactate threshold?
what type of exercise occurs just below the lactate threshold?
where do muscles get their energy at rest and for mild exercise?
from the aerobic respiration of fatty acids
where do muscles get their energy for moderate exercise?
where do muscles get their energy for heavy exercise?
As exercise intensity and duration increase, what channels are inserted into the sarcolemma to allow more glucose into muscle cells?
During intense exercise, what pools give phosphate to ADP to make ATP?
creatine phosphate pool ( CP pool is 5x size of ATP pool>>> DIRECT PHOSPHORYLATION)
What are the two sources of oxygen for the muscles?
myoglobin in muscle fibers, hemoglobin (Hb) in RBCs
what is the protein inside muscle cells that carry oxygen?
what quick source of energy for muscle is produced by the liver, kidneys and a small amount can be obtained by eating meat and fish?
what supplement do some athletes take that increase muscle phosphocreatine by 15-40%?
The conversion of lactic acid from muscles to pyruvic acid requires what two things?
ATP and O2
what describes the phenomenon in which when exercise stops, the rate of oxygen uptake does not immediately return to pre-exercise levels?
oxygen debt (need to give O2 back to myoglobulin)
what seem to be important factors in the onset of fatigue?
metabolic byproducts seem to be important factors in the onset of fatigue. What lowers intracellular pH which interferes with Ca2+ transport and inhibit actin-myosin interaction?
accumulation of lactic acid
metabolic byproducts seem to be important factors in the onset of fatigue. The accumulation of what product , derived from the breakdown of CP can inhibit SR Ca2+ release and actin-myosin interaction?
metabolic byproducts seem to be important factors in the onset of fatigue. What component of APs can contribute to muscle fatigue, especially during sustained maximal muscle contraction?
K+ efflux during AP
what two thin filament proteins do smooth muscle cells lack?
troponin and tropomyosin
Smooth muscle thin filaments do not have troponin and tropomyosin. What other two proteins do they have?
calponin and caldesmon
what effect do thin filament proteins of smooth muscle, calponin and caldesmon have on the head of myosin?
inhibitory (they prevent ATPase activity at the head of myosin)
instead of z-discs, what do smooth muscle cells have?
In smooth muscle cells, what are three ways that Ca2+ can get into the cell?
voltage-gated Ca2+ channels, IP3-gated Ca2+ channels and Ligand-gated Ca2+ channels
Smooth muscle cells: When Ca2+ goes up inside the cell, attaches to calmodulin, making Ca2+-calmodulin complex, which activates what protein by removing the Pi off it?
In smooth muscle cells, what must happen to the head of myosin in order for it to be able to attach to actin?
phosphorylation (active MLCK phosphorylates head of myosin)
what is the head of myosin called in smooth muscle cells?
myosin light chain
When Ca2+ goes up inside smooth muscle cell, creates Ca2+-calmodulin complex. What are two actions of this complex?
phosphorylates MLCK (activating it) and phosphorylates calponin and caldesmon (removing their inhibitory effect on the myosin light chain)
in smooth muscle cells, what greatly increases the ATPase activity of the myosin light chain?
phosphorylation (by active MLCK)
there are 3 ways relaxation of smooth muscle is achieved. what enzyme takes phosphate off of myosin chain which stops contraction?
myosin phosphotase (must be activated by cGMP in order to do this)
there are 3 ways relaxation of smooth muscle is achieved. Stimulation of what receptors increases cAMP, which activates phosphorylase, adding phosphate to MLCL, inactivating MLCK?
beta 2 receptors
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