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66 Cards in this Set
- Front
- Back
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Define sarcolemma.
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the cell membrane of muscle cells.
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Hyperplasia can only occur in which type(s) of muscle?
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Smooth muscle.
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Name the connective tissue that separates muscle fibers.
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Endomysium
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Name the connective tissue that surrounds each bundle of muscle fibers (in skeletal muscle).
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Perimysium
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Name the dense connective tissue that surrounds the entire muscle.
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Epimysium
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What is the length of an myosin thick filament?
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1.6 microns
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What is the length of an actin thin filament?
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1 micron
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What is the major protein of the M line? Name one more (bonus).
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creatine kinase; myomesin
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What does creatine kinase do?
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catalyze transfer of phosphate group from phosphocreatine to ADP--supplying ATP for muscle contraction
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What protein anchors the actin filaments to the Z-line?
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alpha-actinin
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What does desmin do?
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attaches z-lines together laterally (keeps the myofibrils next to each other!)
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What molecule runs alongside actin monomers?
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tropomyosin
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What are the regulatory units of tropomyosin (name and function)?
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TnT- binds troponin to tropomyosin
TnC- binds calcium ions TnI- inhibits actin-myosin interaction |
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In skeletal muscle, what makes up a triad and what do they do?
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A triad consists of a T-tubule and two lateral portions of sarcoplasmic reticulum; at the triad, depolarization of the sarcolemma-derived T tubules is transmitted to the sarcoplasmic reticulum membrane
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What do T tubules do?
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they help provide a uniform contraction of skeletal muscles
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What is the function of the sarcoplasmic reticulum?
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It regulates calcium flow to the muscle, which is necessary for contraction (making calcium available) and relaxation (taking calcium away)
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T or F. During contraction, only thick myosin filaments retain their original length, but not actin.
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F. Both thick and thin filaments retain their original length.
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What is the sliding filament hypothesis?
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During contraction, both thin and thick filaments remain same length, there's only an increase in the amount of overlap between the filaments.
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Type I Fiber --- fast or slow twitch? Red or White?
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slow; continuous contraction; red
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Type II Fiber -- continuous contraction or rapid discontinuous contraction Red or White?
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rapid discontinuous contraction; white
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Which muscle types exhibit cross-striations?
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skeletal and cardiac
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Describe the nuclei of each muscle type (number/location)
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skeletal- many, peripheral
cardiac - one to two, central smooth - one, central |
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Name the junctional complexes located in cardiac muscle.
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adherent junctions (transverse), desmosomes (transverse), gap junctions (lateral)
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Are neuromuscular junctions found in cardiac muscle?
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No.
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What is a diad and in which type of muscle are they typically found?
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Diad- one T tubule and one SR cisterna
found in cardiac muscles |
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40% of cardiac muscle cytoplasm contains what structures? What does this tell you about this muscle type?
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mitochondria; cardiac muscles have need for continuous aerobic metabolism
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Lipofuscin is found in what muscle type and what is it useful for?
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cardiac muscle; useful for determining age
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Atrial muscles contain what endocrine hormone and what is its function?
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atrial natriuretic factor (ANF)--- acts on kidneys to cause sodium and water loss (helps you pee better)
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How are each type of muscle capable of regeneration?
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skeletal - satellite cells
cardiac- cardiac stem cells from bone marrow smooth - mitosis |
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Is tropomyosin complex present in smooth or cardiac muscle?
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No.
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What are the two varieties of smooth muscle?
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Unitary smooth muscle and multi-unit smooth muscle
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Describe and give an example of unitary smooth muscle vs. multi-unit smooth muscle.
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Unitary smooth muscle- smooth myofibers joined by gap junctions to act as one (ie. bladder)
Multi-unit smooth muscle- groups of myofibers each with independent control (ie. inside the eye--focusing of the pupil) |
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T or F. Every cell which contracts is going to have a basement membrane/basal lamina.
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T.
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Name other cells with basement membranes.
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Epithelial cells, adipocytes, endothelial cells
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Smooth muscle has what two intermediate filaments?
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desmin/vimentin (smooth muscle around blood vessels)
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Where is smooth muscle found in the body?
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lines all vessels (arteries/veins); along entire gut; along ureters; in the eye
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Name three non-muscle cells that also contract.
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Myoepithelial cells; myofibroblast; pericyte
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How are smooth muscles innervated/linked?
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gap junctions
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Lots of RER (containing soluble protein for export) is found in what muscle type? Explain the presence of these.
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Smooth muscle; its highly synthetic and responsible for secretion of extensive extracellular matrix (like fibroblasts)
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What other cell type (besides cardiac muscle cells) has an endocrine function?
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Adipocytes release leptin.
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Which muscle tissue has the possibility of stem cell activation/regeneration?
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cardiac muscle
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What are the approximate diameters of each type of myofiber?
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skeletal = 100 microns
cardiac = 30 microns smooth = 10 microns |
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What determines skeletal muscle subtypes (Types I and II)?
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type of motor neuron
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For skeletal muscles, what is neuron:myofiber ratio for precise contractions (ie. extra-ocular muscles)? For posture muscles?
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extra-ocular = 1:1
postural muscles = 1:170 |
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In cardiac muscles, why do the central nuclei have surrounding halos?
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Due to extracted lipid, glycogen and absent myofibrils from fixation
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How can you get hypertrophy in cardiac muscles?
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pathologic hypertension or well-trained athletes
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There are no motor units in cardiac muscle. Why?
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modulated by autonomic nervous system by paracrine secretion to one pace setter region
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Which type of muscle has the corkscrew configuration after contraction?
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smooth muscle
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During contraction, which two bands decrease in size and what increases in size?
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I-band and H-band decrease; region of interdigitation increases
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What is the function of M-band proteins?
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keeps myosin from falling down on each other; keeps them apart
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What is nebulin? Which muscle is it unique to?
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measuring protein for actin; skeletal muscle
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Name tissues with Type 3 reticular fiber scaffolding.
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dermis, lymph node, spleen, bone marrow, adipose tissue, all the contractile muscles (skeletal, cardiac, smooth)
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In a cross-section of the M-band what would you expect to see?
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myosin thick filaments with m-band protein holding them apart
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What are the 5 functions of the S1 globular head of myosin?
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1. bind ATP
2. hydrolyze ATP 3. bind myosin light chain 4. bind actin 5. power stroke (cross-bridge and further interdigitation) |
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How are the myosin light chains (on or off; all the time or some of the time) in skeletal muscles? How about cardiac and smooth muscles?
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in skeletal and cardiac, light chains always on; in smooth muscles, you need LIGHT CHAIN KINASE to phosphorylate and activate myosin light chain
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Which muscle type(s) is "side polar" configuration in terms of myosin?
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myosin thick filament of smooth muscle
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Which muscle type(s) is "bipolar" configuration in terms of myosin?
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skeletal and cardiac
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What is titin? What type of muscle is it found in?
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elastic, huge protein that touches end of myosin and goes into the z-line, can recoil; skeletal and cardiac ONLY
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Is there nebulin in smooth muscle?
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no.
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Which end (positive or negative) of actin is at the z-line?
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positive end
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What proteins are found at the z-line?
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1. alpha actinin
2. cap Z-- helps like actin with alpha-actinin (in skeletal and cardiac) 3. amorphin (glue) 4. filamin (glue) 5. desmin 6. nebulin 7. titin |
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Is there cap Z in smooth muscle?
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no.
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List the steps of muscle contraction (at the level of troponin) in skeletal muscle.
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- calcium binds TnC
- TnI changes conformation, revealing of S1 binding sites to actin - contraction |
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T or F. All muscle types have tropomyosin. But in smooth muscle there's no troponin T, C, and I.
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T.
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What replaces troponin in smooth muscle?
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caldesmin
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List steps in smooth muscle contraction.
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- calcium released from SR vesicles
- calcium binds, activates calmodulin - calmodulin activates myosin light chain kinase which phosphorylates myosin light chain (activates S1 head) - calmodulin ALSO binds calmodulin (insoluble) which is actin bound, causing caldesmin to become soluble, dissociate and allows tropomyosin to uncover myosin s1 binding site on actin |
