Muscular System Flashcards
this tissue is composed of cells that optimize the universal cell property of contractility
muscle tissue
____ contains bundles of very long, multi-nucleated cells with cross-striations. Their contraction is quick, forceful, and usually under voluntary control
skeletal muscle
____ also has cross-striations and is composed of elongated, often branched cells bound to one another at structures called intercalated discs which are unique to this. Contraction is involuntary, vigorous, and rhythmic.
Cardiac muscle
____ consists of collections of fusiform
cells which lack striations and have slow, involuntary
contractions.
smooth muscle
as muscular tissue contracts, it produces heat in a process known as?
thermogenesis
what do you call the involuntary contractions of skeletal muscles that can increase the rate of heat production?
shivering
a property of both muscle and nerve cells wherein it is the ability to respond to a certain stimuli by producing electrical signals called action potentials
electrical excitability
property of muscle wherein it is the ability of muscular tissue to contract forcefully when stimulated by an action potential
contractility
property of muscular tissue wherein it is the ability of the tissue to stretch within limits without being damaged
extensibility
property of muscular tissue classified as the ability of muscular tissue to return to its original strength and shape after contraction or extension
elasticity
In all types of muscle, contraction is caused by the ____. The forces necessary for sliding are generated by other proteins affecting the weak interactions in the bridges the thick and thin filaments.
sliding interaction of actin and myosin filaments
what do you call the cytoplasm of muscle cells (fibers) that consists of glycogen for synthesis of ATP and Myoglobin?
sarcoplasm
what do you call the smooth ER of the muscle cell?
sarcoplasmic reticulum
what do you call the muscle cell membrane?
sarcolemma
what do you call the contractile unit in a striated muscle fiber (cell) that extends from one Z-disc to the next Z-disc
Sarcomere
Skeletal (or striated) muscle consists of muscle fibers,
which are long, cylindrical multinucleated cells with diameters of ____?
10-100 μm
Elongated nuclei are found ____ just under the sarcolemma, a characteristic nuclear location unique to skeletal muscle fibers/cells.
peripherally
muscle cell nuclei are found on the periphery & they’re elongated
Elongated nuclei are found ____ just under the sarcolemma, a characteristic nuclear location unique to skeletal muscle fibers/cells.
peripherally
muscle cell nucleus are found on the periphery & they’re elongated
A small population of reserve progenitor cells called muscle ____ remains adjacent to most fibers of differentiated skeletal muscle.
satellite cells
these satellite cells proliferate and produce new muscle fibers following muscle injury
what do you call the thin connective tissue that immediately surrounds each fascicle?
perimysium
fascicle = bundle of muscle fibers
within fascicles, a very thin, delicate layer of reticular
fibers and scattered fibroblasts called the ____ surrounds the external lamina of individual muscle fibers
endomysium
what do you call the long cylindrical filament bundles that run parallel to the long axis of the fiber in the sarcoplasm?
myofibrils
what do you call the dark bands on the myrofibrils?
A-bands
_A_nisotropic, or birefringent in polarized light microscopy
the light bands on myofibrils are called?
I bands
_I_sotropic, do not alter polarized light
skeletal muscles begin to differentiate when cells called ____ align and fuse together to make longer multinucleated tubes called myotubes.
myoblasts
what do you call the line that bisects the I band?
Z disc
what do you call the repetitive functional subunit of the contractile apparatus that extends from Z disc to Z disc?
Sarcomere
what do you call the bundle of muscle fiber wrapped in perimysium?
fascicle
this is a long cylindrical cell covered by endomysium and sarcolemma. this also contains myofibrils, peripherally-located nuclei, mitochondria, sarco reticulum, t tubules, and terminal cisternae. what is this?
muscle fiber (or cell)
these are the tiny invaginations of the sarcolemma that penetrate deeply into the sarcoplasm and encircle each myofibril near the aligned A- and I-band boundaries of the sarcomeres, what are they?
Transverse (T) Tubules
what do you call the dilated end sacs of the sarcoplasmic reticulum?
terminal cisternae
these are the threadlike contractile elements within the sarcoplasm of the muscle fibers that extend the entire length of fiber
myofibril
what do you call the contractile proteins within myofibrils?
Myofilaments
Thick filaments - Myosin
Thin filaments - Actin, Tropomyosin, Troponin
what do you call the narrow zone in the center of each A band? It contains thick but not thin filaments.
H zone
Area in which supporting proteins that hold the thick filaments together at the center of the H zone
this bisects the h zone
M line
what are the three kinds of proteins that build myofibrils?
- Contractile Proteins
- Regulatory Proteins
- Structural Proteins
A kind of protein from the myofibrils that generate force during contraction
contractile proteins
A kind of protein from the myofibrils that help switch the contraction process on and off
Regulatory proteins
These proteins from the myofibrils keep the thick and thin filaments in the proper alignment
Structural Proteins
A contractile protein classified as the main component of thick filaments
Myosin
A contractile protein classified as the main component of thin filaments that is twisted into a helix.
On each of this protein is a binding site for the myosin head
actin
A regulatory protien that covers myosin-binding sites on actin molecules when skeletal muscle fiber is relaxed, thereby preventing myosin from binding to actin
Tropomyosin
Protein complex that is the binding site of calcium ions, allowing the change of shape that moves tropomyosin away from the myosin-binding sites on actin
Troponin
Part of the Troponin complex wherein this subunit attaches to tropomyosin
Troponin T
Tn_T_ T –> troponin to tropomyosin
Part of the troponin complex characterized as the subunit which binds Ca2+ ions
Troponin C
Tn_C_ –> troponin to calcium
part of the troponin complex that regulates or inhibits the actin-myosin interaction
Troponin I
Tn_I_ –> troponin to inhibit
what do you call the largest protein in our body with scaffolding and elastic properties which supports the myosin and connects them to the Z disc?
Titin
what do you call the structural protein of Z discs that attaches to actin and titin?
a-actinin
Structural protein that forms the M line of a sarcomere and binds to the titin molecules and connects adjacent myosin to one another
Myomesin
this enzyme catalyzes transfer of phosphate groups from phosphocreatine, a storage form of high-energy phosphate grps to ADP
creatine kinase
A bands only have myosin filaments
True or False
False, they contain both myosin and overlapping portions of thin filaments
I bands consist of the portions of the thin filaments which do not overlap the thick filaments in the A bands, which is why I bands stain more lightly than A bands.
True or False
True
I bands = thin filaments onli, A bands = thick + overlapping thin
In the centermost portion of an A band, a lighter zone corresponds to the region with only the rodlike portions of myosin and no actin
True or False
True
I bands = thin filaments onli, A bands = myosin + overlapping thin; H zone = myosin only
what do you call the smooth ER of the skeletal muscle fibers that contains pumps and other proteins for Ca2+ sequestration and surrounds the myofibrils?
Sarcoplasmic Reticulum
This is a structural inelastic protein that wraps around the entire length of each thin filament.
Anchors thin filaments to Z disc and regulates its length during development
Nebulin
Structural protein that links thin filaments of the sarcomere to integral membrane proteins in the sarcolemma, which are attached in turn to protein in connective tissue matrix that surrounds muscle fibers
Dystrophin
contraction is induced when an action potential arrives at a synapse called?
Neuromuscular Junction
Upon arrival of an action potential along the neuromuscular junction, where will it be transmitted?
It will be transmitted along the T-tubules; then it will travel along the terminal cisternae of the sarcoplasmic reticulum
the travel of action potential from neuromuscular junction to T-tubule to terminal cisternae to sarcoplasmic reticulum will trigger Ca2+ release
what do you call the parallel bundles that contains a long series of sarcomeres?
myofibril
what do you call the condition wherein the actin-myoswin crossbridgres become stable, which accounts for the rigidity of skeletal muscles that occurs as mitochondrial activity stops after death?
Rigor Mortis
Neuromuscular junctions, ____, are specialised chemical synapses formed at the sites where the terminal branches of the axon of a motor neuron contact a target muscle cell.
Motor End Plates (MEPs)
what neurotransmitter is contained in the synaptic vesicles in the axon terminal?
acetylcholine
acetylcholine is released in the NMJ to trigger muscle contraction
the space between the axon and the muscle?
synaptic cleft
what enzyme removes acetylcholine from the synaptic cleft, preventing prolonged contact of the transmitter with its receptors?
Acetylcholinesterase
what do you call the autoimmune disorder that involves circulating antibodies against proteins of acetylcholine receptors?
Myasthenia gravis
Antibody binding to the antigenic sites interferes with acetylcholine activation of their receptors, leading to intermittent periods of skeletal muscle weakness. As the body attempts to correct the condition, junctional folds of sarcolemma with affected receptors are internalized, digested by lysosomes, and replaced by newly formed receptors
Identify the type of muscle
Single multinucleated cells that are cylindrical with diameters of 10-100 um and many cm long and has striations; its nucleus is located peripherally and is adjacent to the sarcolemma
Skeletal muscle
Identify the type of muscle
Aligned cells in branching arrangement that are cylindrical in shape with diameters of 10-20 um and are 50-100 um long and has striations; its nucleus is located centrally
Cardiac muscle
Identify the type of muscle
single, small, and closely packed fusiform cells with diameters of 0.2-10 um and are 50-200 um long with no striations and has its nucleus at the center at the widest part of cell
smooth muscle
Identify the type of muscle
T tubules are located at the center of triads at A-I junctions; Sarcoplasmic reticulum is well-developed with two terminal cisternae per sarcomere in triads with T tubule
Skeletal Muscle
Identify the type of muscle
T tubules are located at the dyads of Z discs; Sarcoplasmic Reticulum is less well-developed, 1 small terminal cisternae per sarcomere in dyads with T tubule
Cardiac muscle
Identify the type of muscle
T tubules are absent, and caveolae may be functionally similar; Sarcoplasmic Reticulum is irregular without distinctive organization
Smooth muscle
Identify the type of skeletal muscle
adapted for slow contractions over long periods without fatigue; plenty of mitochondria & myoglobin, surrounded by many capillaries
slow oxidative muscle
Identify the type of skeletal muscle
fibers that are specialized for rapid, short-term contraction; few mitochondria, capillaries, and myoglobin; depending largely on anaerobic metabolism of glucose
fast glycolytic
due to anaerobic metabolism (glycolysis) from glycogen, these fibers appear white
Identify the type of skeletal muscle
fibers that have physiological and histological intermediate between the two other skeletal muscle fiber types
fast oxidative-glycolytic
Identify the type of muscle
consists of tightly knit bundles of cells interwoven in spiraling layers that provide for a characteristic wave of contraction
cardiac muscle
Identify the type of muscle
found in the heart
cardiac muscle
Identify the type of muscle
tongue, eyes, and arms
skeletal muscle
Identify the type of muscle
blood vessels, digestive & respi tracts, uterus
smooth muscle
encapsulated by modified perimysium with concentric layers of flattened cells and thin muscle fibers called intrafusal fibers
muscle spindle
these type of muscle forms complex junctions between interdigitating processes wherein cells w/in one fiber often branch and join with cells in adjacent fibers
cardiac muscle
what do you call the transverse lines that cross the fibers at irregular intervals where the myocardial cells join?
intercalated discs
Transverse regions of these irregular, steplike discs are composed of many desmosomes and fascia adherens junctions, which together provide strong intercellular adhesion during the cells’ constant contractile activity.
intercalated discs
if the transverse regions of intercalated discs have desmosomes and fascia adherens, the longitudinal regions that run parallel to myofibrils are filled with what?
gap junctions
gap junctions provide ionic continuity between the cells. these regions serve as electrical synapses, promoting rapid impulse conduction through many cardiac cells
True or False
Muscle of the heart ventricles is much thicker than that
of the atria, reflecting its role in pumping blood through the cardiovascular system.
True
The junctions between the terminal cisterns of cardiac muscle and T-tubules typically involve only one structure of each type, forming profiles called ____ rather than triads in TEM sections.
dyads
the most common injury sustained by cardiac muscle is due to what?
ischemia
ischemia = tissue damage due to lack of oxygen when coronary arteries are occluded
fibers of these muscle are elongated, tapering, and unstriated cells and they’re enclosed by an external lamina and a network of type I & III collagen
smooth muscle
muscle type that has an endomysium and perimysium but lacks an epimysium
cardiac muscle
fibers of this muscle type is thickest in the middle and tapers at each end; within each fiber is a single, oval, and centrally-located nucleus
smooth muscle
At the smooth muscle cell surface are numerous small plasmalemma invaginations resembling ____, which in these cells compartmentalize various signaling components
caveolae
instead of troponin and tropomyosin, smooth muscle actin uses what?
calmodulin and Ca2+-sensitive myosin light-chain kinase (MLCK)
True or False
Smooth muscle is capable of regeneration through satellite cells
False
Satellite cells are only present in skeletal muscles; smooth muscles is capable of mitosis to replace the damage tissue (regeneration)
The basal lamina of a muscle fiber is part of which structure?
a. Perimysium
b. Epimysium
c. Fascia
d. Endomysium
e. Sarcoplasmic reticulum
d. Endomysium
With the transmission electron microscope skeletal muscle fibers can be seen to contain structures called triads. What do the two lateral components of a triad represent?
a. Attachment sites for thick myofilaments
b. Sites for calcium sequestration and release
c. Sites for impulse conduction into the fiber
d. Sites for ATP production
e. Sites for synthesis of proteins to be secreted outside the cell
b. Sites for calcium sequestration and release
2 terminal cisternae, 1 transverse tubule
Which characteristic is unique to cardiac muscle?
a. Contain centrally located nuclei
b. Striated
c. Often branched
d. Multinucleated
e. Lack T-tubules
c. often branched
In smooth muscle calcium released by the smooth ER initiates contraction by binding to what protein?
a. Actin
b. Calmodulin
c. Desmin
d. Myosin light chain kinase
e. Tropomyosin
b. Calmodulin
Which feature typifies T-tubules?
a. Evaginations of the sarcoplasmic reticulum
b. Sequester calcium during muscle relaxation, releasing it during contraction
c. Carry depolarization to the muscle fiber interior
d. Overlie the A-I junction in cardiac muscle cells
e. Rich supply of acetylcholine receptors
c. carry over depolarization to the muscle fiber interior
Which characteristic is unique to smooth muscle?
a. T-tubules lie across Z lines
b. Each thick filament is surrounded by six thin filaments
c. Thin filaments attach to dense bodies
d. Cells are multinucleated
e. Cells have centrally located nuclei
c. thin filaments attach to dense bodies
In one type of muscle, numerous gap junctions, desmosomes, and adherens junctions are specifically localized in which structures?
a. Myofilaments
b. Dense bodies
c. Sarcomeres
d. Neuromuscular spindles
e. Intercalated discs
e. Intercalated discs
A man’s body is in rigor mortis. This state of rigor mortis is due to which one of the following?
a. Inhibition of Ca2+ leakage from the extracellular fluid and sarcoplasmic reticulum
b. Enhanced retrieval of Ca2+ by the sarcoplasmic reticulum
c. Failure to disengage tropomyosin and troponin from the myosin active sites
d. Absence of ATP preventing detachment of the myosin heads from actin
e. Increased lactic acid production
d. Absense of ATP preventing detachment of the myosin heads from actin
A 5-year-old boy sustains a small tear in his gastrocnemius muscle when he is involved in a bicycle accident. Regeneration of the muscle will occur through which of the following mechanisms?
a. Dedifferentiation of muscle cells into myoblasts
b. Differentiation of muscle satellite cells
c. Fusion of damaged myofibers to form new myotubes
d. Hyperplasia of existing muscle fibers
e. Differentiation of fibroblasts to form myoblasts
b. Differentiation of muscle satellite cells
In one of his biceps muscle fibers at rest, the length of the I band is 1.0 μm and the A band is 1.5 μm. Contraction of that muscle fiber results in a 10% shortening of the length of the sarcomere. What is
the length of the A band after the shortening produced by muscle contraction?
a. 1.50 μm
b. 1.35 μm
c. 1.00 μm
d. 1.90 μm
e. 0.45 μm
a. 1.50 um
A-band = dark part of the sarcomere, has myosin & thin filament overlaps; remember that thin filaments move toward the center (m-line)
In one of his biceps muscle fibers at rest, the length of the I band is 1.0 μm and the A band is 1.5 μm. Contraction of that muscle fiber results in a 10% shortening of the length of the sarcomere. What is
the length of the A band after the shortening produced by muscle contraction?
a. 1.50 μm
b. 1.35 μm
c. 1.00 μm
d. 1.90 μm
e. 0.45 μm
a. 1.50 um
A-band = dark part of the sarcomere, has myosin & thin filament overlaps; remember that thin filaments move toward the center (m-line)
