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80 Cards in this Set

  • Front
  • Back
strong, quick, discontinuous voluntary contraction is the activity of which type of muscle?
skeletal muscle
activity of cardiac muscle
strong, quick continuous involuntary contraction
which muscle type has weak, slow involuntary contraction
smooth muscle
skeletal muscle CELLS are referred to as
fibers
general appearance of skeletal muscle cells
roughly cylindrical, elongate and multinucleate ("syncitium")
loose CT surrounding the entire muscle, also called fascia
epimysium
CT which divides the muscle into smaller functional units called muscle fascicles
perimysium
CT which divides the muscle fascicles into individual muscle fibers
endomysium
a bundle of several muscle fibers is called
fascicle
fascicles are surrounded by
perimysium
principle cytoplasmic component of the muscle fiber
myofibrils
myofibrils are composed of serially repeating segments of identical structures known as
sarcomeres
myofibrils are composed of what two myofilaments?
actin and myosin
arrangement/orientation of myosin filaments
antiparallel
myosin filaments are held down at which part of the sarcomere?
M-line
A band
dark band
I band
light band
Z-line
bisect the pale I bands
H band
central zone w/in the A band
M line
marks the center of the H band
what binds myosin at the M line?
myomesin
what is the functional unit of the myofibril?
sarcomere
what are the limits of the sarcomere?
Z line
cell membrane of a muscle fiber
sarcolemma
cytoplasm of a muscle fiber
sarcoplasm
principal role of the sarcoplasmic reticulum
sequester calcium
where are the thousands of nuclei in a skeletal muscle fiber located?
in the periphery of the fiber beneath the sarcolemma
what is the function of glycogen in muscle contraction?
energy store that is mobilized during contraction
where do the invaginations of the T-tubule system occur in skeletal muscle?
at the level of transition between the A and I bands twice in every sarcomere
in skeletal muscle, the association of the T-tubules with the terminal cisternae of the SR form what?
triads
what surrounds the sarcolemma in skeletal muscle?
basal lamina and reticular fibers
cells that are located w/in the basal lamina which can divide and contribute new muscle fiber in response to minor injury
satellite cells
function of satellite cells
they divide and contribute to new muscle fiber following an injury that leaves the basal lamina and satellite cells intact
what replaces large deficits in skeletal muscle?
noncontractile connective tissue
where does the connection between depolarization and muscle contraction occur in skeletal muscle?
at the triad
components of a triad
T-tubule and 2 terminal cisterns
how does a depolarization of a skeletal muscle fiber lead to contraction?
depolarization
SR releases Ca ions sequestered in the terminal cisternae into the sarcoplasm
Ca ion release allows actin and myosin to interact
sarcomeres shorten and muscle contracts
binding of actin and myosin that becomes stabilized when ATP is not available
rigor mortis
how many motor end plates does each skeletal muscle fiber have?
one
one nerve may innervate a hundred muscle fibers in what type of skeletal muscle?
postural
one nerve may innervate as few as three muscle fibers in what type of skeletal muscle?
ocular or digital muscles
where the muscle fiber sarcolemma expands at the neuromuscular junction
junctional folds
autoimmune disease where antibodies directed against Ach receptors on the sarcolemma result in fewer Ach receptors available for binding of Ach released from motor neuron
results in weaker muscle contraction
myesthenia gravis
type of muscle that contracts spontaneously, rhythmically and continuously
cardiac muscle
where does cardiac muscle exist?
in myocardium of the heart and proximal portions of the aorta and vena cava
how many nuclei does a cardiac muscle cell have?
1 or 2 central nuclei
what lines each cardiac cell?
external (basal) lamina
poles of the cardiac cell nucleus
where mitochondria and glycogen are commonly located
sarcoplasmic cone
what enables myocardium to "wring out" blood from the chambers of the heart?
the arrangement of cardiac muscle in a whorled pattern
how are cardiac cells joined?
intercalated disks
specialized junctional complexes that appear as dark transverse lines between cardiac muscle fibers
intercalated disks
anchoring sites for the cardiac sarcomere nearest the end of the cells
fascia adherens (transverse region only)
bind cardiac cells to prevent separation during contraction
macula adherens/desmosome (in both transverse and lateral components)
provide direct electrotonic communications between cardiac cells
gap junctions
passes the stimulus for cardiac contraction from cell to cell
gap junctions
what are the 5 differences between cardiac and skeletal muscle?
1. cardiac muscle has larger T-tubules
2. SR of cardiac muscle is poorly developed
3. cardiac cell T-tubule systems form dyads, not triads
4. dyads are located at Z lines in cardiac and at the A-I junction in skeletal
5. cardiac muscle has more and bigger mitochondria
what is the function of the nervous innervation of cardiac muscle?
to speed up or slow down the intrinsic beat
where do the sympathetic and parasympathetic nervous system branches terminate in cardiac muscle?
NEAR, not on, the muscle cells
what initiates the stimulus for contraction in cardiac muscle?
sinoatrial node
how do purkinje fibers communicate with the cardiac muscle cells?
via gap junctions
how do purkinje fibers differ from cardiac muscle cells?
they are larger, have more gap junctions, lower myofibril content, and higher glycogen content
hypertrophy
enlargement of muscle fibers
smooth muscle is prominent in the walls of what 2 systems?
respiratory and GI
how does the speed of contraction of smooth muscle compare with skeletal?
smooth contracts ~10x slower
smooth muscle can contract up to how much of their length?
75%
spindle shaped cell with a single centrally located nucleus and an eosinophilic cytoplasm
smooth muscle cell
where are cytoplasmic organelles generally located in smooth muscle cells?
the conical regions at the ends of the centrally located nuclei
most of the sarcoplasm of smooth muscle is occupied by thin actin filaments which insert into what?
dense bodies
location of dense plaques
dispersed in cytoplasm or associated with cell membrane
dense bodies are equivalent to what of striated muscle?
Z lines
What are the 4 ways that the smooth muscle contractile apparatus differs from skeletal?
1. thick and thin filaments are not arranged in sarcomeres
2. actin and intermediate filaments insert into dense bodies
3. dense bodies are connected to actin and myosin filaments
4. during contraction, actin pulls dense bodies forming a corkscrew-shaped nucleus
which of the 3 types of muscle is capable of undergoing mitosis in response to injury?
smooth muscle
how do the uterus muscle fibers respond to hormones during pregnancy?
increase in number (hyperplasia) and size (hypertrophy)
new smooth muscle cells can arise from what?
undifferentiated mesenchymal cells present among differentiated ones
cells in the walls of small blood vessels that are capable of differentiating into smooth muscle cells for growing blood vessels
pericytes
which part of the sarcomere decreases in width during contraction?
I band
does the A band width change during skeletal muscle contraction?
no
what activates calcium-gated channels on the sarcoplasmic reticulum?
voltage sensor proteins in membrane of T-tubules
contraction of smooth muscle is stimulated by what?
endocytosis of calcium vesicles
what happens when calcium is brought into smooth muscle cell?
calcium binds to calmodulin which leads to myosin phosphorylation