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60 Cards in this Set

  • Front
  • Back
3 basic types of muscle cells
skeletal
cardiac
smooth
skeletal muscle cell characteristics
has striations
large cells
regular pattern
rounded cells
multinucleate near cell edge
What are skeletal m. cells referred to as?
fibers bc they are very large and multinucleated...they are a synciium
Cardia Muscle cells characteristics
striated
branched/interconnected cells
irregular distribution/shape
nucleus is centrally located
skeletal m. activity
strong,quick discontinuous voluntary contractions
cardiac m. activity
stron quick continuous involuntary contractions
smooth m. cells characteristics
smallest m.fiber
regular profile
fusiform(spindle shape) cell
differing sizes of cells
nucleus centrally located
muscle activity of smooth m.
weak,slow involuntary contractions
why do we see striations in cardiac and skeletal m.?
due to presence of actin and myosin.

called muscle fibers
whay is most of muscle mass of body?
skeletal m.
where are nuclei in skeletal m. cells?
right beneath sarcolemma
sarcolemma
muscle plasma membrane and the underlying basal lamina
epimysium of skeletal m.
outermost layer of skeletal m. fiber. it is loose connective tissue that suurounds the entire muscle. Superficial fascia around the muscle.
perimysium of skeletal m
CT that serpartes the muscle tissue into fascicles. the fascicles are the functinoal units of the muscle that work together as a coordinated contractile unit due to shared innervation patterns
endomysium of skeletal m.
CT that penetrates the perimysium to surround individual m. fibers

highly vascularized to provides Oxygen and nutrients to the fibers
where are caps in skeletal m.
between the m. fibers
cytoplams of m.fiber
sarcoplasm
satellite cells in skeletal m.

what limits the ability of the satellite cells?
located wi basal lamina between the basal lamina the plasma membrane.

the divide and give rise to new cells in response to injury or trauma

if the basement membrane is ruptured, satellite cells cannot repair the injury and the fibroblasts have to replace the damaged tissue w/ CT giving a CT scar

if the integrity of the basal lamina is preserved, the satellite cells can repair damaged m. fibers
what is myofibrils?
within the m.fibers
the myofibrils have actin and myosin
what part of skeletal m. CT is continuous w/ the dense regular CT of the tendon?
the CT of endomysium and perimysiuam are continuous w/dense regular CT of tendon
components of skeletal m.
muscles are composed of muscle fascicles which are made up of muscle fibers (multinucleate syncium)
components of myofibrils
within the cytoplasm there are myofibrils that are made up of myofilaments (actin and myosin) responsible for contraction of the muscle

actin-thin filaments
myosin-thick filaments
A band of skeletal m.
darker staining bc of prescence of myosin
I band of skeletal m.
lo density bc of actin only!!
Z band of skeletal m.
bisects the I bands

Z line contains the aspha actinin the actin is linked to
Z line to Zline
length of one sarcomere
sliding filaments in skeltal m.
actin and myosin filaments slide towards each other during contraction w/o reduction of length of either filament

the A band remains the same thickness in the contracted and relaxed state since the myosin does not change in size

the I bands get smaller because the Zlines are being moved together
what surrounds the myofilaments of skeltal m.?
sarcoplasmic reticulum

bascially like a modified smooth ER
T Tubules of skeletal m.
a membranous tubule at regular limits that will penetrate the sarcolemma and will surround the myofibrls

Terminal cisternae of sarcoplasma reticulum are on sides of Tubules
triad
seen in skeltal m.

configuration of one t tubule plus the two adjacent terminal cisterae
point in skeletal m. when excitation becomes contraction
at the triad
where are triad in skeltal m. found?
at A/I junction
function of Ttubules in skeletal m.
brings the wave of depolarization from the plasma membrane down into the muscle fiber

as they pass adjacent to the terminal cisternae they stimulate Ca release from the sarcoplasmic reticulum and this Ca release initiates contraction
pale staining part in center of A band
H band
what is each myofibril in skeletal m. surrounded by?
sarcoplasmic reticulum
junctional folds of skeletal m.
plasma membrane of muscle has invaginations called junctional folds that have the ACh receptors there

the invagination increase SA for receptors
describe what happens at the neuromuscular junction in skeletal m.
wave of depolarization arises from an action potential from the motor neuron of the SC. this is a mylinated axon that terminates as an expansion in contact with the sarcolemma of the muscle fiber

the AP causes the release of ACh into the synaptic cleft between the motor neuron and the muscle fiber

ACh binds to ACh receptros on the muscle fiber membrane
Myasthenia gravis
Abs are produced to ACh receptors which block the receptors and cause m. weakness
motor unit
neuron and the muscle fibers it innervates
how do cardiac m. cells differ from skeletal m. cells?
cardiac cells are:

smaller

branch to interconnect to other cardiac m. cells

make up myocardium of heart

contract rhythmically in response to nerve impulses

no satelite cells

only one or two n. that are centrally located

highly vascualrized CT surrounding it
can cardiac cells regenerated
they have limited regeneration capacity bc they do not have satellite cells
where are nuclei in cardiac cells?
centrally located
intercalated disks
where cardiac m. fibers attach
sarcoplasmic cones
individual myofibrils running longitudinally being forced to go aroundthe nucleus leaving some cytoplasm left on each side of the nucleus
what holds cardiac cells together?
fascia adherens which runs vertically in the muscle fiber
where are gap junctions in cardiac m? Why are they located there?
horizontally the fibers have gap junctions they are placed horizontally so they will not be subject to stress

gap junctions are necessary for the wave of contraction passing through the cells so that there is a coordinated contraction of neighboring cells so the gap junctions allow a wave of depolarazation
how do t tubules in cardiac m. differ from skeletal?
t tubules are larger in diameter

sarcoplasmic reticulum is not well developed it is very thin

the terminal cisterne are small and there is not a complimentary one on the other side

t tubules align at the Z line instead of the A-I junction
dyad
in cardiac m. cells the t tubules are associated w/ only one terminal cistern
where are intercalated disks found in cardiac m.
at the Z line
what innvervates cardiac m.?
specialized fibers called purkinje fibers
does cardiac m. have motor endplates?
no they contract spontaneously
heart contraction
contraction is initiated at the SA node and moves to the AV node and then moves on to the purkinje fibers
purkinje fibers
have fewer myofibrils than cardiac m. cells are paler staining and are larger

purkinje fibers also have more gap junctions bc they conduct impulses
smallest of m.cell type
smooth m. cells
smooth m. cells shape
spindle, fusiform shape with tapered ends the are reminiscent of fibroblasts

n. are centrally located

there are actin/myosin filament but w/ no regular pattern (no striations)
how do smooth m. cells initiate contraction?
through endocytosis of Ca

vessicles are taken into the cell. and Ca binds to calmodulin causing contraction
how do smooth m. cells communicate w/one another?
nia gap junctions like cardia m.
what type of m. cell has the highes capacity for regeneration?
smooth m. cells they can undergo mitosis
dense bodies
what smooth m. connects to it anchors the actin.

dense bodies occur throughout the cell and are often associated w/ membranes in crisscross pattern
what happens to the dense bodies as the cell contracts?
as the cell contracts the dense bodies come closer to each other ruffling the cell and causing the nucleus to take on a cork screw appearance