6.1 lect - types of muscle Flashcards
2 types of muscle cells can exist outside of “muscle tissue,” what are they, what germ layers are they derived from, and where are they found?
- myofibroblasts, from mesenchyme, ct
- myoepithelial cells, from ectoderm, epithelia
which free muscle cells come from the mesoderm and which come from the ectoderm?
mesoderm - myofribroblasts
ectoderm - myoepithelial cells
RBCs dispersed in connective tissue probably indicates…
a wound
myosin expressed in connective tissue =
a myofibroblast
myosin expressed in epithelial tissue =
a myoepithelial cell
myofibroblast
myosin expressed in connective tissue
myosin expressed in epithelial tissue
myoepithelial cell
where might you expect to find myoepithelial cells?
basally in glandular epithelium to help squeeze out secretions
myofibroblasts are derived from __
mesenchyme
myoepithelial cells are derived from __
ectoderm
visceral smooth muscle =
smooth muscle surrounding visceral organs
appearance of a myofibroblast LM
fusiform, basophilic cytoplasm
this cell has ~shape of a fibroblast when relaxed but contracts into a corkscrew shape
smooth muscle cell
actin, dense bodies, and intermediate filaments are components of what cell type?
smooth muscle cell
what are the intermediate filaments in smooth muscle?
arteries / veins - vimentin
most other places - desmin
how are dense bodies attached to one another
intermediate filaments (to transmit force)
arteries / veins - vimentin
most other places - desmin
greek root for muscle
latin root for muscle
sarco
myo
sarcolemma
muscle plasma membrane
muscle plasma membrane
sarcolemma
pinocytotic vesicles in smooth muscle plasma membrane
caveoli
- regulate intracellular Ca++ concentrations
- slow regulation but ok because smooth muscle acts slowly / gradually
T/F smooth muscle has no sarcoplasmic reticulum
false
does have sarcoplasmic reticulum for Ca++ sequestration, but caveoli are the primary means of regulating intracellular Ca++ concentrations…
sarcomeres are associated into __
myofibrils
myofiber
membrane bound element of muscle
- syncytium in skeletal muscle
- myocite in smooth and cardiac muscle
myocite
individual muscle cells in cardiac and smooth muscle
T/F myocites exist in skeletal muscle
false?
no myocites, just syncyctiums of myofibers?
how to tell smooth muscle from skeletal muscle
smooth - centra nucleus, no striations
skeletal - peripheral multinucleated, striations
T/F striations are parallel to sarcomere arrangement
false
striations = alternating A bans and I bands
T/F striations are perpendicular to sarcomere arrangement
true
striations = alternating A bans and I bands
how does weight lifting change skeletal muscle?
increased diameter of fibers
T/F weight lifting increases the number of myofibers
false
increases diameter of myofibers
T/F a skeletal muscle fiber is typically as long as the whole muscle
true
dark band in striation
A band
light band in striation
I band
dark band in center of light band in striation
Z line
light band in center of dark band in striation
H zone
dark band in center of light band in center of dark band in striation
M line
how many myofibrils in a membrane bound myofiber
hundreds
T/F from largest to smallest, muscle elements include: myofiber myofibril sarcomere myofilaments
true
3 connective tissue investments surrounding muscle tissue
endomysium - surrounds myofiber
perimysium - surrounds fascicles
epimyseium - surrounds multiple fasicles (muscle as a whole), connects muscle to tendon
T/F blood vessels can be found in endo, peri, and epimysium
true?
smaller in endomysium
larger in perimysium
any blood vessels in epimysium?
T/F adipose and nervous tissue are possible in perimysium
true
how does skeletal muscle tissue arise?
somite myotome myoblasts (muscle progenitor cells) myocites functional syncytium myofibrils
satellite cells in muscle
within the external lamina outside sarcolemma
-presumably capable of regenerating myofibers in case of damage
within the external lamina outside sarcolemma
-presumably capable of regenerating myofibers in case of damage
satellite cells in muscle
T/F endomysium contains external lamina
true
external lamina is outside all plasmalemma
external lamina of muscle
surrounds all plasmalemma -yes within endomysium -yes within perimysium -yes within epimysium surround ALL PLASMALEMMA
T/F external lamina = external membrane
true
same thing
this is ~ the basement membrane of muscle
external lamina
what are the components of the external lamina?
same as basement membrane
- lamina lucida
- lamina densa
- lamina reticularis (type IV collagen)
striated muscle encompasses…
skeletal muscle
cardiac muscle
what muscle types are not striated?
smooth muscle
a myocyte that persists outside the sarcolemma of a muscle fiber, but inside the external membrane
satellite cell
alpha-actinin
protein of Z line holding actin
protein of Z-line holding actin
alpha-actinin
myomesin and C-protein
form M line holding myosin together
materials that form M line holding myosin together
myomesin and C-protein
myomesin
forms M line with C-protein to hold myosin together
C-protein
forms M line with myomesin to hold myosin together
nebulin and titin
hold myosin to Z-line
materials that hold myosin to Z-line
nebulin and titin
nebulin
with titin holds myosin to Z line
titin
with nebulin anchors myosin to Z line
costamere
where myofibrils are bound to plasmalemma by intermediate filaments and dystrophin
where myofibrils are bound to plasmalemma by intermediate filaments and dystrophin
costameres
dystrophin
protein that binds myofibrils to plasmalemma with intermediate filaments at costameres
protein that binds myofibrils to plasmalemma with intermediate filaments at costameres
dystrophin
how are sarcomeres anchored within myofiber?
anchored to plasmalemma at costameres by intermediate filaments and dystrophin
types of skeletal muscle
type I - red (slower, non-fatigue, aerobic)
type IIa - intermediate
type IIb - white (faster, fatigue, anaerobic)
T/F muscle fibers can change type on spectrum from red to white in response to use
true
connective tissue connected to external membrane of muscle
endomysium
connective tissue fascia that binds the anatomical form of the muscle to the surrounding tissues
epimysium
order skeletal, cardiac, and smooth muscle according to size
skeletal (largest)
cardiac
smooth (smallest)
T/F cardiac myocytes are much smaller than skeletal muscle fibers but larger than smooth muscle myocites
true
how many nuclei in a cardiac myocite
1-2
sarcoplasmic cone
lighter area where myofibers bend around centrally located nucleus in cardiac myocyte
T/F like skeletal muscle, cardiac myocyte nuclei are squished to perifery
false
sarcoplasmic cone = lighter area where myofibers bend around centrally located nucleus in cardiac myocyte
adjacent myocites are connected electrically through … and bound physically through …
gap junctions
fascia adherens
fascia adherens in cardiac muscle tissue
binds cardiac myocites together physically
intercalated disk
modified myocites for conducton of electrical signals through heart
purkinje fibers
-fewer myofilaments
these cardiac myocytes will have fewer myofilaments than others
purkinje fibers
-specialized for conduciotn
intercalated disk
fascia adherens
- connect cytoskeletal actin of joined cells
- cadherins + actin
the intercalatd disk (fascia adherens) in cardiac muscle is most similar to what structure in epithelial tissue?
zonula adherens (adherens junction)
- connect cytoskeletal actin of joined cells
- cadherins + actin
T/F desmosomes correspond to zonula adherens
false
- desmosomes correspond to macula adherens (spot weld) junctions - cadherins + keratin intermediate filaments
- zonula adherens = cadherins + actin
synonym for desmosome
macula adherens (spot weld) junctions -cadherins + keratin intermediate filaments
evolutionarily oldest form of muscle
smooth muscle
dense bodies / dense plaques
anchoring proteins for myofilaments in smooth muscles (homologues of z-lines)
-connected to each other via intermediate filaments
involuntary muscle includes…
smooth muscle
cardiac muscle
2 classes of smooth muscle
unitary - acts as one mechanical unit
multiunit - ~1:1 axon:cell ratio for finer control
will the iris have unitary or multiunit smooth muscle?
multiunit
~1:1 axon:cell ratio for finer control
T/F smooth muscle cells in the uterine myometrium are hormonally responsive and grow up to 200 microns in length during pregnancy
true
how are smooth muscle cells in the uterine myometrium hormonally responsive?
grow up to 200 microns in length during pregnancy
neuromuscular junction
specialized structure joining nerve axon with muscle
most specialized in skeletal muscle, but present in rudimentary form in smooth muscle too
specialized structure joining nerve axon with muscle
most specialized in skeletal muscle, but present in rudimentary form in smooth muscle too
neuromuscular junction
junctional folds
local invaginations of the sarcolemma underneath the point of contact with the axon, designed to increase surface area and number of ACh receptors
local invaginations of the sarcolemma underneath the point of contact with the axon, designed to increase surface area and number of ACh receptors
junctional folds
muscle spindles
- sensory structures in muscle to sense position and stretch-state
- composed of modified muscle fibers (bag and chain fibers) with sensory neurons that sense position and stretch and gamma motor neurons that alter sensitivity
- encapsulated by its own perimysium
sensory structures in muscle to sense position and stretch-state
muscle spindles
composed of modified muscle fibers (bag and chain fibers) with sensory neurons that sense position and stretch and gamma motor neurons that alter sensitivity
muscle spindle
bag and chain fibers
modified muscle fibers in a muscle spindle that includes sensory neurons to sense position and stretch and gamma motor neurons to alter sensitivity
modified muscle fibers in a muscle spindle that includes sensory neurons to sense position and stretch and gamma motor neurons to alter sensitivity
bag and chain fibers
gamma motor neuron
motor neuron specific to muscle spindle to modify sensitivity of sensory neurons to position and stretch
motor neuron specific to muscle spindle to modify sensitivity of sensory neurons to position and stretch
gamma motor neurons
golgi tendon organ
like a muscle spindle with specialized muscle fibers and sensory and motor neurons
- positioned between muscle fibers and connecting tendon
- primarily associated with reflexive responses of the muscles
positioned between muscle fiber and tendon,
~like a muscle spindle with specialized muscle fibers and sensory and motor neurons
golgi tendon organ
primarily associated with reflexive response of muscles
golgi tendon organ
muscle spindle is homologous in structure and function to…
golgi tendon organ
golgi gendon organ is homologous in structure and function to…
muscle spindle
difference between muscle spindle and goligi tendon organ?
- muscle spindle: specialized muscle fibers and nerves to sense position and stretch, in muscle itself
- golgi tendon organ: specialized muscle fibers and nerves to sense position and stretch, between muscle and tendon, mostly for reflexive response of muscle
T/F unitary and multiunit smooth muscle is on somewhat of a spectrum depending on nerve:myocyte ratio
true
3 subclasses of muscle
-striated (I,IIA,IIB skeletal; standard, endocrine, conducting cardiac)
-smooth (unitary, multiunit)
single cell (myofibroblast, myoepithelial)
how do you tell unitary from multiunit smooth muscle apart on H&E?
very difficult, need to know anatomy
-perhaps with special nerve stain
intracellular actin of neighboring cells meet at …
zonula adherens
(adherens junctions)
catenin + actin
how is actin anchored to dense bodies in smooth muscle?
f-actin tethered to dense bodies by a-actin
a-actin
tethers f-actin to dense bodies in smooth muscle
T/F there exist smooth muscles that are under voluntary control
false
smooth muscle Never under voluntary control (by definition, as far as we know…, in humans)
between unitary and multiunit smooth muscle, which would you call myogenic and which would you call neurogenic?
unitary - myogenic (single axon many gap juncitons)
multiunit - neurogenic (axon:myocite ~1:1)
iris, erector pilli, large blood vessels, and small airways of the lung contain unitary or multiunit smooth muscle?
multiunit
fine control
do caveoli appear on P or E face in freeze fracture?
both
endocytosing vesicles will appear similarly on both E and P face
T/F caveoli can be associated with cardiac muscle
false
smooth muscle only
-Ca++ release from SR in cardiac initiated by action potential, sarcolemma, T-tubules, sarcoplasmic reticulum
-Ca++ release from SR in sooth muscle initiated by caveoli
T/F caveoli can be associated with skeletal muscle
false
smooth muscle only
-Ca++ release from SR in skeletal initiated by action potential, sarcolemma, T-tubules, sarcoplasmic reticulum
-Ca++ release from SR in sooth muscle initiated by caveoli
T/F caveoli can be associated with smooth muscle
true
smooth muscle only
-Ca++ release from SER in sooth muscle initiated by caveoli
dyad
where t-tubule meets a terminal cisterna of SR in cardiac myocites @ Z-lines
where t-tubule meets a terminal cisterna of SR in cardiac myocites @ Z-lines
dyad
how many feet in a dyad
2
1 terminal cisterna of SR
1 t-tubule
where does a dyad rest on a cardiac myocite?
at Z-lines
the specific name for the zonula adherens in cardiac muscle
fascia adherens
T/F intercalated disks are composed of gap junctions
false
yes, there are gap junctions there, but gap junctions also appear laterally; the intercalated disk is due to the fascia adherens (cadherins + actin)
T/F the t-tubule contains extracellular space
true
triad
where t-tubule meets 2 terminal cisternae of sarcoplasmic reticulum
-located where I band meets A band (right where it needs to deliver calcium)
where t-tubule meets 2 terminal cisternae of sarcoplasmic reticulum
triad
-located where I band meets A band (right where it needs to deliver calcium)
located where I band meets A band (right where it needs to deliver calcium)
triad
where t-tubule meets 2 terminal cisternae of sarcoplasmic reticulum
T/F cardiac myocytes are usually binucleated
false
binucleaton possible, but usually mononucleated
cytoplasmic space devoid of myofibrils but full of organelles in cardiac myocyte
sarcoplasmic cone
-caused because myofibrils spanning entire cardiac myocite must get around nucleus
caused because myofibrils spanning entire cardiac myocite must get around nucleus
sarcoplasmic cone
cytoplasmic space devoid of myofibrils but full of organelles
T/F actin filaments span the entire length of a cardiac myosite
false myofibrils (composed of multiple sarcomeres) span the entire length of cardiac myocyte
