Muscle Tissue (Histology) Oct30 M2 Flashcards
embryonic origin of muscular tissue
mesoderm
what muscle type see no myofibrils on cross section
SM
what muscle type is multinucleated
skeletal
nucleus location in SM, SkM, CM
SM and CM: central
SKM: peripheral
different bands and lines of striated muscles
A band: dark. I band: light. pseudoband H: lighter one in A band. M line in middle of H. Z line in middle of I.
other names for plasma membrane in muscle
plasmalema or sarcolema
SkM and CM: what can be seen around the cells on LM
CT: fibrocytes
cardiac muscle special thing around nucleus and why
halo (lighter halo) bc of golgi apparatus
name of region where two cardiac muscle cells join
intercalated disk
what muscle type has satellite cells
skeletal muscle
function of satellite cells
potential to repair muscle. if tearings, it divides and replces the muscle in that area
location of satellite cells around the muscle
between the sarcolema and the BM
BM present in what muscle types
all
name of junction at end of skeletal muscle and with what structure
musculotendinous junction (with CT of tendon)
other structure seen around SkM on cross section
reticular fibers (CT with collagen type III)
SM cells size compared to cardiac and SkM
much smaller diameter for SM cells
what muscle type under voluntary vs involuntary control
voluntary is skeletal
hypertrophy vs hyperplasia: for what muscle types these terms are
SM: hyperplasia
SKM and CM: hypertrophy
SKM hypertrophy: normal or not + mechanism
Normal: Production of myoglobin and increase in number of myofibrils in cytoplasm
Cardiac muscle hypertrophy normal or abnormal
abnormal sometimes
why use the term hyperplasia for SM
bc it’s the NUMBER of cells that increases, not their size
most abundant tissue in the body
SKM
3 tissue layers around SKM
epimysium, perimysium, endomysium
epimysium location and def
surrounds all the SKM. thick layer of CT
perimysium location and def
surrounds a bundle or fascicle of muscle cells. Think filaments (septa) of CT
cells found in perimysium and what they do
fibrocytes. attach to other fibrocytes with gap junctions
endomysium location
around cells
endomysium content (5)
capillaries, nerve fibers, fibrocytes, reticular fibers, BM
branching principle through epi, peri and endo mysium
vessels and nerves branch and become smaller from epi to peri to endo mysium
the endomysium is essentially a ____
basement membrane
shape of sarcolema at the junctional complexes (musculotend. junction)
finger like projections of the sarcolema
what is found in the finger-like projections
actin filaments that insert in dense areas near on inner side of plasmalema called dense bodies
what is found on external portion of finger like projections
BM interacts with collagen fibers of the CT
how many myofibrils in one cross section of striated muscle
1500
number of myosin and actin filaments in one myofibril
thin (actin): 3000
thick (myosin): 1500
shape or configuration obtained when cutting cross section of myofibril
hexagon
cross section of striated muscle depends on what
depends on region where we cut
4 diff cuts that can give diff cross sections of striated muscle
Through: I band, A band (dark portion), pseudo band H but not the middle, M line
sarcomere size and def
2-3 microns. structure from one Z line to the other
what is found at the M line (3)
cross bridges of myosin
creatine kinase
myomesin
protein at Z line and function
alpha actinin. anchors actin
what cratine kinase does at the M line and why
converts phosphocreatine + ADP to ATP + creatine (and can also do the opposite reaction)
Reason: ATP obtained is necessary in contraction of SKM and CM
myomesin at M line, function
not known
gross components of myosin molecule
2 heavy chains and 4 light chains
name of myosin molecule subunits (3)
light meromyosin (LMM) heavy meromyosin (HMM) divided into HMM subunit 1 and HMMS-2
what LMM corresponds to
two heavy chains halves that are far from light chains
what HMMS-1 corresponds to (in terms of heavy and light chains)
region beyond the split of the heavy chains (the two heads)
what HMMS-2 corresponds to
two heavy chains halves that are between LMM and split of heavy chains
what enzyme cuts myosin into LMM and HMM
chymotrypsin
what enzyme cuts HMM into HMMS-1 and HMMS-2
papain
head of myosin corresponds to what subunit and what does it contain
HMMS-1. ATPase acivity where ATP cleaved into ADP and phosphate
purpose of the phosphate myosin obtains in ATPase activity
is what generates energy for contraction
HMMS-1 has binding site for what
actin
actin monomers name and charact.
G-actin. Very polarized.
actin filaments name and charact.
F-actin. Slightly twisted, contain groove between molecules of actin.
molecule found in F-actin groove
tropomyosin. is in the groove along all the length
what molecule attaches to tropomyosin
troponin
troponin subunits
TnI, TnC, TnT
TnI function
inhibits actin myosin interaction
TnC function
binds calcium
TnT function
anchors to tropomyosin
What Ca release allows in striated muscle (mechanism for contraction)
binds troponin (TnC). Config change. Myosin already bound to ATP binds actin. Binding activates ATPase. Phosphate release allows bending of myosin and pulling
the sarcoplasmic reticulum is basically the _____
endoplasmic reticulum
what changes in size at contraction and what doesn’t
sarcomere and pseudoband H decrease. Actin and myosin length unchanged.
nebulin function
covers completely F-actin and serves to anchor it to alpha actinin on Z line
Titin function
anchors myosin to the Z line
