Muscle Tissue (Histology) Oct30 M3 Flashcards
shape of the SR in striated muscle
regular. has tubules (segments of SR) and cisternae (lateral sacs of SR)
T-tubule def
invagination of the plasmalema that goes very deep in cell
SR cisternae name near T-tubule
terminal cisternae
Triad def.
cisterna-T tubule-cisterna combination
what is found between adjacent cisternae (SR component)
connecting tubules of SR
location of triad in SKM
at junction of A and I band.
location of triad in cardiac muscle
near Z line
what is found at the terminal cisternae + function
Calcium ATPase (Ca pump) pumps Ca in the SR
What makes the Ca release from the SR
depolarization of the membrane due to membrane potential coming from outside, via the T tubule
perimysium appearance on cross section
appears enlarged (histology artefact) bc tissue was put on hot plate for it to spread
On EM, what we see between adjacent myofibrils within the cytoplasm
mitochondria and glycogen molecules that appear as dark dots
T-F: axon myelinated in SKM NMJ + explan.
True. Myelinated by Schwann cells that form myelin sheaths
appearance of postsynaptic membrane (sarcolema) in NMJ
is folded.
space name between pre and post synaptic membrane at NMJ
synaptic cleft
other name for NMJ
terminal button
NMJ neurotransmitter
ACh
cardiac muscle NMJ neurotransmitter
Ach if PSS
NE if SS
SKM NMJ postsyn. receptor nd function
AchR, binds Ach. Makes Na+ flow in and K+ flow out
AchR type of receptor and conformation
ligand-gated. 5 subunits: two alpha, 1 gama, 1 beta, 1 delta encoded by diff genes
Why do we say that the AchR at the NMJ is immunologically protected
No Abs normally produced against it
Myastenia gravis cause (autoimmune disease)
Ab produce against AchR at NMJ
AChE function at the synaptic cleft
splits ACh into acetate and choline, both recycled by presynaptic neuron
location of BM at NMJ
BM of striated muscle is continuous with BM of Schwann cells (which wraps around axon) and doesn’t enter T tubules. Also no BM between Schwann and axon
heart layers from outside to inside (not only heart wall)
fibrous pericardium, serous pericardium (parietal lamina and visceral lamina or epicardium), myocardium, endocardium
three layers forming the wall of the heart
epicardium (visceral lamina of serous pericardium), myocardium, endocardium
fibrous pericardium charact.
CT around the heart (external capsule)
epicardium charact.
covers the heart and part of the blood vessels
myocardium charact.
thickest part of heart wall. made of cardiac muscle fibers (cells)
endocardium charact.
thin membrane of endothelium, CT and SM tissue
percardial cavity separates what layers
parietal lamina of serous peric. and visceral lamina (epicardium) of serous peric.
what muscle type has cells that sometimes branch
cardiac
what muscle type has highest density of capillaries
cardiac muscle
what is the BM at intercalated disks
is in fact two BMs that attach
two portions of intercalated disks
north south portion and east west (or west east) portion
3 junction zones at ICs and which part of IC they’re in
Zonula adherens and macula adherens (desmosome) in north south
Gap junction in east west portion
Zonula adherens charact
'’Z line like’’: alpha actinin at the plasmalema anchors F-actin
Desmosome (macula adherens) charact
plaque with proteins called plaquoglobins and intermediate filaments anchoring there
Gap junction charact.
The 2 BMs become very close. Interaction between them bc have pores there
Gap junction pores names and components
connexons. each has 6 connexin molecules
heart: type of connexin molecule and consequence of mutation
connexin 48. mutation is lethal.
gap junction function
allow passage of ions of calcium
why gap junctions necessary in cardiac muscle
Ca flows between the cells so available everywhere. as in Ca available to all the troponin in SKM
cardiac muscle: why SR is complex
- sometimes have terminal cisternae, sometines not
- sometimes have triad at level of Z line, sometimes not
cardiac muscle SR similarities with SKM SR
T tubules, calcium pump
why difficult to see myofibrils in SM
mainly actin there and not much myosin. + not organized in sarcomeres
something special happening in SM at contraction
shape of nucleus changes
special structure at sarcolema of SM
vesicles that don’t detach called caveoles (that could do function of T tubules?)
what do we see outside SM cells near them (equivalent to endomysium)
reticular fibers
Dense bodies on SM cells plasma membrane: what they are
contain alpha actinin like proteins achoring the actin filaments (are rich in alpha actinin) (Z line like)
SM mechanism of contraction: what Ca does
binds myosin light chain kinase (MLCK)
SM mechanism of contraction: what MLCK does
phosphorylates the light chains of the myosin to displace the head previously attached to the tail. Head can bind acin
SM mechanism of contraction: how close myosin is to actin and how myosin is organized in SM cell
myosin close to actin b4 contraction but doesn’t bind. Myosin is as individual molecules
SM speed of contraction and what this makes it good for
slow. makes it good for peristaltic movement, lumen contraction of blood vessels.
how SM shape changes from before to after contraction
more elongated to more round and less elongated
SM relaxation: how
Ca levels decreased, inactivation of MLCK.
Ehlers-Danlos syndrome affects what + consequence
affects CT, joints and vessel walls. Severe form called vascular Ehlers-Danlos causes walls of blood vessels, intestines or uterus to rupture
Ehlers-Danlos syndrome cause
mutation of reticular fibers. causes wall ruptures (in aorta, digestive system, etc.)
Myasthenia gravis: symptoms and explanation
fluctuating muscle weakness and fatigue. The Ab binding to AchR inhibits the excitatory effect of Ach on AchR at the NMJ
Muscular dystrophy: give two types
Duschenne and Becker
Muscular dystrophy: two mutations that can give that
mutation in laminin or dystrophin
what dystrophin does + associated diseases
DMD. BMD. is at muscle fiber membrane. links actin to dystroglycans in sarcolemma which are linked to laminin.
what laminin does
Are part of the basement membrane. interacts with dystroglycans at the sarcolemma
