Muscle Tissue (Histology) Oct30 M3

Question 1

shape of the SR in striated muscle

Answer 1

regular. has tubules (segments of SR) and cisternae (lateral sacs of SR)

Question 2

T-tubule def

Answer 2

invagination of the plasmalema that goes very deep in cell

Question 3

SR cisternae name near T-tubule

Answer 3

terminal cisternae

Question 4

Triad def.

Answer 4

cisterna-T tubule-cisterna combination

Question 5

what is found between adjacent cisternae (SR component)

Answer 5

connecting tubules of SR

Question 6

location of triad in SKM

Answer 6

at junction of A and I band.

Question 7

location of triad in cardiac muscle

Answer 7

near Z line

Question 8

what is found at the terminal cisternae + function

Answer 8

Calcium ATPase (Ca pump) pumps Ca in the SR

Question 9

What makes the Ca release from the SR

Answer 9

depolarization of the membrane due to membrane potential coming from outside, via the T tubule

Question 10

perimysium appearance on cross section

Answer 10

appears enlarged (histology artefact) bc tissue was put on hot plate for it to spread

Question 11

On EM, what we see between adjacent myofibrils within the cytoplasm

Answer 11

mitochondria and glycogen molecules that appear as dark dots

Question 12

T-F: axon myelinated in SKM NMJ + explan.

Answer 12

True. Myelinated by Schwann cells that form myelin sheaths

Question 13

appearance of postsynaptic membrane (sarcolema) in NMJ

Answer 13

is folded.

Question 14

space name between pre and post synaptic membrane at NMJ

Answer 14

synaptic cleft

Question 15

other name for NMJ

Answer 15

terminal button

Question 16

NMJ neurotransmitter

Answer 16

ACh

Question 17

cardiac muscle NMJ neurotransmitter

Answer 17

Ach if PSS

NE if SS

Question 18

SKM NMJ postsyn. receptor nd function

Answer 18

AchR, binds Ach. Makes Na+ flow in and K+ flow out

Question 19

AchR type of receptor and conformation

Answer 19

ligand-gated. 5 subunits: two alpha, 1 gama, 1 beta, 1 delta encoded by diff genes

Question 20

Why do we say that the AchR at the NMJ is immunologically protected

Answer 20

No Abs normally produced against it

Question 21

Myastenia gravis cause (autoimmune disease)

Answer 21

Ab produce against AchR at NMJ

Question 22

AChE function at the synaptic cleft

Answer 22

splits ACh into acetate and choline, both recycled by presynaptic neuron

Question 23

location of BM at NMJ

Answer 23

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

Question 24

heart layers from outside to inside (not only heart wall)

Answer 24

fibrous pericardium, serous pericardium (parietal lamina and visceral lamina or epicardium), myocardium, endocardium

Question 25

three layers forming the wall of the heart

Answer 25

epicardium (visceral lamina of serous pericardium), myocardium, endocardium

Question 26

fibrous pericardium charact.

Answer 26

CT around the heart (external capsule)

Question 27

epicardium charact.

Answer 27

covers the heart and part of the blood vessels

Question 28

myocardium charact.

Answer 28

thickest part of heart wall. made of cardiac muscle fibers (cells)

Question 29

endocardium charact.

Answer 29

thin membrane of endothelium, CT and SM tissue

Question 30

percardial cavity separates what layers

Answer 30

parietal lamina of serous peric. and visceral lamina (epicardium) of serous peric.

Question 31

what muscle type has cells that sometimes branch

Answer 31

cardiac

Question 32

what muscle type has highest density of capillaries

Answer 32

cardiac muscle

Question 33

what is the BM at intercalated disks

Answer 33

is in fact two BMs that attach

Question 34

two portions of intercalated disks

Answer 34

north south portion and east west (or west east) portion

Question 35

3 junction zones at ICs and which part of IC they're in

Answer 35

Zonula adherens and macula adherens (desmosome) in north south Gap junction in east west portion

Question 36

Zonula adherens charact

Answer 36

''Z line like'': alpha actinin at the plasmalema anchors F-actin

Question 37

Desmosome (macula adherens) charact

Answer 37

plaque with proteins called plaquoglobins and intermediate filaments anchoring there

Question 38

Gap junction charact.

Answer 38

The 2 BMs become very close. Interaction between them bc have pores there

Question 39

Gap junction pores names and components

Answer 39

connexons. each has 6 connexin molecules

Question 40

heart: type of connexin molecule and consequence of mutation

Answer 40

connexin 48. mutation is lethal.

Question 41

gap junction function

Answer 41

allow passage of ions of calcium

Question 42

why gap junctions necessary in cardiac muscle

Answer 42

Ca flows between the cells so available everywhere. as in Ca available to all the troponin in SKM

Question 43

cardiac muscle: why SR is complex

Answer 43

- sometimes have terminal cisternae, sometines not | - sometimes have triad at level of Z line, sometimes not

Question 44

cardiac muscle SR similarities with SKM SR

Answer 44

T tubules, calcium pump

Question 45

why difficult to see myofibrils in SM

Answer 45

mainly actin there and not much myosin. + not organized in sarcomeres

Question 46

something special happening in SM at contraction

Answer 46

shape of nucleus changes

Question 47

special structure at sarcolema of SM

Answer 47

vesicles that don't detach called caveoles (that could do function of T tubules?)

Question 48

what do we see outside SM cells near them (equivalent to endomysium)

Answer 48

reticular fibers

Question 49

Dense bodies on SM cells plasma membrane: what they are

Answer 49

contain alpha actinin like proteins achoring the actin filaments (are rich in alpha actinin) (Z line like)

Question 50

SM mechanism of contraction: what Ca does

Answer 50

binds myosin light chain kinase (MLCK)

Question 51

SM mechanism of contraction: what MLCK does

Answer 51

phosphorylates the light chains of the myosin to displace the head previously attached to the tail. Head can bind acin

Question 52

SM mechanism of contraction: how close myosin is to actin and how myosin is organized in SM cell

Answer 52

myosin close to actin b4 contraction but doesn't bind. Myosin is as individual molecules

Question 53

SM speed of contraction and what this makes it good for

Answer 53

slow. makes it good for peristaltic movement, lumen contraction of blood vessels.

Question 54

how SM shape changes from before to after contraction

Answer 54

more elongated to more round and less elongated

Question 55

SM relaxation: how

Answer 55

Ca levels decreased, inactivation of MLCK.

Question 56

Ehlers-Danlos syndrome affects what + consequence

Answer 56

affects CT, joints and vessel walls. Severe form called vascular Ehlers-Danlos causes walls of blood vessels, intestines or uterus to rupture

Question 57

Ehlers-Danlos syndrome cause

Answer 57

mutation of reticular fibers. causes wall ruptures (in aorta, digestive system, etc.)

Question 58

Myasthenia gravis: symptoms and explanation

Answer 58

fluctuating muscle weakness and fatigue. The Ab binding to AchR inhibits the excitatory effect of Ach on AchR at the NMJ

Question 59

Muscular dystrophy: give two types

Answer 59

Duschenne and Becker

Question 60

Muscular dystrophy: two mutations that can give that

Answer 60

mutation in laminin or dystrophin

Question 61

what dystrophin does + associated diseases

Answer 61

DMD. BMD. is at muscle fiber membrane. links actin to dystroglycans in sarcolemma which are linked to laminin.

Question 62

what laminin does

Answer 62

Are part of the basement membrane. interacts with dystroglycans at the sarcolemma