Module 16 - Muscle Flashcards
3 types of muscle cell
smooth
skeletal and cardiac (striated)
2 functions of skeletal muscle
movement
heat generation
what is muscle fiber
single muscle cell
smallest part of muscle tissue
aka a myocyte
name of a bundle of muscle fibres
fascicle
name the sheath of connective tissue surrounding bundle of muscle fibres
perimysium
name of connective tissue that surrounds individual muscle fibres
endomysium
name the outer layer of muscle
epimysium
what is a triad made up of
T tubule
terminal cisternae
what is the sarcolemma
cell memb of msucle fibre
NOT to be confused with endomysium which is connective tissue on top of this
sarcomere sections in order left to right
Z line
I band (crosses over 2 sarcomeres)
A band
H zone
M line
see diagram
what is thick filament made up of
myosin and titin
what is thin filament made up of
actin and nebulin
which of the filaments connects to the M line
thick filament
what happens when muscle contracts to the filaments
thin move closer together
thick filaments have contractin in titin at the end
cross section - what filaments are present in A band
thick and thin filaments
cross section - what filaments are present in H zone
thick filaments
cross section - what filaments are present in I band
thin filaments
qhat is optimum srcomere length fro highest contrac force
1.1-1.2 micometres
how many types of myosin
9
8 skeletal/cardiac
1 smooth
(myosin = hexamer, 2 heavy chains, 2 regulatory light chains, 2 heavy chains)
what type of actin is found in muscle
filamentous actin
tropomyosin structure
2 alpha helixes in coiled coil
1 for every 7 actin
what are the 3 components of troponin and what do they do
T = binds with tropomyosin
C = binds Ca2+ during contraction
I = binds with actin and inhibits myosin by covering binding sites
what happens when ATP binds to myosin
myosin dissociates froma actin
ATP hudrolysed to ADP and Pi
mysoin moves along
Pi dissociates
ADP dissociates
what molecule regulates contration and how
Ca2+
binds to TnC = causes it to move and uncover binding sites on myosin
name the channel in SR that allows main movement of Ca2+ into the cytoplasm
ryanodine receptor
what channel acts as a voltage sensor and activates the ryanodine receptor
L type Ca channels (DHP) in the sarcolemma memb
what receptor allows resotration of Ca balance
SERCA receptors in SR memb
moves Ca frm cyto back into SR
what triggers the DHP receptor to activate
depolarisation of sarcolemma memb
via AP being passed down
after nACh receptors are activated
name process that occurs when neuron meets muscle fibre and neruomuscular junction
aborization
basiclaly it just splits into branches
what type of disease is myasthenia gravis
autoimmune disorder attacking skeletal muslce
leading to muscle weakness and fatigue
who is MG most common in
women 20-40
how do we know thymus gland may be involved in MG
many have thymomas
Removal of the thymus gland can prove beneficial for many patients
where are the ACh binding sites in nACHr
between alpha and delta and alpha and epsilon on extracellular side
what does 2nd TM domain of nAChr form
the inner lining of ion channel
where to antibodies in MG target on nACHr
extracellular parts of alpha subunits
aka the main immunogenic region MIR
what are the 3 pathological mechanisms of MG
1 - antibody binding causes receptors to be internalised (endocytosis)
2 - end plate region destroyed/simplified by immune system
3 - antibodies can act as comp ant and dont allow Ach to bind (this is least important one, others have more effect)
3 types of treatment for MG
AChesterase inhibitors (reversible) (end in -stigmine)
Immunosuppressants (azathioprine)
Plasma therapy/plasmapheris/plasma exchange (removes the autoantibodies form circ)
name the irreverisble AChEsterase inhibitor
sarin
vry deadly
what AA does sarin bind to in AChEsterase that inhibits it
serine
forms sarin-serin complex = cant be recycled
2 reasons why sarin causes flaccid paralysis
- nAChr get desensitised after being exposed for long time
- =memb constantly depolarise and Na+ channels get inactivated
what 3 AAs control enzymatic activity of AChEsterase
serine
glutamate
histidine
2 antidotes for sarin
injecting atropine as a muscarinic antagonist
pralidoxime = recycles AChesterase (only effective if used quick)
what tissue from electric fish is used to study nicotinic receptors
electroplaque
Elecetrocytes
has lots of nAChr
orginally derived form msucle
