L15 Alt In Skel Musc Func Flashcards Preview

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LO2: outl phys of NMJ and desc pthogenesis and clinic feats of myasthenia gravis.

-NM transm- each musc cell 1 MN. 1MN can inner multip fibres. MN sits in end pl groove in sarcolemma in folded reg, lot AchR. AP down MN, at end= Ach rel, diff X cleft, bind nicotinic achR on folded end pl reg=contrac.
-AP arriv=open presyn volt dep Ca chann=Ach vesic merge end axon and rel. bind post syn R=open Na chann=Na in=depol X mem=elec flow X cell mem down TT. At termin cist SR=Ca rel, bind TnC, uncov BS. Rate Ach rel over time- v quick init to peak then decr rate to stat. Ach termin by Achesterase= not reactiv so can rep musc movem quick. At high MN firing rates, Ach rel decr. Only 25% AchRs needs occup so still contrac once rate rel levs off.
-NMJ disords- myasthenia gravis.
Autoimm destr end pl AchRs (IgG Ab against). Loss junc folds at end pl. widening of syn cleft.
Symps- fatigue, sudd fall due to decr Ach rel. diffic sust contrac. High lev Ach rel start then decr.
Prim signs- droop eyelids (ptosis), doub vis as eye unsynch. Gen state health, fatigue, emot. Symps fluc as imm cond. event w/c as cant sust post.
tx- Achesterase inhib eg pyridostigmine= in cleft longer. Imm supp, decr IgG activ. Plasmapheresis- rem harmf Ab from serum. Thymectomy rem abn T.


LO3: state how NM transm disrup in botulism and organoP poison.

Toxins aff NMJ:
-aff neuronal Na chann- block syn transm compl. Post a nd pre syn mem. V deadly.
-Ca chann-block Ach rel. painkiller in v rare cases, into CSF. If not rep to morphine, lot s/e. V potent.
-musc Na chann-
-AchR chann- plant extract, kill by paral and asphyx, not leave init unless eg ulcer. Another one From snakes, v tox.
-Achesterase- insecticide and chem war eg sarin. Contrac resp musc and can't breathe out- lot s/e. Eg eye drop for galucoma- incr press dam vis.
-Ach rel- eg tetanus toxin=spasm. Botulinum toxin in soil and canned food if not heat. Botox contrac smooth musc under skin. V deadly.
-K chann- snake, eff conduc.


LO4: desc patholog of DMD

-musc dystrophy- genet disords. Prog musc weakn and wasting. Types: diff age present aff diff parts.
-duchenne MD- most ser life lim, present yng. Comp bench dytrophin prot-long rod shaped=link btw cell mem and actin.
-Beckers MD=shoulders and thighs. Alt and truncated dystrophin.
-limb girdle MD defic of sarcoglcans.
-congenital mersosin defic MD- 50% defic merosin aka laminin 2.
-histol changes- musc fibres Fluor stained for dystrophin- norm=sig arnd mem. With DMD no sig and musc fibs diff sizes, gaps btw them due to dam and cell death Due to tear. Repl of fibres with CT and fat. Small dam cells present.
Musc fib dam in DMD due to prot abn. Musc fibs tear apart on contrac- mem not move with musc as dytrophin not join sarcolemma=shears. Liberates cell cont eg CK enz to blood. Ca ent cell=necrosis. Pseudohypert swell init as dam cells died repl by fat and CT, but is false.
-presentat- slowness, falls, musc weakn, diffic stand (gowers sign), in kids. Contractures- musc rigid and stiff with CT can't extend-imbal btw antag and agon musc.
-tx- steroid eg prednisolone- corticosteroid, slows rate dam. not true inflamm proc but helps maint musc. Anab ster no eff! No cure so genet research (gene therap, SC etc). Try stim dytrophin prod by transf genet sig of stim from other SC.
-skel musc disorders-
Myopathy eas=prim musc dis. Musc dystrophy, inflamm myopathy eas, myopathy eas secondary to systemic dis.
Denervat- loss nerve supp, neurol cause.
-inflamm- eg polymyositis (vir imm cond lot inflamm skel musc). Myalgia. Influ-acute milder form of polymyositis.
-electrolyte imbal- ion chann disrup eg cramp/sust contrac. Diuretic therap (hypokal eg tx for incr BP, can decr K, can=cramps etc. Counter with supplem/banana).
-thyrotoxicosis- rep incr metab rate. Incr BMR and prot catab. Overact thyr=lot thyroxine etc=breakd musc more than build.
-hypoPT- hypocalcaemia= tetany. Underact PT=low Ca=sust contrac.
-channelopathies- eg malig hyperthermia.


LO5L outl pathophys of malig hyperthermia

-incr intracell Ca. S/e of volatile anaesthetics. Effs ion chann in SR for Ca, so all Ca in SR rel. sust contrac all skel musc=lot heat.


LO1: desc proc of skel musc remod and relev to atrophy and hypert.

Skel musc func: movem, posture, stabil of jnts, heat gen.
-skel musc composit- fascicles to fibres to myofibrils to myofilams-contractile prots can incr or decr in number.
-remod- musc changes over time. A and M repl ev 2wk. Prots in filams change quant. Can't incr numb muscle fibres, just incr size each. Destr more than repl=atrophy and musc waste eg age. Repl more than destr=hypert incr musc cell size eg exerc.
Amnt A/M, CT, metab compons changes.
-exerc and skel musc- metab adap. SR swell. Incr vol mito. Incr Z band width. Incr ATPase. Incr dens of TT sys. Incr no contractile prots. Little ev for hyperplasia.
-high resis exerc eg weights at high intens near max. Eg 70-90% intens (of 1 rep max), short duration (3 sets of eg 8-12 reps), modest freq (2-3D per wk). Stims metab activ. Stim intra tile prot synth (ATM)= incr X bridges=incr pow. Fatter musc fibres. Incr by 8-10%. Incr musc mass and strength may= hypert (myosat fus/div).
-endurance exerc- eg low int 30-60 min, 5d/wk. Incr endur w/o hypert. Stim synth of mito prots, vasc changes allow incr O use, Mb func. Incr metab capac. Shift to oxid metab (lips)=decr blood fat and chol.
-disuse atrophy- eg bed rest, limb immob, sedent behav. Loss prot= decr fibre diam=decr pow. Rehab exerc.
-Musc atrophy with age- slow init over 30. 50% loss musc mass by 80=sarcopenia. Decr X bridge, aff basic Mobil. Also affs temp regul so eld sedent hypoth.
-Denervat atrophy- neurogenic musc atrophy. Lose motor neuron supp to musc due to eg trauma, MND, spinal dis. Sign of lower MN lesions- weakn, flaccidity, musc atrophy. Re innerv in 3 mnth for recov, if not paral.
-spinal musc atrophy- ant from SC where MN come from dam and degen. Picked up early, early death as kid. MN died, musc atrophy. Decr X bridge and pow. Atrophic fibres small, angularis, bright E stain pink. Appar incr no nuc.
-adj of musc length- sarcomeres= Z-Z. Incr by sust stretching 30-60sec freq. for exerc or rehab. Unclear Ho. Anim study sugg addit sarcomeres?? Changes in neurology (pain, stretch Rs, stretch reflex) and vasoelastic props (CT alignment). Decr length if immob.