Physiology of Skeletal Muscle
Majesty Gonzales, Mildred Gonzales, Rachelle Heredia & Anne Kaw Summary
Twitch is a muscle contraction that occurs in a response to a stimulus wherein it is responsible for the eneration of an action potential in a muscle fiber! "n this e#periment, the effect of raded response, load, pulse fre$uency, and muscle fatiue on the contraction of the fro astrocnemius was determined usin a %ymoraph and owerlab set up! Keywords' s%eletal muscle, stimulus, twitch
Introduction
(%ele (%eleta tall musc muscle less compr compris isee about about
A muscle contraction that occurs in
)*+ )*+ of the mamm mammal als s body body mass ass and and
response nse
acco accoun unts ts for for -*+ -*+ of a huma human nss rest restin in
responsible for the eneration of an action
meta metabo boli licc
1*21*2-3! 3!
potential in a muscle fiber! (ince each
(%eletal muscles are 4oluntary muscles that
muscle muscle comprises comprises indi4idual indi4idual muscle muscle cells, cells,
shor horten ten
cont contra ract ctiions ons
the contraction of indi4idual muscle cells,
enerated by s%eletal muscles are used for
can cause 4aried contractions in the muscle!
two functions' mo4ement and posture of the
The The diff differ erent ent der deree ee of contr contrac acti tion on that that
body! 5or a s%eletal muscle contraction to
occurs
occu occurr ther theree must must be a neur neural al stim stimul ulus us,,
responses! These responses are due to the
calcium in the muscle cells, and enery from
chane in fre$uency of stimulation and the
AT ./an &0ierath, 1*2-3! The eneration
chan chane e in the numb number er of muscl usclee cell cellss
of an action potential and the transduction of
stimulated
elec electr tric ical al
&Reiani, 1*223!
rate rate ./a ./an n
or
cont contra ract ct!!
ener enery y
into into
&0ie &0iera rath th,,
The
an
intr intrac acel ellu lula lar r
chemical sinal trier the interaction of the
to
in
a
a
stimulus,
muscle
to
a
twitch,
pro produc duces
contract
is
raded
(chiaffino,
Thre Thresh shol old d is the the lowe lowest st le4e le4ell of
myof myofil ilam ament ents, s, namely namely actin actin and and myosi myosin n
stimulation
that
triers
a
muscle
.Reconditi, et al!, 1*223! Muscle contraction
cont contra ract ctio ion! n! "f the the stim stimul ulus us is incr increa ease sed d
occurs because of the slidin mechanism of
abo4e threshold, the strenth of contraction
the myosin head on the actin, which forms a
strenth will increase with stimulus intensity
cross bride .Reconditi, et al!, 1*223!
as more muscle fibers undero contraction! 6hen the stimulus strenth reaches a certain
le4el, no further increase in tension occurs, since
all
muscle
fibers
are
Frog Dissection
already
The The fro fro was was doub double le9p 9pit ithe hed d and and
contractin! The three basic staes that occur
usin a scalpel or sharp scissors, the s%in of
durin a twitch are the latent period .the
the fro was cut around its abdomen! The
time between the application of the stimulus
s%in was peeled down and off the les of the
and the occurre occurrence nce of contrac contractio tion3 n3 .7a .7ai,
fro and it was %ept moist at all times with
1*2*3 1*2*3,, cont contra ract ctio ion n time time .tim .timee from from the the
Riners solution! A lass probe was used to
contraction to the pea% of tension3, and the
e#pose the sciatic ner4e from between the
rela#ation time .from the pea% tension to the
thih muscles down to the %nee! A 1:9cm
point where the tension returns to the
piece of stron thread was then slipped
baseline3!
under the Achilles tendon at the heel of the
(%eletal (%eletal muscle fatiue fatiue is defined as
fro and it was securely tied to the tendon!
the decreasin force or contraction of the
The astro astrocnem cnemius ius muscle muscle was carefu carefully lly
muscle muscle in respons responsee to contract contractile ile acti4i acti4ity ty!!
dissec dissected ted away from from the tibio9 tibio9fib fibula ula bone
Muscle fatiue can be caused by a number
and it was left attached to the %nee! The
of factors such as the loss of AT in the
foot, thih muscles, and the other muscles
muscl usclee
was remo4ed, lea4in the sciatic ner4e and
whi which
resul esults ts to cess cessat atiion
of
contra contracti ction, on, decline decline in contra contracti ction on due to
ast astro rocne cnemi mius us atta attach ched ed to the the %nee! %nee! The The
chemi emical
fiber
tibio9fibula bone ;92* mm was cut below
the
the %nee %nee usi usin bone bone shear hearss or stro stron n
stim stimula ulati tion on of ner4 ner4es es to crea create te impul impulse sess
scissors! The femur was then cut close to the
$uic% enouh to maintain the stimulus and
hip joint!
caus causee
etri dish until it was ready to mount!
contraction,
inhibition and
of
the
calc calciu ium m rele releas asee
muscle cle
decrease ase
in
.la .lace ce,, 7amada mada,,
8ruton, &6esterblad, 1*2*3! "n this this e#pe e#peri rime ment nt,, the the effe effect ct of
A Proc Proced edur ures es for for Kymo Kymogr grap aph h
A!2 Graded Response
raded response, load, pulse, fre$uency, and
The
muscle cle9ner4e
set9up
was
muscle fatiue on the contraction of the fro
prepared in the %ymoraph! The Kymoraph
ast astro rocn cnem emiu iuss was was dete determ rmin ined ed usin usin a
was then set at slow paper speed and the
%ymoraph and owerlab set up!
muscl usclee
was was
sti stimul mulated ated
with with -=! -=! The
stim stimul ulus us was was chec chec%e %ed d if it prod produc uced ed a Materials and Methods
twitch! The 4oltae was increased at 2!:=
inter4al until a twitch was produced! =oltae oltae
An in vitro preparation of the
and response to twitch heiht was recorded!
ast astro rocn cnem emiu iuss
muscl usclee
was was
made made!!
The The
The process was continued until there was
%ymoraph %ymoraph drum was set at moderate speed
no increase in twitch heiht obser4ed with
then the muscle was stimulated at ma#imal
an incr increa ease se in 4olta 4oltae! e! The The resp respon onse se in
4oltae once and it was allowed 2: seconds
heiht aainst 4oltae was plotted!
reco4ery! The muscle was %ept moist at all times times with with Riner Rinerss soluti solution! on! The muscle muscle
A!1 /ffect of
was stimulated twice then it was rested for
The The femu femurr was was clam clampe ped d and and the the
anot another her 2: seco seconds nds and and the the musc muscle le was was
thread was attached to the Kymoraph le4er
stimulated aain with - consecuti4e stimuli!
arm! The weiht pan was haned under the
The process was continued with increasin
muscle and recorded as the 0ero
number of stimuli until the muscle ceased to
The Kymoraph le4er was adjusted so that
contra contract! ct! The number number of muscle muscle twitch twitches es
any contraction in the muscle was recorded
was recorded at each fre$uency!
in the upper part of the drum! The drum was rotated at a 4ery low speed then the muscle
B Proc Proced edur uree for for Pow Power er La La >
was was stim stimul ulat ated ed with with a sin sinle le ma#i ma#ima mall
Mountin the muscle for recordin
4olt 4olta ae! e! The The proc proces esss was was then then e4ery e4ery 2* secon conds!
5i4e
and
mount ounted ed in the micro micropos posit itione ionerr mountin
stimul stimulate ated d with with a sinle sinle pulse! pulse! Another Another :
brac%et! The cable was plued into the
rams was added and stimulated aain after
bac% of the Bridge the Bridge Pod. A Pod. A small metric ruler
2* seconds! More weihts were added until
was taped to the side of the micropositioner
the the
dras drasti tica call lly y
to use as a reference when adjustin heiht!
reduced reduced!! The weiht weiht lifted lifted by the muscle muscle
The Bridge The Bridge Pod was connect connected ed to the Pod the Pod
aainst the contraction heiht was plotted!
Port on "nput "nput 2 of the the owe ower< r ab>!! The The
bipolar stimulator handle was mounted to
weiht lifted was plotted!
the rin usin a clamp! The femur of the
cont contra ract ctio ion n
ram ramss
hei heiht ht
was
was was
added
The Force The Force Transducer Transducer was securely
fro was clamped to the rin stand usin a A!- /ffect of ulse 5re$uency, Tetanus and
femur clamp! The thread was then attached
Muscle 5atiue
throuh the hole in the metal tab of the Force
Transducer !
The
anle
of
the
micropositioner was adjusted such that the
scre screen en inst instru ruct ctio ions ns were were foll followe owed! d! The The
ast astro rocne cnemi mius us was was perp perpen endi dicul cular ar to the the
owe ower< r ab> stim stimul ulat ated ed the the musc muscle le with with
table! table! The micropositioner was was raised usin
increasin strenth and the results for each
the adjustment %nob so that the muscle was
contraction was recorded!
4ertical but not under tension! The muscle was rinsed with Riners solution to %eep it
8!1 /ffect of load on contraction force
mois moist! t! The The bipo bipola larr stim stimul ulat ator or was was then then
The muscle was %ept moist and the
positioned such that both stimulus leads
stimulator handle was positioned correctly!
were touchin the middle of the muscle! The
The The posi positi tion on of the the micr microp opos osit itio ione nerr was was
8?@ .B93 leads from the stimulator handle
note noted d usin usin the the rule rulerr and and this this was was the the
were attached attached to the Output .B93 .B93 connectors
reference position! "n , Setup was
on the front of the ower!
chos chosen en from the the menu menu bar and Stimulator
(ettin up the software
was was sele select cted ed!! The The 4alu 4aluee in 4olts 4olts for for the the
Csin Csin the the comp comput uter er,, owe ower< r >
suprama#imal suprama#imal stimulus stimulus 4oltae 4oltae calculated calculated
was opened! opened! rt>;!* ;!* was launche launched! d!
was inputted in the Amplit Amplitude ude ield ield or the
The The Frog Muscle Folder was chosen from
Dutput field! "n , Macro , Macro from from the
the Experiments Gallery then th the Frog
menu enu bar bar was was selec electe ted d then hen the the Muscle
Muscle Settings file file was was opene opened! d! A two9 two9
Tensio nsion. n. The on9scr on9screen een instr instruct uction ionss were were
chan channe nell empt empty y data data file file appe appear ared ed!! The The
foll follow owed ed to recor record d the the data data!! After fter each each
8rid 8ride e od od was was sele select cted ed from from the Force
recordin, at least 2* seconds was waited to
channel pop9up menu! The %nob on the front
allo allow w the the musc muscle le to reco reco4e 4err befo before re the the
of the 8ride od was used to adjust the
micropositioner
sinal so that it read zero! The DK button
millimeter! At the end of the recordin, the
was clic%ed to start the ne#t e#ercises!
micropositioner was was returned to its oriinal
wasraised
by
o ne
position and the tension of the muscle was 8!2 The raded response The muscle was %ept moist and it
releas released ed by turnin turnin the adjust adjustmen mentt %nob! %nob! The results were recorded in table )9E!
was was made made sure sure that that both both lead leadss from from the the stimul stimulato atorr are touchi touchin n it! "n , t>,
8!- /ffect of pulse fre$uency on contraction
Macro was Macro was selected from the menu bar then
force
Graded Graded Respons Responsee was was chos chosen en!! The The on9 on9
The muscle as %ept moist at all times
select selected! ed! The on9scr on9screen een instr instructi uctions ons were were
and the stimul stimulato atorr handle handle was positi positione oned d
follow followed! ed! The ower b> stimul stimulate ated d the
correctly correctly!! "n , , Macro Macro was was chosen
muscle continuously with a stimulus inter4al
form the menu bar then Stimulus Fre!uency
of 1*ms 1*ms for for -* seco second nds! s! The The reco record rdin in
was select selected! ed! The on9scr on9screen een instru instructi ctions ons
duration was ): secon ds! After the recordin
were followed! followed! The ower ower stimulated stimulated
stop stopped ped,, a comment was added to the data
the muscle with twin pulses )**ms, 1**ms,
trace called Fatigue. called Fatigue.
2**ms *ms,
:*ms,
and
1*ms *ms
apart!
/ach
recor recordi din n appe appeare ared d in a separ separat atee bloc bloc%! %!
Analysis for PowerLa!
6hen hen
8!2 The raded response
the recor ecordi din n was was
com complet plete, e, a
"omment was was added to each bloc% of data
Mar#er .M3
was
placed
on
the
with the stimulus inter4al! The results were
baseline of the wa4eform in the 5orce
recorded in Table )9F!
channel channel!! The $aveorm "ursor was placed at the top of the last contraction pea%! The
8!) Tetanus
pea% heiht for each of the pea%s was
The The musc muscle le was was %ept %ept mois moistt at all all
recor corded ded! The data in Table )9) was
and and
was was
reco record rded ed,, star starti tin n at the the last last poin pointt and and
positioned correctly! "n , Macro
wor%in bac%wards to the beinnin of the
was chosen from the menu bar and Tetanus
trace! 5rom the data, the minimum 4oltae
was select selected! ed! The on9scr on9screen een instru instructi ctions ons
re$uired was determined to elicit a ma#imal
were followed! followed! The ower ower stimulated stimulated
contraction called the ma#imum e#citation
the muscle for one second with continuous
4olta 4oltae! e! The 4alue 4alue for the supram suprama#i a#imal mal
pulses at inter4als )**ms, 1**ms, 2**ms,
stimulus was determined by multiplyin the
:*ms, :*ms, and 1*ms! "omments "omments were added to
4oltae by 2!:! The 4alues were recorded in
the data to indicate the stimulus inter4al!
Table )9:!
8!: Muscle 5atiue
8!1 The effect of load on contraction force
times imes
the
stim timulat ulator or
hand handle le
The muscle as %ept moist at all times
The Mar#er was was retu return rned ed to its its
and the stimul stimulato atorr handle handle was positi positione oned d
restin position by clic%in the lower left
correctly correctly!! "n , , Macro Macro was was chosen
corn corner er of the the t> docum document ent!! The The
form the menu bar then Fatigue was
$aveorm "ursor was used to measure the
baseline 4alue and called the preload the preload orce.
'aseline was was place placed d in the the Force channel
The ra% t%itc& t%itc& orce orce with the the $aveorm
imme immedi diat atel ely y
"ursor was was dete determ rmin ined ed by plac placin in the the
wa4eform wa4eform cursor was used to determine determine the
cursor on the ma#imum 4alue in the bloc%!
ma#imum contraction force and these 4alues
The results were entered in Table )9E! (teps
were
1 and and - were were repe repeat ated ed for for the the othe otherr 2*
ma#i ma#ima mall stim stimul ulat atio ion n in Table ble )9! )9! The The
bloc%s! The net t%itc& orce orce was calculated
contraction force at t 2,:,2*,2:,1*,1:, and
by subtractin the preload value from the
-* secon econds ds were were det determi ermine ned d aft after the
ra% t%itc& orce 4alue! orce 4alue!
stimul stimulati ation! on! The result resultss were were record recorded ed in
prio priorr
reco ecorded
to
stim stimul ulat atio ion! n!
inclu cludin
the
time
The The
of
Table )9! 8!8!- The The effe effect ct of stim stimul ulus us fre$ fre$ue uency ncy on contraction force The
data
"esults and Discussion
were
e#ami amined ned
from
/#ercise - and there were fi4e bloc%s of
(. )ymograp& (.( Graded response
reco record rded ed data data!! 5or 5or each each data data bloc bloc%, %, the the
"n this acti4ity, a sciatic ner4e still
ma#imum contraction force of the first and
attached to an isolated s%eletal muscle of a
second second pea%s pea%s were were determ determine ined d usin usin the
toad toad was subject subjected ed to increa increasin sin stimul stimulus us
mar%er mar%er and wa4efo wa4eform rm cursor cursor!! The result resultss
4oltae of -, )!:, E, F!:, and 21 =!
were recorded in Table )9F!
Kymo Kymor raph aph was was used used whic which h showe showed d the the analoue analoue reist reistrat ration ion of respons responses es of the
8!) Tetanus The
scia sciati ticc ner4e ner4e meas measur ured ed with with the the aid aid of a data
were
e#ami amined ned
from
/#ercise ) and there were fi4e bloc%s of reco record rded ed data data!! The The maximum maximum contraction contraction orce for each stimulation re!uency was dete determ rmiined ned
and and the resu resullts
were were then then
recorded in Table )9;!
8!: Muscle 5atiue The
data
were
e#ami amined ned
from
/#er /#erci cise se :! The The mar#er on th the %aveorm
metric ruler!
#ale $%Graded response without weiht
(.* Eect o +oad "n this acti4ity, the effect of load was
6ithout weiht =oltae ae Heiht of the pea% .mm3 2 ) !: F E 21 F !: 2) 2) 21 2:
in4es n4esti tia ate ted d
wit with
: :
cent centa4 a4o o
coin coinss
atta attach ched ed to an isol isolat ated ed s%el s%elet etal al musc muscle le subjected with increasin stimulus 4oltae!
#ale &%Graded response with weiht
6ith : : centa4os weiht =oltae Heiht of the pea% .mm3 * ) !: E 22 F !: 22 2) 21 2:
20 15 10 5 0 2
4
6
8
10
12 12
14 14 20
Figure $% Graded response without weiht
15 10
The threshold 4oltae which is the 5
mini minimu mum m stim stimul ulus us re$ui re$uire red d to induc inducee a response is -=! As the stimulus 4oltae is
0 2
4
6
8
10
12 12
14 14
increased beyond the threshold 4oltae, the heiht of the pea% enerated by the response
Figure &% Graded response with weiht
also also increa increases ses!! As a result result,, increas increasin in the
As a result, the muscle still enerated
stimulus 4oltae results in an increase of the
forc forcee or diff differ eren entt pea% pea%s! s! "ncr "ncrea easi sin n the the
force produced by the whole muscle! This is
stimulus 4oltae still results in an increase
due due to more ore muscl usclee fibe fibers rs and and motor otor
of the force produced by the isolated s%eletal
neur neuron onss are are act acti4ate 4ated d and and leads eads to an
musc muscle le!! 8ut 8ut beca becaus usee the the wei weiht htss were were
increase in muscle force! Ma#imal 4oltae
attache attached d to the s%elet s%eletal al muscle, muscle, the force force
of 21 = was reached when all of the muscle muscle
enerat enerated ed was lower than than that that of withou withoutt
fibers ha4e been acti4ated!
weihts! This is may be due to the 4elocity
at which muscle shortens dependin on the
of muscle fatiue will result in the decrease
load it has to bear .Meijer, 2;3!
o4er time of the force!
(., Eect o Pulse Fre!uency- Tetanus Tetanus and
*. Po%erla'
Muscle Fatigue
*.( Graded response
This This e#perim e#periment ent aims aims to determi determine ne the
effect
of
puls ulse
fre$uen uency! cy!
ulse
fre$uency is the number of action potentials ene enera rate ted d
per per
minu minute te!!
(tim (timul ulat atin in
the the
isol isolat ated ed s%el s%elet etal al muscl musclee twic twicee with with the the shor shorte test st time time inte inter4 r4al al with with 2: seco second ndss rela#ation rela#ation between the stimuli stimuli will result result in an increase of force enerated! "f the force of contraction with each subse$uent allows the muscle to fully rela#, it would be treppe! Treppe, also %nown as the staircase effect, is where there is more force produced than the
Table -! Graded response of fro muscle to increasin stimulus =oltae )! : E 21
1!: ? *!*22; *!*22F *!*21: *!*2): *!*2E:
-? *!*2:) *!*2:E *!*2;: *!*1*E *!*1-1
-!: ? *!*1-1 *!*1-1 *!*1-1 *!*1-1 *!*1-1
The The e#pe e#peri rime ment nt prop propos osed ed that that as tensi tension on on the muscle increased increased,, force force of contraction would increase until a phase at which which an additi additiona onall tensio tension n would would cause cause stability of the enery that was obser4ed!
pre4ious muscle twitch! "f the muscle is stimulated repeatedly with stimuli arri4in consec consecuti uti4ely 4ely with with short short time time inter4 inter4al, al, it would
be
wa4e
summation!
6a4e
summ summat atio ion n resu result ltss to a stro strone nerr musc muscle le contra contracti ction on because because the muscle muscle twitch twitches es o4erlap with each other due to repeatedly stimulatin the muscle! The effect of tetanus on the isolated s%eletal muscle will result in an increase of the force as the stimulus fre$uency increases to a point where there is no further increase in the force! This point is called the ma#imal tetanic tension! Dn the other hand, the effect
*.* T&e eect o load on contraction orce
phenomena of summation, tetanus, and e4en e4entu tual al fati fatiu uee of the the musc muscle le and and the the respecti4e fre$uencies at which each were obser4ed!
1!) Tetanus This This 5iure -! /ffect of load on contraction force
e#pe e#peri rime ment nt
effect
of
stretchin
the
rela relati tion onsh ship ip
amon amon fre$ fre$uen uency cy of simu simula lati tion on and and the the resultin
The
pro4 pro4id ides es
contraction
astrocnem nemius
force
muscle!
of
the
(ummation, on,
sarcomere on the force of contraction of fro
incomp incomplet letee tetanu tetanus, s, and comple complete te tetanus tetanus,,
s%el %eleta etal
usin
are characteristics of muscle contraction that
ower
were obser4ed by radually increasin the
of sarc sarcom omer eree stre stretc tch h was was dete determ rmin ined ed by
fre$uency stimulation!
muscle cle
was
recorded ded
raisin raisin the force transd transduce ucerr to which which the ast astro rocne cnemi mius us musc muscle le was was atta attach ched ed and and measurin the resultin chanes in baseline
1!: Muscle 5atiue "n orde orderr to obse obser4 r4ee the the onse onsett of
on the software in rams! The resultin force
fatiue, the stimulator was set to complete
of contraction of the muscle at ma#imum
teta tetanu nuss as dete determ rmin ined ed in the the pre4 pre4io ious us
response stimulation was also measured in
e#periment!
rams! 'onclusion
*., *., T&e ee eect ct o stim stimul ulus us re! re!ue uency ncy on contraction orce
"ncreasin "ncreasin the fre$uency fre$uency of stimuli stimuli on the muscle would cause contractile force
"ncreasin the fre$uency of stimuli
to incr increas easee its its ma#i ma#imu mum m poin pointt thro throu uh h
on the muscle would cause contractile force
diff differ erent ent occur occurre rence nce of contr contrac acti tion on and and
to summ summat atee and and incr increas easee to a ma#i ma#imu mum m
e4entual fatiue of the muscle!
point without rela#ation and remain there for a peri period od of time time befo before re slow slowly ly show showin in decay in force! The results from e#periments three and four e#plain the occurrence of the
"r4in "r4in,, M! .1*22 .1*223!M 3!Moti otion on of myosin myosin head
"eferences
/an /an,, 8!,&0 8!,&0ie iera rath th,,
! .1*2.1*2-3! 3! /#erc /#ercis isee
dom domains ains
duri durin n
act acti4at i4atiion
and and
force orce
metabolism metabolism and the molecular reulation reulation of
de4elopment in s%eletal muscle! roceedins
s%eletal muscle adaptation! @ell Metabolism!
of the ?ational Academy of (ciences, 2*;
d#!doi!orB2*!2*2EBj!cmet!1*21!21!*21
.2F3,
F1-E9F1)*!
doi'
2*!2*F-Bpnas!2*2;--*2*; Meijer Meijer,, K! .2;3 .2;3!! Muscle Mec&anics T&e Eect o Stretc& and S&ortening on S#eletal Muscle Force! Force! Cni4ersity of Twente! Twente!
(chiaffino, (!, &Reiani, @! .1*223! 5iber Types Types in Mammalian (%eletal Muscles
lace,
?!,
7amada,
T!,
8ruton,
!,
6esterblad, H! .1*2*3! Muscle fatiue' from obse obser4 r4at atio ions ns
in
huma humans ns
to
hysioloic hysioloical al Re4iews, Re4iews, 2.)3, 2))F92:-2! 2))F92:-2! doi' 2*!22:1Bphysre4!***-2!1*2* 2*!22:1Bphysre4!***-2!1*2*
unde underl rlyi yin n
mechanisms studied in intact sinle muscle
7ai, i,
fibr ibres! es!
rela#at #ation
/urop uropea ean n
hysioloy,
our ournal nal
22*.23,
of 292:!
Appli pplied ed doi'
2*!2**FBs**)129*2*92);*9*
Reco Recondi nditi ti,, M!, M!, 8run 8runel ello lo,, /!, /!,
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