Experiment 4 - Physiology

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 fatiue on the contraction of the fro astrocnemius was determined usin a %ymoraph 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 nss 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 der deree 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 enery from

chane in fre$uency of stimulation and the

AT ./an &0ierath, 1*2-3! The eneration

chan chane 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

&Reiani, 1*223!

rate rate ./a ./an n

or

cont contra ract ct!!

ener enery y

into into

&0ie &0iera rath th,,

The

an

intr intrac acel ellu lula lar  r 

chemical sinal trier 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

triers

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 strenth of contraction

the myosin head on the actin, which forms a

strenth will increase with stimulus intensity

cross bride .Reconditi, et al!, 1*223!

as more muscle fibers undero contraction! 6hen the stimulus strenth reaches a certain

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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 staes 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 les of the

and the occurre occurrence nce of contrac contractio tion3 n3 .7a .7ai,

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

Riners 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

thih 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 fatiue fatiue 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 fatiue 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, thih 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% enouh to maintain the stimulus and

hip joint!

suprama#imal suprama#imal stimulus stimulus 4oltae 4oltae calculated calculated

was opened! opened! ;!* ;!* 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 8ride 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 8ride od was used to adjust the

micropositioner

sinal 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 oriinal

wasraised

by

o ne

 position and the tension of the muscle was 8!2 The raded response The muscle was %ept moist and it was was made made sure sure that that both both lead leadss from from the the

releas released ed by turnin turnin  the adjust adjustmen mentt %nob! %nob! The results were recorded in table )9E!

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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 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 $aveorm "ursor   was placed at the top of the last contraction pea%! The

8!) Tetanus

 pea% heiht 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 beinnin of the

was chosen from the menu bar and Tetanus

trace! 5rom the data, the minimum 4oltae

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 4oltae! 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

4oltae by 2!:! The 4alues were recorded in

the data to indicate the stimulus inter4al!

Table )9:!

8!: Muscle 5atiue

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

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 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 $aveorm

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

4oltae of -, )!:, E, F!:,  and 21 =!

were recorded in Table )9F!

Kymo Kymor raph aph was was used used whic which h showe showed d the the analoue analoue reist reistrat 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

recorded in Table )9;!

were were then then

metric ruler!

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#ale $%Graded response without weiht

(.* Eect o +oad  "n this acti4ity, the effect of load was

6ithout weiht =oltae ae Heiht of the pea% .mm3 2 ) !: F E 21 F !: 2)  2) 21 2:

in4es n4esti tia 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 4oltae!

#ale &%Graded response with weiht

6ith : : centa4os weiht =oltae Heiht 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 weiht

15 10

The threshold 4oltae 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 4oltae is

0 2

4

6

8

10

12 12

increased beyond the threshold 4oltae, the heiht of the pea% enerated by the response

Figure &% Graded response with weiht

14 14

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at which muscle shortens dependin on the

of muscle fatiue will result in the decrease

load it has to bear .Meijer, 2;3!

o4er time of the force!

(., Eect 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  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 strone nerr musc muscle le

Table -! Graded response of fro muscle to increasin stimulus =oltae )! : 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 enery that was obser4ed!

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 phenomena of summation, tetanus, and e4en e4entu tual al fati fatiu uee of the the musc muscle le and and the the respecti4e fre$uencies at which each were obser4ed!

1!) Tetanus This This 5iure -! /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