chapter 1 structure & function

8/18/2019 Chapter 1 Structure & Function.

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CHAPTER 1:

Structure and Function of the Muscular, Neuromuscular,Cardiovascular and Resirator! S!stems



"#$ectives :

• AFTER C"MP%ET&"N "F TH&SCHAPTER: – 'escri#e macro and micro structures

– descri#e slidin( )lament theor!*

– 'escri#e muscle )#er t!es and itsinvolvement in sorts

– 'escri#e C+ and resirator! s!stems*



MSC%AR S-STEM

Each s.eletal muscle is an or(an* – it contains muscle tissue, connective tissue, nerves and #lood vessels*

Fi#rous connective tissue /eim!sium0 covers more than 23

s.eletal muscles* • Macrostructure and Microstructure:

– Eim!sium is continuous 4ith the tendons at theend of the muscle*

–

Tendon is attached to the #oneeriosteum/ connective tissue over the #one0

– %im# muscles have t4o attachments ro5imal anddistal*

– Trun. muscles have t4o attachments suerior andinferior*



MSC%AR S-STEM

– Muscle )#ers are also referred toas muscle cells*

– Muscle )#ers are multi nucleated

– Muscle )#ers are (roued in#undles called fasciculi*

– Each fasciculus is surrounded #!erim!sium*

– Each muscle )# is surrounded #!endom!sium*

– Endom!sium is continuous 4iththe )#er6s mem#rane,

sarcolemma* – All the connective tissues

eim!sium, erim!sium andendom!sium are continuous 4iththe tendon so tension develoedin the mus cell is transmitted to

the tendon*



MSC%AR S-STEM

• Neuromuscular $unction:

– The $unction #et4een themotor neuron and mus

)#er it innervates is calledmotor end late*

– Each mus cell has onl! 1neuromus $unction

– A motor neuron can

innervate man! mus )#ers* – A motor neuron and the

mus )#ers it innervatesare called motor unit*



MSC%AR S-STEM

• &NTER&"R STRCTRE "F A MSC%E F&7ER: – Sarcolasm: contains contractile comonents, stored

(l!co(en, fats, en8!mes, or(anelles such as mitochondriaand Sarcolasmic Reticulum*



MSC%AR S-STEM

• Cross #rid(es rotrude a4a!from the m!osin )lament atre(ular intervals*

• Actin )laments consist of t4o

strands arran(ed in dou#le heli5• M!osin and actin are or(anised

in the the sarcomere /smallestfunctional unit of s.eletal mus0*

• Sarcomere are reeated in the

entire len(th of the mus )#er*



MSC%AR S-STEM

– M!osin )laments are anchored toeach other at the M #rid(e in thecentre of the sarcomere*

– Actin )laments are anchored at the 9line at either ends of the sarcomere*

–

; actin surround each m!osin and 2m!osin surround each actin*

– alternatin( dar. and li(ht atternsdue to m!osin and actin )laments*

– 'ar. A #and corresonds 4ith theali(nment of the m!osin )laments*

– & #and corresonds 4ith actin in <ad$acent sarcomeres*



MSC%AR S-STEM

– H 8one is the area in thecenter of the sarcomere4here onl! m!osin areresent*

–

'urin( mus contraction H8one decreases as the actinslides over the m!osinto4ards the center of thesarcomere*

–

& #and also decreases durin(mus contraction*



MSC%AR S-STEM

– Each m!o)#ril issurrounded #! s!stem oftu#ules called thesarcolasmic reticulum*

– Calcium is stored in thevesicles of SR*

– T tu#ules runerendicular to SR

– Action otential travels

throu(h T tu#ules 4hichreleases calcium fromthe vesicles located atthe terminal end of theSR*



MSC%AR S-STEM

• S%&'&N= F&%AMENT THE"R- : – the actin at each end slides in4ards on

m!osin ullin( the 9lines* – Restin( Phase: little Ca is resent in the

m!o)#ril, most of it is in the SR so ver!fe4 m!osin are en(a(ed* No tension is

develoed and hence the mus is said to#e at rest*



MSC%AR S-STEM

• S%&'&N= F&%AMENT THE"R- :

– E5citation ContractionCoulin( Phase :

•

SR stimulated to release CA• CA #inds to troonin C

• Moves the other rotein )ltroom!osin

• E5oses the #indin( site onactin

• Thus the cross#rid(e heads#ind to actin

> The amount of force roduced is directl!related to the num#er of cross#rid(es#ound to actin cross sectionall! at thatinstance*



MSC%AR S-STEM

• S%&'&N= F&%AMENT THE"R- : – Contraction Phase :

• Ener(! for cross #rid(e ?e5ion comes fromh!drol!sis of ATP catal!8ed #! m!osinATPase*

• Another ATP should relace A'P on m!osin

head for the head to detach and recoc.*• This allo4s the contraction rocess to

continue*

• CA is availa#le contraction rocess continues

•

CA not availa#le results in rela5ation*



MSC%AR S-STEM


–Rechar(e Phase :• the se@uence of events of muscle

shortenin(: – CA #indin( to troonin actom!osin comle5

formation

–

cross#rid(e ?e5ion – dissociation of actin and m!osin

– recoc.in( of m!osin cross#rid(e heads isreeated over and over , this occurs as lon( as CAis availa#le,

– ATP is availa#le for uncoulin( of actom!osincom le5 and m osin ATPase is availa#le to



MSC%AR S-STEM


–Rela5ation Phase :• "ccurs 4hen stimuli from the motor

nerve stos

• CA umed #ac. to SR and thus

reventin( the coulin( of actom!osin*• Rela5ation is due to actin and m!osin

returnin( to their un#ound state*



MSC%AR S-STEM



NER"MSC%AR S-STEM

• Muscle )#ers are innervated #! motorneurons that transmit imulse in the form

of electrochemical si(nals*• A motor neuron has terminal #ranches at

the end of the a5on that innervates man!mus )#ers*

• The 4hole structure determines the mus)#er t!e, function and involvement ine5ercise*



NER"MSC%AR S-STEM

• Activation of themuscles:

– hen motor neuron )res all the)#ers that it serves (et active

and develo force* – Control deends on the num#er

of )#ers in a motor unit / e(*E!e and @uads0

– A mus is activated #! the arrivalof action otential / AP0to thenerve terminal

– Act!l choline is released – Acet!lcholine diBuses across

the NM

– "nce suDcient amount ofact!lcholine is released anaction otential is (enerated

–

This causes e5citation of thesarcolemma thus )#er contracts



NER"MSC%AR S-STEM

• Activation of themuscles:

– Allor none rincile /either all)#ers contract or the! don6t contract

at all0 e*( (un )re* – Each AP results in a short eriod of

activation of mus )#er referred to ast4itch*

– Summation of t4o t4itches #eforecomlete rela5ation of the )rst t4itchresults in (reater force*

– 'ecrease in time interval #et4eenthe t4itches results in hi(her forces*

– At Hi(h fre@uenc! stimuli t4itchesmer(e and fuse eventuall!/ tetnitetnus0



NER"MSC%AR S-STEM

• Muscle )#er t!es: – fast t4itch and slo4 t4itch/ #ased on

t4itch time0

– FT has short t4itch time/ develos hi(hea. force and rela5es raidl!0 and viceversa for ST*

–

Multile )#er t!es e*( t!e &, t!e &&Aand t!e && G*



NER"MSC%AR S-STEM



NER"MSC%AR S-STEM

Motor nit Recruitment Patterns 'urin( E5ercise :

– Muscles have a#ilit! to (radate force for a smooth,co ordinated atterns of movement*

– Firin( fre@uenc!:•

var!in( force outut is es im for smaller muscles*• At lo4 forces most of the motor units are activated*

• &ncrease force out ut is achieved due to increase infre@uenc!*

– Recruitment:•

Force can #e varied #! var!in( the no of motor unitsrecruited*

• &n %ar(e muscles motor units are activated at near titanicfre@, increase in force outut are achieved #! recruitin(more motor units*



NER"MSC%AR S-STEM

• Comlete motor neuron oolactivation is not ossi#le in untrainedindividuals*

• nder most circumstances activationof the FT units are not ossi#le athi(h fre@uenc! for ma5 force to #e

reali8ed*



NER"MSC%AR S-STEM



NER"MSC%AR S-STEM

• Preloadin(: – Ma5 force does not occur earl! in R"M if mus is unloaded

rior to mus action es* durin( fast movements*

– Mus )#er do not run the entire len(th of the mus*

– Some )# that are active in the earl! R"M 4ill not #eactive if the! are not loaded rior to mus action*

– %iftin( 4ei(hts reloads the muscle to develo suDcientforce to overcome inertia*

–

&so.inetic, h!draulics and friction #ased aaratus do notreload

– Research su((est reloadin( earl! in the R"M durin(hi(h velocities is im to develo stren(th*



NER"MSC%AR S-STEM

• Proriocetion: – Proprioception is the rocess #! 4hich the #od! can var!

muscle contraction in resonse to incomin( informationre(ardin( e5ternal forces, #! utili8in( stretch recetors in themuscles to .ee trac. of the $oint osition in the #od!*

– are seciali8ed sensor! recetors located in $oints, mus andtendons*

– Sensitive to ressure and tension*

– roriocetors alon( 4ith vesti#ular s!stem Rela! info a#outmus d!namics to the CNS* i*e .inesthetic sense, ositions of

#od! arts 4ith resect to (ravit!*

– this info is rocessed at su#conscious level* consciousactivit! is not dedicated to4ards tas.s such as maintainin(osture or osition of #od! arts*



NER"MSC%AR S-STEM

• Muscle sindles: – Modi)ed )#ers enclosed in a

sheath of connective tissue arealso called as intrafusal )#ers*

– Provide info re(ardin( chan(ein len(th and rate of chan(e inlen(th*

– Sensor! neuron of the mussindles s!nases 4ith themotor neuron*

– Mus that erform recise

movements have man! mussindles er unit of mass tohel control e5act contractileactivit!*

– Mus sindles facilitate musactiviation*

– E( is .nee $er. re?e5



NER"MSC%AR S-STEM

• =ol(i tendon or(ans: – %ocated in tendons near

musculo tendinous $unction*

– The! are in series 4ith themus )#ers*

– The! (et activated 4hentendon is stretched due totension in the mus*

– Sensor! neuron of the =T"s!nases 4ith an inhi#itor!

inter neuron 4hich in turns!nases 4ith the motorneuron*

– =T" inhi#its mus activation*



NER"MSC%AR S-STEM

• "lder muscle: – Sarcoenia loss of si8e and stren(th of

muscle*

– Mus function is reduced* – &ts more ronounced in 4ei(ht #earin(

e5tensor mus*

–

Mus atroh! is due to losses in num#erand si8e of mus )#ers es* t!e &&*



CAR'&"+ASC%AR S-STEM

• Primar! roles of the C+ s!stem: – Transort of "< n nutrients

– Removal of 4aste roducts

– Re(ulation of acid#ase function, temand other h!siolo(ical functions*




• Heart: – &s a muscular

or(an*

–

Has interconnected#ut searateums*

– Atria and theventricles*

– Atrium ums the#lood to theventricles*

– +entricles um

the #lood to the



CAR'&"+ASC%AR S-STEM• +alves :

– Consists of atrioventricular /A+0valves 4hich revents the ?o4 of#lood from ventricles to the atriumdurin( s!stole/ ventricularcontraction0*

– A+ valve consists of tricusid and

mitral/ #icusid0 valve* – Also consists of semilunar valves

4hich revents the #ac. ?o4 of#lood from ulmonar! arter! andaorta #ac. to the ventricles durin(diastole / ventricular rela5ation0*

–

Semilunar valves consists ofulmonar! valve and aortic valve*

– Each valve closes assivel! i*e4hen a #ac.4ard ressure (radientushes the valves a(ainst it*

– "ens durin( a f4d ressure(radient*




• Conduction s!stem: – A secialised electrical

conduction s!stem controls themechanical contraction of theheart*

– SA node: intrinsic acema.er

rh!thmic electrical imulse areinitiated*

– &nternodal ath4a!s: conductsimulse from SA node to A+node*

– A+ node : imulse is dela!ed

#efore reachin( the ventricles* – A+ #undles: conducts imulse to

the ventricles

– %eft and ri(ht #undles furtherdivide into Pur.in$e )#ers:transmits imulse to all arts ofthe ventricles




• conduction s!stem of the heart is controlled #! the C+ centerof the medulla*

• hich transmits si(nals throu(h s!mh* and aras!mh*nervous s!stem/ comonents of Autonomic Nervous S!stem0*

• Atria are sulied 4ith #oth s!mh and ara s!mh*

• +entricles e5clusivel! 4ith s!mh

• Stimulation of S!mh NS accelerates the deolari8ation of theSA node thus ma.in( the heart to #eat faster*

• Para s!mh slo4s the dischar(e of SA node thus slo4in( the

heart rate*• RHR ran(es from ;3 to 133#m

• 7elo4 ;3 is #rad!chardia

• A#ove 133 is tach!cardia




• Electrocardio(ram: is the electricalactivit! of the heart at the surfaceof the #od!*

• comrises of P 4ave, IRS comle5J T 4ave*

• P 4ave and IRS comle5 are

electrical deolari8ation / electricalstimulus leadin( to mechanicalcontraction0

• T 4ave is reolari8ation of theventricle

• 'eolari8ation : – &s the reversal of the mem#rane

electrical otential / from ne(ative toositive inside and vice versa outsidethe mem#rane0*

• Reolari8ation : – recover! from the state of

deolari8ation*




• 7lood vessels: – Closed circuit

s!stem 4ith <comonents:

• Arterial s!stem:carries #lood a4a!from the heart*

• +enous s!stem:returns #loodto4ards the heart*




• Arteries : – Raidl! transort #lood a4a! from the heart*

– Has stron( muscular 4alls to 4ithstand hi(h ressure of #loodumed #! the heart*

– 'ivided into arterioles , control vessels throu(h 4hich #loodenters the caillaries*

– Arterioles can alter #lood ?o4 to the ca* &n resonse to thetissues needs, 'ue to its stron( mus 4alls #! dilation orconstriction*

• Caillaries : – alls are ver! thin and ermea#le

– Allo4 e5chan(e of "<, ?uids, nutrients, electrol!tes, hormonesetc* #et4een #lood and interstitial ?uid of the tissues*




• +eins :

– +enules collect #lood from caillaries*

– =raduall! conver(e into lar(er veins*

– Transorts #lood #ac. to the heart*

– alls of the veins are thin co8 of lo4 ressure*

– This allo4s it to constrict or dilate to (reaterde(ree*

– Thus acts as reservoirs* – Some veins have valves reventin(

retro(rade #lood ?o4*




• 7lood : – Paramount functions is the transort of "< to the tissues for

cell meta#olism and removal of C"< from the tissues to thelun(s*

– transort of "< is done #! haemo(lo#in*

– Haemo(lo#in la!s an im role as an acid#ase #uBer• /in the resence of increased h!dro(en ions, hemo(lo#in has less

aDnit! for o5!(en and this means that hemo(lo#in 4ill KunloadKo5!(en more readil! in the caillaries of meta#olicall! active tissues4hich are li#eratin( HL ions and C"<, #oth of 4hich contri#ute to a

more acidic H environment this roert! is .no4n as the 7ohr

eBect**0 /car#onic anh!drase0

C"< L H<" OOOOOOOOOOOO H<C"2 OOOOOOOOOOOO HL L HC"2

car#on dio5ide L 4ater car#onic acid h!dro(en ion L #icar#onate ion



RESP&RAT"R- S-STEM

• Primar! function of the s!stemis #asic e5chan(e of "< andC"<*

• Air asses throu(h the noseand nasal cavities humidif!in(,

4armin( and urif!in( the air*• Air is transorted to the lun(s

throu(h trachea, #ronchi and#ronchioles*

• Air travels throu(h <2

(enerations of #ronchioles#efore it reaches the alveoli*

• E5chan(e of (ases haens atthe alveoli*



RESP&RAT"R- S-STEM

• Movement of air in and out of the lun(s haen

due to e5ansion and recoil of the lun(s*• %un(s do not activel! e5and and recoil #ut it is

acted uon to do so: – 7! do4n4ard J u4ard movement of the diahra(m

/ len(then J shorten chest cavit!0

– J #! elevation J deression of the ri#s / to increase J

decrease front to #ac. diameter of the chest0

• 'urin( #reathin( at rest: – 'urin( insiration, Contraction of diahra(m creates

ne(ative ressure/ vaccum0 in the chest cavit!, 4hichdra4s air in the lun(s*

– 'urin( e5iration diahra(m rela5es, elastic recoil ofthe lun(s, chest 4all and a#do comresses the lun(sand e5els the air out*

• #reathin( durin( e5e: – Elastic forces alone are not o4erful enou(h to rovide

necessar! resirator! resonse*

– 'urin( insiration, elevation of the ri#s is done #!e5ternal intercostals, serratus anterior, scaleni andsternocleidomastoid*

– 'urin( e5iration, deression of the chest is done #!internal intercostals, rectus a#do, e5ternal o#li@ues,internal o#li@ues and transversus*



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chapter 1 structure & function

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