Musculoskeletal System - Muscles.pptx

7/24/2019 Musculoskeletal System - Muscles.pptx

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Musculoskelet

al System -MusclesYear 11 Human BiologyATAR Unit 1 & 2


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Unit Objectives

The muscular system is organised tomaintain posture and produce movement;

muscle fre contractions can e e!plainedusing the sliding flament theory"

#ovement results $rom the actions o$paired muscles% ith others acting asstailisers% to produce the re'uired

movement"


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Introduction (Recap of

knowledge#uscle cells $orm long% thin fres (aility to

contract)"

#uscles allo ones to move and maintaincontrol (skeletal muscles)"

Smoot! muscles (i"e" stomach% intestines) *involuntary muscles"

#ardiac muscle (heart)" #aintain contractions"

#uscles are +extensible, (aility to stretch) and+elastic, (aility to return to normal)"


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Structure of skeletal

muscles#uscle cells are held together in undles"

Red meat is muscle and it is these bundles

that give meat its stringy appearance.

#uscle is a $orm o$ connective tissue" Thismuscle allos $or movement (via

contractions)"Bundles o$ muscles $orm tendons"


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Myo$brils structure

The myofrils are actually made o$ manysmaller myo$laments(made of protein)% hich

are the actual units involved in musclecontractions"

There are to types o$ myoflamentsThic. (composed o$ the protein myosin)

Thin (composed o$ the protein actin)


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Myo$brils

structurehen a musclefre otains

energy and isactivated y anerve impulse *these thic. and

thin proteins slidepast each other(causing themyofrils to

shorten)"


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Myo$brils structure

/t is these thic. and thin flaments that gives abanded e%ect to the muscle"

#yofrils can e divided into units calledsarcomeres"

The striated appearance o$

s.eletal muscle is dueto variations in theactinand myosincontent in di3erent

parts o$ the sarcomere"


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Muscle Structure Summary

Skeletal muscle is made up of

&undles of muscle $breseach of which

contains

Myo$brilswhich contain

Myo$lamentsof two types

'ctin and myosin


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Sliding ilament Model

(SMSliding ilament Model is used to e!plain homuscles contract"

hen muscles contract% the sarcomeress!orten"

This model suggest that this occurs becauseactin and myosin laments slide over oneanother.


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(SMActin flaments slide over the myosin flament *the ) lines are drawn closerand the sarcomereis shortened"

4nergy is re'uired $orshortening o$ the

muscles fres"

4nergy is releasedhen AT5 rea.s

don to A65"


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' bands * contain oth myosin7actin

* +one * contains myosin only (M line through the centre)

I bands contain actin only

) lines are dense% frous lines hich cross the I bandsand are attached to actin"

Sarcomereis eteen to ) lines


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Overview of contractions

1" #uscle fre is stimulated (i"e" nerve impulse)

2" -alcium (-a) ions are released

8" Thin (actin) flaments move to middle o$sarcomere

9" #uscle fres contract (energy7AT5 re'uired)

:" #uscle tension increases

" #uscles rela!ed * pro


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Muscles working toget!er

Muscles only contract"

They pull ones together% ut not pushing them

apart"

/$ muscles contract (pulling a one in onedirection)% another set o$ muscles must contract

to pull the one in the opposite direction"Hence hy muscles are grouped in pairs"

These pairs are called antagonistic muscles

(moving opposite)" =uch as triceps7iceps"


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'ntagonistic Muscles


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Origin* end o$ the muscle f!ed to a stationary one

Insertion* attachment o$ the other end o$ the

muscle (the moveale one)&elly* >eshy portioneteen the tendonsand insertion

'gonist,prime mover *muscle that causeda desired action


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Synergistsare muscles that help the prime mover(i.e. the muscle that is intended to move)"

They may produce the same movement as the primemover (agonist) or support the e!ing" Also called a $.ator"


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Muscle 0one

#uscle tone is not caused y constantcontractions o$ the same fres% ut y many

di3erent fres ta.ing turns to contract"?ires are ale to relieve one another sosmoothly that the contraction can e .ept uplong periods o$ time"

1ostureo$ a person depends on muscle tone"


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Gastrocnemius


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inal 2ink

4stalishing the fnalconnection eteen

ones and muscles"

E.g. Triceps and

biceps connectedto the humerusand radius.

Musculoskeletal System - Muscles.pptx

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