Class 2012 - Muscular System - 2

8/2/2019 Class 2012 - Muscular System - 2

1/47

THE MUSCULAR SYSTEM

PREPARED BY

T.N.LEWANAVANUA

FIJI SCHOOL OF NURSING

repetitio est mater studiorum

repetition is the mother oflearning


2/47

The Muscular System


3/47

There are four characteristics associatedwith muscle tissue:

Excitability

Contractility

Extensibility

Elasticity

- Tissue can receive & respond to stimulation

- Tissue can shorten & thicken

- Tissue can lengthen

- After contracting or lengthening, tissuealways wants to return to its resting state


4/47

The characteristics of muscle tissue enable it toperform some important functions, including:

Movement both voluntary & involuntary

Maintaining posture Supporting soft tissues within body cavities

Guarding entrances & exits of the body

Maintaining body temperature


5/47

Skeletal Muscle

Cardiac Muscle

Smooth Muscle

Muscle Tissue


6/47

Types of muscle tissue:

Skeletal muscle tissueAssociated with & attachedto the skeleton

Under our conscious(voluntary) control

Rapid contraction Microscopically the tissueappears striated

Cells are long, cylindrical &multinucleate


7/47

Cardiac muscle tissue Makes up myocardium of heart

Unconsciously (involuntarily) controlled Microscopically appears striated Cells are short, branching & have a single nucleus Cells connect to each other at intercalated discs


8/47

Smooth (visceral) muscle tissueMakes up walls of organs & blood vessels

Tissue is non-striated& involuntaryCells are short, spindle-shaped & have a singlenucleus Tissue is extremely extensible, while still retainingability to contract


9/47

Anatomy of skeletal muscles

Skeletalmuscle

fiber (cell)

MuscleFascicle

Surrounded byperimysium

Surrounded byendomysium

endomysium

perimysium

Skeletalmuscle

Surrounded byepimysium

epimysium

tendon


10/47


11/47

Z line Z line


12/47


13/47


14/47


15/47

Microanatomy of a Muscle Fiber (Cell)

sarcolemma

transverse(T) tubules sarcoplasmic

reticulumterminalcisternae

myofibril

thinmyofilament

thick myofilament

triad

mitochondria

nucleus


16/47


17/47

Sarcomere Relaxed


18/47


19/47


20/47

Binding Site Tropomyosin

Troponin


21/47


22/47


23/47


24/47


25/47

Muscle Contraction Summary

Nerve impulse reaches myoneural junction

Acetylcholine is released from motor neuron

Ach binds with receptors in the musclemembrane to allow sodium to enter

Sodium influx will generate an action potentialin the sarcolemma


26/47

Muscle ContractionContinued

Action potential travels down T tubule

Sarcoplamic reticulum releases calcium

Calcium binds with troponin to move thetroponin, tropomyosin complex

Binding sites in the actin filament areexposed


27/47

Muscle ContractionContinued

Myosin head attach to binding sites andcreate a power stroke

ATP detaches myosin heads andenergizes them for another contaction

When action potentials cease themuscle stop contracting


28/47

Motor Unit


29/47

Motor Unit Ratios

Back muscles1:100

Finger muscles1:10

Eye muscles1:1


30/47


31/47

Creatine

Molecule capable of storing ATP energy

Creatine + ATP Creatine phosphate + ADP


32/47

Muscle Fatique

Lack of oxygen causes ATPdeficit

Lactic acid builds up fromanaerobic respiration


33/47

Muscle Atrophy

Weakening and shrinking of a

muscle

May be causedImmobilization

Loss of neural stimulation


34/47

Muscle Hypertrophy

Enlargement of amuscle

More capillariesMore mitochondria

Caused by

Strenuous exerciseSteroid hormones


35/47

Steroid Hormones

Stimulate musclegrowth and

hypertrophy


36/47

Muscle Tonus

Tightness of a muscle

Some fibers always

contracted


37/47

Tetany

Sustained contraction of amuscle

Result of a rapid successionof nerve impulses


38/47

Tetanus


39/47

Refractory Period

Brief period of time

in which muscle cells

will not respond to astimulus


40/47


41/47

Skeletal MuscleCardiac Muscle


42/47

Isometric Contraction

Produces no movement

Used inStanding

SittingPosture


43/47

Isotonic Contraction

Produces movement

Used inWalking

Moving any part of the

body


44/47

Key Note

Skeletal muscle fibers shorten

as thin filaments interact with

thick filaments and slidingoccurs.


45/47

These physiological processesdescribe what happen at thecellular level

But what about at the organlevel?


46/47

Anatomy of the Muscular System

OriginMuscle attachment that remainsfixed

InsertionMuscle attachment that moves

ActionWhat joint movement a muscleproducesi.e. flexion, extension, abduction,

etc.


47/47

For muscles to create a movement,they can onlypull, not push

Muscles in the body rarely work alone,& are usually arranged in groupssurrounding a joint

A muscle that contracts to create thedesired action is known as an agonistorprime mover

A muscle that helps the agonist is a

synergistA muscle that opposes the action of theagonist, therefore undoing the desiredaction is an antagonist

Class 2012 - Muscular System - 2

Documents