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Flashcards in Muscles & Movement Deck (13):

3 types of muscles?



Components of skeletal muscle

Muscle -> fascicles (cell bundles) -> muscle fibres (cells) -> myofibrils -> myofilaments


Properties of muscles (4)

1. Excitability (equated w/ excitability)
2. Contract ability (stimulation causes muscles to contract)
3. Elasticity (ability to return to original length when tension released)
4. Extensibility: capable of extending in length in response to contraction of opposing muscle


Composition of myofibrils

-myofibrils formed from chain of repeating units called sarcomeres
-are the functional contractile unit of a skeletal muscle fibre
-defined as distance from one Z disc to another

-each sarcomere shortens as muscle fibres contract
-thick (myosin) and thin (actin) filaments interact
-regulartory proteins in thin = tropomyosin & troponin
-energy (ATP) causes myosin heads to move along actin filaments, shortening myofibrils and contracting muscle


Muscle attachments - origin & Insertion

Origin: less mobile attachment of muscle (aka proximal/fixed/broad)
Insertion: more mobile attachment or muscle (aka distal/mobile/narrow)

*muscle has both an insertion and origin


Muscle terminology;-

Intrinsic vs extrinsic

Isotonic vs isometric

Intrinsic: on inside relative to other body parts
Extrinsic: on outside " " " "

Isotonic: movers (I.e biceps)
Isometric: stabilisers (I.e infraspinatus- stabilises shoulder)


Groups of skeletal muscles based on primary actions;-




Agonist: (aka prime mover) - muscle that contracts to produce a particular movement (I.e. Extending forearm)

Antagonist: muscle whose actions oppose that of agonist - used to stabilise

Synergist: muscle that assists the agonist in performing action


Skeletal Muscle Characteristics and 5 functions

-Striated (marked by stripes or bands)
-single muscle may contain 100s of 1000s of fibres
-body movement
-maintenance of posture
-temp. regulation (heat produced during contraction)
-Storage & Movement of materials
-Support (i.e. pelvic floor)


Cardiac Muscle characteristics

-individ. muscles arranged in thick bundles w/in heart wall
-striated, but shorter & thicker than skeletal
-1 or 2 nuclei
-form Y shaped branches to join to adjacent muscle cells at junctions called intercalated discs
-are AUTORHYTHMIC = individ. cells can generate muscle impulse w/out nervous stimulation
-dependent on calcium for contractions
-large no. of mitochondria to generate large amount of ATP needed for constant work


Smooth Muscle Characteristics

-composed of short muscle cells w/ fusiform shape
-single, centrally located nucleus
-do have thick & thin filaments - not precisely aligned (sacromeres not easily visible)
-slow contraction, resistant to fatigue (sustained over long period of time)
-is involuntary


Atropy vs. Hypertrophy

Atropy: Wasting of tissue that results in reduction of muscle size, tone & power
-from decreased stimulation
-when extreme atrophy occurs, loss of gross muscle function permanent

Hypertrophy: An increase in muscle ire size
-Increase in number of myofibrils per fibre in fast fibres
-may be increased by exercising
-results in more mitochondria, larger glycogen reserves and increases ability to produce ATP


Levers & Joint Biomechanics;-

First, second and third class lever (plus examples)

Lever: elongated, rigid object that rotates around fixed point called a fulcrum (e.g. seesaw)
-First Class Levers: Fulcrum in middle b/w effort & resistance (e.g. pair of scissors, atlantoccipital joint of neck
-Second Class levers: Resistence b/w fulcium & applied effort - small force can balance large weight (i.e. foot is depressed *rare in body)
-Third class lever: Effort applied b/w resistance and fulcrum *most common*
e.g. elbow


Naming skeletal muscles

-Names usually provide clue to their identification

-Muscle action
-Specific body region
-muscle attachments
-orientation of muscle fibres (i.e rectus)
-muscle shape & size
-muscle heads/tendons of origin