Muscles & Movement Flashcards
Components of skeletal muscle
Muscle -> fascicles (cell bundles) -> muscle fibres (cells) -> myofibrils -> myofilaments
3 types of muscles?
- Skeletal
- Cardiac
- Smooth
Properties of muscles (4)
- Excitability (equated w/ excitability)
- Contract ability (stimulation causes muscles to contract)
- Elasticity (ability to return to original length when tension released)
- 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
Antagonist
Synergist
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
Functions:
-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
Examples;-
- Muscle action
- Specific body region
- muscle attachments
- orientation of muscle fibres (i.e rectus)
- muscle shape & size
- muscle heads/tendons of origin
