Download Ch6 Power Point - Muscles

Chapter 6
Muscular System
Prefixes that refer to muscle:
myo-, mys- = muscle;
sarco- = flesh
Body movements (see pg 198-199)
 Flexion – decreases joint angle – brings bones closer
Ex. Knee, elbow, bending forward at hip
Extension – increases joint angle – moves bones apart
 Ex. Straightening knee, elbow
 Hyperextension – greater than 180 degrees
Rotation – movement around longitudinal axis
Abduction – movement of limb away from midline
Adduction – movement of limb toward midline
Circumduction – proximal end is still; distal end moves in a circle
Dorsiflexion – flexing foot
Plantar flexion – pointing foot
Inversion – turn sole of foot medially
Eversion – turn sole of foot laterally
Supination – forearm rotates laterally – palms anterior – radius and ulna are
parallel
Pronation – forearm rotates medially – palms posterior – radius and ulna
cross
Opposition – touching thumb to fingertips
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Muscle types
 Skeletal
 Multinucleate
 Made
of skeletal
muscle fibers –
largest
 Attach to skeleton
 Aka striated or
voluntary muscle
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Endomysium – connective
tissue around each fiber
Perimysium – fibrous
membrane around several
fibers
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Forms a bundle called a
fascicle
Epimysium – tougher
connective covering
around several fascicles
Blends into tendons or
aponeuroses
 Smooth
 Aka visceral, nonstriated,
involuntary muscle
 Single nucleus
 Found in hollow visceral
organs
 Layered: circular layer
and longitudinal layer
 Alternately contract
and relax
 Causes movement of
material inside organ
 Cardiac
 Aka
striated, involuntary muscle
 Branching fibers joined by
intercalated discs
Muscle functions
 Producing movement
 Maintaining posture
 Stabilizing joints
 Generating heat – byproduct
Skeletal muscle anatomy
 Sarcolemma – plasma membrane
 Microfibrils – fill cytoplasm
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Have light (I) bands and dark (A) bands
Made of units called sarcomeres
 Has 2 types of myofilaments
 Thick filaments – made of myosin
 Thin filaments – made of actin
 Anchored to Z disc
 H zone (bare zone) center where thin filaments do
not meet
Skeletal Muscle Activity
 Two properties that allow muscles to function
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Irritability – ability to receive/respond to stimuli
Contractility – ability to shorten
 Motor unit – a neuron and the muscle cells it
stimulates
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Axons (extensions of neuron) branch into axon
terminals which form neuromuscular junctions
with muscle cells
 Don’t actually touch at junction – synaptic
cleft (gap) filled with interstitial fluid
 Nerve impulse triggers release of
neurotransmitter acetylcholine (Ach) which
diffuses across synaptic cleft and attaches to
sarcolemma
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Allows Na ions to move into the cell and K
ions to move out
More Na enters causing an electrical current –
action potential
Current moves across muscle cell and causes
contraction
Sliding filament theory
 Myosin heads attach to the thin filaments
pulling them inward
 The heads attach and release several times
gripping a farther point on the thin filament
each time.
Energy Production
 Phosphorylation of ADP by creatine
phosphate (CP)
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CP is found only in muscle cells
CP transfers a phosphate to ADP to make
ATP
 Aerobic respiration
 95% of ATP production
 Oxidative phosphorylation in mitochondria
 Breakdown of glucose, fatty acids, proteins
 Anaerobic glycolysis/lactic acid fermentation
Graded responses
 Muscle cells follow the “all-or-none” law – if stimulated the entire
cell will contract
 Muscles are thousands of cells and have graded responses –
different degrees of shortening
 Graded reactions are produced in 2 ways
 Changing frequency of muscle stimulation
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Muscle twitches – single, brief contractions
Unfused (incomplete) tetanus – is a time to relax between
impulses
Fused (complete) tetanus – rapid impulses with no relaxation
between – contractions are sustained
Changing the number of muscle cells stimulated
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Contractions are slight or vigorous depending on what work has
to be done
 Muscle fatigue – muscle is unable to contract
even though it is being stimulated
 Results from oxygen debt
 Muscle contractions
 Isotonic contractions – filaments slide,
muscle shortens and movement occurs
 Ex. Bending knee, rotating arms, smiling
 Isometric contractions – filaments are
unable to slide, tension increases
 Muscle tone – state of continuous partial
contractions
Exercise
 Aerobic/endurance – result in stronger,
more flexible muscles – more resistant
to fatigue
 Blood
supply increases, cells form more
mitochondria, store more oxygen
 Resistance/isometric – causes muscles
to increase in size – pits muscles
against an (nearly) immovable object
5 golden rules of skeletal muscle
activity
 All muscles cross at least one joint (with a few
exceptions)
 The bulk of the muscle lies proximal to the joint
crossed
 All muscles have at least 2 attachments: the origin
and the insertion
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Origin – attachment to an immovable or less movable
bone
Insertion – attachment to the movable bone
 Muscles only pull; never push.
 During contraction, the muscle insertion moves
toward the origin.
Interaction of muscles
 Prime mover – major responsibility for a
movement
 Antagonists – oppose or reverse a movement
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These 2 may interchange – biceps and triceps
moving elbow
 Synergists – help stabilize prime movers
which cross numerous joints
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You can make a fist without bending wrist
 Fixators – stabilize the origin of prime movers
Naming muscles
 Direction of muscle fibers
Rectus – straight; oblique – slanted
Size of muscle
 Minimus, maximus, longus
Location of muscle
 Named for bone which they are associated with
Number of origins
 Biceps, triceps, quadriceps
Location of origin and insertion
 Sternocleidomastoid – origin is sternum and clavicle;
insertion is mastoid process
Shape of muscle
 Deltoid – triangular
Action of muscles
 Flexor, extensor, adductor
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Fascicle arrangement – determines
range of motion and power (see pg 203)
 Circular – arranged in concentric rings – sphincters
 Convergent – have a single insertion – triangular/fan-
shaped
 Parallel – straplike
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Fusiform – spindle-shaped with expanded belly
 Pennate – short fascicles attach obliquely to a central
tendon
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Unipennate – insert into 1 side of tendon
Bipennate – insert into opposite sides of tendon
Multipennate – insert into several sides of tendon