ANAT LEC Ch.9 The Muscular System

Skeletal, Cardiac, Smooth

Muscle can be divided into 3 types

Smooth muscle

• NON-Striated, Spindle shaped

• UNI nucleated

• Usually in walls of internal organs

• INvoluntary
  Ex. Pushes fluid/solids along DIGESTIVE tract and other systems

Cardiac Muscle

• Striated, Branched

• UNI nucleated

• Only in Heart walls

• INvoluntary
  Ex. Pushes BLOOD thru vessels of the cardiovascular system

Skeletal Muscle

• Non-Striated, tubular

• Multi Nucleated

• Attached to skeleton

• VOLUNTARY

  Ex. Moves the BODY by pulling on the bones

4 Shared Muscle type properties

Excitability, Contractibility, Extensibility, Elasticity

Excitability Def

Ability to respond to STIMULATION (nerves & hormones)

Contractibility Def

Ability to SHORTEN/EXERT a TENSION harnessed by connective tissue (tendons)

Extensibility Def

Ability to CONTRACT over a range of RESTING

Elasticity Def

Ability to RETURN to its original LENGTH after contraction

directly or indirectly attached to bones

Skeletal muscle are contractile organs _____

Epimysium

Dense IRREGULAR connective tissue that SURROUNDS muscle

Perimysium

DIVIDES muscle into internal compartments containing the FASCICLES

Endomysium

SURROUNDS each muscle FIBER

Sarcolemma

Membrane of skeletal muscle is

Sarcoplasm

The cytoplasm of skeletal muscle is

Network of TRANSVERSE Tubules (T Tubules) extending into the sarcoplasm

• Helps with EXCITIBILITY

Deep indentations in the sarcolemma form

100-1000

Sarcoplasm contain ______ myofibrils

Sarcomeres

The smallest functional unit of muscle fibers are ____

Thin Filaments are made up of

4 proteins

• F-Actin

• Nebulin

• Tropomyosin

• Troponin

Tropomyosin & Troponin Characteristics

• Regulatory proteins

• Tropomyosin: Covers active site PREVENTING actin-Myosin interaction

• Troponin: Holds tropomyosin in place, MUST MOVE in order to initiate contraction

Thick Filaments Characteristics

• Composed of bundles of MYOSIN

• Form cross-Bridges when interacting w/Thin filaments during CONTRACTION

Muscle exerts a PULL/TENSION

• ONLY PULL, NO PUSH

A CONTRACTION occurs when

Interactions b/w THIN & THICK filaments in ea. sarcomere

• Sliding Filament Theory

  • Microscopic level, contraction = size change in A/I/H/Z bands, zone, lines

Contractions RESULT from

Motor Unit (MU) Characteristics

Is a SINGLE motor neuron and all the muscle fibers it controls

• Smaller MU = Finer control of movement

• Larger MU = more force generated

Muscle contraction occurs when MU are stimmed

• AMOUNT of MUs involved

• FREQUENCY of stim of the MUs

Force is determined by

Hypertrophy Characteristics

• Results from REPEATED/EXHAUSTIVE stim

• muscles DEVELOP more MYOFIBIRILS & MITOCHODRIA

• Enlarges size of muscle belly

Ex. Bulking muscle

you do NOT grow NEW muscle cells

Atrophy Characteristics

• Lack of regular stimulation to the muscle

• Loss of muscle tone/mass

• muscle is smaller and weaker

  • due to loss of intracellular contractile proteins

3 Fiber types

1. White Fibers (fast)

2. Red Fibers (slow)

3. Pink Fibers (intermediate)

Fast (WHITE) Fiber Characteristics

• Large diameter

• Densely packed myofibrils

• Large Glycogen reserves

• Few Mitochondria

MAJORITY of skeletal muscle is FAST type due to their rapid response when stimmed

Slow (RED) Fiber Characteristics

• Slow to fatigue

• Small diameter, more mitochondria

• 3x longer to contract

Ex. Help hold your arm up (for long periods of time)

Intermediate (PINK) Fiber Characteristics

• Mix of slow and fast

• Fast Contraction speed

• Mitochondria amt= intermediate

• Fatigue resis. = intermed

Convergent Muscle

• Force produced

• Split along multiple axes

• Produce more force than parallel muscles of same size

Origin

• the fixed/most PROXIMAL pt. of attachment

Muscles begin at the

Insertion

• the moving part

• most DISTAL pt. of attactment

Muscles terminate at the

4 Skeletal groups (based on actions)

Agonist, Antagonist, Synergist, & Fixators

Agonist

Prime mover of a limb

Antagonist

Actions opposed the agonist

Synergist

Assits the Agonist in a particular move

Fixators

Stabilize joints