Muscular System. Functions: 1.Movement 2.Stabilization 3.Storing and moving substances internally...
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Transcript of Muscular System. Functions: 1.Movement 2.Stabilization 3.Storing and moving substances internally...
Muscular System
Functions:
1. Movement
2. Stabilization
3. Storing and moving substances internally
4. Thermogenesis
Properties:
Excitability
Contractility
Extensibility
Elasticity
Skeletal Muscle
•Striated
•Multiple Nuclei
•Long fibers
•Tendons and bones
•Voluntary movement
Cardiac Muscle
•Striated
•Intercalated discs
•Branched fibers
•Heart
•Involuntary movement
Smooth Muscle
•Not striated
•Spindle shaped fibers
•Walls of hollow organs
•Involuntary movement
Muscle Names
Direction of fascicles (ex. Rectus, transverse, oblique)
Size (ex. Maximus, longus, latissimus)
Shape (ex. Deltoid, trapezius, orbicularis)
Action (ex. Flexor, abductor, pronator)
Number of origins (ex. Biceps, triceps)
Location (ex. Temporalis, frontalis)
Origin and insertion (ex. Sternocleidomastoid)
Deep FasciaEpimysium – superficial
Perimysium – surrounds fascicles
Endomysium – surrounds fibers
Join to form tendons and aponeuroses
Motor unitsMotor neuron and all the fibers contacted
“All or nothing”
Neuromuscular junction - synapse between neuron and motor end plate
Acetylcholine (ACh)
Excitation-contraction couplingAction potential moves down T-
tubules to SR
SR releases calcium through release channels
Ca2+ binds to troponin - moves complex and opens binding sites
Contraction begins
Ca2+pumps and calsequestrin
Sliding Filament MechanismCa2+ binds to troponin
Myosin binding sites open
ATP hydrolysis energizes myosin
Crossbridges form
Power stroke (ADP released)
Detachment (New ATP binds)
Muscular controlPrecision vs. power - how many fibers are in the
motor unit?
Twitch contraction
Refractory period
Muscular controlWave summation due to increased frequency
of stimulation Tautness of elastic components + partial filament
contraction Tetanus (unfused and fused)
Muscular control
Motor unit recruitment - more active units
Tone - small numbers of motor units always active (weak, involuntary contractions)
Muscle Action
•Origin/Insertion
•Muscles work in groups:•Agonist•Antagonist•Synergist
Isotonic vs. Isometric
Isotonic -muscle changes length (generates movement)
Isometric - muscle holds position