voluntary, striated

Body movement, stablizing position & joints, generating heat/ thermogenesis

involuntary, striated

Autorhythmicity, hormone & neuro-transmitters

Intercalated discs, contain desmosomes & gap junctions

No epimysium, only Peri & Endo, contracted 10-15 times longer than Skeletal muscle tissue

involuntary, nonstriated

Storing/ moving substance, sphincters

Common, Visceral (single-unit) s.m.t., in skin & tubular arrangements (walls of blood vessels, hollow organs)

Multi-unit s.m.t., individual fibers with its own motor neuron terminals, contract only the specific fiber only (Walls of large artery, airways, hair follicles, iris)

Structure: # Thick : Thin filament = 1:15-20, Intermediate filaments (no regular pattern of overlap), no striation, no Transverse tubules (instead, pouchlike caveolae Ca2+), dense bodies (Zdisc), contract rotates as corkscrew turns, opposite direction as relax

Physiology: Relative comparason, contraction starts slower, last much longer, Ca2+ from IS. Fluid & SR, calmodulin (regulatory protein) activates myosin light chain kinase,

1. Slow oxidative (SO) fibers, twitch contraction 100-200msec, Aerobic, Red m.f., e.g. Maintain posture/ aerobic endurance activities

2. Fast oxidative-glycolytic (FOG) fibers, twitch contraction <100msec,, Aerobic & anaerobic, Red m.f., e.g. walking & sprinting

3. Fast glycolytic (FG) fibers, Anaerobic, Whiite m.f., e.g. rapid, intense movements of short duration

Aveolar connective tissue (c.t.) + adipose c.t. (triglycerides for insulating) + Nerves (blood & lympatic vessels)

Epimysium c.t. {outer c.t. Wrap *Perimysium}

Fascicle (Bundle of *Myocytes)

Tendon (connection to bone periosteum or other muscles)

Somatic motor neurons (Axon-Brain & S.cord)

Capillaries

I band (thin filaments only)

A band (overlapping filaments)

I band (thin filaments only)

Myosin (Thick filament)

Actin (Thin filament), site Tn-I

Titin (Spring-back, link M-line, through thick filament, to Z-disc)

a-Actinin

Myomesin (M-line)

Nebulin (Thin filament)

Dystrophin (Links Actin & Sarcolemma to ECMatrix)

Frequency of stimulation

Amount of stretch before contraction

Nutrient and Oxygen availablility

# of Muscle Fibers per Motor Units

Motor unit recruitment

Myogram = Record of muscle contraction (20-200 msec, msec=0.001sec)

Frequency of Stimulation

Small amount of tautness or tension due to weak involuntary contractions

Small groups of Motor units alternatively active/ inactive,

Steady pressure for Smooth muscle fibers e.g. gastroinstestinal tract, blood vessels.

Isotonic contraction (equal tension)

Isometric contraction (tension generated < resistance to move an object), no change in muscle length, hold book. can assist stablilise some joints.

1. Creatine phosphate (15s)

2. Anerobic Glycolysis (2mins)

3. Aerobic respiration (2mins-hrs)

Muscle Fatigue

Central Fatigue

Recovery oxygen uptake / Oxygen debt

3 ways of Restoration of metabolic conditions to resting level

1. Release of acetycholine (ACh)

2. Activation of ACh receptors

3. Production of muscle action potential at motor end plate

4. Termination of ACh activity

Excitation-Contraction Coupling at triad (TCTTTC)

Muscle Contracton Cycle

Forcefulness of muscle contraction Dependent factors = Length of sarcomeres before muscle contraction begins

Optimal length 2.0-2.4um (very close to resting length in most muscle), zone of overlap between thick and thin filament (H-zone)

1. Nerve Action potential @ Somatic Motor Neuron (SMN) triggers release ACh

2. ACh binds to receptors @ Motor End Plate (MEP), trigger a muscle action potential

3. Acetylcholinesterase breakdown ACh until another Nerve Action potential from SMN release next wave of ACh.

4. Release of Ca++ @ Sarcoplasmic Reticulum (SR) into sarcoplasm = A muscle action potential travel along T. Tubule triggers a change in Voltage-gated Ca++ channels

5. Exposing myosin-binding sites @ ACTIN = Ca++ binds to troponin on thin filament by adjusting the tropomyosin

6. Contraction = Myosin heads bind to actin, undergo power strokes and release; thin filaments are pulled toward center of sarcomere.

7. Close of Ca++ Release Channels; Ca++-ATPase pumps use ATP to restore low level of Ca++ in the sarcoplasm

8. Blocking of myosin-binding sites on ACTIN = Tropomyosin return to original shape

9. Muscle relaxes

Structure of Somatic motor neurons (SMN)

Protein transporters

Motor end plate

Ion channels / Gates

Neurotransmitters

Action potential (A.P. +30 m. Volt)

Threshold potential, (T.P., -55 m.Volt)

Resting Membrane potential (R.M.P., -90 m.Volt)