http://www.youtube.com/watch?v=CepeYFv
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MUSCULAR SYSTEM:
MAJOR STRUCTURE: Muscles. Tendons.
Ligaments
MAJOR FUNCTION: Ability to contract (or
shorten) providing body with movement;
posture
REMEMBER:
3 Types of MUSCLE TISSUE:
1.Skeletal
2.Cardiac
3.Smooth
SEE CHART :
Hand out!
MUSCLES of BODY: DIAGRAMS
(superficial muscles)
- Mr. Muscle man (anterior & Posterior)
- Facial muscles
Quiz on Diagram of Muscles and MAJOR
movements – Bonus only on Friday 2/3
SKELETAL MUSCLE = structure
MUSCLE CELLS = elongated  MUSCLE
FIBERS
ENDOMYSIUM = connective tissue sheath
that encloses a muscle fiber
PERIMYSIUM = several sheathed muscle
fibers
wrapped in a courser fibrous
membrane
FASCICLE = bundle of fibers
EPIMYSIUM = connective tissue
surrounding the fascicles (covers the entire
muscle
MUSCLE FIBER (cell)–ANATOMY (p186)
Skeletal MUSCLE fibersMULTINUCLEATED,
LONG STRIATIONS
Plasma Membrane = Sarcolemma
MYOFILAMENTS = Actin (thin) and myosin (thick)
filaments
ACTIN = Thin myofilaments (protein) made of
contractile protein (move )
MYOSIN = thick myofilaments made of protein
and contain ATPase enzymes for
splitting ATP for power
STRIATED FIBERS = due to light (I ) and dark
bands (A) along the length of the muscle fiber
SARCOMERE = repeating units of the actin and
myosin filaments; Z LINE to Z LINE (disc)
LIGHT & DARK BANDS (actin & myosin):
MLINE
A BAND = length of the myosin (thick) Dark
band
I BAND = ONLY actin (in between the two myosin
filaments)  light band w dark running thru)
H ZONE = center of myosin filament – NO actin
(dark with light on either side)
Z LINE = end of sarcomere; Z line to Z line =
sarcomere (dark line)
M-LINE = middle of sarcomere (dark line); middle
of the “H” zone
PHYSIOLOGY of a MUSCLE CONTRACTION:
Steps involved in the Sliding Filament Mechanism:
1. An action potential (nerve impulse) arrives at
the axon terminal of a motor neuron at the
neuromuscular junction (where nerve meets up
with muscle)
2. Acetylcholine (neurotransmitter – chemical
that travels the message across the synapse
between the neuron and muscle)is released
and changes the charge between the inside of
the cell and the outside of cell along the
sarcolemma (plasma membrane of a muscle
fiber)
3. Opens Ca2+ ion channels to flow into
sarcoplasm (cytoplasm in muscle fiber)
4. Calcium binds to troponin ; tropomyosin
changes shape, exposing binding sites
(tropomyosin)
TROPONIN = “groove” site on actin myofilament
which releases the tropomyosin
TROPOMYOSIN = binding sites on actin that bind
to myosin “heads”
CONTRACTION BEGINS
5. – Myosin binding to actin forms a CROSS
BRIDGE
CROSS BRIDGE FORMATION = myosin “head’
attaches to actin myofilament at tropomyosin
6. POWER STROKE: As ATP releases ADP
and P, the myosin head pivots and bends –
pulling the actin filament closer together
decreasing the H ZONE toward the M-LINE
(center of sarcomere) – continues until muscle
fiber is fully contracted (repeats itself)
7. CROSS BRIDGE detachment – After ATP
attaches to the myosin, the link between the
myosin and the actin weakens and myosin
head is released breaking the cross bridge
8. As ATP is hydrolyzed to ADP and P, the
myosin head returns to its prestroke position
(cocked position).
YouTube - Muscle contraction
http://www.youtube.com/watch?v=gJ309L
fHQ3M
ISOTONIC and ISOMETRIC CONTRACTIONS:
ISOTONIC = muscle shortens upon contraction
EX: bending the knee
ISOMETRIC = myosin myofilaments are
‘spinning their wheels’ and the tension in
the muscle keeps increasing but muscle fiber
is NOT shortening
EX; pushing against the wall  biceps
brachii cannot shorten any more but still
undergoing contraction
WHERE does the body get the ATP to move
myosin heads?
1. Direct phosphorylation of ADP by creatine
phosphate
- Creatine phosphate (CP) is found in muscle
fibers but not other cell types
- Store 5 x more CP as ATP (depleted in 15
seconds)
2. Aerobic Respiration (glycolysis, Kreb’s Cycle,
and Electron Transport Chain = 38 ATP)
- Muscles use 95% aerobic respiration
3. Anaerobic Respiration (Glycolysis and lactic
Acid formation)
- Produces ONLY 5% ATP from 1 glucose
molecule but is 2 ½ times faster than aerobic
respiration (lasts 30-40 seconds)
MUSCLE FIBER TYPES:
- Based on speed of contraction & major
pathways for forming ATP
1. SLOW OXIDATIVE FIBERS = aerobic ATP,
speed = slow, great for endurance activities;
color = RED (due to high myoglobin content)
2. FAST OXIDATIVE FIBERS = Aerobic ATP
(some anaerobic ), speed = fast; sprinting &
walking; Color = red – pink
3. FAST GLYCOLYTIC FIBERS = uses
anaerobic ATP; short-term intense or powerful
(hitting a baseball); color= white (due to low
myoglobin content)