Transcript The Sliding Filament Theory

The Sliding Filament Theory
The Sliding Filament Theory
Troponin
complex
The Sliding Filament Theory
REVIEW:
Cycle
The Contraction
Sliding Filament Theory article & Concept Map
- As you read the
article that
tells you
experiments that led
closer to
day
skeletal muscle, be
about the first
scientists
the presentunderstanding of
looking for…
5 Golden Rules of Skeletal Muscle
Activity
Muscles & Body Movements
• Movement is attained due to a muscle moving an attached bone
• Muscles are attached to
points
• Origin
• Attachment to
• Insertion
• Attachment to
at least 2
moveable bone
immovable bone
Isotonic Contractions
• Isotonic Contraction:
• Example: lifting dumbbells
with arm
• Tension (effort) increases &
muscle fibers shorten &
lengthen
• Concentric contraction:
• Tension (effort) exceeds
resistance (weight) & muscle
shortens
• Eccentric contraction:
• Resistance exceeds tension
(effort) & muscle lengthens
(due to gravity)
Isometric Contractions
• Isometric Contraction:
• Example: pushing against a wall
• Tension (effort) never exceeds resistance
(weight)
• Muscle does NOT change length
Muscle Relaxation
• Relaxation of muscle
fibers
• Passive process
• Combo of elastic forces, opposing muscle contractions &
gravity to elongate a contracted muscle
• Elastic force: some energy used to stretch tendons in
contraction phase forces a recoil
• Opposing muscle contractions: muscles move in antagonistic
pairs
• Gravity: pulls down muscle to extended position
Rigor mortis
Within 3-4 hours after death
• Dying muscle cell membranes become more permeable
to Ca+ ions
• Promotes myosin cross-bridge binding
• After death, circulation of nutrients ends
• Without ATP, Ca+ ions are not removed & crossbridges cannot detach from
actin sites so muscles become
locked in place – “stiff”
• Rigor mortis disappears as
muscle proteins break down
several hours after death
(48-60 hours)
Effect of Exercise on Muscles
• Exercise increases muscle size, strength
& endurance
• Aerobic (endurance/
cardiovascular) exercise (biking,
jogging) results in stronger, more
flexible muscles with greater
resistance to fatigue
• Makes body metabolism more
efficient
• Improves digestion &
coordination
• Resistance (isotonic & isometric)
exercise (weight-lifting) increases
muscle size & strength
Fast vs. Slow-Twitch Muscles
• Fast Twitch Fibers
• Most skeletal muscle fibers
• Contract in 0.01 sec or less after
stimulation
• Large in diameter
• Contain densely-packed myofibrils
• Have large glycogen reserves & few
mitochondria
• Produce powerful contractions
• Fatigue rapidly
• “white muscle fibers”
Fast vs. Slow-Twitch Muscles
• Slow Twitch Fibers
• ~Half the diameter of fast fibers
• Take 3x as long to contract after stimulation
• Specialized to continue contracting for
extended periods
• Contain extensive network of capillaries &
has higher oxygen supply
• Contain red pigment myoglobin
• Contain more mitochondria than fast
fibers
• “red muscle fibers”
• Intermediate Fibers
• Contain properties of fast fibers & slow
fibers
Tetanus
• Many toxins, drugs & diseases may interfere with
occurring at the neuromuscular junction
events
• Tetanus: infection of Nervous System from potentially deadly
bacteria Clostridium tetani
– Bacteria spreads & makes poison called tetanospasmin
– Poison blocks nerve signals from spinal cord to skeletal
muscles, causing severe
muscle spasms
– Prolonged muscle
contractions,
spasms &
stiffness
– Spasms can be so
powerful that they tear
the muscles or cause
fractures of the spine