Download muscles!!

3 Types of Muscles
• Smooth
• Cardiac
• Skeletal
Smooth Muscle
•
•
•
•
•
No striations
Single nucleus
No/underdeveloped transverse tubules
Involuntary
Contracts in waves called peristalsis
Peristalsis
• Educational:
• http://www.youtube.com/watch?v=o18UycW
RsaA
Cardiac Muscle
• Like skeletal muscle but found only in the
heart
• Mononucleated
• Involuntary
• Well developed transverse tubule system
• Contracts as a unit
Skeletal Muscles
•
•
•
•
•
Move bones at joints
Voluntary
Striated
Multiple nuclei
Transverse tubules systems– WELL DEVELOPED
Structure of a muscle
Know
this!
Myofilaments
• Within each myofibril are myofilament.
• Filaments:
– Actin: Thin
– Myosin: Thick
• When a muscle contracts, actin slides past the
myosin, shortening the sarcomere.
Tropomyosin-troponin complex
• Calcium is like a key.
• Tropomyosin is like a chain around your bike
tires
• Troponin is the lock attached to the chain.
• The tires are the crossbridge of actin and
myosin
• The pedals are like ATP
The Sarcomere:
The functional unit of the muscle
Sliding Filament Theory
Neuromuscular Junction
• Where the terminal button of the motor
neuron meets the motor endplate of the
muscle. Includes the synaptic cleft.
• Acetylcholine (ACh)is the neurotransmitter for
muscles.
• The synaptic vesicles release ACh into the
synapse where it stimulates ACh receptors on
the muscle fiber to begin contraction.
1. Sarcoplasmic reticulum releases calcium ions
2. Calcium binds to the actin filaments sites, opening
them.
3. Myosin heads form cross bridges with actin at the
binding site.
4. Cocked position -> Power stroke
5. ATP binds to cross bridge, releasing myosin from
the actin
6. ATP breakdown provides energy to “cock”
unattached myosin cross bridge.
7. Process repeats as long as there is ATP and
calcium available.
Energy Supply
• Myofibrils need oxygen for cellular respiration,
which creates a lot of ATP.
– Muscles can also use creatine phosphate to make ATP.
• Glycolysis does not need oxygen but only makes a
small amount of ATP. A by-product of this reaction
is lactic acid.
Muscle Conditions
• Muscle fatigue: Lactic acid build up
• Muscle cramps: A lack of ATP.
• Soreness : Rips in the muscle.
Slow oxidative twitch
• Slow-oxidative twitch muscles have a protein
called myoglobin which temporarily holds
oxygen. This makes the muscle look dark or
red.
• That way, slow-oxidative twitch is used for
aerobic long distance exercise.
Fast Twitch Glycolytic
•
•
•
•
Uses glycolysis.
White meat because few myoglobin proteins
Short distance, anaerobic
Less mitochondria
Fast twitch oxidative
• In the middle of slow twitch oxidative and fast
twitch glycolytic
• Well vascularized
• Pink meat
Types of Contractions
• Isotonic: Change in length
– Concentric: Shortening of the distance (flexing)
– Excentric: Elongating muscle (extending)
• Isometric: Change in force
• Tetanus
– Fused: Smooth contraction
– Unfused: Shaky contraction
Disease
• Myasthenia Gravis (MG): Autoimmune
disorder that attacks receptors for ACh at
neuromuscular junctions.
– Symptoms: Abnormal muscle weakness (esp.
facial muscles), chronic fatigue, trouble breathing
Things to ponder
• Do all muscles have fascia?
– Discuss with class