Download Muscles and Muscle Tissue

Energy for Muscle Contraction
• Must have constant supply of ATP for
contraction to be maintained.
• Creatine phosphate (CP) can also be used b/c
of its high energy bond.
• Cellular respiration or catabolism of food
generates more ATP or CP.
• Some muscle fibers ensure an uninterrupted
supply of glucose by storing it as glycogen.
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Providing Energy for Muscle
Contraction
Direct phosphorylation of ADP by
reaction with creatine phosphate
Energy Source: CP
Oxygen Use: None
1 ATP per CP  Creatine and ATP
are the products
NRG supply lasts 15 sec
Providing Energy for Muscle Contraction
• Anaerobic glycolysis and lactic acid formation
– Anaerobic- without oxygen
• 2 ATP
• Lactic acid accumulation (eventually reconverted to glucose in
the liver)
• Heavy breathing helps to restore oxygen debt.
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Energy source is glucose
No oxygen is used
2 ATP per glucose, lactic acid
30-60 sec. worth of energy
Providing Energy for Muscle
Contraction
• Aerobic Respiration/Oxidative
Phosphorylation
– Aerobic- with oxygen
• 36-38 ATP
• Myoglobin pigment in muscles holds oxygen
when muscles are at rest (muscles with much
myoglobin are called red fibers; white fibers do
not have much myoglobin).
Energy Systems used during
contraction
VI. All-or-none Priciple
1. Muscle cells do not partially contract. They either
do or they do not.
2. The minimum level of stimulation required to
cause a fiber to contract is the threshold stimulus.
Muscle Twitch
Response of a muscle to a
single brief threshold
1. Latent Period: few ms
between stim. & contrac.
coupling
2. Contraction: cross-bridges
active
3. Relaxation: begins with
Ca2+ moving into SR
Wave summation
• Muscle responds to the frequency and strength of
simulation
Muscle Contractions
• Isotonic: Moving montraction
Muscle Contraction
• Isometric: Myofilaments are skidding instead of
sliding and the tension in the muscle keeps
increasing
Exercise
• Endurance: Aerobic
– Stronger, flexible muscles
– Greater resistance to fatigue
– Increase in blood supply
– Fibers form more mitochondria
– Store more oxygen
Exercise
• Resistance or Isometric Exercise
– Increased muscle size
– Increase strength
– Enlargement of individual fibers
– More mitochondria
Muscle Fatigue and Oxygen Debt
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Muscle fatigue: unable to contract
May result from oxygen debt
Oxygen Debt must be paid back
Rapid breathing: continues until the amount of
oxygen needed to get rid of the accumulated lactic
acid by making ATP and creatine reserves
• Before a skeletal muscle fiber can
contract, it has to receive an
impulse from a nerve cell.
• Generally, an artery and at least
one vein accompany each nerve
that penetrates the epimysium of a
skeletal muscle.
• Branches of the nerve and blood
vessels follow the connective tissue
components of the muscle of a
nerve cell and with one or more
minute blood vessels called
capillaries.