Begins immediately after activity ends

1
Recovery period

• Begins immediately after activity ends
• Pyruvate from lactate requires O2
• Glucose back to muscle (stored as glycogen)
• Oxygen debt (excess post-exercise oxygen
  consumption)
• Amount of oxygen required during resting period
  to restore muscle to normal conditions
• Heat Loss- Body temperature regulation role

2
Types of skeletal muscle fibers

• Fast fibers
• Slow fibers
• Intermediate fibers

3
Figure 10.21 Fast versus Slow Fibers
Figure 10.21
4
Fast fibers

• Large in diameter
• Contain densely packed myofibrils
• Large glycogen reserves
• Relatively few mitochondria
• Produce rapid, powerful contractions of short
  duration

5
Slow fibers

• Half the diameter of fast fibers
• Take three times as long to contract after
  stimulation
• Abundant mitochondria
• Extensive capillary supply
• High concentrations of myoglobin
• Can contract for long periods of time

6
Intermediate fibers

• Similar to fast fibers
• Greater resistance to fatigue

7
Muscle performance and the distribution of muscle
fibers

• Pale muscles dominated by fast fibers are called
  white muscles
• Dark muscles dominated by slow fibers and
  myoglobin are called red muscles
• Training can lead to hypertrophy of stimulated
  muscle

8
Hypertrophy
Hypertrophy- increased mitochondria, glycolytic
enzymes, glycogen, and myodibrils - opposite
of atrophy
9
Physical conditioning

• Anaerobic endurance
• Time over which muscular contractions are
  sustained by glycolysis and ATP/CP reserves
• Aerobic endurance
• Time over which muscle can continue to contract
  while supported by mitochondrial activities

10
Structural characteristics of cardiac muscle

• Located only in heart
• Cardiac muscle cells are small
• One centrally located nucleus
• Short broad T-tubules (no triads)
• Dependent on aerobic metabolism
• No terminal cisternae (flattened membrane disks)
  of SR SR tubules contact PM
• More myogloblin (O2 storing protein in muscle
  cells) and mitochondria
• Intercalated discs where membranes contact one
  another

11
Figure 10.22 Cardiac Muscle Tissue
Figure 10.22
12
Functional characteristics of cardiac muscle
tissue

• Automaticity- due to pacemaker cells of the
  Sinoatrial node
• Contractions last longer than skeletal muscle
• Do not exhibit wave summation
• No tetanic contractions (s. tetanus) possible

13
Structural characteristics of smooth muscle

• Nonstriated
• Lack myofibrils and sarcomeres
• Thin filaments anchored to dense bodies
• Involuntary
• No T tubules
• loose network of SR
• Thick filaments scattered with more cross-bridges
• Thin filaments anchored to dense bodies (desmin)
• Adjacent cells bound at dense bodies

14
Figure 10.23 Smooth Muscle Tissue
Figure 10.23
15
Functional characteristics of smooth muscle

• Contract when calcium ions interact with
  calmodulin
• Activates myosin light chain kinase
• Functions over a wide range of lengths
• Plasticity
• Multi-unit smooth muscle cells are innervated by
  more than one motor neuron, thus are motor units
• Visceral smooth muscle cells are not always
  innervated by motor neurons
• Neurons that innervate smooth muscle are not
  under voluntary control