Muscular Control of Movement Chapters 17 and 18

1
Muscular Control of Movement Chapters 17 and 18

• Review of Gross Anatomy
• 430 voluntary muscles in the body.
• The muscle is
• 75 water,
• 20 protein,
• and 5 inorganic salts and other substances.

2
Types of Muscles

• 1. Smooth - blood vessels and organs.
• 2. Cardiac - heart.
• 3. Skeletal - movement muscles.

3
Origins and Insertions

• The origin of the muscle is the relatively stable
  skeletal part to which the muscle attaches.
• This is usually more proximal.

4
Origins and Insertions

• The insertion of the muscle is the more mobile
  skeletal part to which the muscle attaches and is
  more distal.

5
Connective Tissue Components
6
The Structure and Function of Skeletal Muscle

• An individual muscle cell is called a muscle
  fiber.
• A muscle fiber is enclosed by a plasma membrane
  called the sarcolemma.

7
Sarcolemma
8
The Structure and Function of Skeletal Muscle

• The cytoplasm of a muscle fiber is called the
  sarcoplasm.
• The extensive tubule network found in the
  sarcoplasm includes
• t-tubules - allow communication and transport of
  substances throughout the muscle fiber
• sarcoplasmic reticulum - which stores calcium.

9
Sarcoplasm
10
The Structure and Function of Skeletal Muscle

• Myofibrils are composed of sarcomeres, the
  smallest functional units of muscle.
• A sarcomere is composed of filaments of two
  proteins, which are responsible for muscle
  contraction.

11
The Structure and Function of Skeletal Muscle

• Myosin is a thick filament, folded into a
  globular head at one end.
• An actin filament is composed of actin,
  tropomyosin, and troponin.

12
(No Transcript)
13
(No Transcript)
14
The Structure and Function of Skeletal Muscle

• One end of each actin filament is attached to a z
  disk.

15
Sarcomere

• The bands are named according to their optical
  properties.
• The I band (isotropic) - velocity of light is
  same in all directions.
• Contains actin only.

16
Sarcomere

• A band (anisotropic) - light does not scatter
  equally.
• Contains both actin and myosin.
• Z disk (zwischen) - German word for between.

17
(No Transcript)
18
Sarcomere

• H zone - center of A band.
• Contains myosin only.

19
The Sliding Filament Theory

• Muscle action is initiated by a motor nerve
  impulse.

20
The Sliding Filament Theory

• The action potential travels along the
  sarcolemma, then through the tubule system, and
  eventually causes stored calcium to be released
  from the sarcoplasmic reticulum.

21
(No Transcript)
22
The Sliding Filament Theory

• Calcium binds with troponin, and then troponin
  lifts the tropomyosin molecules off of the active
  sites on the actin filament, opening these sites
  for binding with the myosin head.

23
The Sliding Filament Theory

• Once it binds with the actin active site, the
  myosin head tilts, pulling the actin filament so
  that the two slide across each other.
• The tilting of the myosin head is the power
  stroke.

24
(No Transcript)
25
(No Transcript)
26
The Sliding Filament Theory

• Energy is required before muscle action can
  occur.
• The myosin head binds to ATP, and ATPase found on
  the head splits ATP into ADP and Pi, releasing
  energy to fuel the contraction.

27
The Sliding Filament Theory

• Muscle action ends when the calcium is actively
  pumped out of the sarcoplasm back into the
  sarcoplasmic reticulum for storage.
• This process, leading to relaxation, also
  requires energy supplied by ATP.

28
Skeletal Muscle and Exercise

• Most skeletal muscles contain both ST and FT
  fibers.

29
(No Transcript)
30
Skeletal Muscle and Exercise

• The different fiber types have different ATPases.
  
• The ATPase in the FT fibers acts faster,
  providing energy for muscle action more quickly
  than the ATPase in ST fibers.

31
Skeletal Muscle and Exercise

• FT fibers have a more highly developed
  sarcoplasmic reticulum, enhancing the delivery of
  calcium needed for muscle action.

32
Skeletal Muscle and Exercise

• Motor neurons supplying FT motor units are larger
  and supply more fibers than do neurons for ST
  motor units.
• Thus FT motor units have more fibers to contract
  and can produce more force than ST motor units.

33
Skeletal Muscle and Exercise

• The proportions of ST and FT fibers in an
  individuals arm and leg muscles are usually
  quite similar.

34
Skeletal Muscle and Exercise

• ST fibers have high aerobic endurance and are
  well suited to low-intensity endurance activities.

35
Skeletal Muscle and Exercise

• FT fibers are better for anaerobic activity.
• FTa fibers are well utilized in explosive bouts
  of exercise.

36
Skeletal Muscle and Exercise

• Fiber type is predominantly determined by
  genetics.
• Composition will change over the course of your
  life as FT fibers atrophy and die.

37
Classification of Muscle Fibers

• Characteristic Type I Type IIa TypeIIb
• Oxidative capacity High Mod. High Low
• Glycolytic capacity Low High Highest
• Contractile speed Slow Fast Fast
• Fatigue resistant High Moderate Low
• Motor unit strength Low High High

38
Characteristics of Muscle Fiber Types

• Characteristic ST FTa FTb
• Fibers per motor neuron 10-180 300-800 300-800
• Motor neuron size Small Large Large
• Nerve conduction velocity Slow Fast Fast
• Contraction speed (ms) 110 50 50
• Type of myosin ATPase Slow Fast Fast
• Sarcoplasmic Ret. Dev. Low High High

39
Motor Units

• A motor unit consists of a single motor neuron
  and all the muscle fibers it supplies

40
Neuro-muscular Interaction

• Motor units give all-or-none responses.
• For a unit to be recruited into activity, the
  motor nerve impulse must meet or exceed the
  threshold.
• Threshold of excitation.

41
Neuro-muscular Interaction

• When this occurs, all muscle fibers in the motor
  unit act maximally.
• If the threshold is not met, no fibers in that
  unit act.

42
Neuro-muscular Interaction

• More force is produced by activating more motor
  units, and thus more muscle fibers.

43
Neuro-muscular Interaction

• In low-intensity activity, most muscle force is
  generated by ST fibers.
• As the resistance increases, FTa fibers are
  recruited, and at even higher intensities, the
  FTb fibers are activated.

44
Ramping of Muscle Fibers
45
Neuro-muscular Interaction

• The same pattern of recruitment is followed
  during events of long duration.

46
Muscle Action

• Muscles involved in a movement can be classified
  as
• agonists (prime movers)
• antagonists (opponents or resistors)
• synergists (assistants)
• fixator, neutralizer, stabilizer

47
Muscle Action

• The three main types of muscle action are
• concentric, in which the muscle shortens
• static, in which the muscle acts but the joint
  angle is unchanged
• eccentric, in which the muscle lengthens.

48
Generation of Force

• The number of motor units activated.
• Force production can be increased by recruiting
  more motor units.
• The type of motor units activated.
• The size of the muscle.

49
Generation of Force

• The muscles initial length when activated.
• Force production can be maximized if the muscle
  is stretched 20 prior to action.
• At this point, the amount of energy stored and
  the number of linked actin-myosin cross-bridges
  are optimum.

50
(No Transcript)
51
Generation of Force

• The angle of the joint.
• All joints have an optimal angle at which the
  muscles crossing the joint function to produce
  maximum force.
• This angle varies with the relative position of
  the muscles insertion on the bone and the load
  placed on the muscle.

52
Generation of Force

• The muscles speed of action.
• Speed of action also affects the amount of force
  produced.
• For concentric action, maximum force can be
  achieved with slower contractions.
• The closer you get to zero velocity (static), the
  more force can be generated.

53
Muscle Action

• With eccentric actions, however, faster movement
  allows more force production.

Eccentric
Concentric
54
Requirements for Large Muscle Development

• Proper nutrition
• 65 CHO, 20 Fat, 15 Protein
• Resistance Training
• Genetics
• Hormonal Secretion Levels
• Testosterone and Androgens

55
ACSM Strength Guidelines

• F 2-3 days per week.
• I intensity
• gt85 of max for strength,
• 50-65 for muscular endurance.
• T duration
• 30-90 secs per set,
• 8-12 reps,
• 14 workrest ratio
• S resistance of any type.

56
Types of Training

• Isometric
• muscular tension,
• no movement.

57
Types of Training

• Isotonic - muscular tension, movement.
• Set resistance
• Variable resistance

58
Types of Training

• Isokinetic - muscular tension, speed of movement
  is controlled.

59
Strength Training Myths

• Strength training will cause muscle boundness.
• Women who strength train will become
  masculinized.
• Strength training reduces speed.
• No pain - No gain.

60
Strength Training Myths

• It takes hours of training daily to gain muscle
  mass.
• Food supplements will speed up or cause muscle
  and strength development.
• Anabolic steroids are a safe and effective aid.