1. Neuromuscular Fundamentals
Anatomy and Kinesiology
420:024

2. Outline Introduction Structure and Function Fiber Arrangement
Muscle Actions
Role of Muscles
Neural Control
Factors that Affect Muscle Tension

3. Introduction Responsible for movement of body and all of its joints
Muscles also provide:
Over 600 skeletal muscles comprise approximately 40 to 50% of body weight
215 pairs of skeletal muscles usually work in cooperation with each other to perform opposite actions at the joints which they cross
Aggregate muscle action:

4. Muscle Tissue Properties
Irritability or Excitability
Contractility
Extensibility
Elasticity

5. Outline Introduction Structure and Function Fiber Arrangement
Muscle Actions
Role of Muscles
Neural Control
Factors that Affect Muscle Tension

6. Structure and Function
Nervous system structure
Muscular system structure
Neuromuscular function

7. Figure 14.1, Marieb & Mallett (2003). Human Anatomy. Benjamin Cummings.

8. Nervous System Structure
Integration of information from millions of sensory neurons  action via motor neurons
Figure 12.1, Marieb & Mallett (2003). Human Anatomy. Benjamin Cummings.

9. Nervous System Structure
Organization
Brain
Spinal cord
Nerves
Fascicles
Neurons
Figure 12.2, Marieb & Mallett (2003). Human Anatomy. Benjamin Cummings.
Figure 12.7, Marieb & Mallett (2003). Human Anatomy. Benjamin Cummings.

10. Nervous System Structure
Both sensory and motor neurons in nerves
Figure 12.11, Marieb & Mallett (2003). Human Anatomy. Benjamin Cummings.

11. Nervous System Structure
The neuron: Functional unit of nervous tissue (brain, spinal cord, nerves)
Dendrites:
Cell body:
Axon:
Myelin sheath:
Nodes of Ranvier:
Terminal branches:
Axon terminals:
Synaptic vescicles:
Neurotransmitter:

12. Dendrites Cell body Axon Myelin sheath Node of Ranvier Terminal ending
Terminal branch
Figure 12.4, Marieb & Mallett (2003). Human Anatomy. Benjamin Cummings.

13. Neurotransmitter: Acetylcholine (ACh)
Figure 12.8, Marieb & Mallett (2003). Human Anatomy. Benjamin Cummings.
Terminal ending
Synaptic vescicle
Neurotransmitter: Acetylcholine (ACh)

14. Figure 12. 19, Marieb & Mallett (2003). Human Anatomy
Figure 12.19, Marieb & Mallett (2003). Human Anatomy. Benjamin Cummings.

15. Structure and Function
Nervous system structure
Muscular system structure
Neuromuscular function

16. Classification of Muscle Tissue
Three types:
1. Smooth muscle
2. Cardiac muscle
3. Skeletal muscle

17. Muscular System Structure
Organization:
Muscle (epimyseum)
Fascicle (perimyseum)
Muscle fiber (endomyseum)
Myofibril
Myofilament
Actin and myosin
Other Significant Structures:
Sarcolemma
Transverse tubule
Sarcoplasmic reticulum
Tropomyosin
Troponin

18. Figure 10.1, Marieb & Mallett (2003). Human Anatomy. Benjamin Cummings.

19. Figure 10.4, Marieb & Mallett (2003). Human Anatomy. Benjamin Cummings.

21. Figure 10.8, Marieb & Mallett (2003). Human Anatomy. Benjamin Cummings.

22. Structure and Function
Nervous system structure
Muscular system structure
Neuromuscular function

23. Neuromuscular Function
Basic Progression:
1. Nerve impulse
2. Neurotransmitter release
3. Action potential along sarcolemma
4. Calcium release
5. Coupling of actin and myosin
6. Sliding filaments

24. Nerve Impulse What is a nerve impulse? -Transmitted electrical charge
-Excites or inhibits an action
-An impulse that travels along an axon is an ACTION POTENTIAL

25. Nerve Impulse How does a neuron send an impulse?
-Adequate stimulus from dendrite
-Depolarization of the resting membrane potential
-Repolarization of the resting membrane potential
-Propagation

26. -70 mV Nerve Impulse What is the resting membrane potential?
-Difference in charge between inside/outside of the neuron
-70 mV
Figure 12.9, Marieb & Mallett (2003). Human Anatomy. Benjamin Cummings.

27. Propagation of the action potential
Nerve Impulse
What is depolarization?
-Reversal of the RMP from –70 mV to +30mV
Propagation of the action potential
Figure 12.9, Marieb & Mallett (2003). Human Anatomy. Benjamin Cummings.

28. Nerve Impulse What is repolarization? -Return of the RMP to –70 mV
Figure 12.9, Marieb & Mallett (2003). Human Anatomy. Benjamin Cummings.

29. +30 mV
-70 mV

30. Neuromuscular Function
Basic Progression:
1. Nerve impulse
2. Neurotransmitter release
3. Action potential along sarcolemma
4. Calcium release
5. Coupling of actin and myosin
6. Sliding filaments

31. Release of the Neurotransmitter
Action potential  axon terminals
1. Calcium uptake
2. Release of synaptic vescicles (ACh)
3. Vescicles release ACh
4. ACh binds sarcolemma

32. Figure 12.8, Marieb & Mallett (2003). Human Anatomy. Benjamin Cummings.
Ca2+
ACh

33. Figure 14.5, Marieb & Mallett (2003). Human Anatomy. Benjamin Cummings.

34. Neuromuscular Function
1. Nerve impulse
2. Neurotransmitter release
3. Action potential along sarcolemma
4. Calcium release
5. Coupling of actin and myosin
6. Sliding filaments

35. Ach

36. AP Along the Sarcolemma
Action potential  Transverse tubules
1. T-tubules carry AP inside
2. AP activates sarcoplasmic reticulum

37. Figure 14.5, Marieb & Mallett (2003). Human Anatomy. Benjamin Cummings.

38. Neuromuscular Function
1. Nerve impulse
2. Neurotransmitter release
3. Action potential along sarcolemma
4. Calcium release
5. Coupling of actin and myosin
6. Sliding Filaments

39. Calcium Release AP  T-tubules  Sarcoplasmic reticulum
1. Activation of SR
2. Calcium released into sarcoplasm

40. CALCIUM
RELEASE
Sarcolemma

41. Neuromuscular Function
1. Nerve impulse
2. Neurotransmitter release
3. Action potential along sarcolemma
4. Calcium release
5. Coupling of actin and myosin
6. Sliding filaments

42. Coupling of Actin and Myosin
Tropomyosin
Troponin

43. Blocked
Coupling of actin and myosin

44. Neuromuscular Function
1. Nerve impulse
2. Neurotransmitter release
3. Action potential along sarcolemma
4. Calcium release
5. Coupling of actin and myosin
6. Sliding filaments

45. Sliding Filament Theory
Basic Progression of Events
1. Cross-bridge
2. Power stroke
3. Dissociation
4. Reactivation of myosin

46. Cross-Bridge Activation of myosin via ATP -ATP  ADP + Pi + Energy
-Activation  “cocked” position

47. Power Stroke ADP + Pi are released Configurational change
Actin and myosin slide

48. Dissociation
New ATP binds to myosin
Dissociation occurs

49. Reactivation of Myosin Head
ATP  ADP + Pi + Energy
Reactivates the myosin head
Process starts over
Process continues until:
-Nerve impulse stops
-AP stops
-Calcium pumped back into SR
-Tropomyosin/troponin back to original position

51. Outline Introduction Structure and Function Fiber Arrangement
Muscle Actions
Role of Muscles
Neural Control
Factors that Affect Muscle Tension

52. Shape of Muscles & Fiber Arrangement
Muscles have different shapes & fiber arrangements
Shape & fiber arrangement affects

53. Shape of Muscles & Fiber Arrangement
Two major types of fiber arrangements

54. Fiber Arrangement - Parallel
Parallel muscles
Categorized into following shapes:
Flat
Fusiform
Strap
Radiate
Sphincter or circular

55. Fiber Arrangement - Parallel
Flat muscles
Modified from Van De Graaff KM: Human anatomy, ed 6, Dubuque, IA, 2002, McGraw-Hill.

56. Fiber Arrangement - Parallel
Fusiform muscles
Figure 3.3. Hamilton, Weimar & Luttgens (2005). Kinesiology: Scientific basis for human motion. McGraw-Hill.

57. Fiber Arrangement - Parallel
Strap muscles
Figure 8.7. Hamilton, Weimar & Luttgens (2005). Kinesiology: Scientific basis for human motion. McGraw-Hill.

58. Fiber Arrangement - Parallel
Radiate muscles
Modified from Van De Graaff KM: Human anatomy, ed 6, Dubuque, IA, 2002, McGraw-Hill.

59. Fiber Arrangement - Parallel
Sphincter or circular muscles
Modified from Van De Graaff KM: Human anatomy, ed 6, Dubuque, IA, 2002, McGraw-Hill.

60. Fiber Arrangement - Pennate
Pennate muscles

61. Fiber Arrangement - Pennate
Categorized based upon the exact arrangement between fibers & tendon
Modified from Van De Graaff KM: Human anatomy, ed 6, Dubuque, IA, 2002, McGraw-Hill.

62. Fiber Arrangement - Pennate
Unipennate muscles

63. Fiber Arrangement - Pennate
Bipennate muscle

64. Fiber Arrangement - Pennate
Multipennate muscles
Bipennate & unipennate produce more force than multipennate

65. Outline Introduction Structure and Function Fiber Arrangement
Muscle Actions
Role of Muscles
Neural Control
Factors that Affect Muscle Tension

66. Muscle Actions: Terminology
Origin (Proximal Attachment):

67. Muscle Actions: Terminology
Insertion (Distal Attachment):

68. Muscle Actions: Terminology
When a particular muscle is activated:
Examples:
Bicep curl vs. chin-up
Hip extension vs. RDL

69. Muscle Actions
Action:
Contraction:

70. Muscle Actions
Muscle actions can be used to cause, control, or prevent joint movement or

71. Types of Muscle Actions
MUSCLE ACTION (under tension)
Isometric
Isotonic
Concentric
Eccentric

72. Types of Muscle Actions
Isometric action:

73. Types of Muscle Actions
Isotonic (same tension):
Isotonic contractions are either concentric (shortening) or eccentric (lengthening)

74. Types of Muscle Actions
Concentric contractions involve muscle developing tension as it shortens
Eccentric contractions involve the muscle lengthening under tension

75. What is the role of the elbow extensors in each phase?
Modified from Shier D, Butler J, Lewis R: Hole’s human anatomy & physiology, ed 9, Dubuque, IA, 2002, McGraw-Hill

76. Types of Muscle Actions
Isokinetics:

77. Types of Muscle Actions
Movement may occur at any given joint without any muscle contraction whatsoever

78. Outline Introduction Structure and Function Fiber Arrangement
Muscle Actions
Role of Muscles
Neural Control
Factors that Affect Muscle Tension

79. Role of Muscles
Agonist muscles

80. Role of Muscles
Antagonist muscles

82. Role of Muscles
Stabilizers

83. Role of Muscles
Synergist

84. Role of Muscles
Neutralizers

85. Outline Introduction Structure and Function Fiber Arrangement
Muscle Actions
Role of Muscles
Neural Control
Factors that Affect Muscle Tension

86. Factors That Affect Muscle Tension
Number Coding and Rate Coding
Length-Tension Relationship
Force-Velocity Relationship
Angle of Pull
Uniarticular vs. Biarticular Muscles
Cross-sectional Diameter
Muscle Fiber Type
Pennation

87. Number Coding & Rate Coding
Difference between lifting a minimal vs. maximal resistance is the number of muscle fibers recruited (crossbridges)
The number of muscle fibers recruited may be increased by

88. Number Coding & Rate Coding
Number of muscle fibers per motor unit varies significantly

89. Number Coding & Rate Coding
As stimulus strength increases from threshold, more motor units (Number Coding) are recruited & overall muscle contraction force increases in a graded fashion
From Seeley RR, Stephens TD, Tate P: Anatomy & physiology, ed 7, New York, 2006, McGraw-Hill.

90. Number Coding & Rate Coding
Greater contraction forces may also be achieved by increasing the frequency or motor unit activation (Rate Coding)
Phases of a single muscle fiber contraction or twitch
Stimulus
Latent period
Contraction phase
Relaxation phase

91. Number Coding & Rate Coding
Latent period
Contraction phase
Relaxation phase
From Powers SK, Howley ET: Exercise physiology: theory and application to fitness and performance, ed 4, New York, 2001 , McGraw-Hill.

92. Number Coding & Rate Coding
Summation
When successive stimuli are provided before relaxation phase of first twitch has completed, subsequent twitches combine with the first to produce a sustained contraction
Generates a greater amount of tension than single contraction would produce individually
As frequency of stimuli increase, the resultant summation increases accordingly producing increasingly greater total muscle tension

93. Number Coding & Rate Coding
Tetanus
From Powers SK, Howley ET: Exercise physiology: theory and application to fitness and performance, ed 4, New York, 2001 , McGraw-Hill.

94. All or None Principle Motor unit Typical muscle contraction

95. Factors That Affect Muscle Tension
Number Coding and Rate Coding
Length-Tension Relationship
Force-Velocity Relationship
Angle of Pull
Uniarticular vs. Biarticular Muscles
Cross-sectional Diameter
Muscle Fiber Type
Pennation

96. Length - Tension Relationship
Maximal ability of a muscle to develop tension & exert force varies depending upon the length of the muscle during contraction
Passive Tension
Active Tension

97. Length - Tension Relationship
Generally, depending upon muscle involved

98. Length - Tension Relationship
Generally, depending upon muscle involved

99. Figure 20. 2, Plowman and Smith (2002)
Figure 20.2, Plowman and Smith (2002). Exercise Physiology, Benjamin Cummings.

100. Factors That Affect Muscle Tension
Number Coding and Rate Coding
Length-Tension Relationship
Force-Velocity Relationship
Angle of Pull
Uniarticular vs. Biarticular Muscles
Cross-sectional Diameter
Muscle Fiber Type
Pennation

101. Force – Velocity Relationship
When muscle is contracting (concentrically or eccentrically) the rate of length change is significantly related to the amount of force potential

102. Force – Velocity Relationship
Maximum concentric velocity = minimum resistance
As load increases, concentric velocity decreases
Eventually velocity = 0 (isometric action)

103. Force – Velocity Relationship
As load increases beyond muscle’s ability to maintain an isometric contraction
As load increases
Eventually

104. Muscle Force – Velocity Relationship
Indirect relationship between force (load) and concentric velocity
Direct relationship between force (load) and eccentric velocity

105. Factors That Affect Muscle Tension
Number Coding and Rate Coding
Length-Tension Relationship
Force-Velocity Relationship
Angle of Pull
Uniarticular vs. Biarticular Muscles
Cross-sectional Diameter
Muscle Fiber Type
Pennation

106. Angle of Pull
Angle between the line of pull of the muscle & the bone on which it inserts (angle toward the joint)
With every degree of joint motion, the angle of pull changes
Joint movements & insertion angles involve mostly small angles of pull

107. Angle of Pull Angle of pull changes as joint moves through ROM
Most muscles work at angles of pull less than 50 degrees
Amount of muscular force needed to cause joint movement is affected by angle of pull – Why?

108. Angle of Pull
Rotary component - Acts perpendicular to long axis of bone (lever)
Modified from Hall SJ: Basic biomechanics, New York, 2003, McGraw-Hill.

109. Angle of Pull
If angle < 90 degrees, the parallel component is a stabilizing force
If angle > 90 degrees, the force is a dislocating force
What is the effect of >/< 90 deg on ability to rotate the joint forcefully?
Modified from Hall SJ: Basic biomechanics, New York, 2003, McGraw-Hill.

110. Factors That Affect Muscle Tension
Number Coding and Rate Coding
Length-Tension Relationship
Force-Velocity Relationship
Angle of Pull
Uniarticular vs. Biarticular Muscles
Cross-sectional Diameter
Muscle Fiber Type
Pennation

111. Uni Vs. Biarticular Muscles
Uniarticular muscles
Ex: Brachialis
Ex: Gluteus Maximus

112. Uni Vs. Biarticular Muscles
May contract & cause motion at either one or both of its joints
Advantages over uniarticular muscles

113. Advantage #1
Can cause and/or control motion at more than one joint

114. Advantage #2
Can maintain a relatively constant length due to "shortening" at one joint and "lengthening" at another joint (Quasi-isometric)
- Recall the Length-Tension Relationship

115. Advantage #3 Prevention of Reciprocal Inhibition
This effect is negated with biarticular muscles when they move concurrently
Concurrent movement:
Countercurrent movement:

116. What if the muscles of the hip/knee were uniarticular?
Ankle
Muscles stretched/shortened to extreme lengths! Implication?

117. Figure 20. 2, Plowman and Smith (2002)
Figure 20.2, Plowman and Smith (2002). Exercise Physiology, Benjamin Cummings.

118. Quasi-isometric action? Implication?
Hip
Knee
Ankle

119. Active & Passive Insufficiency
Countercurrent muscle actions can reduce the effectiveness of the muscle
As muscle shortens its ability to exert force diminishes
As muscle lengthens its ability to move through ROM or generate tension diminishes

120. Factors That Affect Muscle Tension
Number Coding and Rate Coding
Length-Tension Relationship
Force-Velocity Relationship
Angle of Pull
Uniarticular vs. Biarticular Muscles
Cross-sectional Diameter
Muscle Fiber Type
Pennation

121. Cross-Sectional Area Hypertrophy vs. hyperplasia
Increased # of myofilaments
Increased size and # of myofibrils
Increased size of muscle fibers

122. Factors That Affect Muscle Tension
Number Coding and Rate Coding
Length-Tension Relationship
Force-Velocity Relationship
Angle of Pull
Uniarticular vs. Biarticular Muscles
Cross-sectional Diameter
Muscle Fiber Type
Reflexes
Pennation

123. Muscle Fiber Characteristics
Three basic types:
1. Type I:
-Slow twitch, oxidative, red
2. Type IIb:
-Fast twitch, glycolytic, white
3. Type IIa:
-FOG

124. Factors That Affect Muscle Tension
Number Coding and Rate Coding
Length-Tension Relationship
Force-Velocity Relationship
Angle of Pull
Uniarticular vs. Biarticular Muscles
Cross-sectional Diameter
Muscle Fiber Type
Reflexes
Pennation

125. Effect of Fiber Arrangement on Force Output
Concept #1: Force directly related to cross-sectional area  more fibers
Example: Thick vs. thin longitudinal/fusiform muscle?
Example: Thick fusiform/longitudinal vs. thick bipenniform muscle?
Concept #2: As degree of pennation increases, so does # of fibers per CSA