1. Neuromuscular Fundamentals
Anatomy and Physiology of Human Movement
420:050

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
Protection
Posture and support
Produce a major portion of total body heat
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 - muscles work in groups rather than independently to achieve a given joint motion

4. Muscle Tissue Properties
Irritability or Excitability - property of muscle being sensitive or responsive to chemical, electrical, or mechanical stimuli
Contractility - ability of muscle to contract & develop tension or internal force against resistance when stimulated
Extensibility - ability of muscle to be passively stretched beyond it normal resting length
Elasticity - ability of muscle to return to its original length following stretching

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: Receptor sites
Cell body: Integration
Axon: Transmission
Myelin sheath: Protection and speed
Nodes of Ranvier: Saltatory conduction
Terminal branches: Increased innervation
Axon terminals: Connection with muscular system
Synaptic vescicles: Delivery mechanism of “message”
Neurotransmitter: The message

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. Skeletal Muscle: Properties
Extensibility: The ability to lengthen
Contractility: The ability to shorten
Elasticity: The ability to return to original length
Irritability: The ability to receive and respond to stimulus

18. 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

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

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

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

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

24. 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

25. 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

26. 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

27. -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.

28. 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.

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

30. +30 mV
-70 mV

31. 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

32. 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

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

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

35. 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

36. Ach

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

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

39. 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

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

41. CALCIUM
RELEASE
Sarcolemma

42. 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

43. Coupling of Actin and Myosin
Tropomyosin
Troponin

44. Blocked
Coupling of actin and myosin

45. 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

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

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

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

49. Dissociation
New ATP binds to myosin
Dissociation occurs

50. 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

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

53. Shape of Muscles & Fiber Arrangement
Muscles have different shapes & fiber arrangements
Shape & fiber arrangement affects
Muscle’s ability to exert force
Range through which it can effectively exert force onto the bones

54. Shape of Muscles & Fiber Arrangement
Two major types of fiber arrangements
Parallel & pennate
Each is further subdivided according to shape

55. Fiber Arrangement - Parallel
Parallel muscles
fibers arranged parallel to length of muscle
produce a greater range of movement than similar sized muscles with pennate arrangement
Categorized into following shapes:
Flat
Fusiform
Strap
Radiate
Sphincter or circular

56. Fiber Arrangement - Parallel
Flat muscles
Usually thin & broad, originating from broad, fibrous, sheet-like aponeuroses
Allows them to spread their forces over a broad area
Ex: Rectus abdominus & external oblique
Modified from Van De Graaff KM: Human anatomy, ed 6, Dubuque, IA, 2002, McGraw-Hill.

57. Fiber Arrangement - Parallel
Fusiform muscles
Spindle-shaped with a central belly that tapers to tendons on each end
Allows them to focus their power onto small, bony targets
Ex: Brachialis, biceps brachii
Figure 3.3. Hamilton, Weimar & Luttgens (2005). Kinesiology: Scientific basis for human motion. McGraw-Hill.

58. Fiber Arrangement - Parallel
Strap muscles
More uniform in diameter with essentially all fibers arranged in a long parallel manner
Enables a focusing of power onto small, bony targets
Ex: Sartorius, sternocleidomastoid
Figure 8.7. Hamilton, Weimar & Luttgens (2005). Kinesiology: Scientific basis for human motion. McGraw-Hill.

59. Fiber Arrangement - Parallel
Radiate muscles
Also described sometimes as being triangular, fan-shaped or convergent
Have combined arrangement of flat & fusiform
Originate on broad aponeuroses & converge onto a tendon
Ex: Pectoralis major, trapezius
Modified from Van De Graaff KM: Human anatomy, ed 6, Dubuque, IA, 2002, McGraw-Hill.

60. Fiber Arrangement - Parallel
Sphincter or circular muscles
Technically endless strap muscles
Surround openings & function to close them upon contraction
Ex: Orbicularis oris surrounding the mouth
Modified from Van De Graaff KM: Human anatomy, ed 6, Dubuque, IA, 2002, McGraw-Hill.

61. Fiber Arrangement - Pennate
Pennate muscles
Have shorter fibers
Arranged obliquely to their tendons in a manner similar to a feather
Reduces mechanical efficiency of each fiber
Increases overall number of fibers “packed” into muscle
Overall effect = more crossbridges = more force!

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

63. Fiber Arrangement - Pennate
Unipennate muscles
Fibers run obliquely from a tendon on one side only
Ex: Biceps femoris, extensor digitorum longus, tibialis posterior

64. Fiber Arrangement - Pennate
Bipennate muscle
Fibers run obliquely on both sides from a central tendon
Ex: Rectus femoris, flexor hallucis longus

65. Fiber Arrangement - Pennate
Multipennate muscles
Have several tendons with fibers running diagonally between them
Ex: Deltoid
Bipennate & unipennate produce more force than multipennate

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

67. Muscle Actions: Terminology
Origin (Proximal Attachment):
Structurally, the proximal attachment of a muscle or the part that attaches closest to the midline or center of the body
Functionally & historically, the least movable part or attachment of the muscle
Note: The least movable may not necessarily be the proximal attachment

68. Muscle Actions: Terminology
Insertion (Distal Attachment):
Structurally, the distal attachment or the part that attaches farthest from the midline or center of the body
Functionally & historically, the most movable part is generally considered the insertion

69. Muscle Actions: Terminology
When a particular muscle is activated
It tends to pull both ends toward the center
Actual movement is towards more stable attachment
Examples:
Bicep curl vs. chin-up
Hip extension vs. RDL

70. Muscle Actions
Action - when tension is developed in a muscle as a result of a stimulus
Muscle “contraction” term is exclusive in nature
As a result, it has become increasingly common to refer to the various types of muscle contractions as muscle actions instead

71. Muscle Actions
Muscle actions can be used to cause, control, or prevent joint movement or
To initiate or accelerate movement of a body segment
To slow down or decelerate movement of a body segment
To prevent movement of a body segment by external forces

72. Types of Muscle Actions
Muscle action (under tension)
Isometric
Isotonic
Concentric
Eccentric

73. Types of Muscle Actions
Isometric action:
Tension is developed within muscle but joint angles remain constant
AKA – Static movement
May be used to prevent a body segment from being moved by external forces
Internal torque = external torque

74. Types of Muscle Actions
Isotonic (same tension) contractions involve muscle developing tension to either cause or control joint movement
AKA – Dynamic movement
Isotonic contractions are either concentric (shortening) or eccentric (lengthening)

75. Types of Muscle Actions
Concentric contractions involve muscle developing tension as it shortens
Internal torque > external torque
Causes movement against gravity or other resistance
Described as being a positive action
Eccentric contractions involve the muscle lengthening under tension
External torque > internal torque
Controls movement caused by gravity or other resistance
Described as being a negative action

76. 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

77. Types of Muscle Actions
Movement may occur at any given joint without any muscle contraction whatsoever
referred to as passive
solely due to external forces such as those applied by another person, object, or resistance or the force of gravity in the presence of muscle relaxation

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
The activated muscle group during concentric or eccentric phases of movement
Known as primary or prime movers, or muscles most involved

80. Role of Muscles Antagonist muscles
Located on opposite side of joint from agonist
Have the opposite concentric action
Also known as contralateral muscles
Work in cooperation with agonist muscles by relaxing & allowing movement
Reciprocal Inhibition

82. Role of Muscles Stabilizers Surround joint or body part
Contract to fixate or stabilize the area to enable another limb or body segment to exert force & move
Also known as fixators

83. Role of Muscles Synergist Assist in action of agonists
Not necessarily prime movers for the action
Also known as guiding muscles
Assist in refined movement & rule out undesired motions

84. Role of Muscles Neutralizers
Counteract or neutralize the action of another muscle to prevent undesirable movements such as inappropriate muscle substitutions
Activation to resist specific actions of other muscles

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
Uniarticular vs. Biarticular Muscles
Cross-sectional Diameter
Muscle Fiber Type

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
Activating those motor units containing a greater number of muscle fibers (Number Coding)
Activating more motor units (Number Coding)
Increasing the frequency of motor unit activation (Rate Coding)

88. Number Coding & Rate Coding
Number of muscle fibers per motor unit varies significantly
From less than 10 in muscles requiring precise and detailed such as muscles of the eye
To as many as a few thousand in large muscles that perform less complex activities such as the quadriceps and gastrocnemius

89. Number Coding & Rate Coding
Greater contraction forces may also be achieved by increasing the frequency or motor unit activation (Rate Coding)

90. All or None Principle Motor unit Typical muscle contraction
Single motor neuron & all muscle fibers it innervates
Typical muscle contraction
The number of motor units responding (and number of muscle fibers contracting) within the muscle may vary significantly from relatively few to virtually all
All of the fibers within the motor unit will fire when stimulated by the CNS
All or None Principle - regardless of number, individual muscle fibers within a given motor unit will either fire & contract maximally or not at all

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

92. 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

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

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

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

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

97. Force – Velocity Relationship
As load increases beyond muscle’s ability to maintain an isometric contraction, the muscle begins eccentric action
As load increases, eccentric velocity increases
Eventually velocity = maximum when muscle tension fails

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

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

100. Uni Vs. Biarticular Muscles
Uniarticular muscles
Cross & act directly only on the single joint that they cross
Ex: Brachialis
Can only pull humerus & ulna closer together
Ex: Gluteus Maximus
Can only pull posterior femur and pelvis closer together

101. Uni Vs. Biarticular Muscles
Cross & act on two different joints
May contract & cause motion at either one or both of its joints
Advantages over uniarticular muscles

102. Advantage #1 Can cause and/or control motion at more than one joint
Rectus femoris: Knee extension, hip flexion
Hamstrings: Knee flexion, hip extension

103. 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

104. Advantage #3 Prevention of Reciprocal Inhibition
This effect is negated with biarticular muscles when they move concurrently
Concurrent movement:
Concurrent “lengthening” and “shortening” of muscle
Countercurrent movement:
Both ends “lengthen” or “shorten”

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

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

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

108. Active & Passive Insufficiency
Countercurrent muscle actions can reduce the effectiveness of the muscle
As muscle shortens its ability to exert force diminishes
Active insufficiency: Diminished crossbridges
As muscle lengthens its ability to move through ROM or generate tension diminishes
Passively insufficiency: Diminished crossbridges and excessive passive tension

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

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

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

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