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

2. Outline Introduction Structure and Function Muscle Actions
Role of Muscles
Neural Control

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 Muscle Actions
Role of Muscles
Neural Control

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

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

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

14. 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

15. 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

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

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

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

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

21. 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

22. 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

23. 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

24. -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.

25. 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.

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

27. +30 mV
-70 mV

28. 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

29. 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

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

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

32. 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

33. Ach

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

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

36. 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

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

38. CALCIUM
RELEASE
Sarcolemma

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. Coupling of Actin and Myosin
Tropomyosin
Troponin

41. Blocked
Coupling of actin and myosin

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

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

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

46. Dissociation
New ATP binds to myosin
Dissociation occurs

47. 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

49. Outline Introduction Structure and Function Muscle Actions
Role of Muscles
Neural Control

50. 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

51. 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

52. 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

53. 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

54. 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

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

56. 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

57. 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)

58. 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

59. 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

60. 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

61. Outline Introduction Structure and Function Muscle Actions
Role of Muscles
Neural Control

62. 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

63. 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

65. 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

66. 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

67. 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

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