1. Chapter 2 Neuromuscular Fundamentals PPT Series 2A
EXSC 314
Chapter 2 Neuromuscular Fundamentals PPT Series 2A

2. Skeletal Muscles
Skeletal muscle contraction produces the force that causes joint movement.
Skeletal Muscles also:
Provide protection
Provide dynamic stability of joints
Contribute to posture and support
Produce a major portion of total body heat (How?)

3. Skeletal Muscles
FYI - Over 600 skeletal muscles comprise approximately 40% to 50% of body weight. There are 215 pairs of skeletal muscles that usually work in cooperation with each other to perform opposite actions at the joints they cross
Aggregate muscle action - Muscles work in groups rather than independently to achieve a given joint motion.

4. Muscle Nomenclature Muscles are usually named by: Shape
Action and Shape
Size
Action and Size
Number of divisions
Shape and location
Direction of fibers
Location and attachment
Location
Location and number of divisions
Points of attachment
Action

5. Muscle Nomenclature
Shape:
Deltoid
Rhomboid

6. Muscle Nomenclature
Size:
Teres Minor
Gluteus Maximus

7. Muscle Nomenclature Number of Divisions: Triceps brachii
Direction of Fibers: External abdominal oblique
Triceps brachii

8. Muscle Nomenclature
Location: Rectus femoris Palmaris longus

9. Muscle Nomenclature Points of Attachment: Extensor hallucis longus
Flexor digitorum longus
Coracobrachialis

10. Muscle Nomenclature Action: Supinator Extensor digiti minimi
Erector spinae

11. Muscle Nomenclature Action and shape: Adductor magnus Action and size:
Pronator quadratus
Adductor magnus

12. Muscle Nomenclature Shape and location : Serratus anterior
Location and attachment :
Serratus anterior
Brachioradialis

13. Muscle Nomenclature
Location and Number of Divisions: Biceps femoris

14. Muscle Grouping and Naming
Muscles are often grouped together for appearance and shared function (action).
Examples:
Shape – Hamstrings (Biceps Femoris, Semitendinosus, Semimembranosus)
Number of divisions – Quadriceps (Medius, Lateralis, Intermedius)
Location – Abdominal (Oblique: external, internal, Transverse, Rectus)
Action - Rotator Cuff

15. Shape of Muscles and Fiber Arrangement
Cross-section diameter
A factor in muscle’s ability to exert force
Keeping all other factors constant, a muscle with a greater cross-section diameter will be able to exert a greater force
Muscle’s ability to shorten
Longer muscles can shorten through a greater range
More effective in moving joints through large ranges of motion

16. Shape of Muscles and Fiber Arrangement
Muscles have different shapes and fiber arrangements. Shape and fiber arrangement determine:
Muscle’s ability to exert force
ROM the muscle can effectively exert force onto the bones
Major types of fiber arrangements
Parallel and Pennate
Each is further subdivided according to shape

17. Shape of Muscles and Fiber Arrangement
Parallel muscles
Fibers arranged parallel to the length of the muscle
Produce a greater range of movement than similar-sized muscles with a pennate arrangement
Categorized into the following shapes:
Flat
Fusiform
Strap
Radiate
Sphincter or circular

18. Fiber Arrangement - Parallel
Flat muscles
Example - Rectus abdomins
Usually thin and broad, originating from broad, fibrous, sheet-like aponeuroses (Link)
Allows muscles to exert forces over a broad area

19. Fiber Arrangement - Parallel
Fusiform muscles
Example – Biceps brachii
Spindle-shaped with a central belly that tapers to tendons on each end
Muscle exerts power on small, bony targets

20. Fiber Arrangement - Parallel
Strap muscles
Example - Sartorius
More uniform in diameter with essentially all fibers arranged in a long parallel manner
Muscles can exert power on small, bony targets

21. Fiber Arrangement - Parallel
Radiate muscles
Example - Pectoralis major
Also described sometimes as being triangular, fan- shaped, or convergent
Have combined arrangement of flat and fusiform
Originate on broad aponeuroses and converge onto a tendon

22. Fiber Arrangement - Parallel
Sphincter or circular muscles
Technically, endless strap muscles
Surround openings and function to close them upon contraction
Example - orbicularis oculi muscle surrounding the eye

23. Fiber Arrangement - Pennate
Pennate muscles
Have shorter fibers
Fibers are arranged obliquely to tendons in a manner similar to a feather
Arrangement increases the cross-sectional area of the muscle, thereby increasing the power
Categorized based on the exact arrangement between fibers and tendon
Unipennate
Bipennate
Multipennate

24. Fiber Arrangement - Pennate
Unipennate muscles
Example - Biceps femoris
Fibers run obliquely from a tendon on one side only

25. Fiber Arrangement - Pennate
Bipennate muscle
Example - Rectus femoris
Fibers run obliquely on both sides from a central tendon.

26. Fiber Arrangement - Pennate
Multipennate muscles
Example - Deltoid
Have multiple tendons with fibers running diagonally between the tendons
Bipennate and unipennate produce the strongest contractions

27. Muscle Tissue Properties
Skeletal muscle tissue has four properties related to force production and movement: Irritability or excitability, contractility, extensibility, and elasticity.
Irritability or excitability - Muscle property of being sensitive or responsive to chemical, electrical, or mechanical stimuli
Contractility - Ability of muscle to contract and develop tension or internal force against resistance when stimulated
Extensibility - Ability of muscle to be passively stretched beyond its normal resting length
Elasticity - Ability of muscle to return to its original length following stretching.

28. Muscle Terminology
Intrinsic - Pertaining usually to muscles within or belonging solely to the body part on which the muscle exerts force. Extrinsic - Pertaining usually to muscles that arise or originate outside of (proximal to) the body part on which the muscle exerts force.

29. Muscle Terminology
Action - Specific movement of a joint resulting from a concentric contraction of a muscle that crosses the joint. Actions are usually caused by a group of muscles working together.
Any of the muscles in the group can be said to cause an action, even though it is usually an effort of the entire group
A muscle may cause more than one action either at the same joint or a different joint depending upon the characteristics of the joint crossed by the muscle

30. Muscle Terminology
Innervation - Segment of the nervous system responsible for providing a stimulus to muscle fibers within a specific muscle or section of the muscle
A muscle may be innervated by more than one nerve, and a particular nerve may innervate more than one muscle or section of a muscle

31. Muscle Terminology
Amplitude - Range of muscle fiber length between maximal and minimal lengthening Gaster (belly or body) - Central, contractile portion of the muscle that generally increases in diameter as the muscle contracts
Tendon - Fibrous connective tissue, often cordlike in appearance, that connects muscles to bones and other structures
Two muscles may share a common tendon
A muscle may have multiple connecting tendons

32. Muscle Terminology
Aponeurosis - A tendinous expansion of dense fibrous connective tissue that is sheet- or ribbon-like in appearance and resembles a flattened tendon.
Aponeuroses serve as a fascia to bind muscles together or as a means of connecting muscle to bone.
Palmar aponeurosis

33. Muscle Terminology
Fascia - A sheet or band of fibrous connective tissue that envelopes, separates, or binds together parts of the body such as muscles, organs, and other soft-tissue structures of the body.
In some regions, (wrist and ankle), fascial tissue forms a retinaculum to retain tendons close to the body

34. Muscle Terminology
Origin - Structurally, the proximal attachment of a muscle or the part that attaches closest to the midline or center of the body. Functionally and historically, the origin is the least movable part or attachment of the muscle.
Insertion - Structurally, the distal attachment or the part that attaches farthest from the midline or center of the body. Functionally and historically, the most movable part is generally considered the insertion

35. Muscle Terminology
In some movements the “fixed” or “stable” end may be reversed.
Example - Biceps curl exercise
Biceps brachii origin (least movable bone) is on the scapula and its insertion (most movable bone) on the radius
HOWEVER, The movable end may be reversed…
Example - Pull-up
Radius is relatively stable and the scapula moves up
End of PPT Series 2A