1. Muscles – Working Together to Create Movement!
PSK 4U
Unit 4 Day 5

2. Muscles Pull!
Muscles pull (by contracting and relaxing) by working in opposing pairs or groups.
Muscles cannot push.
Sometimes muscles attached directly to bone, but more often they are joined to bone by tendons.

3. How Muscles Attach to Bone
Indirect Attachment – the epimysium (sheath of connective tissue that surrounds the exterior of the muscle fibre) extends past the muscle as a tendon and then attaches to the periosteum of bone. This is most common.
Direct Attachment – the epimysium adheres to and fuses with the periosteum.
Bone markings present where tendons meet bones
Tubercles, trochanters, and crests

4. Basic Muscular Principles
Skeletal muscles contract only if stimulated to do so
Skeletal muscles produce movements by pulling on bones
Bones serve as levers and joints serve as fulcrums on these levers
Muscles that move a body segment do not usually lie over that part (e.g. bicep flexes elbow but is in upper arm)
Skeletal muscles almost always act in groups rather than individually (prime movers/agonists, antagonists, stabilizers/fixators, synergists)

5. Force of Muscle Contraction
The force of contraction is affected by:
The relative size of the muscle
Larger muscles have larger and more muscle fibers
Larger fibers can generate more force than smaller fibers
More muscle fibers can generate more force than fewer fibers
The number of muscle fibers contracting
Greater numbers of motor units generate more force than smaller numbers of motor units
Degree of muscle stretch
Muscles contract strongest when muscle fibers are % of their normal resting length

6. Force of Muscle Contraction
Figure 9.20 (a)

7. Isometric and Isotonic Contractions
Isometric muscle contraction
Tension (force) does not exceed resistance (load)
important in postural muscle function
Isotonic muscle contraction
Tension exceeds resistance
tension while shortening = concentric
tension while lengthening = eccentric

8. Agonist and Antagonist Pairs
Agonist– muscle that contracts to produce movement of the body part (prime mover)
Synergists – assist in the action of the agonists but are not primarily responsible for action; known as guiding muscles they assist in refined movements and rule out undesired motions
Antagonist – muscle that opposes or counteracts the agonist (movement).
It lengthens when the agonist contracts shortens.

9. AGONIST (Prime Mover) ANTAGONIST
Examples of opposing muscles and muscle groups
AGONIST (Prime Mover)
ANTAGONIST
Elbow flexion
Shoulder abduction
Medial shoulder rotation
Knee extension
Wrist flexion
Dorsi flexion
Trunk flexion
Hip flexion

10. Examples of opposing muscles and muscle groups
AGONIST (Prime Mover)
ANTAGONIST
Elbow flexion
Biceps brachii
Triceps brachii
Shoulder abduction
Deltoid
Latissimus Dorsi
Medial shoulder rotation
Pectoralis major
Infraspinatus
Knee extension
Quadriceps
Hamstrings
Wrist flexion
Flexor carpi radialis
Extensor carpi radialis
Dorsi flexion
Tibialis anterior
Gastrocnemius
Trunk flexion
Rectus abdominis
Erector spinae group
Hip flexion
Iliopsoas
Gluteus maximus

11. Fixators/Stabilizer
Muscles that are active isometrically (muscle does not shorten or lengthen) in order to fixate an area when the agonist contracts
Fixators/ Stabilizers - increase tension to stabilize a joint that is more proximal to allow function at a distal joint
Example: When performing a push-up, the serratus anterior stabilizes the shoulder girdle during the downward stage in order to prevent adduction

12. Origins and Insertions
Origin – is least moveable part or the part of the muscle that attaches closest to the midline. It is the proximal attachment.
Insertion – is the most moveable part or the part of the muscle that attaches farther from the midline. It is the distal attachment.
The origin usually stays fixed and the insertion moves closer to it

13. NAMING MUSCLES: Tips
Most skeletal muscles have names that describe some feature of the muscle.
Often several criteria are combined into one name.
Associating the muscle's characteristics with its name will help you learn and remember them.
The following are some terms relating to muscle features that are used in naming muscles.

14. Size:
vastus (huge)
maximus (large)
longus (long)
minimus (small)
brevis (short)

15. Shape: deltoid (triangular) rhomboid (like a rhombus
with equal and parallel sides)
latissimus (wide)
teres (round)
trapezius (like a trapezoid, a four-sided figure with two sides parallel).

16. Direction of fibers: rectus (straight) transverse (across)
oblique (diagonally)
orbicularis (circular)

17. Location: gluteus (buttock) brachii (arm) supra- (above)
pectoralis (chest)
gluteus (buttock)
brachii (arm)
supra- (above)
infra- (below)
sub- (under or beneath)
lateralis (lateral).

18. Number of origins: biceps (two heads) triceps (three heads)
quadriceps (four heads)
Triceps Brachii
Origin
long head: infraglenoid tubercle of scapula
lateral head: upper half of the posterior surface of humerus medial head: distal two thirds of the posterior surface of humerus

19. Origin and insertion:
sternocleidomastoid (origin on the sternum and clavicle, insertion on the mastoid process)
brachioradialis (origin on the brachium or arm, insertion on the distal end of radius at the styloid process)

20. Action: adductor (to adduct a structure) flexor (to flex a structure)
abductor (to abduct a structure)
adductor (to adduct a structure)
flexor (to flex a structure)
extensor (to extend a structure)
levator (to lift/elevate a structure)

21. squeeze limbs in towards the median line of the body
The name given to a muscle reveals the main kind of functional movement that muscle permits.
ADDUCTOR MUSCLES
squeeze limbs in
towards the
median line of
the body
ie. – adductor longus,
adductor brevis,
adductor magnus
attached along the
femur – squeeze
thighs together

22. ABDUCTOR MUSCLES
”push out” from the median line of body.
ie- abductor digiti minimus manus, abductor pollicis longus, abductor pollicis brevis
EXTENSOR MUSCLES
extend the limbs and increase the angle between two limbs.
movement is usually directed backwards (with exception of the knee joint)
ie- extensor carpi radialis brevis, extensor carpi radialis longus, extensor carpi ulnaris
run from humerus along back of the forearm to the metacarpal bones

23. FLEXOR MUSCLES
withdraw the limbs and decrease the angle between bones on two sides of a joint.
ie- flexor
carpi radialis,
flexor carpi
ulnaris
from humerus
along inside of
forearm to
metacarpal bones
– flex wrist

24. HOMEWORK Start working on Muscles Origin/Insertion Chart
Start colouring in muscles in chart on pages in your workbooks!
Wednesday – more memorizing!