1. Muscular System Muscles are responsible for all types of body movement
3 basic muscle types are found in the body
Skeletal muscle
Cardiac muscle
Smooth muscle

2. Characteristics of Muscles
Muscle cells are elongated (muscle cell = muscle fiber)
Contraction of muscles is due to the movement of microfilaments
All muscles share some terminology
Prefix myo refers to muscle
Prefix mys refers to muscle
Prefix sarco refers to flesh

3. Comparison of Types of Muscle

4. Types of Muscle, cont.

5. Skeletal Muscle Characteristics
Most attach to bones by tendon
Cells are multinucleate
Striated—have visible binding
Voluntary
Cells surrounded & bundled by connective tissue

6. Smooth Muscle Characteristics
Has no striations
Spindle-shaped cells
Single Nucleus
Involuntary—no conscious control
Found mainly in the walls of hollow organs

7. Characteristics of Cardiac Muscle
Has striations
Usually has a single nucleus
Joined to another cardiac muscle cell
Involuntary
Found only in the heart

8. Skeletal Muscle Functions of Skeletal Muscle
Muscle Fibers blend into a connective tissue attachment
Tendon—cordlike structure
Aponeurosis—sheet-like structure
Properties of Muscle
Irritability – ability to receive and respond to a stimulus
Contractibility – ability to shorten when an adequate stimulus is received
Extensibility – ability to lengthen when an adequate stimulus is received
Elasticity – ability to return to normal shape
Functions of Skeletal Muscle
Produce Movement
Maintain posture
Stabilize joints
Generate Heat
Sites of Muscle Attachment
Bones
Cartilage
Connective tissue coverings

9. Anatomy of a Muscle Cell

10. B. Anatomy of Skeletal Muscles - Gross Anatomy
All three layers attach muscle to bone
Surrounds muscle
Bundle of muscle fibers
Surrounds each muscle fiber, and tie adjacent fibers together
Divides muscle into compartments, each contain a bundle of muscle fibers called fascicle

11. Naming Skeletal Muscles
Action
Origin
&
Insertion
Shape
Number Of
Origins
Size
Location
Direction of
Muscle
Fibers
Skeletal

12. Direction of Muscle Fibers
Relative to the Midline
RECTUS = parallel to the midline
Rectus Abdominus
TRANSVERSE = perpendicular to midline
Transverse Abdominus
OBLIQUE = diagonal to midline
External Oblique

13. Location Structure near which muscle is found
FRONTALIS = near FRONTAL bone
OCCIPITALIS = near OCCIPITAL bone

14. Size Relative Size of Muscle MAXIMUS = largest MEDIUS = middle
Gluteus Maximus
MEDIUS = middle
Gluteus Medius
MINIMUS = smallest
Gluteus Minimus
LONGUS = longest
Fibularis Longus
BREVIS = short
Fibularis Brevis
TERTIUS = shortest
Fibularis Tertius

15. Number of Origins Number of tendons of origin BICEPS = Two
Biceps Brachii
Biceps Femoris
TRICEPS = Three
Triceps Brachii
QUADRICEPS = Four
Quadriceps Femoris

16. Shape Relative Shape of the Muscle DELTOID = triangular shape Δ
TRAPEZIUS = trapezoid shape  SERRATUS = saw-toothed ♒
RHOMBOIDEUS = rhomboid shape 
TERES = round ○

17. Origin & Insertion Origin – attachment to an immoveable bone
Insertion – attachment to a movable bone
ILIO COSTALIS= attaches to the ilium & ribs (costal = ribs)

18. Action NAME ACTION EXAMPLE FLEXOR EXTENSOR ABDUCTOR ADDUCTOR LEVATOR
Decrease angle at a joint
Flexor Carpi Radialis
EXTENSOR
Increase angle at a joint
Extensor Carpi Ulnaris
ABDUCTOR
Move bone away from midline
Abductor Pollicis Longus
ADDUCTOR
Move bone toward midline
Adductor Longus
LEVATOR
Produce upward movement
Levator Scapulae
DEPRESSOR
Produce downward movement
Depressor Labii Inferioris
SUPINATOR
Turn palm upward/anterior
Supinator
PRONATOR
Turn palm downward/posterior
Pronator Teres

19. Types of Muscle--Actions
Prime mover (Agonist) – muscle with the major responsibility for a certain movement
Antagonist – muscle that opposes or reverses a prime mover
Synergist – muscle that aids a prime mover in a movement and helps prevent rotation
Fixator – stabilizes the origin of a prime mover

21. Muscle contractions require energy
Blood vessels deliver oxygen and nutrients to produce ATP
Muscle contractions are under stimulation from the CNS
Voluntary control
Axons connect to individual muscle fibers

22. Microanatomy – Sarcolemma and T-Tubules
Very large cells
100’s of nuclei
Cell membrane
pores open to T-tubules
Network of narrow tubules
filled with extracellular fluid
form passageways through muscle fiber

23. Myofibrils Cylinder as long as entire muscle fiber
Each fiber contains 100s to 1000s
Responsible for contraction
When myofibrils contract the whole cell contracts
Consist of proteins
Actin – thin filaments
Myosin – thick filaments

24. Sarcoplasmic Reticulum
Specialized form of SER
Tubular network around each myofibril
In contact with T-Tubule
Cisternae – expanded chambers of SR, store Calcium

25. Sarcomere Smallest functional unit of muscle fiber
Each myofibril contains 10,000 sarcomeres end to end
Interaction between thick and thin filaments cause contraction
Banded appearance

26. Thick and Thin Filaments
twisted actin molecules
Each has an active site where they interact with myosin
Resting – active site covered by tropomyosin which is held in place by troponin
Thick
Myosin
Head attaches to actin during contraction
Can only happen if troponin changes position, moving tropomyosin to expose active site

27. Sliding Filaments and Cross Bridges
Sarcomere contraction – Sliding Filament Theory
Thin filaments slide toward center of sarcomere
Thick filaments are stationary
Myosin head attaches to active site on actin (cross bridge)
Pull actin towards center, then detaches

28. Questions
How would severing the tendon attached to a muscle affect the ability of the muscle to move a body part?
Why does skeletal muscle appear striated when viewed through a microscope?
Where would you expect the greatest concentration of calcium ions in resting skeletal muscles to be?

29. Control of Muscle Fiber Contraction
Under control of the nervous system

30. Neuromuscular Junction
Link between NS and muscle
Motor neuron – control skeletal muscle fibers
Synaptic terminal
Acetylcholine (Ach) – chemical released by neuron to communicate with other cells
Triggers change in sarcolemma which triggers contraction

31. Action potential travels to axon of motor neuron
Ach is released into synaptic cleft
Ach diffuses across synaptic cleft & binds to Ach receptors on sarcolemma
This changes permeability to sodium
Sudden rush of sodium into sarcolemma
Causes action potential sarcolemma
Action potential spreads over entire sarcolemma, down t-tubules to cisternae
Cisternae release massive amounts of calcium
Increase in calcium – sarcomeres contract
Ach broken down by AchE

33. The Contraction Cycle Resting sarcomere Step 1 Step 2 Step 3 Step 4
ADP + P attached to myosin head (stored energy)
Step 1
Ca+ binds to troponin exposing active site on actin
Step 2
Myosin head attaches to actin
Step 3
Pulling of crossbridge towards center of sarcomere
ADP + P released (energy used)
Step 4
Myosin head binds another ATP
Detachment of cross bridge
Step 5
ATP ADP + P, reactivation of myosin head
The Contraction Cycle

35. Questions
How would a drug that interferes with cross-bridge formation affect muscle contraction?
What would you expect to happen to a resting skeletal muscle if the sarcolemma suddenly became very permeable to calcium ions?
Predict what would happen to a muscle if the motor end plate did not contain acetylcholinesterase.