1. The Muscular System

2. The Muscular System
Muscles are responsible for all types of body movement
Three basic muscle types are found in the body
Skeletal muscle (striated & voluntary)
Cardiac muscle (striated & involuntary)
Smooth muscle (non striated & involuntary)

3. Skeletal, Cardiac & Smooth Muscles

4. Characteristics of Muscles
Skeletal and smooth muscle cells are elongated (muscle cell = muscle fiber)
Contraction of muscles is due to the movement of microfilaments
All muscles share some terminology
Prefixes myo and mys refer to “muscle”
Prefix sarco refers to “flesh”

6. Skeletal Muscle Characteristics
Most are attached by tendons to bones
Cells are multinucleate
Striated—have visible banding
Voluntary—subject to conscious control

7. Connective Tissue Wrappings of Skeletal Muscle
Cells are surrounded and bundled by connective tissue which gives strength even though muscle fibers are soft & fragile.
Endomysium—encloses a single muscle fiber
Perimysium—wraps around a fascicle (bundle) of muscle fibers
Epimysium—covers the entire skeletal muscle
Fascia—on the outside of the epimysium

8. Connective Tissue Wrappings of Skeletal Muscle
Figure 6.1

9. Skeletal Muscle Attachments
Epimysium blends into a connective tissue attachment
Tendons— muscle to bone (cord like)
Mostly collagen fibers
Often cross a joint due to toughness and small size
Aponeuroses—sheet-like structures
Attach muscles indirectly to bones, cartilages, or connective tissue coverings

11. Skeletal Muscle Attachments
Sites of muscle attachment
Bones
Cartilages
Connective tissue coverings

12. Smooth Muscle Characteristics
Lacks striations
Spindle-shaped cells
Single nucleus
Involuntary—no conscious control
Found mainly in the walls of hollow organs and blood vessels

13. Cardiac Muscle Characteristics
Striations
Usually has a single nucleus
Branching cells
Involuntary
Found only in the
heart

14. Cardiac Muscle Characteristics
Figure 6.2b

15. Skeletal Muscle Functions
Produce movement
Maintain posture
Stabilize joints
Generate heat

16. Microscopic Anatomy of Skeletal Muscle (pg 188)
Figure 6.3a

17. Microscopic Anatomy of Skeletal Muscle
Figure 6.3b

19. Microscopic Anatomy of Skeletal Muscle
Sarcomere—contractile unit of a muscle
fiber
Organization of the sarcomere
Myofilaments
Thick filaments = myosin filaments
Thin filaments = actin filaments

20. Microscopic Anatomy of Skeletal Muscle
Figure 6.3c

21. Microscopic Anatomy of Skeletal Muscle
Thick filaments = myosin filaments
Composed of the protein myosin
Myosin filaments have heads (extensions, or cross bridges)
Myosin and actin overlap somewhat
Thin filaments = actin filaments
Composed of the protein actin
Anchored to the Z disc

22. Microscopic Anatomy of Skeletal Muscle
Figure 6.3d

24. Stimulation and Contraction of Single Skeletal Muscle Cells
Excitability (also called responsiveness or irritability)—ability to receive and respond to a stimulus
Contractility—ability to shorten (forcibly) when an adequate stimulus is received
Extensibility—ability of muscle cells to be stretched
Elasticity—ability to recoil and resume resting length after stretching

25. The Nerve Stimulus and Action Potential
Skeletal muscles must be stimulated by a motor neuron (nerve cell) to contract
Motor unit—one motor neuron and all the skeletal muscle cells stimulated by that neuron

26. The Nerve Stimulus and Action Potential
Figure 6.4a

27. The Nerve Stimulus and Action Potential
Figure 6.4b

28. The Nerve Stimulus and Action Potential
Neuromuscular junction
Association site of axon terminal of the motor neuron and muscle

29. The Nerve Stimulus and Action Potential

30. The Nerve Stimulus and Action Potential
Synaptic cleft (synapse)
Gap between nerve and muscle
Nerve and muscle do not make contact
Area between nerve and muscle is filled with interstitial fluid
Neurotransmitter is released by the axon terminal into synaptic cleft to stimulate the skeletal muscle

31. The Nerve Stimulus and Action Potential
Figure 6.5b

32. Transmission of Nerve Impulse to Muscle
Neurotransmitter—chemical released by nerve upon arrival of nerve impulse
The neurotransmitter for skeletal muscle is acetylcholine (ACh)
Acetylcholine attaches to receptors on the sarcolemma stimulating the muscle

33. The Sliding Filament Theory of Muscle Contraction
Activation by nerve causes myosin heads (cross bridges) to attach to binding sites on the thin filament
Myosin heads then bind to the next site of the thin filament and pull them toward the center of the sarcomere
This continued action causes a sliding of the myosin along the actin
The result is that the muscle is shortened (contracted)

34. The Sliding Filament Theory of Muscle Contraction
Figure 6.7a–b

35. The Sliding Filament Theory
Figure 6.8a

36. The Sliding Filament Theory
Figure 6.8b

37. The Sliding Filament Theory
Figure 6.8c

38. Contraction of skeletal muscle
all or nothing
Graded responses occur
- changing frequency of stimulation
- changing the number of muscle cells
contracted

39. TYPES OF MUSCLE CONTRACTIONS
Isotonic- muscle shortens and movement occurs.
Isometric- muscles DO NOT shorten.
Muscle tone- state of continuous partial
muscle contracton.
Flaccid –soft & flabby
Hypertonicity- increased tone

40. Energy for muscle contraction
Aerobic respiration –
uses oxygen
provides 36 ATP per glucose molecule
CO2 & H2O are end products as well
Anaerobic respiration-
without oxygen
provides 2 ATP per glucose molecule
lactic acid is an end product

41. Fast and Slow Twitch Muscle Fibers
It is generally accepted that muscle fiber types can be broken down into two main types: slow twitch (Type I) muscle fibers and fast twitch (Type II) muscle fibers.

42. Slow Twitch (Type I)
more efficient at using oxygen to generate more fuel (known as ATP) for continuous, extended muscle contractions over a long time. They fire more slowly than fast twitch fibers and can go for a long time before they fatigue. Therefore, slow twitch fibers are great at helping athletes run marathons and bicycle for hours.

43. Fast Twitch (Type II)
use anaerobic metabolism to create fuel, they are much better at generating short bursts of strength or speed than slow muscles. However, they fatigue more quickly. Fast twitch fibers generally produce the same amount of force per contraction as slow muscles, but they get their name because they are able to fire more rapidly. Having more fast twitch fibers can be an asset to a sprinter since she needs to quickly generate a lot of force.

44. Those are your three different types of muscles fibers
Those are your three different types of muscles fibers. You’re born with these fibers in certain proportions, and they will affect how successful you are at either developing as a long distance guy, or a sprinter guy.  Most bodies have 50% of Type 1 and 50% of Type 2, but many elite athletes (world class marathon runners, Olympic sprinters) can have up to 80% of one or the other.  Obviously a sprinter with 80% fast twitch fibers will have a better chance of being fast than somebody with only 30% fast twitch fibers.

45. BODY MOVEMENTS FLEXION / EXTENSION ROTATION ABDUCTION / ADDUCTION
CIRCUMDUCTION
DORSIFLEXION / PLANTAR FLEXION
INVERSION / EVERSION
SUPINATION / PRONATION
OPPOSITION