1. MUSCLE and MUSCLE TISSUE
Chapter 11

2. Muscles are distinguished by their ability to turn ATP (chemical energy) into work (mechanical energy)
Muscles do their work in one way – they contract
myo – (Greek) “muscle”
Sarco – (Greek) “flesh”

3. Muscle Types Skeletal Attached to and covers bones Striations
“voluntary”
Powerful but tire easily

5. Cardiac
Isolated; found only in heart
Striated
“involuntary”
Contraction is regular and controlled by neural transmission

7. Visceral
“Smooth”
Involuntary
No striatons
Contraction is slow and sustained

9. Functions Movement Locomotion and manipulation by skeletal muscle
Blood coursing – cardiac muscle
Propulsion and/or squeezing of substances – smooth muscle

10. Posture Maintenance
Skeletal muscle
Counteracts gravity
Heat Generation
By-product of muscle metabolism and contractile activity
Skeletal muscle (40% of body mass) is responsible

11. Properties
Excitability – ability to receive and respond to a stimulus (usually a neurotransmitter)
Contractility – ability to shorten when stimulated
Extensibility – ability to be stretched or extended – to a point
Elasticity – resumes its resting length

12. Skeletal Muscle – Gross Anatomy

13. Epimysium – connective tissue covering entire muscle structure
Fascicle – bound and separated by perimysium
Muscle fibers – bound and separated by endomysium
Myofibrils- composed of myofilaments

14. Myofilaments - composed of actin and myosin protein fibers
Connective tissue sheaths provide strength to the fragile muscle fibers; allow a route of entry and exit for blood and nerve fibers

15. Metabolic Supply
Nerve endings
Vascularity

16. Muscle Attachment
Direct attachment: epimysium to periosteum of bone.
Indirect attachment: epimysium forms a tendon to epimysium of another muscle or periosteum of bone.

17. Fascicle Arrangement Pattern influences range of motion and power
Long fibers = more range of motion
Power related to number of muscle fibers
See page 244 of text

18. Microscopic Anatomy of Skeletal Muscle
Typically cylindrical, long, multinucleated

19. Sarcolemma (cell membrane) – forms elongated tubes deep into the cell interior – “T tubules”
Sarcoplasm – with stored glycogen and myoglobin

20. Sarcoplasmic Reticulum
Specialized smooth E.R.
Connected to sarcolemma (plasma membrane); provides passage for neurotransmitter, glucose, oxygen, etc. into fiber
Regulates intracellular levels of Ca+ (holds and releases Ca+ on demand)
Sarcomeres – smallest contractile unit of muscle fiber; made of myofibrils

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23. Myofibrils – 80% of cell volume; contractile element of cell
Alternating bands of dark and light along length; give myofibril “striated” appearance
Banding due to 2 distinct protein filaments (“myofilaments”) within sarcomere

24. Myofilaments

25. Thick filaments – composed of myosin protein
Tail with 2 heads at one end – “cross bridges”
Heads contain ATPases
Tails bundled together with heads studded outward

26. Thin filaments – composed of actin protein
Strands of protein coil around each other to give appearance of twisted pearl necklace

27. Sliding Filament Theory
Thin filaments slide past thick filaments causing a myofibril overlap
During contraction, thin filaments penetrate deeper
Causes sliding

28. Physiology of Muscle Contraction
Requires ACh & Ca+
Stimulation by neurotransmitter
ACh receptors on sarcolemma cause Na+ to flood muscle cell
Na+ causes sarcoplasmic reticulum to release Ca+
Ca+ binds to actin = exposing actin/myosin binding sites

29. Myosin heads bind to exposed actin heads (exposed in presence of Ca+ which moves molecules covering actin binding sites)

30. Myosin head binds, forming cross bridges, using energy from previous ATP hydrolysis
Myosin head releases ADP (energy), thereby pulling myofilaments = “power stroke”

31. Ca+ is reabsorbed, myosin cross bridges are broken, muscle relaxes.
???What causes rigor mortis???

34. Muscle Contraction – Gross Level
Muscles respond in an “all-or-none” fashion
150 muscle fibers/motor nerve, one neuron + all the fibers it innervates = one motor unit

35. Fibers within a motor unit are scattered throughout
Muscles requiring fine motor control have fibers of one nerve close together - fingers

36. Muscle Mechanics Wave summation – recruit more cells
Tetanus – sustained contraction
Series of twitches
Summation
Tetanic contraction

37. Isotonic – muscle length varies
Isometric – muscle length stays the same
Muscle tone – slight contraction at rest

38. Muscle Metabolism
When ATP synthesis < ATP use then one of several things happens because muscles store very little ATP:
ADP + creatine phosphate
Aerobic respiration
Anaerobic respiration
Muscle fatigue
Contractures – permanent shortening
Oxygen debt – lactic acid buildup

39. Animation: Energy Sources for Prolonged Exercise
Please note that due to differing operating systems, some animations will not appear until the presentation is viewed in Presentation Mode (Slide Show view). You may see blank slides in the “Normal” or “Slide Sorter” views. All animations will appear after viewing in Presentation Mode and playing each animation. Most animations will require the latest version of the Flash Player, which is available at
Please note that due to differing operating systems, some animations will not appear until the presentation is viewed in Presentation Mode (Slide Show view). You may see blank slides in the “Normal” or “Slide Sorter” views. All animations will appear after viewing in Presentation Mode and playing each animation. Most animations will require the latest version of the Flash Player, which is available at

40. Force, Velocity, & Duration of Contraction
Velocity and duration – dependent upon fiber types
Slow twitch, fatigue resistant
Fast twitch, fatigue vulnerable
Fast twitch, fatigue resistant
Most muscles are a mixture; some areas of body specialize

41. Slow Twitch Muscle Fibers
Red fibers
Most myoglobin
Good blood supply
Ex. Chicken leg
marathon runners
Slow-twitch fibers (Type I)
Always oxidative
Resistant to fatigue

42. Fast Twitch Fibers Fast-twitch glycolytic fibers (Type IIb)
White fibers (less myoglobin)
Poorer blood supply
Susceptible to fatigue
Least endurance
Contract rapidly
Ex. Chicken breast;
sprinters

43. Disuse
Muscle atrophy when not used; this is due either to enforced bedrest, immobilization, paralysis, etc.
Muscles atrophy 5% of their strength/day when immobile; thus the reason for “skinny” limbs that have been in a cast.