1. Anatomy & Physiology

2. Muscles are responsible for causing movement in the body. Three types: Skeletal Cardiac Smooth What are their differentiating characteristics? Some Prefixes that relate to muscles: -Myo & -mys refer to muscle directly -Sacro refers to “flesh”

5. Cells are surrounded and bundled by connective tissue Endomysium—wraps around 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 *chicken breast example

6. Epimysium blends into one of the following connective tissue attachments Tendons—cord-like structures Mostly made of collagen fibers Connect _________ to ______________. Aponeuroses—sheet-like structures Attach muscles indirectly to bones, cartilages, or connective tissue coverings *Think of it as “roots” of a muscle.

7. Name 4 characteristics of Smooth Muscle: 1. Appearance: 2. Nuclei: 3.Common Location: 4.Action:

8. Name 5 characteristics: 1. Appearance: 2. Location: 3. Nuclei: 4. Action: 5. Other:

9. In this chapter we will be focusing mainly on skeletal muscle What are the 4 main functions: 1. 2. 3. 4.

10. Sarcolemma— specialized plasma membrane of muscle cells Myofibrils—long organelles inside muscle cell Light and dark band alternate giving muscles a “striated/striped” appearance

11. Light “I” bands Contain thin filaments Another name for “thin filaments”? Dark “A” bands Contain thick filaments

12. Sacromeres are found within myofibrils and are composed of actin and myosin filaments. It is known as the part of the muscle fiber that creates contractions. Structure: Thick filament: Myosin filament Made of protein myosin Have projections called myosin “heads” Has enzymes that break ATP, known as ATPase Thin filament: Actin filament Composed of protein actin Myosin and Actin overlap to create cross bridging

13. Occurs when thick and thin filaments connect during a muscle contraction. The myosin heads help with the binding process. When they’re aren’t in a cross bridge cycle there is a “bare-zone” This occurs when muscle is relaxed

15. Sarcoplasmic reticulum—specialized smooth ER The SR surrounds each myofibril and stores calcium. Calcium is used to aid in muscle contraction. How would a deficiency in electrolytes inhibit the sacroplasmic’s optimum action?

16. Excitability (also called responsiveness or irritability)—ability to receive and respond to a stimulus What are some examples of a stimulus? Contractility—ability to shorten a muscle when needed Extensibility—ability of muscle cells to be stretched/elongated. Elasticity—ability to recoil and resume resting length after stretching. Muscle returns to normal state after a stretch phase

17. A motor nerve which innervates muscle must be stimulated in order to create a contraction. Motor nerves have a neuron/axon They come in contact with a muscle via axon terminals Hence, the term “neuromuscular junction” The nerve endings and muscle cells never directly touch The gap is known as “synaptic cleft” which absorbs the necessary neurotransmitter Commonly used neurotransmitter: acetylcholine/Ach Causes somewhat of a sodium/potassium pump mechanism which creates an unbalanced electrical current The imbalance leads to an “action potential” The action potential travels along the cell and creates a MUSCLE CONTRACTION

21. Neurotransmitter— chemical released by nerve upon arrival of nerve impulse The neurotransmitter for skeletal muscle is acetylcholine (ACh) ACh attaches to receptors on the sarcolemma Sarcolemma becomes permeable to sodium (Na+)

22. Sodium rushes into the cell generating an action potential Once started, muscle contraction cannot be stopped How does it stop? Allowing entry of Potassium ions Neuromuscular Junction

23. Activation by nerve causes myosin heads (cross bridges) to attach to binding sites on the thin filament Thin filament is??? Myosin heads then bind to the next site of the thin filament and pull them toward the center of the sarcomere The attachment/detachment of myosin heads causes crossbridging Result? the muscle is shortened (contracted)

24. Crossbridge cycling

25. Muscle fiber contraction is “all or none” Within a skeletal muscle, not all fibers may be stimulated during the same interval Different combinations of muscle fiber contractions may give different responses Graded responses—different degrees of skeletal muscle shortening

26. Graded responses can be produced by changing The frequency of muscle stimulation The number of muscle cells being stimulated at one time

27. Muscle fiber contraction is “all or none” Once a muscle is stimulated all of it is stimulated but not necessarily the WHOLE muscle Within a skeletal muscle, not all fibers may be stimulated during the same interval Different combinations of muscle fiber contractions may give differing responses Graded responses—different degrees of skeletal muscle shortening

28. Tetanus (summing of contractions) One contraction is immediately followed by another The muscle does not completely return to a resting state The effects are added Leads to a stronger and smoother muscle contraction and Fused (complete) tetanus No evidence of relaxation before the following contractions Results in a sustained muscle contraction

30. Muscle force depends upon the number of fibers stimulated More fibers contracting results in greater muscle tension Depends on action being performed Muscles can continue to contract unless they run out of energy

31. Initially, muscles use stored ATP for energy ATP bonds are broken to release energy Only 4–6 seconds worth of ATP is stored by muscles After this initial time, other pathways must be utilized to produce ATP Muscles ONLY use ATP as their energy source

32. Direct phosphorylation of ADP by creatine phosphate (CP) Muscle cells store CP CP is a high-energy molecule After ATP is depleted, ADP is left CP transfers energy to ADP by adding a phosphate group, to regenerate ATP Supplies are exhausted in less than 15 seconds What exercises/activities would use this energy pathway???

33. Aerobic respiration Glucose is broken down to carbon dioxide and water, releasing energy (ATP) This is a slower reaction that requires continuous oxygen CANNOT occur w/o oxygen A series of metabolic pathways occur in the mitochondria This pathway yields the MOST ATP Appx: 36 ATP/1 glucose molecule

34. What exercises/activities would use this energy pathway???

35. Anaerobic glycolysis and lactic acid formation Reaction that breaks down glucose without oxygen Occurs in cytosol Glucose is broken down to pyruvic acid to produce some ATP Pyruvic acid is converted to lactic acid This reaction is not as efficient, but is fast Huge amounts of glucose are needed Lactic acid produces muscle fatigue Only produces about 5% as much ATP as aerobic respiration

36. What exercises/ activities would use this energy pathway???

37. When a muscle is fatigued, it is unable to contract even with a stimulus Common cause for muscle fatigue is oxygen debt Oxygen must be “repaid” to tissue to remove oxygen deficit Oxygen is required to get rid of accumulated lactic acid Increasing acidity (from lactic acid) and lack of ATP causes the muscle to contract less In extreme cases a person can collapse (i.e. marathon runners)

38. Isotonic contractions Myofilaments are able to slide past each other during contractions The muscle shortens and movement occurs Isometric contractions Tension in the muscles increases The muscle is unable to shorten or produce movement The static resistance causes myofibrils to spin but NOT slide across each other

40. Some fibers are contracted even in a relaxed muscle Different fibers contract at different times to provide muscle tone Muscle is firm and ready for activity The process of stimulating various fibers is under involuntary control

41. Exercise increases muscle size, strength, and endurance Aerobic (endurance) exercise results in stronger, more flexible muscles with greater resistance to fatigue How is this resistance created at the cellular level? Makes body metabolism more efficient Resistance (isometric) exercise (weight lifting) increases muscle size and strength Muscle fibers don’t increase rather the number of myofibrils/myofilaments within the muscle fiber