1. Skeletal Muscle Notes

2. Handy Hints ________– above or upon ________ – around
______________– muscle
________ – Within
________- flesh

3. Function of Muscle Tissue
____________________ – relies on integrated functions of bones, joints and skeletal muscles.
Movement of substances within the body
____________________ muscle – moves blood through the heart, blood vessels
____________________ muscle – movement of blood and food through the intestinal tract
Sperm and egg through the reproductive systems and urine through the urinary system.

4. Function of Muscle Tissue
__________________________ body positions and regulating organ volume – help you stand or sit. Muscle closes off exit routes in certain organs like the stomach
___________________ production – the by- product of muscle contraction is heat. Used to generate as much as 85% of all body heat.

5. Structure of Skeletal Muscle
Skeletal muscle is bound by connective tissue (fascia), attached to bones and is under voluntary control.
Fascia (ct)  ___________ (ct)  periosteum (bone)
This is how muscle is connected to bone
____________________ – a sheet or broad band of fibrous connective tissue under the skin or around muscles.

6. P 82-83

7. Structure of Skeletal Muscle
Three Types of Fascia
_________________________– closely surrounds muscle
_________________________ – inward extension from the epimysium that divides muscle tissue into small compartments called fascicles (bundles of muscle fibers)
Endomysium – surround each muscle fiber within a fascicle

9. Layers of connective tissue allow:
Independent movement of fibers within muscle nerves
Blood vessels to pass through muscle

10. Muscle Cell is a skeletal muscle fiber
Multinuclear – more than one nucleus
___________________ – cell membrane
___________________ – cytoplasm composed of
Numerous mitochondria
Parallel lying thread-like fibers called myofibrils

12. Myofibrils are composed of 2 types of protein filaments
_________________ – thick filament containing protein myosin with projecting cross bridges
_________________ – thin filaments containing protein actin

13. Structure of Skeletal Muscle
Sarcotubular System – triad of skeletal muscle (3 parts)
Sarcoplasmic reticulum (kinda like ER)– network of membrane enclosed tubules that run parallel to myofibrils. At the “A” band the S.R. enlarges to form a pair of terminals.

14. Structure of Skeletal Muscle
____________________– run 90 degrees to the S.R. Function: store, release and reabsorb Ca in order to help activate or release muscle contractions.

15. Structure of Skeletal Muscle
tubules (T-tubules) – tunnel-like extensions of the sarcolemma that pass through the muscle fiber at right angles to the S.R. and between the cisternae. Function to transmit nerve impulse to all fibrils (open to outside)

16. Structure of Skeletal Muscle
____________________________ are filamentous protein molecules contained in muscles. In the presence of calcium ions myosin and actin will slide past each other and form cross-bridges, thereby contracting the muscle.

18. Structure of Skeletal Muscle

19. Structure of Skeletal Muscle
Neuromuscular junction – where the motor neuron and the muscle fiber meet.
_________________________– modified sarcolemma; highly folded, many nuclei; mitochondria
________________________ knob – where the end of the motor neuron branches and terminates
Synaptic vesicles - sacs in the axon terminals filled with chemicals.

20. Structure of Skeletal Muscle
_________________________– neurotransmitter released at a neuromuscular junction. Allows sodium ions to diffuse and produces a muscle action potential (results in a muscle contraction)
__________________________– found in the synaptic cleft. It inactivates acetylcholine so the muscle can get ready for the next action potential

21. Structure of Skeletal Muscle
– 1 motor neuron and 10 or more muscle fibers.

22. Skeletal Muscle Contraction
“ ________________ Theory or Sliding Filament Theory of Skeletal Muscle Contraction”

23. Origin vs. Insertion
___________________________ – muscle attaches to a movable bone ___________________________– muscle attaches to a non movable bone Muscles work in pairs

24. Energy Source for Contraction
1st source – ATP, enough in muscle cell to last 6 to 8 seconds. ADP + P + energy  ATP
Creatine Phosphate - molecule stored in muscle cells, used to produce more ATP quickly during exercise
CP  creatine + P + energy
2nd source – Glucose  cellular respiration  ATP
O2 needs to be present
3rd source – carbohydrates  glucose  ATP
Myoglobin – stores O2 in muscle cells

25. Creatine phosphate  Creatine + phosphate + energy
Lasts 5-10 seconds
ATP ADP +Energy
Creatine phosphate
Creatine phosphate  Creatine + phosphate + energy
Provides energy for prolonged muscular activity as long as nutrients and O2 last. 1 glucose  2 pyruvic acid + Energy (ATP)
Pyruvic acid + O2  CO2 + H2O + Energy (ATP)
Pyruvic acid + no oxygen  lactic acid
After ATP is used up
Produce more ATP during prolonged exercise/ good for short bursts of activity 100 m dash
ATP
Creatine phosphate depleted
Immediate source of energy
Glucose (stored as glycogen)

26. Formula for energy release
Energy Source
When used
How long it lasts
Formula for energy release
1st
ATP
Immediate source of energy
Lasts 5-10 seconds
ATP ADP +Energy
2nd
Creatine phosphate
After ATP is used up
Produce more ATP during prolonged exercise/ good for short bursts of activity 100 m dash
Creatine phosphate  Creatine + phosphate + energy
3rd
Glucose (stored as glycogen)
Creatine phosphate depleted
Provides energy for prolonged muscular activity as long as nutrients and O2 last.
1 glucose  2 pyruvic acid + Energy (ATP)
Pyruvic acid + O2  CO2 + H2O + Energy (ATP)
Pyruvic acid + no oxygen  lactic acid

27. Muscular Responses- all or nothing principle
Threshold Stimulus – minimal strength needed to elicit a muscle contraction. How do we get a “graded response”? While individual muscle fibers will contract to their fullest extent or not at all. But because there are many motor units some are contracting and some are relaxing. Thus the entire muscle can contract a “little” or “ a lot”, such as gently holding a pencil or tightly squeezing a finger.

28. Overworked Muscles
Oxygen Debt – muscular activity is great enough, O2 cannot be supplied fast enough so ATP is produced by anaerobic respiration.
Muscle Fatigue – inability of a muscle to maintain its strength of contraction. Due to lactic acid increase (Ph decrease) causing fibers less responsive to stimuli. Begins to damage the sarcolemma.

29. Isometric vs. Isotonic Muscle Contractions
Isometric – tension increases, muscle length remains the same. Important in maintaining posture.
Isotonic – tension remains the same, muscles shorten, used in movement. Both types are used in most body actions.

30. Fast vs. Slow Twitch Muscle Fibers
White Muscle Fibers (white) – fast contracting, fewer myoglobin, hemoglobin, and mitochondria than red muscles Have extensive SR so it can contract quickly due to ability to store and reabsorb Ca+, but fatigue quickly.

31. Fast vs. Slow Twitch Muscle Fibers
Red Muscle Fibers(dark) – slow contracting, contain myoglobin (iron and oxygen binding protein), hemoglobin, and many mitochondria which can produce ATP to remain contracted for long periods of time without fatigue.