1. Muscular System Chapter 8

2. What are functions of the muscular system? 1.Gross body movement 2.Stabilizing body positions – “Tone” 3.Generate heartbeat 4.Movement substances within the body 5.Regulating organ volumes 6.Producing body heat

3. Properties of Muscle Tissue 1.Electrical Excitability – able to respond to stimuli and send an impulse 2.Contractility – ability to contract forcefully, muscle body shortens 3.Extensibility – ability to stretch 4.Elasticity – ability to return to original length or shape after contraction 5.Rejuvenation – moderate to poor

4. What are the 3 types of muscle tissue? Skeletal Smooth Cardiac

5. Skeletal Muscle Characteristics: * Multinucleated * Striated * Voluntary control Appearance:

6. Smooth Muscle Uninucleated cells Involuntary No striations Location: Internal organs, blood vessels “Peristalsis” movement of digestive tract Usually organized into two sheet-like layers: longitudinal and circular Two types: Visceral and Multiunit

7. Cardiac Striated and uni- nucleated Branching cells Intercalated discs separate cells Rhythmicity Only found in wall of heart Self-exciting tissue Large transverse tubules

9. Aponeurosis, Fascia and Tendons Fascia – “gift wrap” around muscle body or found under skin (spider webs) Tendons - connect muscle to bone Aponeurosis – flat/sheet-like tendon connects muscle to CT

10. Skeletal Muscle Anatomy

11. The Muscle Fiber (cell) Structure Sarcolemma Sarcoplasm Nucleus(i) Sarcoplasmic reticulum Mitochondria Myofibrils 1. Actin (thin) 2. Myosin (thick)

12. Skeletal Muscle Fiber Structure

13. Anatomy of a Myofibril

14. Sarcomere – smallest contracting unit

15. The Sarcomere! Sarcomere: Single contracting unit within a myofibril. Striation pattern is caused by the organization of the myofilaments Length = Z line to Z line I band = only actin region A band = myosin and actin region H zone = only myosin region M line = center of H zone Contraction: Z-line moves towards M line

19. Muscle Body Fascicles Muscle Fibers Myofibrils Myofilaments Largest to Smallest

20. Now that you are familiar with muscle anatomy, what is the physiology of contraction? How does muscle contraction happen? Section 8.3

21. Structures Involved in Contraction Motor Unit: One neuron and all the muscle fibers it connects with. Stronger contractions have more motor units activated.

22. The Neuromuscular Junction: where the neuron meets with the muscle fiber.

23. Now, look at how this process really works… Video: “Sarcomere shortening” The Sliding Filament Theory

24. Muscle Contraction 1.Impulse reaches synaptic bulb. 2.Calcium channels open and calcium enters. 3.Ca causes vesicles to migrate to cell membrane to release neurotransmitter (Acetylcholine = Ach). 4.Vesicles fuse with membrane and release Ach into synaptic cleft (gap). 5.Ach diffuses across the cleft. 6.Ach binds with receptor proteins on motor end plate. 7.Motor end plate depolarizes. 8.Action potential is generated in muscle cell. Video

25. Animation 9. Action Potential moves: along the sarcolemma down the transverse tubules into the sarcoplasmic reticulum 10. Calcium is released from the sarcoplasmic reticulum.

26. Binding site before and after calcium reaches myofilaments. Troponin/tropomyosin complex pulled away by calcium so myosin can bind! VIDEO

27. 11. 12. 13. VIDEO

28. Relaxation Phase… 1.Acetylcholine esterase decomposes Ach and removes it from synaptic gap. 2.ATP binds to myosin causing linkage to release from actin. 3.Actin and myosin filaments slide apart. 4.Calcium ions are actively transported back into the sarcoplasmic reticulum. 5.Muscle fiber relaxes. So what about Rigor Mortis?

29. Section 8.4 How does the muscle fiber get ATP for the contraction? Cell Storage Creatine phosphate Cellular respiration or fermentation

30. Creatine Phosphate Used when current cell supply of ATP runs out. (within 6 sec.) Cannot be used directly as an energy source. Purpose: to transfer stored energy to ADP to make ATP. Creatine supply is exhausted in 30 sec. Activities that benefit: 100 meter dash and weight lifting

31. Aerobic Respiration With oxygen available, glucose is converted into the max amount of ATP! Myoglobin: Oxygen-binding pigment found only in muscle cells.

32. Anaerobic Method of Acquiring ATP Occurs by fermentation Fermentation produces Lactic Acid Lactic acid is carried to Liver to be converted back to glucose Low intensity or moderate exercise can recycle the lactic acid immediately. (not a lot is produced) Can be a good energy source for “stop and go” sports. (soccer, tennis, short-term swimming)

33. ***What if you cannot recycle the lactic acid quickly enough?

34. Oxygen Debt The amount of O 2 liver cells require to convert the lactic acid into glucose + the O 2 muscle cells require to restore stored ATP and creatine phosphate. Training can speed up the process. O 2 Muscle need + O 2 Liver need = Oxygen Debt

36. For most activities, all systems are used. It’s just the percentages differ based on the intensity of the activity. Activity % Creatine Phosphate % Lactic Acid % Aerobic Respiration Sprint9532 Mile155530 Marathon5590

37. Muscle Fiber Types Slow Twitch Not easily fatigued Myoglobin – “red” Use in low intensity activities – Endurance! Not a lot of growth – Lean Lots of mitochondria Fast Twitch Easily fatigued Little myoglobin – “white” Used in high intensity activities – Anaerobic Power! Increase filaments with use – Hypertrophy! Can be irreversibly changed into slow twitch! Genetically, most people are 50% slow, 50% fast twitch Slow Fast

38. What if the muscle cannot contract anymore?

39. Muscle Fatigue Loss of the ability to contract Causes: 1. Lactic acid buildup, pH drops 2. Blood supply interruption 3. Lack of acetylcholine 4. Lack of ATP Cramps: sudden, involuntary contractions or spasms in one or more of your muscles. Possible causes: lack of ATP, dehydration or electrolyte imbalance

40. Muscular Responses Threshold stimulus – minimum amount of stimulus (Ach) needed to cause a contraction. All-or-None Response – a muscle fiber will always fully contract no matter the strength of the stimulus. If the minimum amount of stimulus is not met, no contraction will occur.

41. Muscle contractions can be measured and recorded by: The Myogram Twitch: A single contraction of a muscle fiber.

42. Myogram Recording (Latent)

43. a)Shows a series of twitches with complete relaxation before the next stimulus. b)Summation another stimulus comes before complete relaxation can occur, thus increasing the contraction force. c) Tetanus: Stimulus is held constant, where there is no relaxation.

44. Recruitment Stimulating more motor units in a muscle body to contract. A greater force applied to the muscle or increase the frequency of stimuli will cause this. Muscle Tone Skeletal muscle fibers constantly being stimulated by brain. (involuntary) Stretch receptors in muscles monitor muscle health. Loss of posture tone = collapse

45. How Do I Hypertrophy My Muscles? 1.Do high intensity activities. 2.Use the fast-twitch muscles. 3.Eat protein for building material. 4.Maintain activity or else: atrophy By age 80, there is a 50% decrease in muscle strength!