Chapter 10 Muscular Tissue

1. Chapter 10 Muscular Tissue Lecture slides prepared by Curtis DeFriez, Weber State University

2. Excitation-Contraction Coupling • We will come back to the term excitation-contraction coupling in a little bit • Before we can describe the entire process, from thinking of moving a muscle to actual contraction of sarcomeres, we must first explore the processes that occur at the ___________ junction

3. Neuromuscular Junction • ___________-___________ coupling (___ coupling) involves events at the junction between a motor neuron and a skeletal muscle fiber

4. Neuromuscular Junction • An enlarged view of the neuromuscular junction • The presynaptic membrane is on the neuron while the postsynaptic membrane is the ___________plate on the muscle cell. The two membranes are separated by a space, or “cleft”

5. Neuromuscular Junction • Conscious thought (to move a muscle) results in activation of a motor neuron, and release of the neurotransmitter ___________ (AcCh) at the NM junction • The enzyme _________________ breaks down AcCh after a short period of time

6. Neuromuscular Junction • The plasma membrane on the “far side” of the NMJ belongs to the muscle cell and is called the ___________ • The motor end plate is rich in chemical (___________) - gated sodium channels that respond to AcCh. Another way to say this: The receptors for AcCh are on the ligand-gated ______ channels on the motor end plate

7. Neuromuscular Junction • The ___________ events at the NMJ transmit the electrical events of a neuronal action potential into the ___________ events of a muscle action potential

8. Neuromuscular JunctionInteractions Animation • Neuromuscular Junctions You must be connected to the internet to run this animation.

9. Muscle Action Potential • The muscle __ is propagated over the surface of the muscle cell membrane (___________) via voltage (___________)-gated Na+ and K+ channels

10. Muscle Action Potential • By placing a micropipette inside a muscle cell, and then measuring the electrical potential across the cell membrane, the phases of an _________________ (AP) can be graphed (as in this figure)

11. Muscle Action Potential • The behavior of the _____ and ___ channels, at various points in the AP, are seen in this graphic • Na+ gates open during the ___________ phase • K+ gates open during the ___________ phase

12. Generating An Action Potential • The flow of ions through cell a membrane looks a lot like a "piece" of electricity flowing through a wire (but not as fast) • Generating an AP on the muscle membrane involves the transfer of information from an ___________signal (down the neuron), to a ___________signal (at the NMJ), back to an ___________ signal (depolarization of the sarcolemma) • This added complexity (changing from electrical to chemical back to electrical signals) provides necessary control of the process

13. Excitation-Contraction Coupling

14. Excitation-Contraction Coupling • EC coupling involves putting it all together • The thought process going on in the brain • The AP arriving at the neuromuscular junction • The regeneration of an AP on the muscle membrane • Release of Ca2+ from the sarcoplasmic reticulum • Sliding of thick on thin filaments in sarcomeres • Generation of muscle tension (work)

15. Excitation-Contraction Coupling

16. Excitation-Contraction Coupling • Role Players in E-C coupling • Regenerate AP • The T-tubules • The SR • Ca2+ release • Troponin/Tropomyosin • ATP • Myosin binding • Filaments slide • Muscles contract • The brain • The motor neuron • Acetylcholine (ACh) • Acetylcholinesterase enzyme • Ach receptors on the motor endplate • Na+-K+ channels on the sarcolemma • Na+ flow • K+ flow

17. Contraction of SarcomereInteractions Animation • Contraction of a Sarcomere You must be connected to the internet to run this animation.

18. Sources of Muscle Energy • Stored ______ • 3 seconds • Energy transferred from stored ______________________ • 12 seconds • ___________production • ___________ glucose use • 30-40 seconds

19. Sources of Muscle Energy

20. Sources of Muscle Energy

21. Sources of Muscle Energy

22. Skeletal Muscle Metabolism • In a state of ___________, muscle use of O2 and nutrients is balanced by the production of manageable levels of waste products like • _______ • _______ - 70-80% of the energy used by muscles is lost as heat - muscle activity is important for maintaining body temperature • ___________(anaerobic)

23. Skeletal Muscle Metabolism • ___________, or "Excess Post-Exercise Oxygen Consumption" (EPOC) is the amount of ___________required after exercise in skeletal muscle to: • ___________ ATP stores • ___________ creatine phosphate and myoglobin stores • ___________ lactic acid back into pyruvate so it can be used in the Krebs cycle to replenish ATP

24. Skeletal Muscle Metabolism

25. Muscle Metabolism • Muscle Metabolism You must be connected to the internet to run this animation.

26. Cardiac and Smooth Muscle Metabolism • In response to a single AP, cardiac muscle contracts ____ times longer than skeletal muscle, and must continue to do so, without ______, for the _____ of the individual • To meet this constant demand, cardiac muscle generally uses the rich supply of O2 delivered by the extensive coronary circulation to generate ATP through ___________ respiration

27. Cardiac and Smooth Muscle Metabolism • Like cardiac muscle, smooth muscle (in your deep organs) is ___________ and is not under voluntary control (your heart beats and your stomach digests without you thinking about it). • Unlike cardiac (and skeletal muscle) however, smooth muscle has a low capacity for generating ATP and does so only through ___________ (___________)

28. The Motor Unit • ___________ Unit is composed of a ___________ plus all of the muscle cells it innervates • _______ precision • Fewer muscle fibers per neuron • Laryngeal and extraocular muscles (2-20) • _______ precision • Many muscle fibers per neuron • Thigh muscles (2,000-3,000)

29. The Motor Unit Activities requiring extreme precision (like the subtle and rapid movements of the eye) involve muscles with ___________ motor units (1-4 muscle fibers/neuron)

30. The Motor Unit • ___________ principle of muscle contraction • When an individual muscle fiber is stimulated to depolarization, and an action potential is propagated along its sarcolemma, it must contract to it’s full force—it can’t ___________ contract • Also, when a single motor unit is recruited to contract, all the muscle fibers in that motor unit must all contract at the same time

31. Skeletal Muscle Fiber Types • Skeletal muscle fibers are not all alike in appearance or function. By appearance: • _____ muscle fibers (the dark meat in chicken legs) have a high myoglobin content, more mitochondria, more energy stores, and a greater blood supply • _______ muscle fibers (the white meat in chicken breasts) have less myoglobin, mitochondria, and blood supply

32. Skeletal Muscle Fiber Types • Slow ___________ fibers (SO) are small, appear dark red, are the least powerful type. They are very fatigue resistant • Used for endurance like running a marathon • Fast ______________________ fibers (FOG) are intermediate in size, appear dark red, and are moderately resistant to fatigue. Used for walking • Fast ___________ fibers (FG)are large, white, and powerful • Suited to intense anaerobic activity of short duration

33. Skeletal Muscle Fiber Types

34. Skeletal Muscle Fiber Types • Most skeletal muscles are a mixture of all three types of skeletal muscle fibers; about half the fibers in a typical skeletal muscle are slow oxidative (SO) fibers • Within a particular motor unit all the skeletal muscle fibers are the _______ type • The different motor units in a muscle are ___________ in a specific order depending on the task being performed (fast anaerobic activity for maximal force, etc.)

35. Tension in a Muscle • There is a brief delay called the ___________as the AP sweeps over the sarcolemma and Ca2+ions are released from the sarcoplasmic reticulum (SR) • During the next phase the fiber is actively ___________ • This is followed by ___________as the Ca2+ions are re-sequestered into the SR and myosin binding sites are covered by tropomyosin • Temporary loss of excitability is call the ___________– All muscle fibers in a motor unit will not respond to a stimulus during this short time

36. Tension in a Muscle • A ___________ is recorded when a stimulus that results in contraction (force) of a single muscle fiber is measured over a very brief millisecond time frame

37. Tension in a Muscle • Applying increased numbers of action potentials to a muscle fiber (or a ___________, a muscle, or a muscle group) results in fusion of contractions (___________) and the performance of useful work

38. Tension in a Muscle • Two motor units, one in green, the other in purple, demonstrate the concept of progressive activation of a muscle known as ___________ • Recruitmentallows a muscle to accomplish increasing gradations of contractile strength

39. Muscle TensionInteractions Animation • Control of Muscle Tension You must be connected to the internet to run this animation.

40. Muscle Contraction • ___________ contractions results in ___________Concentric isotonic is a type of muscle contraction in which the muscle shorten while generating force • Eccentric isotonic is a contraction in which muscle tension is less than the resistance (the muscle lengthens) • ___________ contractions results in ___________ • Muscle force and resistance are equal • Supporting objects in a fixed position and posture

41. Muscle Contraction

42. Imbalances of Homeostasis • Exercise-induced muscle damage • After intense exercise electron micrographs reveal considerable muscle damage including torn sarcolemmas and disrupted Z-discs • Blood levels of proteins normally confined only to muscle (including myoglobin and the enzyme creatine kinase) increase as they are released from damaged muscle

43. Imbalances of Homeostasis • ___________ • A sudden involuntary contraction of a single muscle within a large group of muscles – usually painless • ___________ • Involuntary and often painful muscle contractions • Caused by inadequate blood flow to muscles (such as in dehydration), overuse and injury, and abnormal blood electrolyte levels

44. Imbalances of Homeostasis • Disease States and Disorders • ___________ (myofibrosis) • Replacement of muscle fibers by excessive amounts of connective tissues (fibrous scar tissue) • ___________ • Hardening of the muscle caused by calcification • Both myosclerosis and muscle fibrosis occur as a result of trauma and various metabolic disorders

45. Imbalances of Homeostasis • Aging • In part due to decreased levels of physical activity, with aging humans undergo a _____, ___________ loss of skeletal muscle mass that is replaced largely by fibrous connective tissue and adipose tissue • Muscle strength at 85 is about _____ that at age 25 • Compared to the other two fiber types, the relative number of slow oxidative fibers appears to ___________