1. Muscle Physiology Dr. Aisha Riaz
 This is the presentation for Muscle Physiology for Human Anatomy and Physiology II at Oklahoma City Community College.

2. Muscle Tissue Skeletal Muscle Cardiac Muscle Smooth Muscle
There are three types of muscle tissue in the body. Skeletal muscle is the type that attaches to our bones and is used for movement and maintaining posture. Cardiac muscle is only found in the heart. It pumps blood. Smooth muscle is found in organs of the body such as the GI tract. Smooth muscle in the GI tract moves food and its digested products.

3. Skeletal Muscle Long cylindrical cells Many nuclei/cell Striated
Voluntary
Rapid contractions
Skeletal muscle attaches to our skeleton. *The muscle cells a long and cylindrical. *Each muscle cell has many nuclei. *Skeletal muscle tissue is striated. It has tiny bands that run across the muscle cells. *Skeletal muscle is voluntary. We can move them when we want to. *Skeletal muscle is capable of rapid contractions. It is the most rapid of the muscle types.

4. Cardiac Muscle Branching cells One or two nuclei per cell Striated
Involuntary
Medium speed contractions
Cardiac muscle tissue is only found in the heart. *Cardiac cells are arranged in a branching pattern. * Only one or two nuclei are present each cardiac cell. *Like skeletal muscle, cardiac muscle is striated. *Cardiac muscle is involuntary. *Its speed of contraction is not as fast as skeletal, but faster than that of smooth muscle.

5. Slow, wave-like contractions
Smooth Muscle
Fusiform cells
One nucleus per cell
Nonstriated
Involuntary
Slow, wave-like contractions
Smooth muscle is found in the walls of hollow organs. *Their muscle cells are fusiform in shape. *Smooth muscle cells have just on nucleus per cell. *Smooth muscle is nonstriated. *Smooth muscle is involuntary. *The contractions of smooth muscle are slow and wave-like.

7. Microanatomy of Skeletal Muscle
In this unit we will primarily study skeletal muscle. Each muscle cell is called a muscle fiber. Within each muscle fiber are many myofibrils.

8. Dark and light bands can be seen in the muscle fiber and also in the smaller myofibrils. An enlargement of the myofibril reveals that they are made of smaller filaments or myofilaments. *There is a thick filament called myosin and *a thin filament called actin. Note the I band, A band H zone or band and Z disc or line. These will be discussed shortly.

9. Z line
A small section of a myofibril is illustrated here. Note the thick myosin filaments are arranged between overlapping actin filaments. *The two Z lines mark the boundary of a sarcomere. The sarcomere is the functional unit of a muscle cell .We will examine how sarcomeres function to help us better understand how muscles work.

10. A myosin molecule is elongated with an enlarged head at the end.

11. Many myosin molecules form the thick myosin filament
Many myosin molecules form the thick myosin filament. It has many heads projecting away from the main molecule.

12. The thinner actin filament is composed of three parts: actin, tropomyosin and troponin.

15. H Band
Here is a sarcomere illustrating the thin actin and thick myosin filaments. The area of the sarcomere has only myosin is called the H band.

16. Sarcomere Relaxed
Here is another diagram of a sarcomere. Note the A band. It is formed by both myosin and actin filaments. The part of the sarcomere with only actin filaments is called the I band. This is a sarcomere that is relaxed.

17. Sarcomere Partially Contracted
This sarcomere is partially contracted. Notice than the I bands are getting shorter.

18. Sarcomere Completely Contracted
The sarcomere is completely contracted in this slide. The I and H bands have almost disappeared.

19. Which filament has moved as the sarcomere contracted
Which filament has moved as the sarcomere contracted? Note the thick myosin filaments have not changed, but the thin actin filaments have moved closer together.

20. This diagram shows the microanatomy of skeletal muscle tissue again
This diagram shows the microanatomy of skeletal muscle tissue again. *The blue sarcoplasmic reticulum is actually the endoplasmic reticulum. It stores calcium. *The mitochondria are illustrated in orange. They generate ATP, which provides the energy for muscle contractions.

25. Neuromuscular Junction
The next few slides will summarize the events of a muscle contraction.
The nerve impulse reaches the neuromuscular junction (myoneural junction).

26. Acetylcholine is released from the motor neuron.

27. Acetylcholine Opens Na+ Channel
Acetylcholine binds with receptors in the muscle membrane to allow sodium ions to enter the muscle.

28. The influx of sodium will create an action potential in the sarcolemma
The influx of sodium will create an action potential in the sarcolemma. Note: This is the same mechanism for generating action potentials for the nerve impulse. The action potential travels down a T tubule. As the action potential passes through the sarcoplamic reticulum it stimulates the release of calcium ions. Calcium binds with troponin to move tropomyosin and expose the binding sites. Myosin heads attach to the binding sites of the actin filament and create a power stroke. ATP detaches the myosin heads and energizes them for another contraction. The process will continue until the action potentials cease. Without action potentials the calcium ions will return to the sarcoplasmic reticulum.

30. Muscle Contraction Summary
Nerve impulse reaches myoneural junction
Acetylcholine is released from motor neuron
Ach binds with receptors in the muscle membrane to allow sodium to enter
Sodium influx will generate an action potential in the sarcolemma

31. Muscle Contraction Continued
Action potential travels down T tubule
Sarcoplamic reticulum releases calcium
Calcium binds with troponin to move the troponin, tropomyosin complex
Binding sites in the actin filament are exposed

32. Muscle Contraction Continued
Myosin head attach to binding sites and create a power stroke
ATP detaches myosin heads and energizes them for another contaction
When action potentials cease the muscle stop contracting

36. Motor Unit All the muscle cells controlled by one nerve cell
A motor unit is all the muscle cells controlled by one nerve cell. This diagram represents two motor units. Motor unit one illustrates two muscle cells controlled by one nerve cell. When the nerve sends a message it will cause both muscle cells to contract. Motor unit two has three muscle cells innervated by one nerve cell.

37. Motor Unit Ratios Back muscles Finger muscles Eye muscles 1:100 1:10
Motor units come indifferent sizes. *The ratio is about one nerve cell to 100 muscle cells in the back. *Finger muscles have a much smaller ratio of 1:10. *Eye muscles have a 1:1 ratio because of the precise control needed in vision.

38. ATP
ATP or adenosine triphosphate is the form of energy that muscles and all cells of the body use. *The chemical bond between the last two phosphates has just the right amount of energy to unhook myosin heads and energize them for another contraction. Pulling of the end phosphate from ATP will release the energy. ADP and a single phosphate will be left over. New ATP can be regenerated by reconnecting the phosphate with the ADP with energy from our food.

39. Creatine Creatine + ATP Creatine phosphate + ADP
Molecule capable of storing ATP energy
Creatine + ATP
Creatine phosphate + ADP
Creatine is a molecule capable of storing ATP energy. It can combine with ATP to produce creatine phosphate and ADP. The third phosphate and the energy from ATP attaches to creatine to form creatine phosphate.

40. Creatine Phosphate Creatine phosphate + ADP Creatine + ATP
Molecule with stored ATP energy
Creatine phosphate + ADP
Creatine + ATP
Creatine phosphate is an important chemical to muscles. *It is a molecule that is able to store ATP energy. *Creatine phosphate can combine with an ADP * to produce creatine and ATP. This process occurs faster than the synthesis of ATP from food.

41. Muscle Fatigue Lack of oxygen causes ATP deficit
Lactic acid builds up from anaerobic respiration
Muscle fatigue is often due to a lack of oxygen that causes ATP deficit. Lactic acid builds up from anaerobic respiration in the absence of oxygen. Lactic acid fatigues the muscle.

42. Muscle Atrophy Weakening and shrinking of a muscle May be caused by
Immobilization
Loss of neural stimulation
Muscle atrophy is a weakening and shrinking of a muscle. It can be caused by immobilization or loss of neural stimulation.

43. Muscle Hypertrophy Enlargement of a muscle More capillaries
More mitochondria
Caused by
Strenuous exercise
Steroid hormones
Hypertrophy is the enlargement of a muscle. Hypertrophied muscles have more capillaries and more mitochondria to help them generate more energy. Strenuous exercise and steroid hormones can induce muscle hypertrophy. Since men produce more steroid hormones than women, they usually have more hypertrophied muscles.

44. Steroid Hormones Stimulate muscle growth and hypertrophy
Steroid hormones such as testosterone stimulate muscle growth and hypertrophy.

45. Muscle Tonus Tightness of a muscle Some fibers always contracted
Muscle tonus or muscle tone refers to the tightness of a muscle. In a muscle some fibers are always contracted to add tension or tone to the muscle.

46. FAST VS SLOW MUSCLE FIBRES

47. Tetany Sustained contraction of a muscle
Result of a rapid succession of nerve impulses
Tetany is a sustained contraction of a muscle. It results from a rapid succession of nerve impulses delivered to the muscle.

48. Tetanus
This slide illustrates how a muscle can go into a sustained contraction by rapid neural stimulation. In number four the muscle is in a complete sustained contraction or tetanus.

52. Refractory Period
Brief period of time in which muscle cells will not respond to a stimulus
The refractory period is a brief time in which muscle cells will not respond to stimulus.

53. Refractory
The area to the left of the red line is the refractory period for the muscle contraction. If the muscle is stimulated at any time to the left of the line, it will not respond. However, stimulating the muscle to the right of the red line will produce a second contraction on top of the first contraction. Repeated stimulations can result in tetany.

54. Refractory Periods Skeletal Muscle Cardiac Muscle
Cardiac muscle tissue has a longer refractory period than skeletal muscle. This prevents the heart from going into tetany.
Skeletal Muscle
Cardiac Muscle

55. Isometric Contraction
Produces no movement
Used in
Standing
Sitting
Posture
Isometric contractions produce no movement. They are used in standing, sitting and maintaining our posture. For example, when you are standing muscles in your back and abdomen pull against each other to keep you upright. They do not produce movement, but enable you to stand.

57. Isotonic Contraction Produces movement Used in Walking
Moving any part of the body
Isotonic contractions are the types that produce movement. Isotonic contractions are used in walking and moving any part of the body.

61. THE START
This concludes the presentation on Muscle Physiology