1. Essentials of Human Anatomy & Physiology HCT II Muscular System

2. Characteristics of Muscles  Muscle cells are elongated (muscle cell = muscle fiber)  Contraction of muscles is due to the movement of microfilaments  All muscles share some terminology  Prefix myo refers to muscle  Prefix mys refers to muscle  Prefix sarco refers to flesh

3. Skeletal Muscle Characteristics  Most are attached by tendons to bones  Cells are multinucleate  Striated – have visible banding  Voluntary – subject to conscious control  Cells are surrounded and bundled by connective tissue = great force, but tires easily

4. Connective Tissue Wrappings of Skeletal Muscle  Endomysium – around single muscle fiber  Perimysium – around a fascicle (bundle) of fibers Figure 6.1

5. Structure of Skeletal Muscle Tendons- strong cords of fibrous connective tissue that anchor muscle to bone. They have tremendous strength and do not pull away from bone easily –Some are enclosed in a synovial lined tubes and are lubricated by synovial fluid called tendon sheaths.

6. Bursae- small fluid filled sacs made of connective tissue –Also lined with synovial membrane that secretes synovial fluid and lubricates the tendon –Makes it easier for the tendon to move over the bone –Both bursa and tendon sheaths facilitate movement

7. Structure of Skeletal Muscle Fascia- is a form of connective tissue. Its job is to provide a sliding and gliding environment for muscles, to suspend organs in their proper place, to transmit movement from muscle to the bones they are attached to, and to provide a supportive and movable wrapping for nerves and blood vessels as they pass through and between muscles.

8. Connective Tissue Wrappings of Skeletal Muscle  Epimysium – covers the entire skeletal muscle  Fascia – on the outside of the epimysium Figure 6.1

9. Skeletal Muscle Attachments  Epimysium blends into a connective tissue attachment  Tendon  Fascia  Sites of muscle attachment  Bones  Cartilages  Connective tissue coverings

10. Check Point ____C overs the entire skeletal muscle ____ To suspend organs in their proper place, to transmit movement from muscle to the bones they are attached to ____ Around a fascicle (bundle) of fibers ____ strong cords of fibrous connective tissue that anchor muscle to bone ____ Around single muscle fiber ____ Fluid filled sac that helps with movement A.Bursae B.Epimysium C.Perimysium D.Fascia E.Endomysium F.Tendon

11. Function of Muscles  What are the four main functions of Muscle

12. Properties of Skeletal Muscle Activity (single cells or fibers)  Irritability – ability to receive and respond to a stimulus  Contractility – ability to shorten when an adequate stimulus is received  Extensibility- Ability to stretch  Elasticity- Ability to return to its original shape

13. Nerve Stimulus to Muscles  Skeletal muscles must be stimulated by a nerve to contract (motor neruron)  Motor unit  One neuron  Muscle cells stimulated by that neuron

14. Nerve Stimulus to Muscles  Neuromuscular junctions – the junction between a nerve fiber and the muscle it supplies

15. Nerve Stimulus to Muscles  Synaptic cleft – gap between nerve and muscle  Nerve and muscle do not make contact  Area between nerve and muscle is filled with interstitial fluid Figure 6.5b

16. Transmission of Nerve Impulse to Muscle  Sodium rushing into the cell generates an action potential  Once started, muscle contraction cannot be stopped

17. Transmission of Nerve Impulse to Muscle  Neurotransmitter – chemical released by nerve upon arrival of nerve impulse  The neurotransmitter for skeletal muscle is acetylcholine  Neurotransmitter attaches to receptors on the sarcolemma  Sarcolemma becomes permeable to sodium (Na + )

18. Contraction of a Skeletal Muscle  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 differing responses  Graded responses – different degrees of skeletal muscle shortening, rapid stimulus = constant contraction or tetanus

19. Muscle Response to Strong Stimuli  Muscle force depends upon the number of fibers stimulated  More fibers contracting results in greater muscle tension  Muscles can continue to contract unless they run out of energy

20. Energy for Muscle Contraction  Initially, muscles used stored ATP for energy  Bonds of ATP 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

21. Energy for Muscle Contraction  Direct phosphorylation  Muscle cells contain creatine phosphate (CP)  CP is a high-energy molecule  After ATP is depleted, ADP is left  CP transfers energy to ADP, to regenerate ATP  CP supplies are exhausted in about 20 seconds

22. Energy for Muscle Contraction  Anaerobic glycolysis  Reaction that breaks down glucose without oxygen  Glucose is broken down to pyruvic acid to produce some ATP  Pyruvic acid is converted to lactic acid

23. Energy for Muscle Contraction  Anaerobic glycolysis (continued)  This reaction is not as efficient, but is fast  Huge amounts of glucose are needed  Lactic acid produces muscle fatigue

24. Energy for Muscle Contraction  Aerobic Respiration  Series of metabolic pathways that occur in the mitochondria  Glucose is broken down to carbon dioxide and water, releasing energy  This is a slower reaction that requires continuous oxygen

25. Check Point ____Ability to receive and respond to a stimulus ____ability to shorten when an adequate stimulus is received ____Ability to stretch ____Ability to return to its original shape ____ This is a slower reaction that requires continuous oxygen ____Reaction that breaks down glucose without oxygen ____ Initially, muscles used stored _____ for energy A. Irritability B.Extensibility C.Anaerobic D.Elasticity E. Aerobic F.Contractility G.ATP

26. Muscle Fatigue and Oxygen Debt  When a muscle is fatigued, it is unable to contract  The common reason for muscle fatigue is oxygen debt  Oxygen must be “repaid” to tissue to remove oxygen debt  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

27. Types of Muscle Contractions  Isotonic contractions  Myofilaments are able to slide past each other during contractions  The muscle shortens  Isometric contractions  Tension in the muscles increases  The muscle is unable to shorten

28. Muscle Tone  Some fibers are contracted even in a relaxed muscle  Different fibers contract at different times to provide muscle tone  The process of stimulating various fibers is under involuntary control

29. Muscles and Body Movements  Movement is attained due to a muscle moving an attached bone Figure 6.12

30. Muscles and Body Movements  Muscles are attached to at least two points  Origin – attachment to an immoveable bone  Insertion – attachment to a movable bone

31. Effects of Exercise on Muscle  Results of increased muscle use  Increase in muscle size  Increase in muscle strength  Increase in muscle efficiency  Muscle becomes more fatigue resistant

32. Types of Muscles  Prime mover – muscle with the major responsibility for a certain movement  Antagonist – muscle that opposes or reverses a prime mover  Synergist – muscle that aids a prime mover in a movement and helps prevent rotation

33. Movements Produced by Muscle Contractions Flexion – movement reduces the angle between two bones at their joint. Extension – opposite of flexion – increases the angle at a joint. Abduction – moving a body part away from the midline of the body. Adduction – moving a body part toward the midline of the body. Rotation – movement of a body part around an axis.

34. Movements Produced by Muscle Contractions Supination – refers to hand position – movement turns palm up to the anterior position (anatomical position). Pronation – palm of hand turned posteriorly. Dorsiflexion – top of foot is elevated with toes pointing upward. Plantar flexion – foot directed downward (standing on your toes). Circumduction- Moving in a circle at a joint, moving one end of a body part in a circle while the other end remains stationary

35. Identify the motion and the prime mover

36. Two motions