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Chapter 9 Muscular System. Functions of a Muscle Tissue 1.Movement: 1.Skeletal 1.Skeletal - locomotion, vision, facial expression. 2.Cardiac 2.Cardiac.

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Presentation on theme: "Chapter 9 Muscular System. Functions of a Muscle Tissue 1.Movement: 1.Skeletal 1.Skeletal - locomotion, vision, facial expression. 2.Cardiac 2.Cardiac."— Presentation transcript:

1 Chapter 9 Muscular System

2 Functions of a Muscle Tissue 1.Movement: 1.Skeletal 1.Skeletal - locomotion, vision, facial expression. 2.Cardiac 2.Cardiac – blood pumping 3.Smooth 3.Smooth – food digestion 2.Posture 2.Posture - (skeletal) 3.Joint Stability 3.Joint Stability - (skeletal) 4.Heat Generation 4.Heat Generation - (skeletal)

3 Chapter 9 Muscular System 9-2 Three Types of Muscle Tissues Skeletal Muscle usually attached to bones voluntary- under conscious control striated Smooth Muscle walls of most viscera, blood vessels, skin involuntary - not under conscious control not striated Cardiac Muscle wall of heart involuntary - not under conscious control striated

4 Structure of a Skeletal Muscle 9-3 Skeletal Muscle organs of the muscular system skeletal muscle tissue nervous tissue blood Connective tissues and muscle tissue: 1.fascia – covers the muscle 2.tendon – attaches the muscle 3.aponeuroses – muscle to muscle

5 Functional Characteristics of Muscle Excitability Excitability – receive and respond to stimuli Contractility Contractility – shorten forcibly and when stimulated Extensibility Extensibility – stretched or extended Elasticity Elasticity – bounce back to original length

6 Structure of a Skeletal Muscle 9-4 Coverings of a muscle Epimysium 1. Epimysium - outter Perimysium 2. Perimysium - middle. Endomysium 3. Endomysium - inner Organization of Muscle muscle fascicles muscle fibers myofibrils thick and thin filaments

7 Structure of a Skeletal Muscle 9-4 Coverings of a muscle Epimysium 1. Epimysium – connective tissue surrounding the entire muscle Perimysium 2. Perimysium – connective tissue surrounding a fascicle. Endomysium 3. Endomysium – thin connective tissue surrounding each muscle cell Organization of Muscle muscle fascicles fascicles – bundle of muscle cells muscle fibers muscle fibers – a muscle cell myofibrils myofibrils – a long, filamentous organelle found within muscle cells that has a banded appearance thick and thin filaments (myofilament)- thick and thin filaments (myofilament)- actin &myosin filaments sarcomere sarcomere – contractile unit of muscle

8 Skeletal Muscle Fiber 9-5 sarcolemma - sacroplasm sarcoplasmic reticulum transverse tubule triad cisterna of sarcoplasmic reticulum transverse tubule myofibril actin filaments myosin filaments sarcomere

9 Skeletal Muscle Fiber sarcolemma – Plasma membrane surrounding each muscle fiber sarcoplasm – specialized cytoplasm sarcoplasmic reticulum – network of tubes and sacs transverse tubule – tubular organelles that run across fibers, right angles triad cisternae of sarcoplasmic reticulum transverse tubule myofibril – consists of the many, bundled myofilaments actin filaments – thin filaments myosin filaments – thick filaments sarcomere – basic contractile unit of muscle

10 Acting and Myosin Filaments Actin and Myosin

11 Sarcomere 9-6 I band A band H zone Z line M line

12 Sarcomere Structure 9-6 A sarcomere is defined as the segment between two neighboring Z- lines. Z-line- the disc in between the I bands. Appears as a series of dark lines. I-band is the zone of thin filaments that is not superimposed by thick filaments. A-band contains the entire length of a single thick filament. H-band is the zone of the thick filaments that is not superimposed by the thin filaments. Finally, inside the H-zone is a thin M-line formed of cross- connecting elements of the cytoskeleton.

13 Sliding Filament Theory 9-12 When sarcomeres shorten, actin and myosin filaments slide past one another VIDEOVIDEO#1 VIDEO #2

14 Skeletal Muscle Contraction ? How does a muscle contract?

15 Sequence of a Muscle Contraction Brain Spinal Cord Nerve (Action potential) Motor Unit Neuromuscular Junction (Calcium is released) Acetylcholine (Neurotransmitter) Contraction

16 Motor Unit single motor neuron (a single nerve) one motor neuron and many skeletal muscle fibers 9-9

17 Neuromuscular Junction 9-8 site where a motor nerve fiber and a skeletal muscle fiber meet

18 Muscle Contraction 9-10 Action potential causes the release of Ca at the NMJ. a neurotransmitter releases a chemical substance from the motor end fiber, causing stimulation of the muscle fiber That substance is called acetylcholine (ACh) ACh causes the muscle fibers to become stimulated and contract (shorten).

19 Relaxation of a Muscle acetylcholinesterase – an enzyme that breaks down acetylcholine. NMJ muscle impulse stops calcium moves back into sarcoplasmic reticulum myosin and actin action prevented muscle fiber relaxes Cd 9-14

20 Sequence of a Muscle Contraction Brain Spinal Cord Nerve (Action potential) Motor Unit Neuromuscular Junction (Calcium is released) Acetylcholine (Neurotransmitter) Contraction

21 Recruitment of Motor Units 9-22 Recruitment - increase in the number of motor units activated whole muscle composed of many motor units all or none principle as intensity of stimulation or contraction increases, recruitment of motor units continues until all motor units are activated = all or none principle

22 Question ???? We now know how a muscle contracts and relaxes, so is energy needed for that to happen? NOorYES?

23 How is energy that is stored in carbohydrates released? Cellular Respiration Oxygen Glucose Useable Energy is Adenosine triphosphate (ATP) H2O + CO2

24 Adenosine triphosphate (ATP) It serves as a source of energy for many metabolic processes. ATP releases energy when it is broken down into ADP by hydrolysis during cell metabolism.

25 ENERGY The energy used to power the interaction between actin and myosin filaments comes from ATP (useable chemical energy) produced by cellular respiration. ATP stored in skeletal muscle last only about six seconds. ATP must be regenerated continuously if contraction is to continue

26 Two Energy Sources for Contraction 9-15 creatine phosphate – stores energy that quickly converts unusable energy (ADP) to usable energy (ATP) 6 Seconds!! 1) Creatine phosphate (ADP)2) Cellular respiration

27 Cellular Respiration (CR) THREE SERIES OF REACTIONS in CR 1.Glycolysis 2.Citric acid cycle 3.Electron transport chain Produces carbon dioxide water ATP (chemical energy) heat Two Types of Reactions Anaerobic Respiration Anaerobic Respiration (without O 2 ) - produce little ATP Aerobic Respiration Aerobic Respiration (requires O 2 ) - produce most ATP 4-11

28 Anaerobic Reaction (Glycolysis) Recall that glycolysis results in pyruvate acid. If O2 is not present, pyruvate can be fermented into LACTIC ACID. Lactic Acid It is a waste product of pyruvate acid. Occurs in many muscle cells. Accumulation causes muscle soreness and fatigue.

29 Oxygen Supply and Cellular Respiration 9-16 Anaerobic Phase Steps are called glycolysis. occur in the cytoplasm no oxygen produces pyruvic acid and produces lactic acid little ATP Aerobic Phase Steps are called citric acid cycle and electron transport chain. occur in the mitochondrion oxygen produces most ATP / CO2/ H2O

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31 Summary of Cellular Respiration Total ATP Production 2 ATP – Glycolysis 2 ATP – Citrus Acid Cycle 34 ATP – Electron Transport Chain 38 ATP – Total energy released from one molecule of glucose.

32 Oxygen Debt 9-17 oxygen not available glycolysis continues pyruvic acid converted to lactic acid Oxygen debt – amount of oxygen needed by liver to convert lactic acid to glucose

33 What happens to the lactic acid once it has accumulated? The liver filters the blood and rids the body of toxins. Lactic acid is a toxin. liver converts lactic acid to glucose

34 Muscle Fatigue Muscle fatigue- Muscle fatigue- is a state of physiological inability to contract commonly caused from – decreased blood flow – ion imbalances – accumulation of lactic acid Cramp – sustained, involuntary contraction 9-18

35 Muscle Cramp The exact cause of muscle cramps is still unknown, but the theories most commonly cited include: – Altered neuromuscular control – Dehydration – Electrolyte depletion – Poor conditioning – Muscle fatigue – Doing a new activity Muscle Cramp

36 Muscle Tone 9-23 Muscle tone Muscle tone – continuous state of partial contraction -Even when a muscle appears to be at rest, a certain amount of sustained contraction is occurring in its fibers. Atrophy Atrophy – a wasting away or decrease in size of an organ or tissue. Hypertrophy Hypertrophy – Enlargement of an organ or tissue.

37 Types of Contractions 9-24 2. Isotonic – muscle contracts and changes length 2. Concentric – (positive) shortening contraction 1. Eccentric – (negative) lengthening contraction 1. Isometric – muscle contracts but does not change length Two Types Two Types of Isotonic Contractions

38 Types of Contractions

39 Smooth and Cardiac Muscle

40 Smooth Muscle Fibers 9-26 Compared to skeletal muscle fibers shorter single nucleus elongated with tapering ends myofilaments randomly organized no striations

41 Two Types of Smooth Muscle 9-27 Visceral Smooth Muscle Location - walls of most hollow organs (intestine) contractions are slow and sustained rhythmicityexhibit rhythmicity – pattern of repeated contractions peristalsis exhibit peristalsis – wave-like motion that helps substances through passageways. Multiunit Smooth Muscle irises of eye walls of blood vessels contractions are rapid and vigorous similar to skeletal muscle tissue

42 Smooth Muscle Contraction Resembles skeletal muscle contraction interaction between actin and myosin both use calcium and ATP both depend on impulses Different from skeletal muscle contraction hormones affect smooth muscle stretching can trigger smooth muscle contraction smooth muscle slower to contract and relax smooth muscle more resistant to fatigue 9-28

43 Cardiac Muscle Anatomy only in the heart striated uninuclear cells join end-to-end forming a network arrangement of actin and myosin are not as organized as skeletal musclePhysiology self-exciting tissue (Pacemaker) rhythmic contractions involuntary, all or nothing contractions Pumps blood to: 1. lungs for oxygenation 2. body for distribution of O2 and nutrients 9-29


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