3 Chapter 9 Muscular System Three Types of Muscle TissuesSkeletal Muscleusually attached to bonesvoluntary- under conscious controlstriatedCardiac Musclewall of heartinvoluntary - not under conscious controlstriatedSmooth Musclewalls of most viscera, blood vessels, skininvoluntary - not under conscious controlnot striated9-2
4 Structure of a Skeletal Muscle organs of the muscular systemskeletal muscle tissuenervous tissuebloodConnective tissues and muscle tissue:1.fascia – covers the muscle2.tendon – attaches the muscle3.aponeuroses – muscle to muscle9-3
5 Functional Characteristics of Muscle Excitability – receive and respond to stimuliContractility – shorten forcibly and when stimulatedExtensibility – stretched or extendedElasticity – bounce back to original length
6 Structure of a Skeletal Muscle Coverings of a muscle1. Epimysium - outter2. Perimysium - middle3. Endomysium - innerOrganization of Musclemusclefasciclesmuscle fibersmyofibrilsthick and thin filaments9-4
7 Structure of a Skeletal Muscle Coverings of a muscle1. Epimysium – connective tissue surrounding the entire muscle2. Perimysium – connective tissue surrounding a fascicle3. Endomysium – thin connective tissue surrounding each muscle cellOrganization of Musclemusclefascicles – bundle of muscle cellsmuscle fibers – a muscle cellmyofibrils – a long, filamentous organelle found within muscle cells that has a banded appearancethick and thin filaments (myofilament)- actin &myosin filamentssarcomere – contractile unit of muscle9-4
9 Skeletal Muscle Fibersarcolemma – Plasma membrane surrounding each muscle fibersarcoplasm – specialized cytoplasmsarcoplasmic reticulum – network of tubes and sacstransverse tubule – tubular organelles that run across fibers, right anglestriadcisternae of sarcoplasmic reticulumtransverse tubulemyofibril – consists of the many, bundled myofilamentsactin filaments – thin filamentsmyosin filaments – thick filamentssarcomere – basic contractile unit of muscle
12 Sarcomere StructureA 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.9-6
13 Sliding Filament Theory When sarcomeres shorten, actin and myosin filaments slide past one anotherVIDEO#1VIDEO #29-12
14 Skeletal Muscle Contraction ?How does a muscle contract?
15 Sequence of a Muscle Contraction Neuromuscular Junction BrainSpinal CordNerve(Action potential)Motor UnitNeuromuscular Junction(Calcium is released)Acetylcholine(Neurotransmitter)Contraction
16 Motor Unit single motor neuron (a single nerve) one motor neuron and many skeletal muscle fibers9-9
17 Neuromuscular Junction site where a motor nerve fiber and a skeletal muscle fiber meet9-8
18 Muscle ContractionAction 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 fiberThat substance is called acetylcholine (ACh)ACh causes the muscle fibers to become stimulated and contract (shorten).9-10
19 Relaxation of a Muscleacetylcholinesterase – an enzyme that breaks down acetylcholine. NMJmuscle impulse stopscalcium moves back into sarcoplasmic reticulummyosin and actin action preventedmuscle fiber relaxesCd9-14
20 Sequence of a Muscle Contraction Neuromuscular Junction BrainSpinal CordNerve(Action potential)Motor UnitNeuromuscular Junction(Calcium is released)Acetylcholine(Neurotransmitter)Contraction
21 Recruitment of Motor Units Recruitment - increase in the number of motor units activatedwhole muscle composed of many motor unitsas intensity of stimulation or contraction increases, recruitment of motor units continues until all motor units are activated = all or none principle9-22
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 RespirationOxygenGlucoseH2O + CO2Useable Energy is Adenosine triphosphate (ATP)
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 ENERGYThe 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 1) Creatine phosphate (ADP) 2) Cellular respirationcreatine phosphate – stores energy that quickly converts unusable energy (ADP) to usable energy (ATP) 6 Seconds!!9-15
27 Cellular Respiration (CR) THREE SERIES OF REACTIONS in CRGlycolysisCitric acid cycleElectron transport chainProducescarbon dioxidewaterATP (chemical energy)heatTwo Types of ReactionsAnaerobic Respiration (without O2) - produce little ATPAerobic Respiration (requires O2) - produce most ATP4-11
28 Anaerobic Reaction (Glycolysis) Recall that glycolysis results in pyruvate acid. If O2 is not present, pyruvate can be fermented into LACTIC ACID.Lactic AcidIt is a waste product of pyruvate acid.Occurs in many muscle cells.Accumulation causes muscle soreness and fatigue.
29 Oxygen Supply and Cellular Respiration Anaerobic PhaseSteps are called glycolysis.occur in the cytoplasmno oxygenproduces pyruvic acidand produces lactic acidlittle ATPAerobic PhaseSteps are called citric acid cycle and electron transport chain.occur in the mitochondrionoxygenproduces most ATP / CO2/ H2O9-16
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 DebtOxygen debt – amount of oxygen needed by liver to convert lactic acid to glucoseoxygen not availableglycolysis continuespyruvic acid converted to lactic acid9-17
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 FatigueMuscle fatigue- is a state of physiological inability to contractcommonly caused fromdecreased blood flowion imbalancesaccumulation of lactic acidCramp – sustained, involuntary contraction9-18
35 Muscle Cramp Muscle Cramp The exact cause of muscle cramps is still unknown, but the theories most commonly cited include:Altered neuromuscular controlDehydrationElectrolyte depletionPoor conditioningMuscle fatigueDoing a new activity
36 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 – a wasting away or decrease in size of an organ or tissue.Hypertrophy – Enlargement of an organ or tissue.9-23
37 Two Types of Isotonic Contractions Types of ContractionsTwo Types1. Isometric – muscle contracts but does not change length2. Isotonic – muscle contracts and changes lengthTwo Types of Isotonic Contractions1. Eccentric – (negative) lengthening contraction2. Concentric – (positive) shortening contraction9-24
40 Smooth Muscle Fibers Compared to skeletal muscle fibers shorter single nucleuselongated with tapering endsmyofilaments randomly organizedno striations9-26
41 Two Types of Smooth Muscle Multiunit Smooth Muscleirises of eyewalls of blood vesselscontractions are rapid and vigoroussimilar to skeletal muscle tissueVisceral Smooth MuscleLocation - walls of most hollow organs (intestine)contractions are slow and sustainedexhibit rhythmicity – pattern of repeated contractionsexhibit peristalsis – wave-like motion that helps substances through passageways.9-27
42 Smooth Muscle Contraction Resembles skeletal muscle contractioninteraction between actin and myosinboth use calcium and ATPboth depend on impulsesDifferent from skeletal muscle contractionhormones affect smooth musclestretching can trigger smooth muscle contractionsmooth muscle slower to contract and relaxsmooth muscle more resistant to fatigue9-28
43 Cardiac Muscle Anatomy only in the heart striated uninuclear cells join end-to-end forming a networkarrangement of actin and myosin are not as organized as skeletal musclePhysiologyself-exciting tissue (Pacemaker)rhythmic contractionsinvoluntary, all or nothing contractionsPumps blood to:1. lungs for oxygenation2. body for distribution of O2 and nutrients9-29