The Muscular System. Objective: The student will become familiar with the structure and function of the muscular system

Transcription

1 The Muscular System Objective: The student will become familiar with the structure and function of the muscular system 1

2 Question of the day: What moves you? Composition: The musclar system makes up 40-50% of total body weight The muscular system is 75% water 20% proteins Actin and Myosin 5% miscellaneous carbohydrates, fats, and inorganic salts 2

3 Terms to know: Myology: study of muscle Tendons connect bone to muscle Fascia Loose connective tissue Aponeurosis Sheet of connective tissue that connects muscle to muscle Function: The primary function of muscle is to. PULL Muscles work in opposing pairs While one pulls, the other relaxes 3

4 Types of muscle tissue: Cardiac Striated One centrally located nucleus Involuntary control Automatic rhythmic Walls of the heart Skeletal Striated Multinucleated Both involuntary and voluntary control Attached to bones Smooth Non-striated One centrally located nucleus Involuntary control Slow and sustained Lining the internal organs 4

5 Voluntary (skeletal) muscle function: 1. Movement Physical movement of the body 2. Posture Maintain body position 3. Heat production Muscles give of 65% of their energy production as heat Works to maintain a constant body temperature Smooth (involuntary) Muscle function: 1. Movement of substances through body tubes Ex. Peristalsis in the esophagus 2. Expulsion of stored substances Ex. Gallbladder 3. Regulation of the size of openings Ex. Iris of the eye 4. Regulation of the diameter of tubes Ex. Blood vessels 5

6 Characteristics of Muscle Tissue: 1. Excitability (irritability) Abilitiy of muscle to be stimulated to evoke response 2. Contractility Function of muscle as a contractile unit Muscle s ability to contract/shorten 3. Extensibility The ability of a muscle to stretch Characteristics of Muscle Tissue: (cont.) 4. Elasticity The ability of the muscles to return to normal shape after being stretched or muscle contraction 6. Conductivity The ability to conduct an electric impulse along the entire length of the muscle 6

7 Fascia: Loose connective tissue that wraps muscle tissue Superficial fascia: subcutaneous layer that holds skin to muscles Deep fascia: more fibrous than superficial hold muscles together Functions of Fascia: 1. Storehouse for water 2. Insulation 3. Mechanical protection 4. Houses blood vessels and nerves 7

8 Muscle Structure Epimyseum: tissue that wraps the entire muscle (found deep to the fascia) Perimyseum: smaller units of muscle Holds the fascicles together Fascicle: collections of the smaller unit Group of individually wrapped fibers Endomysium: wrapping of the smaller unit Each muscle fiber (myofiber) is surrounded by a plasma membrane individually wrapped in a sheet of endomysium 8

9 Sarcolemma is comparable to the plasma membrane of a muscle fiber Sarcoplasm Liquid environment within a muscle cell that contains calcium ions surrounding the myofibrils Myofibrils are made up of 2 types of filaments (myofilaments) Actin and Myosin Adjacent myofilmaments line up with each other so that the Z-line of one sarcomere lines up with the Z-line of an adjacent myofibrils T-tubules Are extensions of the sarcoplasmic reticulum that run transversely along muscle fibers Hold substances needed for muscle contraction paper/image005.jpg images/sarcomere.gif 9

10 The contractile unit of muscle: Think about it Tendons are continuous with the epimysium surrounding the larger muscle Tendons connect muscle to bone 10

11 Why do we have all of this? All of these components are necessary to create movement Muscle generates movement Muscle is living tissue Requires blood supply and nerve innervation How do muscles create movement? Well actually they don t the Brain does. 11

12 Movement: Movement is initiated in the brain which is part of the Central Nervous System (CNS) with the initiation of an action potential The impulse travels down the spinal cord out to the motor neuron which carries the electrical impulse to the muscle Between the motor neuron and muscle is a synapse 12

13 What is needed to create movement? Mitochondria Power house of the cell Produce energy in the form of ATP with the help of myoglobin T-tubules extension of the sarcoplasmic reticulum Hold substances needed for muscle contraction Myofilaments Actin and myosin Myosin has a hook-like binding site while actin has a bulb shaped binding site These binding sites are not readily available The binding sites on actin and myosin are covered by tropomyosin and troponin This is to keep the binding sites from attaching to one another during a relaxed state 13

14 Sliding Filament Mechanism: 1. Brain says move 2. Impulse travels down spinal cord 3. Impulse travels out spinal nerve to periphery (the muscle you want to move) 4. The impulse travels down the motor neuron 5. The impulse reaches the presynaptic bulb of the motor neuron where (ACh is stored in vesicles, the sarcolemma is semipermeable and polarized due to Na + and K + ions gathering outside the sarcollema) 6. The impulse crosses the neuromuscular junction (NMJ) with the help of ACh The junction of the motor neuron and muscle fiber 8. As soon as the ACh hits the sarcolemma the action potential is stimulated and the permeability of the sarcolemma is changed or depolarized. The wave of depolarization continues down the length of the muscle fiber. 14

15 8. Wave of depolarization releases Ca + ions from the sarcoplasmic reticulum Actin and myosin have on their surface binding sites so that the myofibrils can bind together to create muscle contraction Binding sites are protected by Troponin/ Tropomyosin to prevent the myofibrils from binding to each other when the muscle is at rest Ca + ions push Troponin/Tropomyosin away from the binding sites on actin and myosin, making the binding sites readily available for the creation of cross-bridges 9. ATP (created by the mitochondria by/with myoglobin) allows for a power stroke Pushes the Z-lines of the sarcomere closer together 10. AChE (Acetylcholine Esterase) is secreted which destroys ACh which allows the sarcolemma to go back to its resting state (repolarized) 15

16 What can interfere with muscle contraction? Oxygen debt: can t get enough oxygen into the body so we start to build up lactic acid Lactic acid is poison to the muscles Slows the reclaiming of Ca + ions so the muscles won t fully relax Muscle Fatigue: is largely the result of the depletion of oxygen and/or glycogen Rigor Mortis when muscles tighten after you die When a person dies they no longer posses oxygen so lactic acid builds up and the sarcoplasmic reticulum breaks down releasing Ca + ions and the muscles contract Rigor can last for hours 16

17 3 Major Energy systems for Muscle contraction: (Anaerobic processes) 1. Available ATP 2. Phosphagen system 3. Glycolysis Available ATP: Immediate energy source Good for the first 5-6 seconds of energy expenditure 17

18 Phosphagen system: Contained in muscles High energy molecule creatine-phosphate or phospho-creatine Capable of delivering lots of energy in a short period of time 15 second energy bursts Glycolysis: glucose splitting Breakdown of carbohydrates (glucose = C 6 H 12 O 6 ) The Liver: Stores glucose in the blood Converts stored energy into usable energy 18

19 Muscles contract to create movement: The All-or-none principle states that when a stimulus is applied a muscle fiber will contract completely or not at all No such thing as a partial contraction Strength of contraction depends on the number of fibers stimulated 19

20 How do muscles contact? EMG (electromyogram) find diseases that damage muscle tissue, nerves, or the neuromuscular junctions (nmj) EMG output (myogram): 20

21 Types of muscle contraction: 1. Tetanous: continuous contraction/ continuous stimulation Voluntary movement Single contraction: twitch 2. Wave summation: staircasing effect Types of muscle contraction (cont.) 3. Isotonic: iso = same tonic = force Contraction that remains at the same force throughout 4. Isometric: iso = same metric = length Contraction, no movement 21

22 Types of muscle contraction (cont.): 5. Concentric: muscles shorten while generating force positive lift 6. Eccentric: the muscle elongates while under tension due to an opposing force being greater than the force generated by the muscle. negative lift Rather than working to pull a joint in the direction of the muscle contraction, the muscle acts to decelerate the joint at the end of a movement or otherwise control the repositioning of a load. Movement: Most muscles cross at least one joint Some cross 2 or even 3 joints When muscles contract they pull with equal force from both ends One end of the muscle must be stable to create movement 22

23 Terminology: Origin: immovable end of the muscle Where the muscle starts Insertion: moveable end of the muscle The end of the muscle that the force is applied to Belly: meaty part of the muscle Where the actual muscle contraction occurs Levers: The body moves through a system of levers Muscle pull works around these levers Levers also give the body a mechanical advantage This means that it takes less force to create movement therefore making the muscles job easier 23

24 Classes of levers: Group Actions: Agonist prime mover The muscle that initiates the movement Synergist Muscles that work together to generate movement Antagonist Muscles that work against the prime movers Fixators/Stabilizers Muscles that stabilize a joint or bone so that another muscle can work more efficiently 24

25 How are muscles named? muscles in the body 1. Direction of fibers 2. Location 3. Size of the muscle 4. Number of heads of origin 5. Shape 6. Origins and insertions 7. Action Terminology: Hypertrophy: muscle growth (size) Atrophy: muscle shrinking Myopathy: muscle disease Myoma: muscle tumor Myolatia: muscle softening Myocitis: inflammation of muscle tissue 25

26 Disorders of the muscular system: Fibrosis: increase in the amout of fibrous connective tissue where it is not supposed to be decreasing the ability of the muscles to contract and expand the way they re supposed to Muscular Dystrophy: disintigration of muscle fibers can lead to complete atrophy and loss of motor function Disorders (cont.) Myesthemia Gravis: autoimmune disorder that results in the weakening of the the muscles caused by faulty nmj Abnormal contractions: Muscle spasm: a single muscle group does an uncontrolled contraction Tonic spasm: cramp 26