Ch.10 Muscle Tissue. Copyright 2009, John Wiley & Sons, Inc.

Transcription

1 Ch.10 Muscle Tissue

2 Preview Chapter 10 In groups we will define the following terms 1. Skeletal muscle 2. Smooth muscle 3. Cardiac muscle 4. Sarcomere 5. Myofibril 6. Myofilament 7. Sarcoplasmic reticulum 8. Motor neurons 9. Neuromuscular junction (aka synapse) 10. Neurotransmitter

3 Overview of Muscular Tissue Types of Muscular Tissue The three types of muscular tissue Skeletal Cardiac Smooth

4 Skeletal Muscle Tissue So named because most skeletal muscles move bones Skeletal muscle tissue is striated: Alternating light and dark bands (striations) as seen when examined with a microscope Skeletal muscle tissue works mainly in a voluntary manner

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8 Cardiac Muscle Tissue Found only in the walls of the heart Striated like skeletal muscle Action is involuntary

9 Smooth Muscle Tissue Located in the walls of hollow internal structures Blood vessels, airways, and many organs Lacks the striations of skeletal and cardiac muscle tissue involuntary

10 Overview of Muscular Tissue Functions of Muscular Tissue Producing Body Movements Walking and running Stabilizing Body Positions Posture Moving Substances Within the Body Heart muscle pumping blood Moving substances in the digestive tract Generating heat Shivering increases heat production

11 Overview of Muscular Tissue Properties of Muscular Tissue Excitability Ability to respond to stimuli Contractility Ability to contract forcefully Extensibility Ability to stretch Elasticity Ability to return to an original length

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13 Skeletal Muscle Tissue Connective Tissue Components Fascia Dense sheet of irregular connective tissue that surrounds muscles Epimysium Separates muscle fibers into bundles called fascicles Perimysium Surrounds numerous bundles of fascicles

14 Skeletal Muscle Tissue Endomysium Separates individual muscle fibers from one another Tendon Cord that attach a muscle to a bone Aponeurosis Broad, flattened tendon

15 Skeletal Muscle Tissue Nerve and Blood Supply Neurons that stimulate skeletal muscle to contract are somatic motor neurons

16 Skeletal Muscle Tissue Microscopic Anatomy The number of skeletal muscle fibers is set before you are born Most of these cells last a lifetime Muscle growth occurs by hypertrophy An enlargement of existing muscle fibers Testosterone and human growth hormone stimulate hypertrophy

17 Skeletal Muscle Tissue

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19 Skeletal Muscle Tissue Sarcolemma The plasma membrane of a muscle cell Transverse (T tubules) Tunnel in from the plasma membrane Muscle action potentials travel through the T tubules Sarcoplasm, the cytoplasm of a muscle fiber

20 Skeletal Muscle Tissue Myofibrils Thread like structures which contract. Sarcoplasmic reticulum (SR) Membranous sacs which encircles each myofibril Stores calcium ions (Ca ++ ) Release of Ca ++ triggers muscle contraction Filaments Function in the contractile process Two types of filaments (Thick and Thin) Sarcomeres Compartments of arranged filaments Basic functional unit of a myofibril

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23 Sarcomere

24 Sarcomere

25 Contraction and Relaxation of Skeletal Muscle

26 Skeletal Muscle Tissue Z discs Separate one sarcomere from the next A band I band Thick and thin filaments overlap Lighter, contains thin filaments but no thick filaments H zone M line Center of each A band which contains thick but no thin filaments Supporting proteins that hold the thick filaments together in the H zone

27 Skeletal Muscle Tissue Contractile Proteins Myosin Thick filaments Functions as a motor protein which can achieve motion Convert ATP to energy of motion Actin Thin filaments Actin molecules provide a site where a myosin head can attach Tropomyosin and troponin are also part of the thin filament Structural Proteins Titin Stabilize the position of myosin Dystrophin Links thin filaments to the sarcolemma

28 Contraction and Relaxation of Skeletal Muscle Myosin heads attach to and walk along the thin filaments at both ends of a sarcomere Progressively pulling the thin filaments toward the center of the sarcomere Leading to shortening of the entire muscle

29 Contraction and Relaxation of Skeletal Muscle

30 Contraction and Relaxation of Skeletal Muscle The onset of contraction begins with the SR releasing calcium ions into the muscle cell Where they bind to actin opening the myosin binding sites

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35 Contraction and Relaxation of Skeletal Muscle Botulinum toxin Blocks release of ACh from synaptic vesicles May be found in improperly canned foods A tiny amount can cause death by paralyzing respiratory muscles Used as a medicine (Botox ) Strabismus (crossed eyes) Blepharospasm (uncontrollable blinking) Spasms of the vocal cords that interfere with speech Cosmetic treatment to relax muscles that cause facial wrinkles Alleviate chronic back pain due to muscle spasms in the lumbar region

36 Contraction and Relaxation of Skeletal Muscle Curare A plant poison used by South American Indians on arrows and blowgun darts Causes muscle paralysis by blocking ACh receptors inhibiting Na + ion channels Derivatives of curare are used during surgery to relax skeletal muscles Anticholinesterase Slow actions of acetylcholinesterase and removal of ACh Can strengthen weak muscle contractions Ex: Neostigmine Treatment for myasthenia gravis Antidote for curare poisoning Terminate the effects of curare after surgery

37 Muscle Metabolism

38 Types of Skeletal Muscle Fibers Slow Oxidative Fibers (SO fibers) Smallest in diameter Least powerful type of muscle fibers Appear dark red (more myoglobin) Generate ATP mainly by aerobic cellular respiration Have a slow speed of contraction Very resistant to fatigue Adapted for endurance-type activities such as running a marathon

39 Types of Skeletal Muscle Fibers Fast Glycolytic Fibers (FG fibers) Largest in diameter Generate the most powerful contractions Have low myoglobin content Few mitochondria Appear white in color Generate ATP mainly by glycolysis Fatigue quickly Adapted for intense anaerobic movements of short duration Weight lifting

40 Types of Skeletal Muscle Fibers Fast Oxidative Glycolytic Fibers (FOG fibers) Intermediate in diameter between the other two types of fibers Have a dark red appearance Generate considerable ATP by aerobic cellular respiration Moderately high resistance to fatigue Generate some ATP by anaerobic glycolysis Contribute to activities such as walking and sprinting

41 Smooth Muscle Tissue Physiology of Smooth Muscle Contraction lasts longer than skeletal muscle contraction Contractions are initiated by Ca ++ flow primarily from the interstitial fluid Ca ++ move slowly out of the muscle fiber delaying relaxation Able to sustain long-term muscle tone Prolonged presence of Ca ++ in the cell provides for a state of continued partial contraction Important in the: Gastrointestinal tract where a steady pressure is maintained on the contents of the tract In the walls of blood vessels which maintain a steady pressure on blood

42 Regeneration of Muscular Tissue Hyperplasia An increase in the number of fibers Skeletal muscle has limited regenerative abilities Growth of skeletal muscle after birth is due mainly to hypertrophy Satellite cells divide slowly and fuse with existing fibers Assist in muscle growth Repair of damaged fibers Cardiac muscle can undergo hypertrophy in response to increased workload Many athletes have enlarged hearts Smooth muscle in the uterus retain their capacity for division

43 Online Quiz Search/Google: anatomy and physiology online quiz Look for this website: Go to Chapter 9 Copy and answer #1-20 (skip 5, 10, 11, 16) ONLY COPY THE CORRECT ANSWER!

44 Videos Muscle Contraction: NMJ animation: Crash course: