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Muscular system Physiology
- 1. The Muscular System LECTURE
- 2. (b)2. Cardiac muscle©3. Smooth muscle 1. Skeletal muscle Three Types of Muscular Tissue
- 3. Location Function AppearanceControl Skeletal skeleton movement, heat, posture Striated,, multi- nucleated (eccentric), fibers parallel Voluntary (can be controlled by will) Cardiac heart pump blood continuously Striated, one central nucleus Involuntary (cannot be controlled by will) Smooth muscle G.I. tract, uterus, eye, blood vessels Peristalsis, blood pressure, pupil size, erects hairs no striations, one central nucleus involuntary There Are Three Types of Muscular Tissue
- 4. Slide 4 of16 Which type of muscle are the following? 1. 2. 3.
- 5. Characteristics of Muscles All muscles have 4 common characteristics – Excitability – ability to respond to a stimulus (i.e: nerve impulse) – Contractibility – muscle fibers that are stimulated by nerves contract (become shorter) and causes movement – Extensibility – ability to be stretched – Elasticity – allows the muscle to return to its original shape after it has been stretched
- 6. Sources of heat/energy Whenmuscles work, they produce heat that our body needs to function properly Major source of this energy is ATP When the muscle is stimulated, ATP is released, thus producing heat
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- 8. Skeletal muscleis the only organ of the muscular system Muscular system made up of over 600 different muscles Skeletal muscle is composed of skeletal muscle tissue and also contains nervous tissue, blood vessels and connective tissue Half of the body’s weight is muscle tissue – Skeletal muscle = 40% in males, 32% in females – Cardiac muscle = 10%
- 10. Characteristics of SkeletalMuscle Tissue 1. Long, thin contractile fibers (cells) 2. Striated – have visible banding 3. Under voluntary control 4. Attached to the bones of the skeleton by tendons 5. Cells are surrounded and bundled by connective tissue = great force, but tires easily 6. Allow for movement, facial expressions, breathing, swallowing, writing, talking and singing, posture, heat production, joint stability
- 11. Function of Skeletalmuscles Attach to bones to provide voluntary movement – Tendons: strong, tough connective cords – Fascia: tough, sheet-like membrane Produce heat and energy for the body Help maintain posture Protect internal organs
- 12. Connective Tissue Wrappingsof Skeletal Muscle Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Epimysium – covers whole organ (entire skeletal muscle) Perimysium - covers the fascicles Epimysium – covers individual cells Figure 6.1
- 13. Skeletal Muscle Attachments Copyright© 2003 Pearson Education, Inc. publishing as Benjamin Cummings Epimysium blends into a connective tissue attachment Tendon – cord-like structure Sites of muscle attachment Bones Cartilages Connective tissue coverings
- 14. A muscle, afasciculus, and a fiber all visualized Organization of Skeletal Muscle Tissue
- 15. Organization of afasciculus Organization of Muscle Tissue (Fascicle) Skeletal muscle fibers (cells) are arranged into bundles called fascicles Fascicles are bound by connective tissue
- 16. Organization of MuscleTissue (Muscle Fiber) A single muscle cell is a muscle fiber. Muscle fiber are made up of: Sarcolemma (muscle cell membrane) Sarcoplasma (muscle cell cytoplasm) Myofibrils (myofibrils are made up of thick and thin filaments) Nucleus Mitochondrion Sarcoplasmic reticulum
- 17. Organization of MuscleTissue (Myofibril) Myofibrils are striated – Striations due to arrangement of thick and thin filaments Seen as alternating areas of light and dark bands The length of each myofibril is divided into repeating units called sarcomeres – A sarcomere is the functional unit of skeletal muscle
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- 19. Sarcomere Structure Sarcomereexists from Z-line to Z-line A-Band is dark middle band I-Band – ends of A-Band, thin filaments only Z-disk is in the middle of the I-Band M-line is in the middle of the A-Band Simplified sarcomere scheme
- 20. Thick Filament Structure Composed of many myosin molecules – Each myosin molecule has a tail region and 2 globular heads (crossbridges) Head Tail
- 21. Thin Filament Structure Composed of 3 proteins: 1. Actin protein 2 strands of globular actin molecules twisted into a helix. Actin filaments have binding sites for myosin cross bridges 2. Tropomyosin protein spirals around actin helix. 3. Troponin protein (3 subunits) is attached to actin and holds tropomyosin in place. Call this the troponin-tropomyosin complex. Troponin complex Tropomyosin Actin
- 22. Specialized Organelles ofSkeletal Muscle Sarcoplasmic Reticulum (SR) – a type of ER – - Surrounds each myofibril, running parallel to it – - Stores calcium, when stimulated, calcium diffuses into sarcoplasm Transverse Tubules (TT) – -Extends into sarcoplasm as invaginations continuous with sarcolemma T tubules run between cisternae of SR – - Filled with extracellular fluid – - Cisternae of SR and TT form a triad near where thick and thin filaments overlap
- 23. Relationship of thesarcoplasmic reticulum and T tubules to myofibrils of skeletal muscle Myofibril Myofibrils Triad Tubules of sarcoplasmic reticulum Sarcolemma Sarcolemma Mitochondrion I band I bandA band H zone Z discZ disc Part of a skeletal muscle fiber (cell) T tubule Terminal cisterna of the sarcoplasmic reticulum M line
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- 25. Nerve Stimulus toMuscles Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Skeletal muscles must be stimulated by a nerve to contract (motor neuron) Motor unit One neuron Muscle cells stimulated by that neuron Figure 6.4a
- 26. SlideCopyright © 2003Pearson Education, Inc. publishing as Benjamin Cummings NJ is association site of nerve and muscle Figure 6.5b Neuromuscular junctions (NJ)
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- 28. Sliding Filament Theory A sarcomere is the functional unit of skeletal muscle When a skeletal muscle contracts, sarcomeres shorten This is described by the sliding filament theory
- 29. Sliding Filament Theory Sarcomeres shorten because thick and thin filaments slide past one another Thin filaments move towards the center of the sarcomere from both ends
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- 33. A band staysthe same I band gets smaller H zone gets smaller Sarcomere shortens
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- 36. Sequence of events 1. An action potential arrives at the end of a motor neurone, at the neuromuscular junction. 2. This causes the release of the neurotransmitter acetylcholine. 3 This initiates an action potential in the muscle cell membrane (Sarcolemma). 4. This action potential is carried quickly into the large muscle cell by invaginations in the cell membrane called T-tubules.
- 37. Sequence of events 5. The action potential causes the sarcoplasmic reticulum to release its store of calcium into the myofibrils. 6. Ca2+ causes tropomoysin to be displaced uncovering myosin binding sites on actin. 7. Myosin cross bridges can now attach and the cross bridge cycle can take place. 8. Relaxation is the reverse of these steps.
- 38. CROSS BRIDGECYCLE
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- 41. STEPS OF CROSSBRIDGE CYCLE Step 1: Binding of myosin to actin. ADP and Pi are bound to ATPase site of myosin head. Creates high affinity for actin and the myosin head binds to thin filament. Step 2: Power Stroke. Myosin head pivots and pulls thin filament toward the M-line. Step 3: Unbinding of Myosin and Actin. ATP enters the ATPase site on myosin head triggering a conformational change, decreasing myosin's affinity for actin and detaching myosin from actin. Step 4: Cocking of the Myosin Head. ATP is split by hydrolysis releasing energy which is captured by the myosin molecule and it returns to its high-energy conformation. ADP and Pi remain bound to ATPase site.
- 42. Muscle Relaxation Mechanism 1.Acetylcholinesterase present in the NMJ destroys ACh (preventing continual stimulation) 2. Calcium ions are transported from the sarcoplasm back into the SR 3. Linkages between myosin and actin are broken – Requires ATP binding THEN: The muscle fiber relaxes
- 44. Energy for Contraction Muscle cells require huge amounts of ATP energy to power contraction The cells have only a very small store of ATP Three pathways supply ATP to power muscle contraction
- 45. ATP Supply forContraction Pathway 1 DEPHOSPHORYLATION CREATINE PHOSPHATE Pathway 2 AEROBIC RESPIRATION Pathway 3 GLYCOLYSIS ALONE creatine oxygen glucose from bloodstream and from glycogen breakdown in cells ADP + Pi Relaxation Contraction
- 46. Energy for Contraction ATP initially supplied from cellular respiration If ATP is abundant, is converted to creatine phosphate and stored in skeletal muscles When ATP is low, creatine phosphate supplies phosphate to ADP making ATP CP & ATP stores only good for about a 10 second maximal contraction ATP must then come from cellular respiration or glycolysis
- 47. • *All musclesdo work by contracting, or becoming shorter and thicker. How Muscles Work • *Many skeletal muscles work in pairs. • *Then, the other muscle in the pair contracts to move the b*One muscle in the pair contracts to move the bone in one direction. • one back. *Then, the other muscle in the pair contracts to move the bone back.
- 48. Muscle Pairs Biceps contracted Bicepsrelaxed Triceps relaxed Triceps contracted
- 49. Smooth Muscle Characteristics Copyright© 2003 Pearson Education, Inc. publishing as Benjamin Cummings Has no striations Spindle-shaped cells Single nucleus Involuntary – no conscious control Found mainly in the walls of hollow (intestines, bladder, stomach, uterus, blood vessels) Slow, sustained and tireless Figure 6.2a
- 50. Cardiac Muscle Characteristics Copyright© 2003 Pearson Education, Inc. publishing as Benjamin Cummings Striated and branched Usually has a single nucleus Joined to another muscle cell at an intercalated disc Involuntary Found only in the heart Steady pace! Figure 6.2b
- 51. Special muscles Sphincter(dilator) muscles are openings between – the esophagus and stomach – The stomach and small intestines – Walls of the anus, urethra and mouth Open and close to control passage of substances
- 52. Parts of theMuscular System Latissimus Dorsi •Deltoid •Trapezius •Extensors •Triceps •Gluteals •Hamstring •Achille’s Tendon •Soleus •Gastrocnemius
- 53. The Muscular System •MajorPectoral •Biceps •Flexors •Sartorius •Quadriceps •Abdominals
- 54. Problems of TheMuscular System Pulled or Torn Muscle – Treatment: Medical Help Strain: Soreness due to overwork – Treatment: Rest, ice or heat
- 55. Problems of TheMuscular System Tendonitis: Stretched or torn tendon. – Treatment: Rest and ice to possible surgery Cramp: Muscle unable to relax; feels tight and sore – Treatment: Message / Drink fluids
- 56. Problems of TheMuscular System Muscular Dystrophy: Weakening of the skeletal muscles, eventually inability to walk or stand. – Treatment: No Cure
- 57. The Skeletal /Muscular System Test Questions Latissimus Dorsi Deltoid Trapezius Extensors Triceps Gluteals Hamstring Achille’s Tendon Soleus Gastrocnemius Major Pectoral Biceps Flexors Sartorius Quadriceps Abdominals
- 58. QUESTIONS Types ofmuscle tissue. Characteristics of muscles. Characteristics and functions of skeletal muscle tissue. Structure of Skeletal muscle. Skeletal muscle fiber. Myofibrils structure. Components of sarcomere. Sliding Filament Theory. Excitation-contraction coupling in skeletal muscle. Cross-bridge cycle in skeletal muscle. Skeletal Muscle Energy Metabolism. Frequency-Tension Relation. Tetanus. Characteristics smooth muscle. Characteristics cardiac muscle.