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Chapter 12 Muscles.

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Presentation on theme: "Chapter 12 Muscles."— Presentation transcript:

1 Chapter 12 Muscles

2 About this Chapter Muscle types What muscles do How muscles contract
Contraction to locomotion Roles of smooth muscles

3 Muscles Contract! Generate motion Generate force Generate heat Support

4 Muscular System Functions
Body movement (Locomotion) Maintenance of posture Respiration Diaphragm and intercostal contractions Communication (Verbal and Facial) Constriction of organs and vessels Peristalsis of intestinal tract Vasoconstriction of b.v. and other structures (pupils) Heart beat Production of body heat (Thermogenesis)

5 Properties of Muscle Excitability: capacity of muscle to respond to a stimulus Contractility: ability of a muscle to shorten and generate pulling force Extensibility: muscle can be stretched back to its original length Elasticity: ability of muscle to recoil to original resting length after stretched

6 Muscle Types Cardiac – heart Smooth – internal organs
Skeletal – "voluntary" Attach to bone Move appendages Support body Antagonistic pairs Flexors Extensors

7 Categories of skeletal muscle actions
Categories Actions Extensor Increases the angle at a joint Flexor Decreases the angle at a joint Abductor Moves limb away from midline of body Adductor Moves limb toward midline of body Levator Moves insertion upward Depressor Moves insertion downward Rotator Rotates a bone along its axis Sphincter Constricts an opening

8 Types of Muscle Skeletal Smooth Cardiac Attached to bones
Makes up 40% of body weight Responsible for locomotion, facial expressions, posture, respiratory movements, other types of body movement Voluntary in action; controlled by somatic motor neurons Smooth In the walls of hollow organs, blood vessels, eye, glands, uterus, skin Some functions: propel urine, mix food in digestive tract, dilating/constricting pupils, regulating blood flow, In some locations, autorhythmic Controlled involuntarily by endocrine and autonomic nervous systems Cardiac Heart: major source of movement of blood Autorhythmic

9 Connective Tissue Sheaths
Connective Tissue of a Muscle Epimysium. Dense regular c.t. surrounding entire muscle Separates muscle from surrounding tissues and organs Connected to the deep fascia Perimysium. Collagen and elastic fibers surrounding a group of muscle fibers called a fascicle Contains b.v and nerves Endomysium. Loose connective tissue that surrounds individual muscle fibers Also contains b.v., nerves, and satellite cells (embryonic stem cells function in repair of muscle tissue Collagen fibers of all 3 layers come together at each end of muscle to form a tendon or aponeurosis.

10 Muscle Types Figure 12-1: Three types of muscles

11 Muscle Tissue Types

12 Skeletal Muscle Anatomy
About 40% body mass Muscle fibers – cells Fascicle – bundle Motor unit Muscle sheath Attach to tendons (which attach to bone)

13 Nerve and Blood Vessel Supply
Motor neurons stimulate muscle fibers to contract Neuron axons branch so that each muscle fiber (muscle cell) is innervated Form a neuromuscular junction (= myoneural junction) Capillary beds surround muscle fibers Muscles require large amounts of energy Extensive vascular network delivers necessary oxygen and nutrients and carries away metabolic waste produced by muscle fibers

14 Skeletal Muscle Anatomy
Figure 12-3a-1: ANATOMY SUMMARY: Skeletal Muscle

15 Skeletal Muscle Anatomy
Figure 12-3a-2: ANATOMY SUMMARY: Skeletal Muscle

16 Muscle Fiber Structure
Multiple nuclei Sarcolemma T-tubules Sarcoplasmic reticulum Sarcoplasm Mitochondria Glycogen & ions Myofibrils

17 Muscle Fiber Structure
Figure 12-3b: ANATOMY SUMMARY: Skeletal Muscle

18 Muscle Fiber Structure
Figure 12-4: T-tubules and the sarcoplasmic reticulum

19 Myofibrils: Site of Contraction
Actin – "thin fibers" Tropomysin Troponin Myosin – "thick fibers" Titin – elastic anchor Nebulin – non-elastic

20 Myofibrils: Site of Contraction
Figure 12-3c-f: ANATOMY SUMMARY: Skeletal Muscle

21 Sarcomere: Organization of Fibers
Z disks I band A band H Zone M line Titin Nebulin Figure 12-5: The two- and three-dimensional organization of a sarcomere

22 Sarcomere: Organization of Fibers
Figure 12-6: Titin and nebulin

23 Skeletal Muscle Contraction: Mechanism
Figure 12-11a: Excitation-contraction coupling

24 Skeletal Muscle Contraction: Mechanism
Figure 12-11b: Excitation-contraction coupling

25 Energy for Contraction: ATP & Phosphocreatine
Aerobic Respiration Oxygen Glucose Fatty acids 30-32 ATPs Anaerobic Respiration Fast but 2 ATP/glucose Phosphocreatine ATPs

26 Energy for Contraction: ATP & Phosphocreatine
Figure 12-13: Phosphocreatine


28 Fiber Contraction Speed: Fast Twitch
Rate 2-3 times faster SR uptake of Ca2+ ATP splitting Anaerobic/Fatigue easily Power lifting Fast/delicate Sprint

29 Fiber Contraction Speed: Fast Twitch
Figure 12-15: Fast-twitch glycolytic and slow-twitch muscle fibers

30 Fiber Contraction Speed: Oxidative Fast & Slow
Oxidative Fast Twitch Intermediate speed Anaerobic & aerobic Slow Twitch: Aerobic, less fatigue More mitochondria More capillaries Myoglobin Endurance activities Postural muscles

31 Coordinating the Fibers: Force of Contraction
Excitation and Twitch Length–Tension: more crossbridges: more tension Figure 12-16: Length-tension relationships in contracting skeletal muscle

32 Coordinating the Fibers: Summation to Tetanus
Figure 12-17: Summation of contractions

33 Smooth Muscle Fusiform cells One nucleus per cell Nonstriated
Involuntary Slow, wave-like contractions Smooth muscle is found in the walls of hollow organs. *Their muscle cells are fusiform in shape. *Smooth muscle cells have just on nucleus per cell. *Smooth muscle is nonstriated. *Smooth muscle is involuntary. *The contractions of smooth muscle are slow and wave-like.

34 Smooth Muscle Cells are not striated
Fibers smaller than those in skeletal muscle Spindle-shaped; single, central nucleus More actin than myosin No sarcomeres Not arranged as symmetrically as in skeletal muscle, thus NO striations. Caveolae: indentations in sarcolemma; May act like T tubules Dense bodies instead of Z disks Have noncontractile intermediate filaments

35 Smooth Muscle Grouped into sheets in walls of hollow organs
Longitudinal layer – muscle fibers run parallel to organ’s long axis Circular layer – muscle fibers run around circumference of the organ Both layers participate in peristalsis

36 Smooth Muscle Is innervated by autonomic nervous system (ANS)
Visceral or unitary (single unit) smooth muscle Only a few muscle fibers innervated in each group Impulse spreads through gap junctions Whole sheet contracts as a unit Often autorhythmic Multiunit: Cells or groups of cells act as independent units Arrector pili of skin and iris of eye

37 Smooth Muscle Cell

38 Smooth Muscle Contraction: Mechanism

39 Smooth Muscle Relaxation: Mechanism


41 Contractile fibers are arranged in oblique bundles rather than in parallel sarcomeres



44 Myosin of Smooth Muscle
Different isoform than that found in skeletal muscle Smooth muscle myosin ATPase activity is much slower, contraction is longer Myosin light chain in the myosin head regulates contraction and relaxation

45 Smooth Muscle Relatively little sarcoplasmic reticulum Lacks T-tubules
Chemically linked to the cell membrane, rather than mechanically linked Ca +2 storage is supplemented by caveolae , small vesicles that cluster close to the cell membrane. Voltage/ligand gated Ca +2 channels

46 Single-Unit Muscle

47 Properties of Single-Unit Smooth Muscle
Gap junctions Pacemaker cells with spontaneous depolarizations Innervation to few cells Tone = level of contraction without stimulation Increases/decreases in tension Graded Contractions No recruitment Vary intracellular calcium Stretch Reflex Relaxation in response to sudden or prolonged stretch

48 Multi-Unit Muscle

49 Comparisons Among Skeletal, Smooth, and Cardiac Muscle

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