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Lab 6

Lab 6. Muscles and Muscle Tissue [Lab 7 in the Lab Manual] Gilbert R. Pitts, Ph.D., Joseph R. Schiller, Ph.D., and James F. Thompson, Ph.D. Lab 6 Activities [Lab 7 in the Lab Manual].

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Lab 6

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  1. Lab 6 Muscles and Muscle Tissue [Lab 7 in the Lab Manual] Gilbert R. Pitts, Ph.D., Joseph R. Schiller, Ph.D., and James F. Thompson, Ph.D.

  2. Lab 6 Activities[Lab 7 in the Lab Manual] muscle histology (slides for skeletal, cardiac, isolated smooth muscle cells, and smooth muscle cells in layers) identify structures on sarcomere electron micrograph [ultrastructure] organization and classification of muscles [muscle classifications:  structural and functional] identify the muscles and actions listed on lab guide on models and diagrams recognition and understanding of the latent period, treppe phenomenon, multiple motor unit summation/recruitment, and temporal summation (including tetany) on a graph or a plot (PhysioEx 2: Skeletal Muscle Physiology)

  3. Some Muscle Terminology Myology: the scientific study of muscle muscle fibers = muscle cells myo, mys & sarco: word roots referring to muscle Three Types of Muscle: skeletal, cardiac, and smooth They differ in: microscopic anatomy -- location -- regulation by the endocrine system and the nervous system

  4. Characteristics of Skeletal Muscle • attached primarily to bones • voluntary (conscious) control (usually) • contracts quickly, tires easily (fatigable) • allows for wide range of forces to be generated

  5. Skeletal Muscle Cells • long, cylindrical cells • striated (banded) • multinucleate

  6. Characteristics of Cardiac Muscle • forms most of heart wall (myocardium) • involuntary (unconscious) • autorhythmicity (contracts w/out external stimuli) • fast contraction, non-fatigable • constant rhythm may be modified by neural and hormonal signals

  7. Cardiac Muscle Tissue • striated • uninucleate • branched • intercalated discs

  8. Characteristics of Smooth Muscle • found in the walls of hollow internal structures (digestive, respiratory, reproductive tracts, blood vessels) • arrector pili, pupil of the eye, etc. • involuntary (unconscious) & may be autorhythmic • long, slow contractions, non-fatigable

  9. Smooth Muscle Cells • nonstriated = smooth (no sarcomeres) • uninucleate • may have gap junctions

  10. Smooth Muscle Tissue • Actin and Myosin contractile proteins are present but are not organized into sarcomeres; instead the fibers attach to the dense bodies under the cell membrane

  11. Connective Tissue Wrappings of Skeletal Muscle Tissue • Superficial Fascia: "hypodermis" • Deep Fascia: lines body walls & extremities; binds muscle together, separating them into functional groups • Epimysium: wraps an entire muscle • Perimysium: subdivides each muscle into fascicles, bundles of 10-100 muscle fibers • Endomysium: wraps individual muscle fibers

  12. Attachments (to bone) • insertion: the part of a muscle attached to the bone that moves (relative to a particular motion) • origin: the part of a muscle attached to the stationary bone • direct attachment: epimysium fused to periosteum • indirect attachment: connective tissue wrappings gathered into a tendon or aponeurosis which attaches to an origin or insertion on bone

  13. Attachment Structure • attachments are extensions of connective tissue sheaths beyond a muscle, attaching it to other structures • tendon: cord (of dense regular connective tissue) • aponeurosis: sheet (of dense regular connective tissue) • tendon (synovial) sheaths: allow tendons to slide over bones

  14. Summary of Muscle Structure

  15. Striations /Sarcomeres • Z discs (lines): the boundary between sarcomeres; proteins anchor the thin filaments • A (anisotropic) band: overlap of thick (myosin) filaments & thin filaments • I (isotropic) band: thin (actin) filaments only • Z line: bisects each I band • H zone: thick filaments only • M line: proteins anchor the adjacent thick filaments

  16. Sarcomeres • components of the muscle fiber with myofilaments arranged into contractile units • the functional unit of striated muscle contraction • produce the visible banding pattern (striations) • the myofilaments between two successive z discs • Sliding filament mechanism for contraction

  17. Muscle Function Classification • Muscles can be classified functionally according to their role in producing a particular movement.  • It is rare for only one muscle to cause a particular movement • Usually several muscles participate in producing a movement and perform one of the following functional roles:

  18. Muscle Function Classes • prime mover(s)(= agonists): the muscle(s) primarily responsible for the movement • antagonist(s):  the muscle(s) that oppose (or reverse) the movement caused by the prime mover. • synergist(s):  the muscle(s) that assist the prime mover • fixator(s): the muscle(s) that immobilize the origin of the prime mover

  19. Arrangement of Fascicles • range of motion: depends on length of muscle fibers (fascicles); long fibers = large range of motion • parallel and fusiform muscles • power: depends on total number of muscle fibers; many fibers = great power • convergent, pennate, bipennate, multipennate

  20. Arrangement of Fascicles • circular (sphincters), ex: orbicularis oris • parallel (strap-like), ex: sartorius • fusiform (spindle shaped), ex: biceps femoris • convergent, ex: pectoralis major • long parallel fibers offer greater range of movement

  21. Arrangement of Fascicles • pennate ("feather shaped") • unipennate ex: flexor pollicis longus • bipennate, ex: rectus femoris • multipennate, ex: deltoid • short oblique fibers offer greater power

  22. Naming Skeletal Muscles • Location of the muscle • Shape of the muscle • Relative Size of the muscle • Direction/Orientation of the muscle fibers/cells • Number of Origins • Location of the Attachments • Action of the muscle • Know the muscle names as described in Lab Manual Lab 7 (pp. Lab 7-1 to Lab 7-24)

  23. Muscles Named by Location • Epicranius (around cranium) • Tibialis anterior (front of tibia) tibialis anterior

  24. Naming Skeletal Muscles by Shape Trapezius • Deltoid (triangle) • Trapezius (trapezoid, 2 parallel sides) • Serratus (saw-toothed) • Rhomboideus (rhomboid, 4 parallel sides) • Orbicularis and sphincters (circular) Deltoid Rhomboideus major Serratus anterior

  25. Muscles Named by Size Psoas minor • maximus (largest) • minimis (smallest) • longus (longest) • brevis (short) • major (large) • minor (small) Psoas major

  26. Muscles Named by Direction of Fibers rectus abdominis • Rectus (straight) - parallel to the body’s long axis • Oblique external oblique transversusabdominis Transverse – at right angles to the body’s long axis

  27. Muscles Named for Number of Origins • biceps (2) • triceps (3) • quadriceps (4) biceps brachii

  28. Muscles Named for Origin and Insertion insertion Sternocleidomastoid originates from sternum and clavicle and inserts on mastoid process of temporal bone origins

  29. Muscles Named for Action • Flexor carpi radialis (extensor carpi radialis) –flexes wrist • Abductor pollicis brevis (adductor pollicis) –flexes thumb • Abductor magnus – abducts thigh • Extensor digitorum – extends fingers adductor magnus

  30. Skeletal Muscles Know the muscles, their origins and insertions as described in your Lab Manual 7.

  31. Contraction of a Skeletal Muscle • The Motor Unit = Motor Neuron + Muscle Fibers to which it connects (Synapses)

  32. Myogram: The Recording of Electrical Activity During Muscle Contraction • stimulus: nerve impulse or electrical charge • all or none rule: all the muscle fibers of a motor unit contract all the way • twitch: a single contraction of all the muscle fibers in a motor unit (one nerve signal)

  33. Components of the Myogram • 1. latent period: delay between stimulus and response • 2. contraction phase: tension or shortening occurs • 3. relaxation phase: relaxation or lengthening • refractory period: time interval after excitation when muscle will not respond to a new stimulus

  34. Contraction of a Skeletal Muscle • Graded muscle responses - moving a load • Force of muscle contraction varies depending on needs - how much tension is needed? • Twitch does not provide much force • Contraction force can be altered in 3 ways: 1. changing the frequency of stimulation 2. changing the force of stimulation 3. changing the muscle’s length

  35. Graded Muscle Responses • twitch: a single contraction • wave (temporal) summation: contractions repeated before complete relaxation, leads to progressively stronger contractions

  36. Graded Muscle Responses • unfused (incomplete) tetanus: frequency of stimulation allows only incomplete relaxation • fused (complete) tetanus: frequency of stimulation allows no relaxation

  37. Graded Muscle Responses multiple motor unit summation (= recruitment) • stimulation of more motor units leads to more muscle contraction Increasing the force of contraction is reflected in the increase in EMG activity in this graph increasing percentage of motor units recruited →

  38. Graded Muscle Responses Treppe: the staircase effect • “warming up” of muscle

  39. Contraction of a Skeletal Muscle • Isometric Contraction = Muscle does not shorten • Tension increases

  40. Contraction of a Skeletal Muscle • Isotonic Contraction = tension does not change • Length shortens

  41. Force of Contraction 1. Number of muscle fibers contracting (recruitment) 2. Size of muscle 3. Series elastic elements 4. Degree of muscle stretch

  42. PhysioEx MAP First Screen Select: Exercise 2: Skeletal Muscle Physiology

  43. PhysioEx MAP Next Screen 5 Select and Perform: Skeletal Activities 1-4 and 6;

  44. Exercise 2: Skeletal Muscle Physiology: Activity 1: [screen] We suggest you read the Overview and Introduction and take the Pre-lab Quiz before conducting the Experiment and take the Post-lab Quiz after conducting the Experiment for each of the 5 Activities. You do not need to print out or turn in any of the 5 Pre- and Post-lab quizzes.

  45. Exercise 2: Skeletal Muscle Physiology: Activity 1: [screen] Follow the detailed PhysioEx instructions on pages 7-25 to 7-32 in your manual and record data in the charts in those pages and answer the questions on the pages as you go.

  46. PhysioEx Homework to Turn In You will have four tables of data to print from PhysioEx: Activities 2, 3, 4, & 6 to turn in. You will have 9 questions to answer about the PhysioEx Activities on pp. 7-33 & 7-34 in the Lab Manual to turn in.

  47. End Lab 6 Presentation

  48. Antagonists of the Forearm

  49. Antagonists of the Thigh

  50. Antagonists of the Foot

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