1. Muscles and Muscle Tissue
Lab 7
Muscles and Muscle Tissue
Gilbert R. Pitts, Ph.D., Joseph R. Schiller, Ph.D., and Amy L. Thompson, Ph.D.

2. Lab 7 Activities
Review histology of skeletal, cardiac, and smooth muscle (macerated and intact)
Identify structures of sarcomeres on electron micrographs [ultrastructure]
Describe how the arrangement of fascicles in a muscle relates to power and range of motion
Describe the classification of muscles into functional groups
Describe the conventions used in the naming of muscles
Identify the muscles and their actions on models and diagrams
Use PhysioEx Exercise 2--Skeletal Muscle Physiology to learn basic concepts of muscle physiology: latent period, treppe, multiple motor unit summation/recruitment, and temporal summation (including tetany)

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 to bones
Voluntary (conscious) control (usually)
Contracts quickly, tires easily (fatigable)
Undergoes graded contraction

5. Skeletal Muscle Cells Long, cylindrical cells Striated (banded)
Multinucleate

6. 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

7. 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

8. Characteristics of Cardiac Muscle
Forms most of heart wall (myocardium)
Involuntary (unconscious)
Autorhythmicity (contracts w/out external stimuli)
Fast contraction, non-fatigable
Intrinsic rhythm modified by neural and hormonal signals

9. Cardiac Muscle Cells Striated Uninucleate Branched Intercalated discs
gap junctions
desmosomes

10. 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

11. Smooth Muscle Cells Nonstriated = smooth (no sarcomeres) Uninucleate
May gap junctions

12. Smooth Muscle Cells
Actin and Myosin contractile proteins are not organized into sarcomeres; instead the fibers attach to the dense bodies under the cell membrane

13. Connective Tissue Coverings of Skeletal Muscle
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 muscle fibers
Endomysium: wraps individual muscle fibers

14. 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

15. Attachments (to bone) Derived from connective tissue elements:
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: connective tissue coverings fused directly to periosteum
indirect attachment: connective tissue coverings gathered into a tendon or aponeurosis that attaches to periosteum
tendon: cord (of dense regular connective tissue)
aponeurosis: sheet (of dense regular connective tissue)

16. The Neuromuscular Junction
Structure where motor neuron communicates with skeletal muscle fiber
Two parts:
Axon terminal
Motor end plate
Separated by synaptic cleft

17. Summary of Muscle Structure

18. Muscle Functional Groups
Muscles are classified into functional groups according to their role in producing a particular movement:
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. 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)

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

21. 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

22. Muscles Named by Size Psoas minor Maximus (largest) Minimis (smallest)
Longus (longest)
Brevis (short)
Major (large)
Minor (small)
Psoas major

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

24. Muscles Named for Number of Origins
Biceps (2)
Triceps (3)
Quadriceps (4)
biceps brachii

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

26. 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

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

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

29. 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)  

30. 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

31. 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

32. Graded Muscle Responses
Twitch: a single contraction
Wave (temporal) summation: contractions repeated before complete relaxation, leads to progressively stronger contractions

33. Graded Muscle Responses
Unfused (incomplete) tetanus: frequency of stimulation allows only incomplete relaxation  
Fused (complete) tetanus: frequency of stimulation allows no relaxation  

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

35. Multiple Motor Unit Summation ( Recruitment)
The stimulation of more motor units leads to more forceful muscle contraction  

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

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

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

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

40. PhysioEx MAP Next Screen5
Complete Activities 1-4 and 6;

41. Exercise 2: Skeletal Muscle Physiology: Activity 1-3: [The Muscle Twitch and Latent Period]
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.

42. Exercise 2: Skeletal Muscle Physiology: Activity 1-3: [The Muscle Twitch and Latent Period]
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.

43. Exercise 2: Skeletal Muscle Physiology: Activity 4: [The Effect of Stimulus Frequency …]
Notice the frequency of the stimuli (stimuli/sec) can be adjusted as indicated by the multiple stimuli button

44. Exercise 2: Skeletal Muscle Physiology: Activity 6: [The Skeletal Muscle Length-Tension Relationship]

45. 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 & 7-34 in the Lab Manual to turn in.

46. End Lab 6 Presentation

47. Antagonists of the Forearm

48. Antagonists of the Thigh

49. Antagonists of the Foot