Chapter 10: The Muscle Tissue

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1

Motion results from

Alternating contraction (shortening) & relaxation of muscles

2

The scientific study of muscles

Myology

3

Skeletal muscle tissue

  • Primarily attached to bones
  • Striated
  • Voluntary
4

Cardiac muscle tissue

  • Forms the wall of the heart
  • Striated
  • Involuntary
5

Smooth (visceral) muscle tissue

  • Located in viscera
  • Non-striated (smooth)
  • Involuntary
6

The four functions of muscle tissue

  • Motion
  • Stabilizing body positions
  • Regulating organ volume
  • Generation of heat
7

The characteristics of muscle tissue

  • Excitability (irritability)
  • Contractility
  • Extensibility
  • Elasticity
8

Excitiability (irritability)

The ability to respond to certain stimuli by producing action potentials (impulses)

9

Action potentials

Electrical signals

10

Contractility

The ability to shorten & thicken (contract), generating force to do work

11

Extensibility

The ability to be extended (stretched) without damaging the tissue

12

Elasticity

The ability to return to original shape after contraction or extension

13

The term fascia

Applied to a sheet or broad band of fibrous connective tissue underneath the skin (superficial fascia) or around muscles & organs of the body (deep fascia)

14

Other connective tissue components covering the entire muscle

Epimysium

15

Perimysium

Covering fasciculi

16

Endomysium

Covering individual muscle fibers

17

Tendons & aponeuroses

Extensions of connective tissue beyond muscle cells that attach the muscle to bone or other muscle

18

Tendon (synovial) sheaths

Enclose certain tendons & allow them to slide back and forth more easily

19

Tensosynovitis

Inflammation of the tendon sheaths and synovial membranes of certain joints, especially those of the wrists, shoulders, elbows, fingers, and ankles

20

Nerves (containing motor neurons)

  • Convey impulses for muscular contraction
  • Blood provides nutrients & oxygen for contraction
21

Motor neuron & the muscle fibers it stimulates form

Motor unit

22

Single motor unit may innervate as few as 10 or as many as

2,000 muscle fibers

23

Neuromuscular Junction (NMJ)

Refers to an axon terminal of a motor neuron and the portion of the muscle fiber sarcolemma in close approximation with motor end plate

24

Acetylcholine (ACh)

Released by the synaptic vesicles of a motor neuron, triggers a muscle action potential

25

Skeletal muscle consists of

Fibers (cells) covered by a sarcolemma

26

Fibers (cells) that are covered by a sacolemma contains

Myofibrils that consist of thin & thick filaments (myofilaments)

27

The filaments are compartmentalized

Sarcomeres

28

Thin filaments are composed of

  • Actin
  • Tropomyosin
  • Troponin
29

Thick filaments consist

Mostly of myosin

30

Actin & myosin

Two contractile proteins in muscle

31

Tropomyosin & tropin

Muscle's regulatory proteins

32

Projecting myosin heads that contain actin and ATP binding sites are called

Cross bridges

33

Elastic filaments help

Stabilize the position of thick filaments

34

Sliding of thin filaments; Activated cross bridges attach to actin & a change in orientation of the cross bridges occurs

Power stroke

35

Rigor mortis

State of muscular rigidity following death, results from a lack of ATP to split myosin-actin cross bridges

36

If body temperature decreases

Shivering can help elevate it to normal

37

All-or-nothing principle

Individual muscle fibers contract to their fullest extent; they do not partially contract

38

Twitch contraction

Brief contraction of all the muscle fibers in a motor unit in response to a single action potential

39

Record of a muscle contraction

Myogram

40

Myogram includes three periods

  • Latent
  • Contraction
  • Relaxation
41

The refractory period

Time when a muscle has temporarily lost excitability

42

Skeletal muscles have

Short refractory period

43

Cardiac muscles have

Long refractory period

44

Wave (temporal) summation

Increased strength of a contraction from resulting from the application of a second stimulus before the muscles has completely relaxed after a previous stimulus

45

Sustained muscle contraction that permits partial relaxation between stimullus

Incomplete (unfused) tetanus

46

Sustained contraction that lacks even partial relaxation between stimuli

Complete (fused) tetanus

47

In treppe (staircase effect)

Each of the first few contractions is a little stronger than the last

48

Muscle fibers develops its greatest tension when

There is an optimal overlap between thick & thin filaments

49

Recruitment (multiple motor unit summation)

The process of increasing the number of active motor units that prevents fatigue and helps provide smooth muscular contraction rather than a series of jerky movements

50

Muscle tone

Sustained partial contraction of portions of a relaxed skeletal muscle results in a formness known as

51

Refers to decreased or lost muscle tone; such muscles are said to be flaccid

Hypotonia

52

Hypertonia

Refers to increased muscle tone and may be expressed as either spasticity (stiffness) or rigidity

53

Active tension

Tension generated by contractile elements (thick & thin filaments) is called

54

Passive tension

Tension generated by elastic elements and is not related to muscular contraction is called

55

Isotonic contractions

Occurs when a constant load is moved through the range of motion possible at a joint & include concentric contractions and eccentric contractions

56

Isometric contraction

The muscle does not shorten but tension increases

57

Muscular atrophy

Wasting away of muscles & may be caused by disuse or severing of the nerve supply

58

Muscular hypertrophy

Refers to an increase in the diameter of muscle fibers resulting from very forceful, repetitive muscular activity

59

On demand, skeletal muscle fibers can

Step up ATP production

60

Creatine phosphate (phosphocreatine) and ATP

Constitute the phosphagen system

61

The AEROBIC partial catabolism of glucose to generate ATP and can provide enough energy for about 30-40 seconds of maximal muscle activity occurs in

The glycogen-lactic acid system

62

Muscular activity lasting more than 30 seconds depends increasingly on AEROBIC system (reactions requiring oxygen) and system of ATP production involves the complete oxidation of glucose

Cellular respiration (biological oxidation)

63

Muscle tissue has two sources of oxygen

  • Oxygen can diffuse into muscle fibers from the blood
  • Oxygen is also released by myoglobin inside muscle fibers
64

The aerobic system will provide

Enough ATP for prolonged activity so long as sufficient oxygen and nutrients are available

65

Elevated oxygen use after exercise

Recovery oxygen consumption

66

The inability of a muscle to maintains its strength of contraction or tension and occurs when a muscle cannot produce enough ATP to meet its need

Muscle fatigue

67

Microscopic muscle damage appears to be a major contributing factor to

Muscle soreness that follows bouts of strenous exercise

68

All skeletal muscle fibers are not identical in

Structure and function

69

Color caries according to the content of

Myoglobin

70

Myoglobin is an

Oxygen storing reddish pigment

71

Red muscle fibers have

A high myglobin content while the myoglobin content of white muscle fibers is low

72

Fiber diameter varies as do the

Cell's allocations of mitochondria, blood capillaries, and sarcoplasmic retifulum

73

Contraction veolcity and resistance to fatigue also

Differ between fibers

74

Skeletal muscle fibers are classified as

  • Slow oxidative (type I)
  • Fast oxidative (type II)
  • Fast glycolytic (type IIB)
75

Type I (slow oxidative)

  • Red
  • Aerobic
76

Type IIA (fast oxidative)

  • Pink
  • Anaerobic
  • Glycogen-lactic acid
77

Type IIB (fast glycolytic)

  • White
  • Phosphago system
78

The use of anabolic steriods by athletes

Increase muscle size, strength, and endurance has been shown to have serious side effects, some of which are life-threatening

79

Cardiac muscle tissue

Found only in the heart and is striated ad involuntary

80

Compared to skeletal muscle, cardiac muscle tissues have

  • More sarcoplasm
  • More mitochondria
  • Less well-developed sarcoplasmic reticulum
  • Large transverse tubules located at Z discs, rather than at A-I band junction
  • Myofilaments are not arranged in discrete myfibrils
81

The fibers branch

Freely and are connected via gap junctions

82

Intercalated discs

Provide strength and aid in conduction of muscle action potentials by way of communicating junctions located in the discs

83

Unlike skeletal muscle tissue, cardiac muscle tissue

  • Contracts and relaxes rapidly, continuously, and rhythmically
  • ATP is generated aerobically in large, numerous mitochondria
84

Cardiac muscle can contract

Without extrinsic (outside) stimulation and can remain contracted longer than skeletal muscle tissue

85

Cardiac muscle has

Long refractory period that allows tie for the heart to relax between beats and which prevent tetanus