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Anatomy Chapter 9 and 10 > Anatomy Chapter 9 and 10 > Flashcards

Anatomy Chapter 9 and 10 Flashcards

1
Q

What is the body location of skeletal muscle?

A

Attached to bones or (some facial muscles) to skin

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2
Q

What is the body location of cardiac muscle

A

Walls of the heart

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3
Q

What is the body location of smooth muscle

A

Unitary muscle in walls of hollow visceral organs (other than the heart) multi-unit muscle in intrinsic eye muscles, air ways, large arteries

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4
Q

What is the cell shape and appearance of skeletal muscle?

A

Single, very long, cylindrical, multinucleate cells with obvious striations

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5
Q

What is the cell shape and appearance of the cardiac muscle?

A

Branching chains of cells, uni- or binucleate, striations

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6
Q

What is the cell shape and appearance of the smooth muscle?

A

Single, spindle-shaped, uninucleate; no striation

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7
Q

What are the special characteristics of muscle tissue?

A

Excitability (responsiveness or irritability): ability to receive and
respond to stimuli
Contractility: ability to shorten when stimulated
Extensibility: ability to be stretched
Elasticity: the ability to recoil to resting length

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8
Q

What are muscle functions?

A
  1. Movement of bones or fluids (e.g., blood)
  2. Maintaining posture and body position
  3. Stabilizing joints
  4. Heat generation (especially skeletal muscle)
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9
Q

Describe a muscle (organ)

A

Consists of hundreds to thousands of muscle cells, plus connective tissue wrappings, blood vessels, and nerve fibers and is covered externally by the epimysium

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10
Q

Describe a fascicle (a portion of the muscle)

A

A discrete bundle of muscle cells, segregated from the rest of the muscle by a connective tissue sheath and is surrounded by perimysium

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11
Q

Describe a muscle fiber (cell)

A

An elongated multinucleate cell; it has a banded (striated) appearance and is surrounded by endomysium

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12
Q

Describe a thick filament?

A

Each thick filament consists of many myosin molecules
whose heads protrude at opposite ends of the filament.

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13
Q

Describe a thin filament?

A

A thin filament consists of two strands of actin subunits
twisted into a helix plus two types of regulatory proteins
(troponin and tropomyosin).

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14
Q

Describe ion channels

A
  • Play the major role in changing of membrane potentials
  • Two classes of ion channels:
  • Chemically gated ion channels – opened by chemical messengers such as
    neurotransmitters
  • Example: ACh receptors on muscle cells
  • Voltage-gated ion channels – open or close in response to voltage changes
    in membrane potential
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15
Q

What four steps must occur for skeletal muscle to contract

A
  1. Events at neuromuscular junction
  2. Muscle fiber excitation
  3. Excitation-contraction coupling
  4. Cross bridge cycling
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16
Q

Describe a neuromuscular junction?

A

The region where the motor neuron contacts the skeletal muscle. It consists of multiple axon terminals and the underlying junctional folds of the sarcolemma

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17
Q

What are the sequence of events leading to contraction?

A
  1. Events at the
    neuromuscular
    junction
    2.Muscle fiber excitation
    3.Excitation-contraction coupling
    4.Cross Bridge Cycle
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18
Q

What events occur at neuromuscular junction?

A

-A motor neuron fires an action potential
(AP) down its axon.
-The motor neuron’s axon terminal
releases acetylcholine (ACh) into the
synaptic cleft.
-ACh binds receptors on the junctional
folds of the sarcolemma.
-ACh binding causes a local depolarization
called an end plate potential (EPP).

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19
Q

What occurs in the muscle fiber excitation?

A

The local depolarization (EPP) triggers an AP in the adjacent sarcolemma

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20
Q

What occurs in the excitation-contraction coupling

A

-AP in sarcolemma travels down T tubules.
-Sarcoplasmic reticulum releases Ca2+.
-Ca2+ binds to troponin, which shifts
tropomyosin to uncover the myosin-binding
sites on actin. Myosin heads bind actin.

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21
Q

What occurs in the cross bridge cycle?

A

contraction occurs via cross bridge cycling.

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22
Q

What events occur at the neuromuscular junction

A
  1. AP arrives at the axon terminal
    2.Voltage-gated calcium channels open, calcium enters motor neuron
    3.Calcium entry causes release of ACh neurotransmitter into synpatic cleft
    4.ACh diffuses across to ACh receptors (Na + chemical gates) on sarcolemma
    5.ACh binding to receptors, open gates, allowing Na+ to enter resulting in end plate potential
    6.Acetylcholinesterase degrades ACh
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23
Q

What are the requirements for skeletal muscle contraction?

A
  1. Activation: neural stimulation at a
    neuromuscular junction
  2. Excitation-contraction coupling:
    * Generation and propagation of an action potential along
    the sarcolemma
    * Final trigger: a brief rise in intracellular Ca2+ levels
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24
Q

What are the events at the neuromuscular junction

A

-Nerve impulse arrives at axon terminal
-ACh is released and binds with receptors on the sarcolemma
Electrical events lead to the generation of an action potential

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25
Q

In the relaxed state, thin and thick filaments overlap only what ?

A

Overlap only slightly

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26
Q

What occurs during contraction

A

During contraction, myosin heads bind to actin, detach, and bind
again, to propel the thin filaments toward the M line

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27
Q

As h zones shorten and disappear what else occurs

A

sarcomeres shorten, muscle
cells shorten, and the whole muscle shortens

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28
Q

What occurs when a sarcomere contracts

A

the Z lines move closer together, and the I band
becomes smaller. The A band stays the same width.

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29
Q

What occurs at full contraction

A

the thin and
thick filaments overlap.

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30
Q

ACh effects are quickly terminated by what and what does it prevent

A

by the enzyme
acetylcholinesterase.
Prevents continued muscle fiber contraction in the absence of
additional stimulation

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31
Q

what are the summary of events in the generation and propagation of an action potential in a skeletal muscle fiber?

A
  1. An end plate potential (EPP) is generated at the neuromuscular junction
    2.Depolarization: Generating and propagating an action potential (AP)
  2. Repolarization: Restoring the sarcolemma to its initial polarized state (negative inside positive outside)
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32
Q

What is the latent period?

A

-Time when E-C coupling events occur
-Time between AP initiation and the beginning of contraction

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33
Q

What are the events of excitation contraction coupling

A

AP is propagated along sarcomere to T tubules
Voltage-sensitive proteins stimulate Ca2+ release from SR
Ca2+ is necessary for contraction

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34
Q

What is excitation contraction coupling

A

it is the sequence of events by which transmission of an action potential along the sarcolemma leads to the sliding of myofilaments

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35
Q

What is the cross bridge cycle?

A

It is the series of events during which myosin heads pull thin filaments toward the center of the sarcomere

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36
Q

What occurs in the cross bridge cycle ?

A

1.Cross bridge formation
2.The power (working) stroke
3.Cross bridge detachment
4.Cocking of mysosin head

37
Q

What does a motor unit consist of

A

Consists of One Motor Neuron and All The Muscle Fibers it Innervates

38
Q

Where do the axons of motor neurons extend from

A

from the spinal cord to the muscle

39
Q

What do branching axon terminals form?

A

Form neuromuscular junctions, one per muscle fiber

40
Q

Describe muscle tone

A

-Constant, slightly contracted state of all muscles
-Due to spinal reflexes that activate groups of motor units alternately in response to input from stretch receptors in muscles
-Keeps muscles firm, healthy, and ready to respond

41
Q

What is muscle fatigue

A

Physiological inability to contract

42
Q

When does muscle fatigue occur

A

Occurs when:
Ionic imbalances (K+, Ca2+, Pi) interfere with E-C coupling
Prolonged exercise damages the SR and interferes with Ca2+ regulation and release

43
Q

What occurs rarely, during states of continuous contraction, and causes contractures (continuous contractions)

A

Total lack of ATP

44
Q

Why is extra O2 needed after exercise?

A

For replenishment of
-oxygen reserves
-Glycogen stores
-ATP and CP reserves
Conversion of lactic acid to pyruvic acid, glucose, and glycogen

45
Q

What are isotonic contractions

A

Muscle changes in length and moves the load

46
Q

Isotonic contractions are either what

A

Either concentric or eccentric

47
Q

What occurs in concentric contractions

A

the muscle shortens and does work

48
Q

What occurs in eccentric contractions

A

the muscle contracts as it lengthens

49
Q

Describe isometric contractions

A

-The load is greater than the tension the muscle is able to develop
-Tension increases to the muscle’s capacity, but the muscle neither shortens nor lengthens

50
Q

What is the only source used directly for contractile activities

A

ATP

51
Q

Available stores of ATP are depleted in how many seconds

A

are depleted in 4–6 seconds

52
Q

How is ATP regenerated by

A

-Direct phosphorylation of ADP by creatine phosphate (CP)
-Anaerobic pathway (glycolysis)
-Aerobic respiration

53
Q

What are factors that increase the force of skeletal muscle contraction

A

-High
frequency of
stimulation
(temporal
summation
and tetanus)
-Large
number of
muscle
fibers
recruited
-Large
muscle
fibers
-Muscle and
sarcomere
stretched to
slightly over 100%
of resting length

54
Q

What is velocity and duration of contraction influenced by

A

Influenced by:
Muscle fiber type
Load
Recruitment

55
Q

What are the factors that influence the velocity and duration of skeletal muscle contraction

A

-Predominance of fast glycolytic fibers
-Small Load/Increased recruitment
-Predominance of slow oxidative fibers

56
Q

What is the influence of load on duration and velocity of muscle shortening

A

a. The greater the load, the briefer the duration of muscle shortening
b. The greater the load, the slower the muscle shortening

57
Q

What do long-distance runners have a large number of

A

They have a large number of SO fibers and relatively few FO and FG fibers

57
Q

What do long-distance runners have a large number of

A

They have a large number of SO fibers and relatively few FO and FG fibers

58
Q

What do body builders have a large number of

A

They have a large number of FG fibers and relatively few FO and SO fibers

59
Q

What does Aerobic (endurance) exercise such as jogging, swimming, biking lead to

A

Leads to increased
-Muscle capillaries
-Number of mitochondria
-Myoglobin synthesis
-Results in greater endurance, strength, and resistance to fatigue
-May convert fast glycolytic fibers into fast oxidative fibers

60
Q

What does resistance exercise such as weight lifting or isometric exercises lead to

A

-Muscle hypertrophy
Due primarily to increase in fiber size
-Increased mitochondria, myofilaments, glycogen stores, and connective tissue
-Increased muscle strength and size

61
Q

what are intercalated discs apart of

A

Are part of the cardiac muscle sarcolemma

62
Q

What do intercalated discs contain

A

contain gap junctions and desmosomes.

63
Q

Where can smooth muscle tissue be found in

A

around organs in the digestive, respiratory, reproductive tracts and the iris of the eye.

64
Q

What do intermediate filaments and dense bodies of smooth muscle fibers do

A

Harness the pull generated by myosin cross bridges

65
Q

Smooth muscle are usually in what two layers

A

longitudinal and circular)

66
Q

Longitudinal layer of smooth muscle shows what

A

Shows smooth muscle fibers in cross section

67
Q

Circular layer of smooth muscle shows what

A

shows longitudinal views of smooth muscle fibers

68
Q

What is peristalsis

A

Alternating contractions and relaxations of smooth muscle layers that mix and squeeze substances through the lumen of hollow organs

69
Q

What occurs when longitudinal layer contracts

A

organ dilates and shortens

70
Q

What occurs when circular layer contracts

A

organ constricts and elongates

71
Q

What can happen in hyperplasia

A

Smooth muscle cells can divide and increase their numbers
Example:
estrogen effects on uterus at puberty and during pregnancy

72
Q

Within age what happens to connective tissue and muscle fibers

A

Connective tissue increases and muscle fibers decrease

73
Q

By what age does loss of muscle mass begin

A

by age 30

74
Q

What does regular exercise reverse

A

Reverses Sarcopenia

75
Q

What may block distal arteries, leading to intermittent claudication and severe pain in leg muscles

A

Atherosclerosis

76
Q

In the body a first class lever system does what

A

raises your head off your chest

77
Q

What does the posterior neck muscles do

A

provide the effort

78
Q

What is the atlanto-occipital joint

A

It is the fulcrum

79
Q

What is the weight to be lifted called

A

the facial skeleton

80
Q

Second class leverage in the body is exerted when you do what

A

When you stand on tip-toe

81
Q

What is the exert exerted by when you stand on your tip-top

A

exerted by the calf muscles pulling upward on the heel

82
Q

What is the fulcrum when you stand on tip-toe

A

the joints and the ball of the foot

83
Q

What is the load when you stand on tip-toe

A

the weight of the body is the load

84
Q

In the body what exemplifies a third class leverage

A

flexing the forearm by the biceps brachii muscle

85
Q

Where is the effort exerted by when flexing the forearm

A

proximal radius of the forearm

86
Q

What is the fulcrum when flexing the forearm

A

the elbow joint

87
Q

What is the load when flexing the forearm

A

The hand and distal end of the forearm

Anatomy Chapter 9 and 10 (1 decks)

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