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Muscular Systems > Muscle Lecture Exam > Flashcards

Muscle Lecture Exam Flashcards

1
Q

Name three types of muscle tissue

A

skeletal, cardiac and smooth

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2
Q

Is skeletal, cardiac and smooth muscle tissue all the same

A

no, they differ in structure, location, function and means of activation

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3
Q

What are the five functional characteristics of muscle tissue

A

responsiveness (excitability), conductivity, contractility, extensibility & elasticity

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4
Q

Responsiveness (excitability) is

A

when muscle is stimulated by chemical signals, stretch, and other stimuli, muscle cells respond with electrical changes across the plasma membrane - ion gates open Na+ rushes into cell and K+ rushes our of cell

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5
Q

conductivity is

A

when local electrical charge triggers a wave of excitation that travels along the muscle fiber

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6
Q

contractility is

A

muscle shortens when stimulated enables them to pull on bones and other organs to create movement

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7
Q

extensibility

A

capable of being stretched

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8
Q

elasticity

A

capable of returning to original resting length after being stretched

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9
Q

Which muscle tissue is voluntary

A

skeletal

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10
Q

which muscle tissue is involuntary

A

cardiac and smooth

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11
Q

Which muscle tissue is responsible for locomotion

A

skeletal

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12
Q

Which muscle tissue is responsible for coursing blood through the body

A

cardiac

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13
Q

Which muscle tissue helps maintain blood pressure & squeezes or propels substances (food, feces) through organs

A

smooth

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14
Q

What are the five recognized functions of skeletal muscle

A

produce movement, maintain posture, maintain body temperature and guard body entrances & exits

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15
Q

Skeletal and smooth muscle cells are elongated and are called muscle fibers
True or False

A

True

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16
Q

Muscle contraction in all types depends on two kinds of myofilaments, name them

A

actin and myosin

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17
Q

Describe cardiac muscle

A

occurs only in the heart is striated, involuntary, has intercalated discs and contracts at a fairly steady rate, neural controls allow the heart to respond to changes in bodily needs

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18
Q

Describe smooth muscle

A

found in the walls of hollow “visceral” organs, such as the stomach, urinary bladder & respiratory passages, forces food and other substances through internal body channels; non striated and is involuntary, contractions tend to be slow and sustained

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19
Q

Which muscle is usually in sheets, short and fusiform in shape

A

smooth (visceral) muscle

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20
Q

Describe skeletal muscle

A

voluntary striated attached to bones, muscle fibers (myofibers) as long as 30 cm; exhibits alternating light and dark transverse bands or striations; has multiple nuclei

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21
Q

List the organization level of muscle structure

A

tendon/aponeurosis (sheetlike muscle) to bone - muscle - fascicle - muscle fiber - myofibril - sarcomere - myofilaments (actin & myosin)

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22
Q

Muscles can attach

A

directly or indirectly

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23
Q

muscles that attach directly is when

A

the epimysium of the muscle is fused to the periosteum of the bone

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24
Q

muscles that attach in directly is when

A

connective tissue wrappings extend beyond the muscle as a tendon or aponeurosis

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25
Q

Most are attached in at least two places called the

A

insertion and origin

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26
Q

The site that usually has no movement is the site of

A

origin

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27
Q

The site that usually has movement is the site of

A

insertion

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28
Q

growth of muscle tissue through cellular enlargement is called

A

hypertrophy

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29
Q

growth of muscle tissue through cellular multiplication is called

A

hyperplasia

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30
Q

shrinkage/loss of muscle tissue due to age, disuse or disease is called

A

atrophy

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31
Q

Describe thick filaments

A

made of 200 to 500 myosin molecules - is a long protein - 2 entwined polypeptides (looks like golf clubs) - arranged in a bundle with heads directed outward in a spiral array around the bundled tails - central area is a bare zone with no heads - myosin heads contain actin binding sites & ATPases

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32
Q

ATPases

A

enzyme that split ATP and generate energy for contraction

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33
Q

Describe thin filaments

A

composed of actin - subunits, tropomyosin & troponin, contain the active sites to which myosin heads attach during contraction - there is one small, calcium-binding troponin molecule on each tropomyosin molecule

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34
Q

What are tropomyosin and troponin

A

Subunits on the thin filaments of actin

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35
Q

Why do muscles shorten

A

because their individual sarcomeres shorten - pulls the Z dis closer together - no change in length of the thick or this filaments during shortening - they overlap as the sarcomeres shorten

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36
Q

What is resting membrane potential

A

the membrane “sarcomeres” is polarized (charged), this means the outside surface of the membrane is slightly positive and the inside surface is slightly negative

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37
Q

Muscle cells are electrically excitable

True or False

A

True

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38
Q

Why must muscle cells be polarized?

A

because this creates the resting membrane potential which muscles need in order to respond to stimulation from nerve cells

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39
Q

Membrane potential is defined as

A

voltage across a membrane

40
Q

Membranes are more permeable to K+ than to Na+

True or False

A

True

41
Q

What is peristalsis

A

a wave of constriction traveling along a tubular organ such a the esophagus or ureter, serving to propel it contents

42
Q

What is hyperplasia

A

the growth of a tissue through cellular multiplication, not cellular enlargement

43
Q

What is stress relaxation response or receptive-relaxation response

A

smooth muscle exhibits this, when stretched, it briefly contracts and resists, but then relaxes - this is apparent in the bladder

44
Q

What is muscular dystrophy?

A

a collective term for several hereditary diseases in which the muscles degenerate, weaken and are gradually replaced by fat and fibrous scar tissue.

45
Q

What is the most common type of muscular dystrophy?

A

DMD, Duchenne Muscular Dystrophy

46
Q

Is DMD a sex linked recessive trait the affect about 1 out of every 3,500 live-born boys

A

Yes

47
Q

Describe how DMD progresses

A

Not evident at birth - first noticed when child has difficulty keeping up with other children, falls frequently, and has hard time to stand up - typically diagnosed between the ages of 2 and 10 - order of muscles affected first in the hips, then legs, abdominal, spinal, respiratory and cardiac - muscles shorten like with atrophy, causing postural abnormalities such as scoliosis - usually wheel chair bound by age 10 or 12 and seldom live past 20 - also decline in mental ability - death usually result of respiratory insufficiency, pulmonary infection, or heart failure. DMD is in curable. cause of DMD is a mutation in the gene for the muscle protein dystropin - which causes no coupling between the thin myofilaments and the sarcolemma - sarcomeres move independantly of the sarcolemma creating tears in the membrane - torn membrane admits excess Ca+ into the cell which activates intracellular proteases - these degrade the contractile proteins of the muscle leading to weakness with cellular necrosis - dying muscle fibers replaced with scar tissue - block blood circulation in the muscle - muscle degeneration accelerates in a fatal spiral of positive feedback

48
Q

What is muscle fatigue

A

is the physiological inability of muscles to contract - progressive weakness from use - ATP synthesis declines as glycogen is consumed - sodium potassium pumps fail to maintain membrane potential and excitability - lactic acid inhibits enzyme function - accumulation of extrecellular K+ hyper polarizes the cell - motor nerve fibers use p their acetylcholine

49
Q

What is oxygen debt

A

heavy breathing after strenuous exercise - known as excess post exercise oxygen consumption

50
Q

What is the purpose for the extra oxygen that is part of oxygen debt

A

-replace oxygen reserves - replenish the phosphagen system, reconverting lactic acid to glucose in kidneys and liver - serves the elevated metabolic rate that occurs as long as the body temperature remains elevated by exercise

51
Q

What is depolarization

A

when the Na+ cations override the negative charge inside the membrane, so the inside of the membrane briefly becomes positive - occurs when Na+ channels open and Na+ enters the cell’s sarcoplasm

52
Q

What are the three steps involved in an action potential

A

depolarization, propagation & repolarization

53
Q

What is propagation

A

the local depolarization wave spreads to the adjacent areas of the sarcolemma and opens voltage-regulated Na+ channels

54
Q

What is repolarization

A

sarcolemma is restored to its initial polarized state (resting membrane potential)

55
Q

What is threshold stimulus

A

weakest stimulus capable of producing a response in an irritable tissue

56
Q

What is the all or none phenomenon

A

action potentials are “all-or-none” they either happen completely or they don’t happen at all

57
Q

What is a motor unit

A

one nerve fiber and all the muscle fibers innervated by it

58
Q

Where are small motor units found

A

where fine control is needed such in eye movement

59
Q

Where are large motor units found

A

where strength is more important then fine control is needed such in the gastrocnemius muscle of the calf

60
Q

The point where a nerve fiber meets any target is called a

A

synapse

61
Q

when the target cell is a muscle fiber, the synapse is also called a

A

neuromuscular junction (NMJ) or motor end plate

62
Q

at each synapse the nerve fiber ends in a bulbous swelling called a

A

synaptic knob

63
Q

What is the synaptic cleft

A

the synaptic knob does not directly touch the muscle fiber but is separated from it by a narrow space

64
Q

what organelle is the synaptic knob filled with

A

acetylcholine (ACh)

65
Q

What does ACh function as

A

a chemical messenger from the nerve cell to the muscle cell - stimulates a skeletal muscle fiber

66
Q

ACh receptor

A

located in the sarcolemma

67
Q

Where is acetylcholinesterase (AChE)

A

in the sarcolemma breaks down ACh after the ACh has stimulated the muscle cell - it turns off muscle contraction and allows the muscle to relax

68
Q

What is a myogram

A

a chart that shows the timing and strength of a muscles contraction

69
Q

A minimum voltage necessary to generate an action potential in the muscle fiber is called the

A

threshold

70
Q

Twitch is defined as

A

a single stimulus that cause a quick cycle of contraction and relaxation

71
Q

What is muscle tone

A

a state of continual, partial contraction of resting skeletal or smooth muscle - does not produce active movements - keeps the muscles firm, healthy and ready to respond to stimulus - helps to stabilize joints and maintain posture

72
Q

What is wave summation

A

when new twitch arrives before the previous twitch is over - each new twitch “rides piggyback” on the previous one and generates higher tension - one new wave of contraction added to another

73
Q

the effect produces by wave summation is called

A

incomplete tetanus because it is a state of sustained fluttering

74
Q

What is complete (fused) tetanus

A

the twitches fuse into a single, non-fluctuating contraction

75
Q

What is hypotonia

A

decreased or lost muscle tone - usually an injury to spinal cord causes hypotonic muscles

76
Q

What is hypertonia

A

increased muscle tone - twitches - characterized by muscle stiffness and sometimes associated with a change in normal reflexes

77
Q

What type of contraction is one in which there is a change in muscle length (muscle shortens or lengthens during contraction) - like in doing curls

A

Isotonic contraction - iso means same - tonic means tension

78
Q

What is an Isometric contraction?

A

metric means length - is increasing muscle tension (muscle does not shorten during contraction) - like in holding an object for a while

79
Q

the force exerted on an object by a contracting muscle is called

A

muscle tension

80
Q

the opposing force exerted on the muscle by the weight of the object to be moved is called

A

load

81
Q

concentric isotonic contraction

A

the muscle shortens while maintaining a constant degree of tension - muscle moves a load

82
Q

eccentric isotonic contractions

A

the muscle maintains tension while it lengthens, allowing a muscle to relax without going suddenly limp

83
Q

The three metabolic pathways of ATP generation are

A

direct phosphorylation, glycolysis and aerobic respiration

84
Q

This ATP pathway using creatine phosphate (CP) molecule by CP donating P to ADP to make ATP is called

A

direct phosphorylation - phosphagen system - makes one ATP per CP molecules - think of as sprinter - can provide energy for about 15 seconds

85
Q

Glycolysis or the glycogen-lactid system is

A

ATP production through the energy source of glucose - produces 2 ATP per glucose molecule - can provide enough energy for about 30-60 seconds - also produces to pyretic acid that can be used in anaerobic pathway - muscles obtain glucose from blood and stored glycogen

86
Q

This ATP pathway uses oxygen during the process

A

Aerobic respiration

87
Q

Does glycolysis and direct phosphorylation use oxygen

A

no

88
Q

95% if ATP used in muscle activity comes from

A

aerobic respiration which uses oxygen

89
Q

Glucose + O2 =

A

CO2 + H2O + 36 ATP - aerobic respiration

90
Q

Where is the oxygen found for aerobic respiration

A

from lungs by hemoglobin in red blood cells - in skeletal muscle it is myoglobin

91
Q

what must be present in for skeletal muscle contraction

A

be at resting membrane potential
be stimulated by a nerve ending
propagate an electrical current, or action potential, along its sarcolemma
have a rise in intracellular Ca2+ levels, the final trigger for contraction
can only occur if there is sufficient Ca2+ and ATP energy

92
Q

what neurons stimulate skeletal muscle

A

somatic (voluntary) motor neurons

93
Q

Name a few neuromuscular toxins

A

pesticides, tetanus or lockjaw and flaccid paralysis

94
Q

What happens with the neuromuscular toxin - pesticides

A

bind to acetylcholinesterase and prevent it from degrading ACh - spastic paralysis and possible suffocation

95
Q

What is tetanus or lockjaw?

A

spastic paralysis - the continually contracting muscles caused by toxin Clostridium bacteria - blocks glycine release in the spinal cord an causes overstimulation of the muscles

96
Q

called limp muscles, respiratory arrest

A

flaccid paralysis

Muscular Systems (4 decks)

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