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Medical Assisting > The Muscular System > Flashcards

The Muscular System Flashcards

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USMLE® Step 1 flashcards
1
Q

What are the functions of muscles?

A

-Movement
-Stability
-Control of body openings and passages
-Production of heat

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2
Q

What are sphincters?

A

They are valve-like muscular structures that control the passage of substances into and out of organs such as the stomach and bladder.

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3
Q

How are skeletal striated muscles attached to bones?

A

They are attached to bones through tendons

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4
Q

What happens when skeletal muscles contract?

A

They cause movement

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5
Q

What happens when smooth muscle contracts?

A

It causes movement of the contents in the organs eg food material moves through the intestinal tract

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6
Q

What happens when cardiac muscle contracts?

A

The contraction causes blood to pump blood into blood vessels

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7
Q

How do muscles provide stability to the body?

A

Skeletal muscles hold bones very tightly and hold the vertebrae together to stabilize it.

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8
Q

How do muscles produce heat in the body?

A

They produce heat by releasing heat when muscle contraction occurs. This helps keep the body at a healthy temperature.

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9
Q

What are the three types of muscle tissue?

A
  • skeletal striated muscle
  • smooth muscle tissue
  • cardiac striated muscle
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10
Q

What is muscle tissue made of?

A

Muscle cells called myocytes

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11
Q

What are the muscle cells of skeletal striated tissue called?

A

They are called muscle fibers

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12
Q

Why are the cells of skeletal striated muscle called muscle fibers?

A

It is because they are long in length

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13
Q

What is the cell membrane of a muscle cell called?

A

It is called a sarcolemma

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14
Q

What is the cytoplasm of a muscle cell called?

A

It is called a sarcoplasm

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15
Q

What is the endoplasmic reticulum of a muscle cell called?

A

It is called a sarcoplasmic reticulum

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16
Q

What is most of the sarcoplasm in skeletal striated cells filled with?

A

It is filled with long structures called myofibrils

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17
Q

What produces striations in the muscle tissue?

A

It is the arrangement of actin and myosin filaments in myofibrils that produces striations

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18
Q

What substances control muscle cells?

A

Motor neurons that release Chemical substances known as neurotransmitters

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19
Q

What is the only neurotransmitter that muscle fibers respond to?

A

Acetylcholine

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20
Q

Describe the action of acetylcholine on muscle contraction

A

Acetylcholine causes skeletal muscle to contract.

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21
Q

Describe the action of acetylcholinesterase on muscle relaxation

A

When contraction occurs, an enzyme called acetylcholinesterase in the muscles breaks down the acetylcholine which allows the muscles to relax

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22
Q

What are the characteristics of the contractions in skeletal striated muscles?

A

They are fast to contract and relax

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23
Q

What are the characteristics of contractions in smooth muscle tissue?

A

They are slow to contract and relax

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24
Q

What are the characteristics of cardiac striated muscle?

A

They are groups of muscle cells that contract as a unit

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25
Q

What are the two types of smooth muscle tissue?

A

Multi-unit and visceral

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26
Q

Where is multi-unit smooth muscle found in the body?

A

It is found in the iris of the eye and the walls of the blood vessels

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27
Q

How does multi-unit smooth muscle contract?

A

It contracts in response to neurotransmitter and hormones

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28
Q

What is visceral smooth muscle?

A

Visceral smooth muscle is sheets of muscle cells that closely contact with each other

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29
Q

What is the shape of smooth muscle?

A

It has a fusiform shape like a football or a spindle

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30
Q

What connective tissue surrounds smooth tissue?

A

Endomysium

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31
Q

What is the shape skeletal muscle?

A

It has a long cylindrical shape

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32
Q

What is the shape of cardiac muscle?

A

It is irregularly branched

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33
Q

What is the shape of cardiac muscle?

A

It is irregularly branched

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34
Q

What do visceral smooth muscle cells respond to?

A

They respond to neurotransmitters

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35
Q

Is smooth muscle tissue voluntarily or involuntarily controlled?

A

It is involuntarily controlled, we do not consciously control it, it is controlled via the autonomic nervous system.

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36
Q

What is different about the structure of smooth muscle compared to skeletal and cardiac muscle?

A

Smooth muscle does not have sarcomeres and myofibrils, because of this is lacks the striations of cardiac and skeletal muscle.

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37
Q

What filaments exist in all three muscle types?

A

Myosin and Actin filaments

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38
Q

What are the dot like structures that connect the net like structure running through out the muscle fiber?

A

They are called dense bodies

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39
Q

What do the dense bodies attach to in the cell?

A

They attach to the sarcolemma(cell membrane surrounding a muscle cell)

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40
Q

What is another role played by the dense fibers?

A

They allow for attachment of intermediate filaments such as desmin and vimentin.

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41
Q

What two neurotransmitters are involved in smooth muscle contraction?

A

Acetylcholine and norepinephrine

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42
Q

What is the model used to describe muscle contraction called?

A

It is called the sliding filament model of muscle contraction.

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43
Q

How many nuclei do smooth muscle tissue have?

A

They only have one nucleus

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44
Q

What are tendons?

A

Connective tissues that attach to the periosteum of bones.

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45
Q

What are aponeuroses?

A

Aponeuroses are flat, sheet like tendons that attach muscles to the periosteum of bones or to the skin.

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46
Q

Why are a woman’s muscles smaller than a man’s?

A

Women have fewer muscle fibers and less ability to store glycogen and convert it into energy.

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47
Q

What are the three types of filaments that a sarcomere contains?

A
  1. Thick myosin filaments
  2. Thin Actin filaments
  3. Elastic titin (connectin) filaments
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48
Q

Describe the structure of thick (myosin) filaments in sarcomeres.

A

Myosin filaments are shaped like two golf clubs twisted together:

-the handles or the golf clubs form the tails of the molecules and point towards the sarcomere
-the heads of the clubs for the heads of the molecules and are called myosin heads or cross-bridges. They extend towards the thin filaments.
-The molecules lie parallel to each other

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49
Q

What three proteins do thin filaments contain?

A
  • Actin
  • Tropomyosin
  • Troponin
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50
Q

Describe the structure of thin filaments in sarcomeres.

A

-The molecules are irregularly shaped but appear together as a chain of twisted molecules
-Each molecule has a myosin-binding site where myosin heads bring about contraction

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51
Q

What happens to the myosin-binding site when a muscle is relaxed?

A

The site is blocked by a tropomyosin-troponin complex so that myosin cannot bind to them.

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52
Q

What protein do elastic filaments contain?

A

They contain the protein titin(connectin)

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53
Q

What is the purpose of the protein titin(connectin) in elastic filaments?

A

It helps to stabilize the position of the thick filaments

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54
Q

What are the two regions that sarcomeres are made up of?

A
  1. A-band
  2. I-band
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55
Q

What is the purpose of the two regions of sarcomeres?

A

They give striated muscles their striated appearance

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56
Q

Describe the appearance of A-band region of sarcomeres.

A

-It is darker
-composed mainly of thick filaments with only a few thin filaments
-In the center of the A-band is a narrow H-zone that contains thick filaments only
-the H-Zone is divided by an M-Line of protein molecules that hold the thick filaments together

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57
Q

Describe the I-band of sarcomeres.

A

-it is a lighter zone composed of thin filaments only.

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58
Q

How are sarcomeres separated from each other?

A

They are separated from each other by Z-discs which are narrow regions of dense material.

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59
Q

Describe the role of ATP in muscle contraction.

A

ATP is attached to ATP binding sites in myosin heads.
ATP is split into ADP and P meaning energy has been transferred from ATP to the myosin heads.
Myosin heads are in an excited state and ready to bind to the actin molecules when space becomes available

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60
Q

Describe the role of nerve impulses from the central nervous system in muscle contraction.

A

Nerve impulses trigger acetylcholine release which then triggers a muscle action potential that travels along the sarcolemma and caused the release of calcium which is stored in the sarcoplasmic reticulum.

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61
Q

What role does calcium play in muscle contraction?

A

Calcium binds with troponin on the myosin-binding site and causes the tropomyosin-troponin complex to move away to other sites. This frees up space for the myosin on the thick filaments to bind with the actin filaments binding site.

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62
Q

What is a a power stroke in muscle contraction?

A

A power stroke occurs when the myosin heads bind to the myosin-binding site on the actin and change their shape by swiveling their heads towards the center of the sarcomere.

63
Q

What is the effect of the power stroke in muscle contraction?

A

It causes the thin filaments to draw past the thick filaments. The thin filaments slide inward toward the H-zone , the thick filaments remain in place. The inward sliding causes the Z-discs to come towards each other and the entire sarcomere shortens.

64
Q

Do the lengths of the thin and thick filaments change during contraction?

A

No, they do not

65
Q

What happens after the power stroke?

A

ATP binds to the myosin heads at the ATP binding site causing the heads to detach themselves from the actin

66
Q

Where does the calcium needed for muscle contraction come from?

A

It comes from the sarcoplasmic reticulum

67
Q

What two processes need to happen for muscles to relax?

A
  1. Acetylcholine is broken down
  2. Calcium levels drop
68
Q

What causes the breakdown of acetylcholine in the muscles?

A

An enzyme called acetylcholinesterase breaks down the acetylcholine

69
Q

What happens when acetylcholine is broken down?

A

The breakdown of acetylcholine by acetylcholinesterase stops any further muscle action potential. Calcium is no longer released

70
Q

What happens when the calcium levels drop to cause muscle relaxation?

A

There is no longer enough calcium to bind with the troponin. The tropomyosin-troponin complex moves back over the myosin binding sites in the actin of the thin filaments, preventing the myosin heads from the thick filaments from binding with the actin.

71
Q

What is atony?

A

Atony is a lack of muscle tone

72
Q

What is atrophy?

A

Atrophy is the wasting away of muscles; muscles decrease in size

73
Q

What is hypotonia?

A

A loss of muscle tone; muscles appear loose and flattened and are described as hypotonic

74
Q

What is hypertonia?

A

An increase in muscle tone; muscles appear stiff or rigid, and are described as hypertonic

75
Q

What are the two types of physical contractions that most physical activity fall into?

A

Isotonic and isometric contractions

76
Q

What are isotonic contractions?

A

Isotonic contractions are regular contractions in which muscles shorten and create movements, while the tension in the muscle remains constant.

77
Q

What are the two types of isotonic contractions ?

A
  1. Concentric contractions
  2. Eccentric contractions
78
Q

What are concentric contractions?

A

Concentric contractions occurs when the muscle shortens and generates a movement that decreases the angle on the joint. Example curling a bicep towards you

79
Q

What are eccentric contractions?

A

Eccentric contractions are contractions which lengthen the muscles and increase the angle of the joint. Eg stretching a bicep away from you

80
Q

What are isometric contractions?

A

In isometric contractions, the muscle contracts but it does not shorten and no movement is generated. A plank is an example as you are not shortening ing or lengthening muscles

81
Q

From where do muscles obtain the energy needed to contract?

A

From ATP

82
Q

What are the three ways that muscles obtain ATP?

A
  1. The phosphates system
  2. Glycolysis
  3. Aerobic respiration
83
Q

What is the phosphagen system?

A

Muscles store a small amount of ATP in their fibers and are able to convert it into energy.

84
Q

What is a downside of the phosphagen system?

A

It only provides enough energy for around 15 seconds of maximal muscular activity.

85
Q

What is glycolysis?

A

Glycolysis is the breakdown of glucose in the muscles without the presence of oxygen.

86
Q

What is another name for glycolysis?

A

Anaerobic respiration

87
Q

What is glucose broken down into through glycolysis?

A

It is broken down into pyruvic acid and ATP.

88
Q

What happens to the pyruvic acid and ATP broken down by glycolysis?

A

The ATP is used by the muscles and the pyruvic acid enters mitochondria of the the muscle fiber and is further broken down complete in the presence of oxygen

89
Q

What happens if there is not enough oxygen to completely break down the pyruvic acid?

A

It is converted into lactic acid

90
Q

What happens to the lactic acid that is produced by the muscles?

A

It diffuses into the blood and can be used by the heart muscle fibers, kidneys and liver to produce ATP.

91
Q

What happens when lactic acid accumulates in the muscle tissues and blood?

A

It causes muscle soreness and fatigue

92
Q

What is aerobic respiration?

A

Aerobic respiration occurs in the presence of oxygen. Pyruvic acid is completely broken down into carbon dioxide, water, ATP and heat

93
Q

What is another name for aerobic respiration?

A

Cellular respiration or biological oxidation

94
Q

What are the benefits of aerobic respiration?

A

It provides energy for activities longer than ten minutes as long as there is enough oxygen and nutrients

95
Q

Where do muscles get their glucose from?

A

Carbohydrates which are broken down into glucose and stored in the body as glycogen.

96
Q

Where is glycogen stored in the body?

A

It is stored in the liver and the muscles

97
Q

Where do the muscles get their oxygen from?

A
  1. It is stored in the muscles as myoglobin
  2. It is stored in the blood in the form of hemoglobin
98
Q

Why do muscles experience fatigue?

A
  1. An insufficient supply of oxygen or glycogen
  2. A build up of lactic acid
  3. A failure of action potentials to release adequate acetylcholine
99
Q

What are the three different types of muscle fibers?

A
  1. Fast oxidative
  2. Slow oxidative
  3. Fast glycolytic
100
Q

Why do runners or other athletes breathe fast and heavy after a race?

A

They do something knows as recovery oxygen consumption. The heavy breathing:

  1. restores ATP reserves,
  2. repairs tissues,
  3. removes accumulated lactic acid and 4. cools the body down.
101
Q

How does the color of muscles indicate the amount of myoglobin in them?

A

Red muscle fibers have more myoglobin and white muscle fibers have a low myoglobin content

102
Q

What is the appearance of slow oxidative muscle fibers?

A

They are red in color and small in appearance

103
Q

What is the oxygen supply like for slow oxidative muscle fibers?

A

It contains large amounts of myoglobin, many mitochondria and many blood capillaries. The oxygen supply is high.

104
Q

What is the ATP production like in slow oxidative muscle fibers?

A

They generate ATP by aerobic processes

105
Q

What is the contraction velocity of slow oxidative muscle fibers?

A

They split ATP slowly and therefore have a slow contraction velocity

106
Q

What is the fatigue resistance of slow oxidative muscle fibers?

A

They are very resistant to fatigue

107
Q

What type of activities do slow oxidative muscles perform?

A

They are good for maintaining posture and endurance activities

108
Q

What is the appearance of fast oxidative muscle fibers?

A

Their color is red to pink and they are medium in size

109
Q

What is the oxygen supply like in fast oxidative muscle fibers?

A

They contain large amounts of myoglobin, many mitochondria, and many blood capillaries. Good oxygen supply

110
Q

What is the ATP production in fast oxidative muscle fibers?

A

They generate ATP by aerobic processes

111
Q

What is the contraction velocity of fast oxidative muscle fibers?

A

They split ATP quickly and therefore have a fast contraction velocity

112
Q

What is the fatigue resistance of fast oxidative muscle fibers?

A

They are resistant to fatigue but not as much as slow oxidative muscle fibers

113
Q

What type of activities do fast oxidative muscle fibers perform?

A

Walking and running

114
Q

What is the appearance of fast glycolytic muscle fibers?

A

They are white in color and are the largest muscle fibers

115
Q

What is the oxygen supply of fast glycolytic muscle fibers?

A

They have a low myoglobin content,
Few mitochondria
Few blood capillaries
Oxygen supply is low

116
Q

How do fast glycolytic muscle fibers generate ATP?

A

They generate ATP by anaerobic processes (glycolysis);
cannot supply muscle with ATP continuously

117
Q

What is the Contraction velocity of fast glycolytic muscle fibers?

A

Due to their large diameter they split ATP very quickly and therefore have a strong contraction velocity.

118
Q

What is the fatigue resistance of fast glycolytic muscle fibers?

A

They fatigue easily

119
Q

What activities do fast glycolytic muscle fibers perform?

A

Fast movements, such as throwing a ball

120
Q

How do muscles produce movement?

A

A muscle attaches itself to two bones that for a joint, when the muscle contracts, it pulls the movable bone towards the stationary bone.

121
Q

How many attachment points do muscles usually have?

A

All muscles have at least two attachment points

122
Q

What is the origin attachment point?

A

It is the point where a muscle attaches to the stationary bone

123
Q

What is the insertion point?

A

It is the point where a muscle attaches to the moving bone. During contraction the insertion usually moves towards the origin

124
Q

What is a unique point about the movement of muscles?

A

Muscles only shorten when they contract, therefore they can only pull and never push.

125
Q

How is movement in the body defined by the contraction of muscles?

A

Movement is the action of two muscles acting together or against each other, one muscles contracts to bend the elbow another contracts to make the elbow straight again.

126
Q

What are the pairs that muscles at the joints are usually arranged in?

A

They are usually arranged in pairs of flexors-extensors and abductors- adductors

127
Q

What is the muscle responsible for causing a particular movement called?

A

It is called the prime mover or agonist.

128
Q

What is the muscle that opposes the movement of the prime mover or agonist called?

A

The antagonist, it relaxes and lengthens in a way that ensures that the movement performed by the prime mover is smooth.

129
Q

What are the additional muscles at the joint that ensure a steady movement and help the prime mover function effectively called?

A

They are called synergists and they are usually found alongside the prime mover

130
Q

What are the specialized synergistic muscles that stabilize the bone of the prime mover’s origin so that it can act efficiently?

A

They are called fixators or stabilizers

131
Q

What is flexion?

A

Flexion is bending a body part e.g bending the palm inward

132
Q

What is extension?

A

Extension is straightening a body part eg holding the palm out straight

133
Q

What is hyperextension?

A

Extending a body part past the healthy anatomical position eg bending the palm backward

134
Q

What is dorsiflexion?

A

Moving the ankle to raise the top of the foot towards the leg

135
Q

What is plantar flexion?

A

Moving the ankle to raise the heel and stand on the tips of your toes

136
Q

What is abduction?

A

Moving a body part away from the midline of the body eg taking a step to the left or right

137
Q

What is addiction?

A

Moving a body part to the midline of the body eg moving leg back to the center after taking a step to the left or right

138
Q

What is rotation?

A

Rotation is twisting the a body part eg turning head side to side

139
Q

What is pronation?

A

Turning the palm so the palm is facing downward and the back of the hand of facing forward

140
Q

What is supination?

A

Turning the palm so that the palm of the hand is facing upward.

141
Q

What is inversion?

A

Turning the sole of the foot inward

142
Q

What is eversion?

A

Turning the sole of the foot outward

143
Q

What is retraction?

A

Moving a body part back eg moving chin towards chest

144
Q

What is protraction?

A

Moving a body part outward eg sticking chin out

145
Q

What is elevation?

A

Vertically lifting a body part eg lifting shoulders up

146
Q

What is depression?

A

Vertically lowering a body part eg lowering shoulders

147
Q

What are the two types of fascia available?

A
  1. Deep fascia
  2. Superficial fascia
148
Q

Where in the body is deep fascia found?

A

It is found between the muscles

149
Q

Where in the body is superficial fascia found?

A

It is found under the skin

150
Q

What is another name for superficial fascia?

A

Hypodermis

151
Q

What are the two ways that skeletal muscle attaches to a bone?

A
  1. Direct attachment
  2. Indirect attachment
152
Q

What is direct attachment of muscles to bone?

A

Muscle fibers merge with the periosteum of the bone, forming a strong bone.

153
Q

What is indirect attachment of muscles to bone?

A

The epimysium extends past the muscle as a tendon(a strong fibrous cord). The tendon merges with the periosteum of the bone.

154
Q

Can muscle attach to other muscle?

A

Yes. The muscle epimysium extends as an aponeurosis and fuses with the covering of the other muscle or attaches to bone.

Medical Assisting (21 decks)

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