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Physiology > Muscles > Flashcards

Muscles Flashcards

1
Q

What are the characteristics of muscle tissue?

A

Excitability
Contractility
Extensibility
Elasticity

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2
Q

What is excitability?

A

The ability to receive and respond to stimulus

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3
Q

What is contractility?

A

The ability to produce tension/force when stimulated

“Shortening”

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4
Q

What is extensibility?

A

The ability to be stretched, “lengthen”

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5
Q

What is elasticity?

A

The ability to recoil to resting length

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6
Q

What are the functions of muscle tissue?

A

Movement of bones or fluids
Maintaining of posture and body position
Stabilizing joints
Heat generation (esp. true for skeletal)

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7
Q

What is the difference between skeletal muscles and cardiac and smooth muscles as far as nerve impulses?

A

Skeletal muscles are voluntary
Cardiac/Smooth muscles are involuntary

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8
Q

True or False: Skeletal muscles regenerate after being “torn” during exercise.

A

False. We are born with a set number and that’s how many we have

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9
Q

What is unique about the structure of cardiac muscles?

A

They are branched and connect to each other in chains

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10
Q

What is the epimysium?

A

The top, dense layer of connective tissue covering everything

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11
Q

What are fascicles?

A

Groups of muscle tissue fibers connected together

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12
Q

What is the perimysium?

A

The connective tissue holding fascicles together

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13
Q

What is sarcolemma?

A

The special name for the plasma membrane of muscle cells

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14
Q

What is a myofibril?

A

A stack of fibrous muscle cells (sarcomeres) within the sarcolemma.

This organelle is unique to skeletal muscles

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15
Q

What is a sarcomere?

A

The smallest prt of a myofibril

An A-Band (stacks of overlapping actin and myosin*)between two protein “caps” called Z-Discs.

The middle space between two z-discs is just myosin, this is called the M-line

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16
Q

Which protein is a thin filament and which is a thick filament?

A

Actin: Thin
Myosin: Thick

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17
Q

The thin membrane coating each myofibril is called what?

A

Sarcoplasmic Reticulum

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18
Q

What is a Triad?

A

1 T-tubule aka Transverse tubule of sarcolemma around 2 terminal cisternae storing Ca2+

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19
Q

What are the “contractile proteins”

A

Actin and myosin

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20
Q

What is the difference between troposin and tropmyosin?**

A

Tropomyosin covers actin and myosin heads bind to it

Troponin covers tropomyosin. When it binds to Ca2+ it changes its shape, revealing the active sites

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21
Q

Where does activation happen and what is that?

A

In the motor end plate

A stimulation (AP) travels down a neuron to a neuromuscular junction.

ACh is released into the sarcolemma via exocytosis

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22
Q

What is a neuromuscular junction?

A

A muscle synapse: the place where a muscle neuron’s synaptic bulb meets the motor end plate

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23
Q

Where does excitation take place, what is it?

A

In the muscle membrane (sarcolemma)

The membrane is depolarized, ACh binds to receptors on motor end plates and opens ligand-gated channels, allowing Na+ in and K+ out

This depolarization opens voltage-gates Na+ channels, which causes an AP that changes the shape of T-tubules

The sarcolemma receives an influx of Ca2+, which binds to troponin and exposes the active sites on actin

Note: This is always a nicotinic receptor, EPSP

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24
Q

What happens during Excitation-Contraction?

A

ATP provides energy for mysofilaments to slide together. Myosin heads bind to actin and shorten the sarcomere.

A second ATP causes the mysosin head to unlatch

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25
Q

What is the latent period?

A

The time between excitation and depolarization

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26
Q

What is the Cross-Bridge Cycle?

A

Energized myosin heads attach to actin, this is called the “working stroke” or “power stroke”

The myosin head is cocked back by a second ATP molecule

Note: This will happen as long as ATP and Ca2+ are present

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27
Q

What is meant by muscle relaxation?

A

Ca2+ is pumped back into the SR, tropomyosin rolls back over and covers the binding sites of actin

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28
Q

What is rigor mortis?

A

When a person dies the stored Ca2+ in their terminal cisternae flood the sarcolemma and the ATP still left in their system causes all the myosin to keep cocking forward and contracting until it runs out

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29
Q

What is the difference between isometric and isotonic contractions?

A

Isometric - Tension is constant but muscle length stays the same

Isotonic - Muscle length changes the same but tension remains the same

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30
Q

What is tension

A

The force exerted on the load of an object, created by contraction

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31
Q

True or False: contraction means the muscle shortens

A

False. In concentric contractions the muscle shortens, in eccentric contractions the muscle grows in length

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32
Q

What is a motor unit?

A

A single motor neuron and the muscle fibers it supplies

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33
Q

What parts of the body have more motor end units?

A

Fingers, lips, etc.
Areas where fine, precise motor control is more important

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34
Q

What parts of the body have large motor units?

A

Thighs, back, anywhere that is weight-bearing

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35
Q

What is the definition if a muscle twitch?

A

The response if a muscle to a single, brief threshold stimulus.

It is the simplest contraction observable in a lab

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36
Q

What are the three phases of a muscle twitch?

A

Latent Period - E-C Coupling
Period of Contraction - Cross-Brudge formation, increasing tension
Period of Relaxation - Ca2+ re entering SR, tension declines to 0

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37
Q

What are the factors that affect tension?

A

Type
Load
Recruitment

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38
Q

True or false: If a muscle fiber is re-stimulated after it has relaxed it will have the same magnitude as the initial twitch but if second twitch occurs before relaxation the magnitude will stack

A

True

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39
Q

What do we cal maximum, sustained contraction?

A

Tetanus

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40
Q

What involuntary factors will cause a muscle to relax?

A

Running out of ATP or Ca2+

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41
Q

What is threshold stimulus?

A

The first observable muscle contraction

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42
Q

What controls contraction force?

A

Recruitment. More and larger fibers are recruited as stimulus intensity (load) increases. This is known as the size principle

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43
Q

What is the optimum sarcomere operating length?

A

80-120% of resting length

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44
Q

What is the effect of steroids on skeletal muscles?

A

Increased protein synthesis

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45
Q

What is the effect of HGH on skeletal muscles?

A

An increased number of fibers in myofilaments

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46
Q

What is hypertrophy?

A

An increase in the size of a muscle fiber

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47
Q

What is treppe?

A

aka “The Staircase Effect”, an increased contraction in a response to multiple stimuli of the same intensity due to increased Ca2+ release and heat. A little relaxation occurs, then a stacked magnitude, creating a staircase effect

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48
Q

What is muscle tone?

A

There is a small alternating current passing through muscles at all times due to spinal reflexes responding to stretch receptors. Keeps muscles ready to respond.

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49
Q

How are different muscle fiber types classified?

A

Speed and Metabolic Pathway:

Slow oxidative (red, endurance)
Fast oxidative (pink)
Fast glycolytic (white, power strokes)

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50
Q

True or False: The smaller the load the faster the contraction

A

True

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51
Q

What is the only energy source for contractive activities?

A

ATP

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52
Q

What are the ways ATP is generated for contraction?

A

Stores are depleted in 4-6 seconds
Regenerated via:
10 sec in
Direct phosphorylation of ADP by creatine phosphate
40-40 sec in
Anaerobic pathway (glycolysis)
theb
Aerobic Respiration

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53
Q

What is muscle fatigue and what causes it?

A

The inability to contract

Caused by:
-ionic imbalances (K+, Ca2+, K+, P) interferes with E-C coupling
-Prolonged exercise damaging SR
-A complete and total lack of ATP (rare)

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54
Q

What is a muscle fiber’s membrane called?

A

Sarcolemma

55
Q

What is the sarcolemma called when it is deep in a muscle fiber?

A

A t-tubule

56
Q

What are the Calcium-filled sacs on the side of t-tubules called?

A

Terminal cisternae

57
Q

What organelle contains the thick and thin filaments?

A

Myofibrils

58
Q

Which filament is thick?

A

Myosin

59
Q

Which filament is thin?

A

Actin

60
Q

Where are the cell bodies of motor neurons for the head and neck located and how do they exit the skull?

A

The brianstem, cranial nervea

61
Q

Where are the cell bodies of motor neurons for most muscles and how do they exit the spine?

A

The ventral horn, via spinal nerves

62
Q

For skeletal muscles to contract action potentials have to happen where?

A

In both a motor neuron and a muscle fiber

63
Q

What is the name flor action potential of a sarcolemma? For a motor nerve?

A

Sarcolemma: Excitation

Motor Nerve: Activation

64
Q

What is the name of the invaginated region of the muscle membrane at the NMJ?

A

Motor End Plate

65
Q

What NT excites nicotinic receptors in skeletal muscles?

A

ACh

66
Q

True or False: When the Sacrolemma is at rest Na+ voltage-gates channels are open.

A

False. They are closed

67
Q

An action potential causes a shape change to what protein, allowing Ca2+ to flow into the sarcolemma?

A

A voltage-gated calcium channel on the terminal cisternae of the sarcolemma

68
Q

What do Ca2+ ions bind to in muscle fibers? What does this cause?

A

Troponin, which causes a shape change in neighboring tropomyosin, revealing the bind site on the actin

69
Q

What causes myosin to “cock” position?

A

ATP hydrolyzes

70
Q

What happens if the myosin/actin binding site is not covered?

A

Cross-bridges continue to form, the muscle will continue to contract

71
Q

What is the degree of stretch range at which max tension can be developed in a skeletal muscle?

A

Optimal length (80-120%)

72
Q

What does optimal stretch length indicate?

A

The amount of overlap between thick and thin filaments

73
Q

How is ACh removed from the NMJ?

A

It diffuses away from the membrane or is destroyed by Acetylcholinase

74
Q

What would happen if a person was poisoned with organophosphates?

A

No ACh breakdown could occur, so it would continue to build-up in muscles and the muscles would fasciculate without voluntary input due to continuous contractions

75
Q

How do drugs increase the time ACh is present at the NMJ?

A

They inhibit acetylcholinesterase allowing ACh build-up by preventing it from being broken down

76
Q

What is the definition if muscle tone?

A

A small alternating contraction due to spinal reflexes that keeps muscles contracted somewhat at all times so they are ready for a response

77
Q

What are the three phases of a muscle twitch?

A

Period of Contraction (sarcomeres shorten)
Period of Relaxation (Sarcomeres return to rest)
Latent Period (sarcomeres remain at resting length)

78
Q

What are the three factors affecting tension in a muscle?

A

Stimulus strength
Stimulus frequency
Sarcomere length/muscle size

79
Q

What is twitch summation?

A

An increase in frequency of stimulation on a muscle fiber will cause an increase in tension for each twitch

80
Q

What process is most efficient at making ATP?

A

Aerobic restoration

81
Q

What are the three pathways of aerobic restoration?

A

Glycolosis, Krebs cycle, electron transport chain

82
Q

If oxygen is not available what is pyurvic acid converted to?

A

Lactic acid

83
Q

What’s Oxygen Deficit?

A

The state of depleted resources after exercise

84
Q

What three things must be replenished during Oxygen Deficit?

A

O2, Glycogen, creatine phosphate reserves

85
Q

What do white muscle fibers have that makes up for their lack of capillaries and myoglobin?

A

Many myofibrils (which makes them larger in diameter)

86
Q

What type of activities are white muscle fibers best suited for?

A

Resistance (Anaerobic) Exercise
Short, Powerful strokes

87
Q

What is the other name for white muscle fibers?

A

Fast Glycolitc

88
Q

Why are white muscle fibers bad for endurance?

A

They fatigue quickly

89
Q

What is the other name for red muscle fibers?

A

Slow oxidative

90
Q

What types if activities are red muscle fibers best suited for?

A

Endurance activities

91
Q

What exactly is “slow” or “fast” about different muscle fibers?

A

Speed of oxidation and velocity of contraction

92
Q

What type of muscle fiber is best for distance runners?

A

Red

93
Q

What is a motor unit?

A

A motor nerve and all of the muscle fibers it innervates

94
Q

Where do small motor units tend to be found?

A

In areas of fine motor movement (the eyes, the fingers)

95
Q

What is the advantage if having only a few muscle cells per unit?

A

It allows for Precise control

96
Q

Where do large motor units tend to be found?

A

Weight-bearing muscles (the legs and back)

97
Q

What is the advantage of having large motor units in a muslce?

A

They fatigue leas quickly

98
Q

What is recruitment?

A

The stimulation if additional motor units of a muscle, which strengthens the contraction

99
Q

Temporal summation occurs due to the increased presence of what particle?

A

Ca2+ ions in the sarcoplasm

100
Q

What is mechanism?

A

The process by which muscles contract and relax

101
Q

When carrying something upstairs what kind of contraction is happening in your arms?

A

Isometric

102
Q

True or False: both the A-band and I-band decrease in width as the muscle cell contracts

A

False. Only the I-Band decreases in width

103
Q

True or False: Motor Unit (MU) recruitment usually begins with glycolytic fibers

A

False. Recruitment usually begins with slow oxidative, white fibers are recruited third (last)

104
Q

Why do fast twitch fivers contract faster than slow twitch?

A

Their myosin hydrolyzes ATP faster

105
Q

True or False: When T-Tubules depolarize Ca2+ pumps are activated to pump ions out terminal cisternae into the sarcoplasm

A

False: They are channels, not pumps

106
Q

True or False: Motor unit and motor neuron are terms that can be used interchangeably

A

False. A motor unit includes a motor nerve AND a motor neuron

107
Q

Is force generated during the latent period?

A

No

108
Q

True or False: The number of motor units activated is proportional to the amount of tension produced by a skeletal muscle

A

True

109
Q

Muscles in the back that maintain an erect posture for long periods are mostly what kind of fiber?

A

Slow Oxidative (red)

110
Q

A muscle performing weak-to-medium output for a very long duration would be using what kind of metabolic pathways?

A

Aerobic

111
Q

What can skeletal muscles use to regenerate ATP?

A

Creatine phosphate

112
Q

What is the coupler ion of excitation and contraction in skeletal muscles?

A

Ca2+

113
Q

If you press your hands together you are creating what kind of contraction?

A

Isometric

114
Q

What kind of muscle is able to be stretched to twice its resting length and still produce a contraction force

A

Smooth

115
Q

What kind of receptors to skeletal muscles always have?

A

Nicotinic, which are always excitatory, use ACh

116
Q

What kind of loads result in isometric contractions?

A

Overload

117
Q

What is an EMG measuring?

A

Electrical activity generated by action potentials innervating a muscle

118
Q

True or False: As load increases more and larger units are recruited and the amount of electric activity picked up by an EMG increases.

A

True

119
Q

What is the difference between an isometric and an isotonic contraction?

A

In an isotonic contraction the tension on the muscle remains the same but the length changes.

In an isometric the length if the muscle stays the same but the tension changes

120
Q

What is the difference between an agonist and an antagonist?

A

An agonist is the contraction responsible for a muscle action, an antagonist performs the opposite action

121
Q

What is the difference between a concentric and eccentric contraction?

A

A concentric contraction is a contraction where the muscle shortens, an eccentric contraction is one where the muscle lengthens

122
Q

What is the difference in electrical output between concentric and eccentric contraction?

A

Concentric: Two peaks, when muscle is engaged and at the peak of its contraction

Eccentric: Overall activity is sustained

123
Q

Why does the EMG show activity when the muscle is relaxes?

A

Tonus, the electrical activity that is always pulsing through the body

124
Q

When holding an object does the number of motor units used remain the same?

A

Yes

125
Q

As one reaches physiological fatigue force exerted by muscles drops. Why?

A

ATP use exceeds ATP generation and lactic acid build-up creates a low pH environment, which interferes with ATPase’s ability to break down ATP into ADP and phosphate, to be reused

126
Q

What is fatigue?

A

When a muscle exerts half its maximum force

127
Q

Where is Ca2+ stored in smooth muscle?

A

The extracellular space. When intracellular Ca2+ drops the smooth muscle relaxes

128
Q

Do smooth muscles grow?

A

Yes, they divide and increase in number via hyperplasia

129
Q

How is smooth muscle innervated?

A

Contractions via intrinsic contraction, ANS modulates contractions.

130
Q

What is unique about smooth muscle neuromuscular junctions?

A

They don’t have them :P
They have gap junctions

131
Q

What are varicosities?

A

Bulbous swellings that release NTs

132
Q

What is unique about smooth muscle contraction?

A

It can stretch and still contract, it is rhythmic

133
Q

How does neural control of muscles develop as we grow?

A

Head to toe, proximal to distal

Physiology (17 decks)

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