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Physiology > Muscles > Flashcards

Muscles Flashcards

1
Q

Describe the three types of muscle, including shape and number of nuclei

A

skeletal: striated, cylindrical rods, multiple nuclei per cell
cardiac: striated, cylindrical rods, one nucleus per cell
smooth muscle: no striations, spindle shape, one nucleus

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2
Q

What are the roles of skeletal muscle in maintaining homeostasis

A
  1. Acquisition of nutrients/fuel
  2. processing food (chewing/swallowing)
  3. breathing
  4. escape from harm
  5. generation of heat for temperature control
  6. source of amino acids for times of famine
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3
Q

Why are skeletal muscles big and expensive?

A

30-40% of total body mass
#1 consumer of nutrients, oxygen, uses lots of ATP
high metabolism produces abundant wastes that tend to disrupt ECF homeostasis

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4
Q

What is a muscle cell also known as?

A

muscle fiber, a cylinder

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5
Q

What does the sarcoplasm contain

A

organelles

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6
Q

Describe the muscle structure, going from largest to smallest?

A

whole skeletal muscle (organ), muscle fiber (one cell), myofibrils, thin and thick filaments, myosin and actin

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7
Q

What are myofibrils?

A

organelles, cylinders of intracellular contractile structures arranged in repeating units

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8
Q

Are muscles made of one or several tissue types?

A

several

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9
Q

What is the H-zone?

A

found in A band, strictly myosin

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10
Q

What is the I band?

A

light area, just actin

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11
Q

What is the A band?

A

darker area majority myosin

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12
Q

What is the M line?

A

myosin attachment, found in the middle of the H zone

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13
Q

What is the Z-line?

A

actin attachment

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14
Q

What is a sarcomere?

A

one unit of the repeating thin and thick filament pattern within the myofibril

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15
Q

What is the functional unit of the muscle?

A

sarcomere

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16
Q

What does each myosin molecule containt?

A

a long rod-like segment facing the center of the sarcomere and 2 cross-bridge heads that extend out towards the overlying actin

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17
Q

How many bonding sites does each cross-bridge head have? What are they for?

A

two, one for actin and one for ATP, the binding ATP binding site also serves as an enzyme that hydrolyzes ATP

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18
Q

Describe the structure of thin filaments

A

globular acting (g-actin) molecules come together to form an actin helix or filament-actin (f-actin), appear as a 2 strand pearl necklace

Tm and Tn join and block the binding site for myosin

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19
Q

What do Tropomyosin and Troponin look like?

A

cinnamon stick, mickey mouse head

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20
Q

What is the cystolic calcium concentration during muscle relaxation?

A

low, 100nM

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21
Q

What is the cystolic calcium concentration during muscle activation?

A

high, 1-10 uM

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22
Q

What happens during muscle relaxation?

A

Tn push Tm, Tm blocks binding site

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23
Q

What happens during muscle activation?

A

calcium on Tn, Tn stops pushing Tm, Tm gets out of the way

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24
Q

Do muscles always lengthen during activation?

A

no

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25
Q

What does calcium allow?

A

the myosin cross-bridge and actin can physically interact to cause the muscle to contract

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26
Q

define contraction

A

activation of myosin cross-bridges to exert force on the thin filaments

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27
Q

What is the sarcolemma?

A

plasma membrane and transverse tubules

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28
Q

What is the sarcoplasmic reticulum?

A

smooth(longitudinal) ER and terminal cisternae (calium storage)

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29
Q

Define a motor unit

A

an alpha motor neuron and the multiple muscle fibers it innervates (stimulates)

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30
Q

Describe the relationships between skeletal muscle fibers and alpha-motor neurons

A

each skeletal muscle fiber is stimulates by one alpha motor neuron, and one alpha motor neuron branches to activate multiple fibers within a motor unit.

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31
Q

Where are action potentials propagated on skeletal muscle?

A

sarcolemma

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32
Q

What is excitation -contraction coupling?

A

complex processes connect the action potentials in a motor neuron to the generation of force by cross-bridges

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33
Q

List the events that occur at a neuromuscular junction.

A
  1. motor neuron action potential
  2. Ca2+ enters voltage-gated channels
  3. acetylcholine degradation
  4. acetylcholine binding opens ion channel
  5. Na+ entry
  6. local current between depolarized end plate and adjacent muscle plasma membrane
    7.muscle fiber action potential initiation
  7. propagated action potential in muscle plasma membrane
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34
Q

What is the graded potential in the neuromuscular junction also known as?

A

End Plate Potential, EPP

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35
Q

Where does the synapse of the neuromuscular junction occur?

A

motor end plate

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36
Q

What are end plate potentials?

A

HUGE graded potentials, 1 alpha motor neuron per one muscle fiber AP, always excitatory

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37
Q

What is binding to what in end plate potentials?

A

ACh always binding to nicotinic ACh receptors

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38
Q

Where does inhibition of skeletal muscle occur?

A

CNS

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39
Q

How does Botulinum toxin affect NMJ?

A

presynaptic Ach release, cuts of snare proteins, no contraction

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40
Q

How does Organophosphates affect NMJ?

A

block enzymes that break down Ach

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41
Q

How does Curare affect NMJ?

A

AchR antagonist, post-synaptic

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42
Q

How does Succinylcholine affect NMJ?

A

short term AchR antagonist, post-synaptic

43
Q

List the steps that lead to increased calcium concentration in skeletal muscle.

A
  1. Action potential propagated along muscle cell membrane and into T-tubules
  2. Ca2+ released from lateral sac
  3. Ca2+ binding to troponin removes blocking action of tropomyosin
  4. cross-bridges bind and generate force
  5. Ca2+ removal from the troponin restores tropomysoin
  6. Ca2+ transported back into sarcoplasmic reticulum
44
Q

What type of transport is used to get Ca2+ into the SR?

A

primary active transport

45
Q

What does the DHP receptor do?

A

it is a voltage sensor in the sarcolema, and it opens the Ryanodine receptor to release calcium

46
Q

List the steps of the cross bridge cycle

A
  1. cross-bridge binds the actin
  2. cross-bridge moves
  3. ATP binds to myosin, causing cross-bridge to detach
  4. hydrolysis of ATP energizes the cross-bridge
47
Q

What causes Rigor Mortis?

A

lots of myosin heads bound to actin, no ATP

48
Q

Define a load

A

the amount of force exerted on a muscle by an object (objects mass or weight)

49
Q

Define tension

A

the amount of force exerted by a muscle on an object

50
Q

Describe Isometric Contraction

A

iso=same
metric = length
XB’s are formed and cycle
load = force

51
Q

Describe Isotonic Contraction

A

iso=same
tonic = tone
XB’s are formed and cycle
Load is not equal to force

52
Q

What are the two types of Isotonic contraction

A

eccentric = load greater than force, muscle lengthens
concentric = load less than force, muscle shortens

53
Q

Describe an Isometric Twitch

A

-Force development from a SINGLE action potential
-Each end of the fiber is fixed (immovable)

54
Q

What explains the latent period?

A

everything in excitation- contraction coupling prior to XB formation , lack of calcium

55
Q

What HAS to happen for force development to occur?

A

XB’s are formed

56
Q

What does the frequency is isometric frequency refer to?

A

frequency of stimulation (AKA action potentials from the alpha motor neuron)

57
Q

What are the two types of tetanus?(Isometric)

A

Fused and Unfused

58
Q

What is summating during tension? (Isometric)

A

not graded potentials, calcium and cross bridges

59
Q

What type tetanus is most common is daily life? (Isometric)

A

Unfused tetanus

60
Q

What is happening during unfused tetanus?(Isometric)

A

increased tension due to increased frequency of action potentials

61
Q

What is happening during fused tetanus? (Isometric)

A

amount of calcium has become constant, so tension becomes relatively constant

62
Q

What are the two main things to consider about isometric length?

A

passive force from titin and active force due to the contractile proteins actin and myosin

63
Q

What does L naught represent? (Isometric)

A

ideal length

64
Q

Describe active force (Isometric)

A

implies cross bridges are formed and ATP is being consumed

65
Q

Describe passive force (Isometric)

A

the elastic force from titin

66
Q

Why is the latent period longer in Isotonic twitch compared to isometric?

A

waiting for tension to be greater than load

67
Q

What are the three sources of ATP in metabolisim?

A

creatine phosphate, oxidative phosphorylation in mitochondria, glycolysis in cytosol

68
Q

Describe the mode, location, number of ATP per glucose, rate of ATP production, and waste for Aerobic and Anaerobic metabolism

A

Aerobic:
mode- oxidative phosphorylation
location- mitochondria
#ATP per glucose- 36
Rate of ATP production- slow
waste- CO2 and H2O

Anaerobic:
mode- glycolysis, more dominant with intense muscle activity
location- cytosol
#ATP per glucose- 2
Rate of ATP production- fast
waste- lactic acid

69
Q

What are the functions of ATP in skeletal muscle?

A
  1. Hydrolysis of ATP by the Na+/K+ -ATPase in the plasma membrane maintains Na+ and K+ gradients, which allows the membrane to produce and propagate action potentials
  2. Hydrolysis of ATP by the Ca+ -ATPase in the sarcoplasmic reticulum provides the energy for the active transport of calcium ions into the reticulum, lowering cytosolic Ca2+ to prerelease concentrations, ending the contraction, and allowing the muscle fiber to relax
  3. Hydrolysis of ATP to myosin-ATPase energies the cross-bridges, providing the energy for force generation
  4. Binding of ATP to myosin dissociates cross-bridges bound to actin, allowing the bridges to repeat their cycle of activity (i.e. Allosteric Function)
70
Q

What are the skeletal muscle fiber types categorized by?

A
  1. Rate of myosin ATP hydrolysis (depends of myosin isoform - fast or slow)
  2. Metabolic pathway used to form ATP (oxidative phosphorylation)
71
Q

What are the three basic types of skeletal muscle fiber types?

A

Type 1=slow twitch= slow oxidative (SO)
Type 2A= fast oxidative-glycolytic (FOG)
Type 2X = fast glycolytic (FG)

72
Q

What are type 1 (SO) muscle fibers good for?

A

posture/antigravity/endurance

73
Q

What are type 2A (FOG) muscle fibers good for?

A

fast aerobic excersize activities

74
Q

What are type 2X (FG) muscle fibers good for?

A

high power activities (intense bursts)

75
Q

What drives what type of myosin is expressed?

A

alpha-motor neuron type

76
Q

Which types of fibers are most resistant to fatigue but require longer rest periods?

A

slow-oxidative (SO)

77
Q

Which fibers have medium resistance to fatigue?

A

Fast-oxidative-glycolytic (FOG) fibers

78
Q

Which fibers are least resistant to fatigue but recover rapidly?

A

Fast-glycolytic fibers (FG)

79
Q

What happens when muscles fatigue?

A

build up of H+, ADP, and Pi (LACTIC ACID)
the acid buildup impairs enzymes and calcium movements, i.e. protein function
ie RyR, SR Pumps, thin filament Ca sensitivity

80
Q

Describe what happens when muscles fatigue from low-intensity, long-duration excersize

A
  1. All factors listed for high-intensity, short-duration exersize (e.g. build-up of H+, ADP, and Pi)
  2. Persistent (Ca2+) elevation from leaky RyRs
    -calcium dependent proteases activated and degrade contractile proteins, induces weakness and soreness. SR pumps NOT working normally
  3. Decrease in muscle glycogen, low blood glucose, and dehydration
  4. Central Command Fatigue
    -The CNS(brain) stops sending excitations signals to motor neurons. Muscles may not be fatigued but you stop muscle contractions anyway. Caused by increasing unpleasant, distressful sensations for perceptions or thoughts. Kills your will to go on.
81
Q

How does smooth muscle help maintain homeostasis?

A

-regulates blood flow (change vessel diameter and radius)
-regulates airway diameter and radius
-helps in expulsion of urine from the body
-helps in delivery of baby during childbirth
-helps move food through the digestive tract

82
Q

Name 4 similarities between smooth and skeletal muscle.

A
  1. Both contain thick, myosin filaments and thin, actin filaments
  2. increase in cytosolic Calcium is the key step in the E-C coupling process
  3. ATP is directly used to power cross-bridge cycling
  4. sliding filament mechanism of concentration applies to both
83
Q

Describe the structure of smooth muscle, including what makes it different from skeletal muscles

A

spindle-shaped
very small
single nucleus
form sheets
no transverse tubules
no troponin
unstriated (no sarcomeres, no z-lines)
irregularly developed SR
rely on calcium form both inside and outside the cell
contain dense bodies
innervated by the autonomic division of the peripheral nervous system

84
Q

What is the function of dense bodies?

A

actin attachment in smooth muscle

85
Q

What areas of the nervous system does smooth muscle vs skeletal muscle deal with?

A

smooth = sympathetic/parasympathetic (autonomic)
skeletal= CNS (peripheral)

86
Q

Which type of muscle has sarcomeres?

A

skeletal, not smooth

87
Q

What excites or inhibits smooth muscle cells to contract?

A

neurotransmitters from autonomic axons with varicosities
sympathetic or parasympathetic

88
Q

What does the response of smooth muscle depend on?

A

type of receptor the cell has

89
Q

What type of hormone goes with sympathetic?

A

NorEpi

90
Q

What type of hormone goes with parasympathetic

A

Ach

91
Q

What happens in Alpha-one

A

smooth muscle contracts

92
Q

What happens in beta-two

A

smooth muscle relaxes

93
Q

Describe what happens in cells with pacemaker potentials

A

oscillate to threshold, fire AP
1.Pacemaker Potential spontaneous depolarization to threshold (create AP on their own)
2. action potential upstroke
3. repolarization due to K+ efflux

94
Q

Describe what happens in cells with slow waves

A

no AP alone
1. spontaneous depolarizations BELOW threshold
2. smaller amount of both depol and repol
3. add excitatory NT/Horm, depolarization to threshold

95
Q

What are the inputs influencing smooth muscle contractile activity?

A

-spontaneous electrical activity in the plasma membrane of the muscle cell (pacemakers and slow waves)
-neurotransmitters released by autonomic neurons (Ach NE)
-Hormones (Oxytocin, Estrogen, Progesterone)
-Locally induced changes in the chemical composition (paracrine factors, acidity, oxygen, osmolarity, and ion-concentrations) of the extracellular fluid surrounding the cell
-stretch (mechanoreceptors)( Blood pressure and motitlity)

96
Q

What are the different types of gated channels used to take calcium into a smooth muscle cell? Where are they loacated?

A
  1. Voltage-gated
  2. Ligand-gated (NT/Horm)
  3. Mechano-gated
  4. Metabotropic receptors (NT/Horm)

all located in the sarcolemma

97
Q

What type of channel is used to get calcium into the SR of smooth muscle cells?

A

IP3-ligand-gated Ca2+ channel

98
Q

What is the new function of ATP in muscle contraction that only applies to smooth muscle?

A

phosphorylation of myosin light chain by MLCKinase; separate ATP molecule

99
Q

Which plateau (smooth or skeletal) spans longer?

A

smooth

100
Q

Which type of cells can be stretched to up to 3x their length?

A

smooth muscle due to oblique, irregular arrangement of actin and myosin

101
Q

What type of muscle is thin filament vs thick filament regulation?

A

smooth is thick filament
skeletal is thin filament

102
Q

What afferent path does the tack example align with?

A

anterolateral

103
Q

What afferent path does the knee jerk align with?

A

dorsal column, stretch receptors

Physiology (9 decks)

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