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AP Tignor 1 > Muscle Contraction > Flashcards

Muscle Contraction Flashcards

1
Q

Types of tissue

A

Epithelial
Connective
Nervous
Muscular

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2
Q

Types of muscle tissue

A

Skeletal, cardiac, smooth.

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3
Q

Muscle cells

A

Thanks to their unique protein arrangement they can contract

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4
Q

Skeletal muscle tissue

A

Long, multinucleate, stritated. Can be up to 30 cm in length

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5
Q

Smooth muscle

A

Sickle shaped

No striations

Muscle of involuntary nervous system.
Can constrict airways and blood vessels. Can move food down via peristalsis.

Involuntary

Single nucleus

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6
Q

What causes striations?

A

Sarcomeres: highly organized protein structures

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7
Q

Cardiac muscle

A

Striated
Only one nucleus
Have highly organized actin myosin sarcomeres
Branched
Sometimes a capillary between branching
Have intercalated discs.
Lots of sarcomeres
Huge number of mitochondria. Can make up 35-40% of cell

Dark lines are intercalated discs

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8
Q

Intercalated discs

A

Looks like egg cartons together
Has lots of gap Junctions and desmosomes
Beats in syncytium.
Creates cytoplasm to cytoplasm connections between all cardiac muscle cells. Anchoring junctions prevents shear stress

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9
Q

Ability to repair of muscle tissues

A

Skeletal muscle: a little bit

Smooth muscle: best ability to repair itself

Cardiac muscle : not at all. Amitotic. Causes higher risk of ischemia(stop blood flow) and hypoxia (lack of oxygen).

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10
Q

Cardiomyocyte

A

Cardiac muscle cell death.
That section of heart dies that lost its oxygen supply. Gets filled with connective tissue. Limits heart capacity

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11
Q

Muscle fiber is

A

Muscle cell
Fuse together early on
Can be up to 30 cm in length.filled with cables called myofibrils

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12
Q

Myofibrils

A

Made up of myofilaments (smallest units) like myosin and actin.
Have lots of mitochondria. Needed for muscle movement.

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13
Q

Smallest structure in a muscle cell is

A

Myofilaments. Bundle together to make myofibrils

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14
Q

Endomysium

A

Layer or connective tissue that covers muscle fiber.

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15
Q

Satellite cells in muscles

A

Help muscles grow.
Grow by enhancing or creating more of the myofibrils of the muscle fiber itself.

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16
Q

Muscle fascicle

A

Group of muscle cells together. Column of muscle cells.

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17
Q

Perimysium

A

Around fascicles peri-around

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18
Q

Groups of fascicles together

A

Belly of muscle itself
Surrounded by epimysium

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19
Q

Deep fascia

A

Wraps in and around groups of muscles and organs above epimysium

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20
Q

Possible length of smooth muscle

A

200 micrometers in length

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21
Q

Sarcolemma

A

Plasma membrane around q skeletal muscle cell

Sarcolemma=cell membrane

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22
Q

Myosin

A

Thick filament

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23
Q

Actin

A

Thin filament

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24
Q

-in

A

Protein suffix

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25
Q

Sarcomere

A

Distance between 2 z discs
From halfway between light band to halfway between light band
Including dark band between

Hundreds and thousands in a single muscle cell. All contract at once to make cell shorter

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26
Q

Basic functional protein unit of contraction in skeletal muscle cells and cardiac muscle cells. In smooth muscle, arrangement is different

A

Sarcomere

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27
Q

Z discs made of

A

Titin. One of the biggest proteins made in the human body.

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28
Q

Function of Z discs

A

Anchoring points

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29
Q

Myosin

A

ATP-ase, carries out the motion.
Grab onto actin and change shape pulling against the actin. Shrinks ends of sarcomeres

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30
Q

I band

A

Light band

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31
Q

A band

A

Dark. Mostly myosin with some overlapping actin.

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32
Q

M line

A

Line down middle of connecting myosin strands

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33
Q

As the ends of sarcomere contract

A

I have myosin, I have actin
When sarcomere contracts, the actin gets pulled along the myosin. Neither protein gets shorter, the myosin just rachets the actin past it. As myosin begins to overlap actin during muscle contraction, the I bands get really small and disappear.

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34
Q

Sarcoplasmic reticulum

A

Same as endoplasmic reticulum. Important for the synthesis of proteins

In muscle fibers and around the myofibrils where we find the sarcoplasmic reticulum, it does the normal endoplasmic reticulum stuff, but it becomes an important storage location for calcium.

Important because calcium is part of signaling pathway that leads to muscle contractions taking place. Think about it storing calcium

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35
Q

T-tubules

A

Nearby to sarcoplasmic reticulum. connect the sarcolemma to the inside of the cell. Wrap around in a net-like pattern around myofibrils

Why?

Bring outside of the cell in deep and around myofibrils. When depolarization happens, that depolarization travels very quickly. Rapid transmission of action potentials and help regulate calcium concentration

Recap of action potentials:
When signal arrives(depolarization). Motor neuron plugs into muscle fiber and at the end of synaptic knobs ACh is going to be released and travel across the synaptic cleft to bind to ligand gated receptors on the sarcolemma called motor end plate. Sodium rushes in and starts the depolarization of the next muscle cell

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36
Q

Structures that help myosin pull actin

A

Has two heads, looks like double headed golf club.
Heads have binding sites for actin. Myosin is gonna bind to ATP and change shape. When it changes shape, that gives us one tug on actin. To move great distance have to. Shrink sarcomeres a lot

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37
Q

When is muscle contraction happening

A

As long as calcium is present, it’s been released from sarcoplasmic reticulum, those myosin heads are going to pull. Think tug of war or climbing a rope end over end. Pulling over and over. Each myosin molecules out of the billions of myosin molecules is going to be pulling against that actin.

  1. Reach forward
  2. Pull against it
  3. Let it go
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38
Q

Why don’t myofilaments shrink?

A

They slide past eachother like fingers pushing between fingers. Sliding movement caused by ATPase or myosin

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39
Q

Actin subunits

A

Similar to a ping pong ball. One one side has a little “Velcro” that acts as binding site for myosin.

When not in use, binding sites are: covered up.

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40
Q

Bond between Actin and myosin

A

Super strong bond.
One of strongest in human body

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41
Q

How are actin subunits covered up?

A

Tropomyosin helps cover up actin subunits: when there’s no calcium signal present in sarcoplasm (cytoplasm of muscle cell) it covers up binding sites on actin from myosin

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42
Q

“switch” protein troponin

A

Troponin: has binding site for tropomyosin, Binding site for actin, binding site for calcium

Light switch that tells muscle to contract

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43
Q

Importance of Calcium in muscle contraction

A

No calcium present and bound to troponin, therefore tropomyosin covers actin binding sites. The myosin, even if ATP is present has nothing to grab onto. Myosin has nothing to do.

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44
Q

Motor unit

A

Motor neuron + all of the muscle fibers it innervates in any given muscle

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45
Q

Nervous system innervation of muscles

A
  1. Peripheral motor neuron leaves through ventral root and sends out signal. Motor neuron from somatic motor system. Myelinated
  2. Motor neuron innervates a group of muscle fibers
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46
Q

Motor units

A

Allow same set of muscles to use different amounts of force to pick up different items

Made of: motor neuron+ all the muscle fibers that it innervates.
Come in different kinds

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47
Q

Different kinds of motor units

A

Small, fast,
medium,
huge, slower acting

Recruit motor units from smallest to largest as more force is needed

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48
Q

Neuromuscular junction

A

Where a motor unit meets a muscle.

It’s where the synaptic knob is going to hover over a special part of the sarcolemma called the motor end plate

49
Q

Why does motor end plate wind back and forth?

A

To increase surface area so we can have more ligand gated sodium channels.

50
Q

What happens after depolarization of a muscle fiber?

A
  1. Have to get signal in and around all myofibrils.

At this point ach has been released. (Neurotransmitter of neuromuscular junctions) In voluntary or skeletal system.
Na is going to rush into the cell

51
Q

Openings in sarcolemma

A

Connect to t-tubules

52
Q

Transverse tubules

A

T-tubules
Transverse tubules because they connect and surround myofibrils in the transverse plane along the long cylindrical muscle fiber cell. Cause depolarization to occur in and around all of the myofibrils

53
Q

What happens as signal reaches down into myofibrils?

A

When it gets next to terminal cisterna of sarcoplasmic reticulum

In skeletal muscle these are a swollen area of sarcoplasmic reticulum that specializes in calcium storage

54
Q

When signal gets down and around t-tubules, it’s going to cause

A

Calcium to be released from sarcoplasmic reticulum into sarcoplasm or the cytoplasm of the muscle cell

  1. Calcium is out of sarcoplasm and can bind to troponin.
    What’s going to happen when calcium binds to troponin? Long helical tropomyosin strands unwind exposing the myosin binding sites on actin subunits
  2. Within fraction of millisecond, myosin heads are going to stick to the actin.
  3. Contraction process starts
55
Q

Starting from the outside, describe the process of muscle fiber contraction

A
  1. Depolarization signal reaches the axon terminals whose synaptic knobs are
  2. Depolarization causes calcium to rush into the synaptic knob, causing vesicles with acetylcholine to be released by exocytosis into the synaptic cleft. Ach diffuses across synaptic cleft.
  3. Ach binds to ligand gated sodium channels on motor end plate
  4. Na starts to rush into cell, that action potential travels along the t-tubules
  5. AP gets down to cisterna. Releases calcium into sarcoplasm.
  6. Calcium binds to troponin. Troponin causes tropomyosin to unwind, exposing myosin binding sites
    7.. cycling by pulling on actin and letting it go. Happens billions of time with all the myosins molecules

8.sarcomeres shrink, contracting the muscle cell

  1. Muscle shortens and produces tension
56
Q

Cisterna

A

Collection area, swollen region of sarcoplasmic reticulum filled with calcium

57
Q

How to undo muscle contraction

A

Everything happens in reverse

Store Ca in sarcoplasmic reticulum, break down ACh

  1. Pump calcium back into sarcoplasmic reticulum which requires energy (ATP).
  2. Once calcium is missing from troponin, tropomyosin goes back to it’s normal shape and covers up all of the myosin binding sites

3.ach that’s left is denatured with help of acetylcholinesterase. Some can be pumped back into synaptic knob and remade into acetylcholine. Some of it will diffuse away. Have to get rid of it to stop Na from rushing in. NaK pumps help reestablish concentration gradients.

Undo everything we just did

58
Q

Products of acetylcholinesterase

A

Acetic acid & choline

59
Q

Cross bridge cycling

A

1.when myosin head first connects we have ADP and inorganic phosphate connected to the head.(Myosin has already used ATP, byproducts are left)

  1. ADP and inorganic phosphate are released from myosin head. Shape of myosin head has changed. (Power stroke) Getting ready to pull, think cocking
    When proteins bind something, they usually change shape
  2. As it’s getting ready to pull(power stroke occurs) when we lets those go, it pulls. Use ATP to break that strong bond between myosin head and the myosin binding site on actin subunit. Once that happens, we break away when ATP dissociates into ADP and inorganic Phosphate
  3. Myosin head straightens out again
60
Q

Generates the force necessary to move skeleton

A

Contraction of skeletal muscle

61
Q

Contraction is triggered by

A

Series of molecular events known as the cross-bridge cycle

62
Q

Sarcomere shortens when

A

Myosin heads in thick myofilaments form cross bridges with actin molecules in thin myofilaments

63
Q

When is the formation of a cross bridge initiated?

A

When calcium ions are released from sarcoplasmic reticulum to bind to troponin . Binding causes troponin to change shape

64
Q

Myosin head must be ____ before cross bridge cycle can begin

A

Activated. Occurs when ATP binds to myosin head and is hydrolyzed into ADP and inorganic phosphate. The energy liberated from the hydrolysis of ATP activated the myosin head, forcing it into cocked position.

65
Q

Four steps of cross bridge cycle

A
  1. Cross bridge formation: activated myosin head binds to actin, forming a cross bridge and inorganic phosphate is released..the bond between myosin and actin becomes stronger.
  2. Power stroke: ADP is released and the activated myosin head pivots sliding the thin myofilament towards the center of the sarcomere.

3.cross-bridge detachment: when another ATP binds to the myosin head, the link between the myosin head and the actin weakens and the myosin head detaches

4.reactivation of the myosin head
ATP is hydrolyzed to ADP and inorganic phosphate. The energy released during hydrolysis reactivates the myosin head. ATP is hydrolyzed to ADP and inorganic phosphate. The energy released during hydrolysis reactivates the myosin head, returning it to the cocked position.As long as the binding sites on actin remain exposed, the cross-bridge cycle will repeat. As the cycle repeats, thin myofilaments are pulled toward each other and the sarcomere shortens, causing the whole muscle to contract

66
Q

When does cross bridge cycling end?

A

When calcium ions are actively transported back into the sarcoplasmic reticulum. Troponin returns to its original shape, allowing tropomyosin to glide over and cover the myosin binding site on actin.

67
Q

Pathophysiological example of something that can go wrong with muscle

A

Myasthenia gravis- autoimmune disorder that attacks ligand gated sodium channels that bind ACh. Starts in face, causing partial paralysis of facial muscles.
Usually stops at face.
Can sometimes lead to early mortality.

How to fix: immune suppressants
Some drugs affect acetylcholinesterase in synaptic cleft, ach stays longer to find ligand gated sodium channels in receiving muscle cell

68
Q

How do we power muscle contraction

A

Cellular respiration

Some muscle cells do mostly glycolysis. Generate a little bit of ATP for a short burst of energy

69
Q

Steps of cellular respiration

A
  1. Glycolysis: occurs in cytosol, makes a little ATP and some NADH that can be passed on to next two steps.
  2. Citric acid cycle : in mitochondria, require oxygen as terminal electron acceptor

3.oxidative phosphorylation: in mitochondria, require oxygen as terminal electron acceptor.

After 2&3 lots of ATP is generated

70
Q

Myoglobin

A

Makes muscles red.
Helps bind oxygen and keep it in muscle cells

71
Q

Steps for powering muscle contractions

A
  1. Use free ATP: available ATP in muscle, lasts 2-3 seconds
    2.phosphagen system: creatine phosphate bumps into ADP to make ATP. 4-5 second s
    3.glycolysis: 30s taking glucose in the cytosol and break it down to pyruvate to make a little bit of ATP
    4.oxidative phosphorylation: most energy
    Take pyruvate at end of glycolysis and releases some CO2 and convert it into acetocoenzyme A, enters citric acid cycle and use high powered electrons and use them in electron transport chain to make lots of ATP
72
Q

Fast twitch and slow twitch muscles

A

Fast glycolytic, slow oxidative.
Endurance training increases slow oxidative fibers (red has myoglobin, helps make ATP)

Sprinting training develops what kind of fibers?
White glycolytic fibers

73
Q

Fast twitch fibers

A

Few mitochondria
Low myoglobin
Does lots of glycolysis to make a little ATP

74
Q

Slow oxidative fibers

A

Slow twitch fibers,
Red fibers,
Lots of myoglobin,
Lots of mitochondria,
Active over long haul,
Produce lots of ATP using citric acid cycle and electron transport chain

75
Q

Types of muscle contractions

A

Concentric
Eccentric
Isometric

76
Q

Concentric and centric are types of

A

Isotonic contractions

77
Q

Isotonic contractions

A

Under load, the muscle is actually going to shrink or lengthen under the load. The muscle itself changes length

78
Q

Isometric contractions

A

Muscle is under load,
Does not change length
Holding a weight in place

79
Q

Concentric contraction

A

Muscle contracts, lifting weight

80
Q

Eccentric contraction

A

Muscle elongates
Putting weight down

81
Q

Ideal length of a sarcomere

A

As muscle becomes completely contracted, tension or contractile force is reduced.
At maximum tension: standard distance between Actin and myosin.

When muscles are stretched too far no cross bridges form. Occurs when you pick up really heavy iron weight with either arm. Muscles are stretched out as far as they go.

82
Q

Muscle twitch

A
  1. Single stimulus
    Single muscle twitch
    2.latent period:ach released, sodium goes into muscle cell. Depolarization goes down around t-tubules. Calcium is released and binds to troponin. Tropomyosin has to unbind. Have to do cross bridge cycle.takes around 5 milliseconds
83
Q

Contraction period

A

Cross bridge cycle. Happens again and again
Myosin heads grab actin and let go. Takes another 20 or so milliseconds to reach maximum contraction period

84
Q

Extended relaxation period

A

Pump all calcium back out
Get rid of ACH through ach, or through diffusion through synaptic cleft. Pump sodium back into extra cellular fluid 1/10 of a second

85
Q

Wave summation

A

Signal repeatedly to increase tension. Do summation event . Never lets muscle completely relax. Muscle twitch is not allowed to end completely

86
Q

Tetanus

A

Only achievable through lab or pathology.
Maximum contraction over an extended period of time

87
Q

Atrophied muscle

A

Caused by macrophages with lysosomes. Body streamlines energy use.

Number of myofibrils is significantly lower.

88
Q

Smooth muscle locations

A

Blood vessels, airways, digestive system, urinary system, reproductive system

89
Q

Gap Junctions

A

Connect cytoplasm of one of those cardiac muscle cells to another. Allow muscle cells to work together in syncytium (bunch of cells acting as one big cell)

Have lots of fascia,. adherens junctions and desmosomes

90
Q

Difference between skeletal and cardiac muscle

A

Sarcomeres are well developed
Sarcoplasmic reticulum is well developed, do have t-tubules.,
Cardiac muscle cells do not have cisterna(swollen long regions along t-tubules, not as advanced as storage of calcium) of sarcoplasmic reticulum.

91
Q

In cardiac muscle extracellular calcium

A

May represent up to 40% of calcium needed to lead sarcomere contractions

92
Q

Leading cause of early mortality

A

Cardiovascular disease

93
Q

Ischemia

A

Lack of blood flow to an area, hypoxia, leads to cell death because can’t produce ATP. Cells are amitotic, don’t divide often. Tissue is going to die

94
Q

Dense connective tissue

A

Used to fill gaps, can fill gaps in the heart. Heart never functions the same.

95
Q

Function of spiral pattern of heart tissue

A

Twist or wrenching motion. Twists and contracts.

96
Q

Endocardium

A

Inner lining of heart. Continuous blood vessels connected to the heart

97
Q

Serous membranes around heart

A

Pericardium: around heart

Visceral pericardium: on surface of heart. (Epicardium)

98
Q

Pericardial cavity

A

Filled with serous fluid

99
Q

Parietal pericardium and fibrous pericardium

A

Located on outside

100
Q

Serous pericardium function

A

Serous pericardium allows the heartbeat to beat and move and reduce friction around thoracic cavity and mediastinum

101
Q

Single unit (visceral smooth muscle)

A

Digestive system, urinary system, respiratory system, blood vessels, reproductive system

Functioning like sheets of muscle contracting

Most common

Has varicosities

Instead of motor neuron terminating into smooth muscle, varicosity would wrap around smooth muscle.

102
Q

Multi unit smooth muscle tissue

A

Individual cells are going to be contracting.

Found in eye

103
Q

Varicosities

A

Vesicles with neurotransmitters. Allows for smooth, slow, pulsing contractions of sheets

104
Q

Set of smooth muscle is made of

A

Circular inner layer, makes tube

Longitudinal outer muscle

105
Q

Instead of sarcomere units, smooth muscle cells have

A

Active myosin bundles and dense bodies more like net.
When contracted, net shrinks up. Different than in skeletal and cardiac muscle

106
Q

Deep to circular layer of stomach, we have an

A

Oblique layer of smooth muscle. Let’s stomach carry out wrenching motion.

Only found in stomach

107
Q

Peristalsis

A

Push food down through peristalsis

108
Q

Segmentation

A

Mixing action.

Makes food into single, homogenous mix.

Intestines can carry out peristalsis and segmentation.

109
Q

Submucosal plexus

A

Plexus of autonomic nerves
Meissner’s plexus

In submucosa

110
Q

Myenteric plexus

A

In between layers of the muscle circular to the inside, longitudinal and the outside.

111
Q

What creates complicated intestinal movements

A

Myenteric plexus and submucosal plexus working together

112
Q

Artery

A

Lots of smooth muscle around edge.
Can help raise blood pressure

113
Q

Ruffled endothelium

A

Ruffled layer or simple, squamous epithelium inside of artery.

114
Q

Peripheral nerves

A

Surrounded by perineurium

115
Q

Smooth muscle can be found in

A

Arteries,
Ureters(has longitudinal muscle inside, circular muscle outside)
Bronchioles

116
Q

Sarcolemma

A

Plasma membrane of a muscle fiber

117
Q

Myofibrils

A

Rod-like bundle of contractile filaments (myofilaments) found in muscle fibers (cells).

118
Q

Myofilaments

A

Filament that constitutes myofibrils. Of two types. Actin and myosin

119
Q

Explain cross bridge cycle in your own words

A
  1. The myosin heads have ADP+P from a previous contraction.
  2. Calcium exposes the myosin binding sites on actin when Ca2+ binds to troponin, causing tropomyosin to lift, exposing the myosin binding sites.
  3. The myosin heads bind to the myosin binding sites, causing P to detach from the myosin head.
  4. The myofilaments glide past each other,powered by chemical energy in the heads.

ADP detaches

  1. Gliding motion stops when ATP binds to myosin heads, breaking the Actin-myosin bond.
  2. ATP turns into ADP and P, with the energy released stored in the myosin heads
  3. Presence of Ca 2+ ions reactivates the cycle

AP Tignor 1 (29 decks)

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